JP6713359B2 - Metal part manufacturing method and heat treatment holder - Google Patents

Description

The present invention relates to a method for manufacturing a metal part and a holder for heat treatment.

A configuration is known in which a heat treatment is applied to a steel ring member by a heating device, and then the ring member is cooled to heat-treat the ring member (for example, refer to Patent Document 1).

JP, 2007-297664, A

In the structure described in Patent Document 1, the bar of the basket penetrates the through hole portion of the ring member. As a result, the upper portion of the inner peripheral surface of the ring member is received by the bar, and the ring member is arranged in a suspended position on the bar. Further, the plurality of ring members are received by one bar, and the plurality of rings are heat-treated in a state where they are arranged in a straight line.

With such a configuration, it is difficult for the fluid to flow to the inner peripheral portion of the ring member that is received in the middle portion of the bar among the ring members that are aligned in the bar. Therefore, it is difficult for a processing medium such as gas or oil for heat treatment to enter the inner peripheral side of the ring. As a result, among the plurality of ring members, particularly in the ring member arranged near the center of the ring row, the degree to which the heat treatment gas touches the inner peripheral portion and the degree to contact the outer peripheral portion are greatly different. As a result, the degree of progress of the heat treatment is different between the inner peripheral portion and the outer peripheral portion, especially in the ring member arranged near the center of the ring row, and as a result, the heat treatment quality such as surface hardness and internal hardness varies. Occurs. Further, the heat treatment quality also varies among the plurality of ring members of the ring row.

Therefore, it is conceivable to widen the gap between the ring members in one ring row when heat-treating a plurality of rings at once. As a result, with respect to all the ring members, it is possible to supply sufficient heat treatment medium to the inner peripheral portion of the ring members. As a result, in each ring member, the heat treatment medium can be supplied more uniformly to the inner peripheral portion and the outer peripheral portion, so that a more uniform heat treatment quality can be realized. Further, it is possible to suppress variation in heat treatment quality between ring members. However, in this case, the space required for heat treating one ring member becomes large. Therefore, the number of ring members that can be heat-treated at once decreases. Similar problems exist in circular metal members other than the ring member.

In view of the above circumstances, the present invention can reduce variations in heat treatment quality when heat-treating an object to be treated such as a metal ring member, and can heat-treat more objects at once. , A method for manufacturing a metal part, and a holder for heat treatment.

(1) In order to solve the above problems, a method of manufacturing a metal component according to an aspect of the present invention radiates a circular object to be processed made of metal and heat directed in a predetermined main radiation direction. An arranging step of arranging a plurality of the objects to be processed such that the heat source is opposed to each other and an inferior angle formed by the axial direction of the object to be processed and the main radiation direction is 45° or less (including zero); A heat treatment step of heat-treating a plurality of the objects to be processed, in the disposing step, the object to be processed is in a state in which one end surface in the axial direction of the object to be processed is erected laterally, In addition, a plurality of the one end faces are arranged so as to face the predetermined first arrangement direction side, and the two objects to be processed that are adjacent to the first arrangement direction are the second arrangement direction orthogonal to the first arrangement direction. The positions in are offset from each other.

According to this configuration, by setting the inferior angle to 45° or less (including zero), the heat from the heat source is more evenly transferred to each part of the object to be processed. This makes it possible to further reduce the temperature difference inside the object to be processed when the object to be processed is heated by the heat source. More specifically, the temperature difference of the object to be processed in the circumferential direction can be made smaller. In particular, when the axial direction coincides with the main radiation direction, that is, when the inferior angle is zero, the temperature difference in the object to be processed in the circumferential direction can be significantly reduced. As a result, it is possible to suppress the occurrence of stress imbalance in the object to be processed. For example, the timing at which each part undergoes austenite transformation can be made more uniform within one object. Furthermore, as a result of the occurrence of stress imbalance in the object to be processed, the object to be processed can be heat-treated in a shorter time. As a result, it is possible to further reduce the distortion due to the heat treatment of the circular object to be processed made of metal, and to shorten the heat treatment time of the object to be processed. More specifically, the elliptic distortion in which the object to be processed is distorted into an elliptical shape can be further reduced. For example, when the object to be processed is heated to the A1 transformation point or higher, the temperature of each part in the object to be treated can be made more uniform at the timing of passing the A1 transformation point. As a result, it is possible to suppress the occurrence of transformation stress in the object to be processed. Further, the two objects to be processed that are adjacent to each other in the first arrangement direction are displaced from each other in the second arrangement direction orthogonal to the first arrangement direction. This allows the fluid to more smoothly pass through the inner peripheral portion of each object to be processed. Therefore, for example, a medium (fluid) for heat treatment, such as carburizing gas in the carburizing process, oil and nitrogen gas in the quenching process, can be more smoothly supplied to the inner peripheral side of the workpiece. it can. Further, in each of the objects to be processed, it is possible to suppress variations in the supply degree of the medium at the inner peripheral portion and the outer peripheral portion. As a result, it is possible to further reduce the degree of variation in heat treatment of each object to be processed. Further, it is possible to further reduce the degree of variation in heat treatment among a plurality of objects to be processed. Therefore, heat treatment qualities such as surface hardness and internal hardness of each object to be treated can be made more uniform. Further, the medium for heat treatment is not smoothly supplied to the inner peripheral side of the objects to be processed by increasing the interval between the objects to be processed in the first arrangement direction. Therefore, the space required for heat-treating the object to be processed can be made smaller. As a result, more objects to be processed can be placed at once in a predetermined heat treatment space such as a heat treatment furnace. Therefore, more objects can be heat-treated at once. According to the above, when heat-treating an object to be treated made of metal, it is possible to reduce variations in heat treatment quality, and it is possible to heat-treat more objects to be treated at once.

(2) In some cases, the two objects to be processed that are adjacent to each other in the first arrangement direction are arranged such that the end surfaces facing each other are in contact with each other.

With this configuration, each object to be processed can function as a spacer that defines the position of the object to be processed. For example, in the three processing objects arranged in the first arrangement direction, the first processing object and the third processing object in the first arrangement direction sandwich the second processing object. With such a configuration, the second object to be processed can set the interval between the first object to be processed and the third object to be processed to be the same as the thickness of the second object to be processed. Thereby, a large number of objects to be processed can be arranged more uniformly along the first arrangement direction. Further, since a plurality of objects to be processed can be raised in a state of being in contact with each other, these objects to be processed can be raised autonomously. Therefore, it is not necessary to separately provide a support member for supporting the object to be processed so as not to fall. This allows the objects to be processed to be arranged at a higher density. Therefore, more objects to be processed can be placed at once in a limited space.

(3) In the arranging step, a first row including a plurality of the objects to be processed arranged along the first arranging direction and each of the objects to be processed in the first row are positions in the second arranging direction. A second row including a plurality of the objects to be processed arranged in the first arranging direction in a shifted state, and the objects to be processed in the first row and the objects to be processed in the second row. The processed product may be alternately arranged in the first arrangement direction.

With this configuration, the objects to be processed can be arranged in a zigzag pattern. Accordingly, even if the space for arranging the object to be processed is small, the medium can be evenly distributed to the inner peripheral portion and the outer peripheral portion of each object to be treated. Further, the object to be processed can be arranged more efficiently. As a result, more objects can be heat-treated more uniformly at once in a limited space.

(4) A plurality of the first rows and a plurality of the second rows are alternately arranged in the second arrangement direction, and when the respective rows are viewed from the first arrangement direction, each of the workpieces is In some cases, the regions to be processed in adjacent rows are arranged such that regions having a length equal to or less than half the outer diameter of the products to be processed overlap in the second alignment direction.

According to this configuration, when viewed from the first arrangement direction, the one object to be processed and the one object to be processed are overlapped with the two objects to be processed that are adjacent to each other on both sides in the second arrangement direction. be able to. Thereby, the object to be processed can be more efficiently arranged in the limited space for arranging the object to be processed. As a result, more objects can be heat treated at once in a limited space.

(5) In the arranging step, the plurality of objects to be processed may be arrayed along the main radiation direction.

According to this configuration, it is possible to collectively heat-treat a plurality of objects to be processed while reducing thermal strain.

(6) Both the first arrangement direction and the second arrangement direction may be horizontal.

According to this structure, the space occupied by the plurality of objects to be processed in the vertical direction can be made narrower. Therefore, more objects to be processed can be placed at once in the limited space for heat treatment.

(7) The axial direction may be a direction inclined with respect to the horizontal direction.

With this configuration, it is possible to more appropriately arrange the plurality of objects to be treated in consideration of the weight balance of the plurality of objects to be treated as a whole.

(8) In the arranging step, the predetermined holder may be configured to support the outer peripheral surface of the object to be processed from below.

According to this configuration, the holder supports the outer peripheral surface of the object to be processed from below, thereby suppressing the occurrence of tensile stress in the object to be processed. As a result, the thermal strain caused by the stress of the object to be processed can be significantly reduced.

(9) The holder may be configured to support the object to be processed in line contact or point contact.

According to this configuration, the holder supports the object to be processed in line contact or point contact, so that the holder is in a state in which the expansion and contraction of the object during heat treatment of the object is suppressed. Thus, the object to be processed can be supported. As a result, the strain of the object to be processed due to the heat treatment can be further reduced.

(10) The holder supports the outer peripheral surface of the object to be processed by a first support portion and a second support portion that are separated from each other in the circumferential direction of the outer peripheral surface, and the holder is provided around the central axis of the object to be processed. The angular interval between the first support portion and the second support portion may be set in the range of 20° to 60°.

According to this configuration, by setting the angle range between the first support portion and the second support portion to 20° or more, the stress acting on each portion of the object to be processed supported by these support portions can be made more uniform. .. Therefore, the thermal strain of the object to be processed can be further reduced. In addition, by setting the angle range between the first support portion and the second support portion to 60° or less, when the object to be processed thermally expands by heat treatment, the object to be processed is sandwiched between the two support parts due to expansion. Can be suppressed. Accordingly, it is possible to prevent the object to be processed from being deformed so as to bite into the two support portions.

(11) A holder for heat treatment according to an aspect of the present invention is a holder for heat treatment for holding a plurality of metal objects to be processed which are formed in a circular shape and subjected to heat treatment. The object to be processed and a heat source that radiates heat in a predetermined main radiation direction are opposed to each other, and the inferior angle formed by the axial direction of the object to be processed and the main radiation direction is 45° or less (including zero). ) Is configured to hold the object to be processed, the holder includes a receiving portion for receiving the object to be processed extending along a predetermined first arrangement direction, and the receiving portion is A plurality of the objects to be processed are arranged in a state of being erected such that one end surface in the axial direction of the object to be processed is laterally oriented and the one end surface faces the first arranging direction side. In addition, the two objects to be processed that are adjacent to each other in the first arrangement direction are arranged so as to be offset from each other in the second arrangement direction orthogonal to the first arrangement direction.

According to this configuration, by setting the inferior angle to 45° or less (including zero), the heat from the heat source is more evenly transferred to each part of the object to be processed. This makes it possible to further reduce the temperature difference inside the object to be processed when the object to be processed is heated by the heat source. More specifically, the temperature difference of the object to be processed in the circumferential direction can be made smaller. In particular, when the axial direction coincides with the main radiation direction, that is, when the inferior angle is zero, the temperature difference in the object to be processed in the circumferential direction can be significantly reduced. As a result, it is possible to suppress the occurrence of stress imbalance in the object to be processed. For example, the timing at which each part undergoes austenite transformation can be made more uniform within one object. Furthermore, as a result of the occurrence of stress imbalance in the object to be processed, the object to be processed can be heat-treated in a shorter time. As a result, it is possible to further reduce the distortion due to the heat treatment of the circular object to be processed made of metal, and to shorten the heat treatment time of the object to be processed. More specifically, the elliptic distortion in which the object to be processed is distorted into an elliptical shape can be further reduced. For example, when the object to be processed is heated to the A1 transformation point or higher, the temperature of each part in the object to be treated can be made more uniform at the timing of passing the A1 transformation point. As a result, it is possible to suppress the occurrence of transformation stress in the object to be processed. Further, the two objects to be processed that are adjacent to each other in the first arrangement direction are displaced from each other in the second arrangement direction orthogonal to the first arrangement direction. This allows the fluid to more smoothly pass through the inner peripheral portion of each object to be processed. Therefore, for example, a medium (fluid) for heat treatment, such as carburizing gas in the carburizing process, oil and nitrogen gas in the quenching process, can be more smoothly supplied to the inner peripheral side of the workpiece. it can. Further, in each of the objects to be processed, it is possible to suppress variations in the supply degree of the medium at the inner peripheral portion and the outer peripheral portion. As a result, it is possible to further reduce the degree of variation in heat treatment of each object to be processed. Further, it is possible to further reduce the degree of variation in heat treatment among a plurality of objects to be processed. Therefore, heat treatment qualities such as surface hardness and internal hardness of each object to be treated can be made more uniform. Further, the medium for heat treatment is not smoothly supplied to the inner peripheral side of the objects to be processed by increasing the interval between the objects to be processed in the first arrangement direction. Therefore, the space required for heat-treating the object to be processed can be made smaller. As a result, more objects to be processed can be placed at once in a predetermined heat treatment space such as a heat treatment furnace. Therefore, more objects can be heat-treated at once. According to the above, when heat-treating an object to be treated made of metal, it is possible to reduce variations in heat treatment quality, and it is possible to heat-treat more objects to be treated at once.

(12) The receiving portion may be configured to receive the plurality of objects to be processed in a state of being arranged along the main radiation direction.

According to this configuration, it is possible to collectively heat-treat a plurality of objects to be processed while reducing thermal strain.

(13) In some cases, the receiving portion may be arranged such that the axial direction is a horizontal direction or a direction inclined with respect to the horizontal direction.

According to this configuration, when the axial direction is horizontal, it is possible to suppress tensile stress from being generated in the object to be processed. As a result, the thermal strain caused by the stress of the object to be processed can be significantly reduced. Further, when the axial direction is a direction inclined with respect to the horizontal direction, it is possible to more appropriately arrange the plurality of objects to be processed in consideration of the weight balance of the plurality of objects to be processed as a whole.

(14) The holder may be configured to support the outer peripheral surface of the object to be processed from below.

According to this configuration, the holder supports the outer peripheral surface of the object to be processed from below, thereby suppressing the occurrence of tensile stress in the object to be processed. As a result, the thermal strain caused by the stress of the object to be processed can be significantly reduced.

(15) The holder may be configured to support the object to be processed in line contact or point contact.

According to this configuration, the holder supports the object to be processed in line contact or point contact, so that the holder is in a state in which the expansion and contraction of the object during heat treatment of the object is suppressed. Thus, the object to be processed can be supported. As a result, the strain of the object to be processed due to the heat treatment can be further reduced.

(16) The holder is configured to support the outer peripheral surface of the object to be processed by a first support portion and a second support portion that are separated in the circumferential direction of the outer peripheral surface, The angular interval between the first support portion and the second support portion may be set in the range of 20° to 60°.

According to this configuration, by setting the angle range between the first support portion and the second support portion to 20° or more, the stress acting on each portion of the object to be processed supported by these support portions can be made more uniform. .. Therefore, the thermal strain of the object to be processed can be further reduced. In addition, by setting the angle range between the first support portion and the second support portion to 60° or less, when the object to be processed thermally expands by heat treatment, the object to be processed is sandwiched between the two support parts due to expansion. Can be suppressed. Accordingly, it is possible to prevent the object to be processed from being deformed so as to bite into the two support portions.

(17) The receiving portion includes a plurality of support members extending along the first arranging direction to support a lower portion of the object to be processed, and the supporting members are arranged at a predetermined pitch in the second arranging direction. In some cases, the pair of supporting members adjacent to each other in the second arrangement direction support the object to be processed. The first support portion is formed on one of the support members of the pair of support members, and the second support portion is formed on the other support member of the pair of support members. There is a case.

With this configuration, it is possible to realize a configuration in which the object to be processed is supported stably without falling down with a simple configuration in which the object to be processed is supported by the pair of support members. In addition, since the object to be processed is not suspended, it is possible to suppress the occurrence of tensile stress in the object to be processed during the heat treatment of the object to be processed. As a result, it is possible to prevent tensile stress from being generated as residual stress in the object to be processed. Therefore, the mechanical strength of the object to be processed can be further increased.

(18) Each of the support members may have a facing surface as a surface facing the object to be processed, and the facing surface may extend linearly along the first alignment direction.

With this configuration, for example, the objects to be processed that are adjacent to each other in the first arrangement direction can be arranged close to each other so that their end surfaces are in contact with each other. This allows each object to be processed to function as a spacer that defines the position of the object to be processed. For example, in the three processing objects arranged in the first arrangement direction, the first processing object and the third processing object in the first arrangement direction sandwich the second processing object. With such a configuration, the second object to be processed can set the interval between the first object to be processed and the third object to be processed to be the same as the thickness of the second object to be processed. Thereby, a large number of objects to be processed can be arranged more uniformly along the first arrangement direction. Further, since a plurality of objects to be processed can be raised in a state of being in contact with each other, these objects to be processed can be raised autonomously. Therefore, it is not necessary to separately provide a support member for supporting the object to be processed so as not to fall. This allows the objects to be processed to be arranged at a higher density. Therefore, more objects to be processed can be placed at once in a limited space.

(19) The heat treatment holder includes a bottom frame portion to which the receiving portion is attached, and a plurality of bottom frame portions that extend upward from both ends of the bottom frame portion in the first alignment direction and are held by the receiving portion. A pair of vertical frame parts arranged so as to sandwich the object to be processed may be further provided, and each vertical frame part may be formed in a mesh shape.

According to this structure, the vertical frame portion can receive the object to be processed, so that the object to be processed can be prevented from collapsing. Further, since the vertical frame portion is formed in a mesh shape, the medium for heat treatment can be smoothly introduced from the outer side to the inner side of the holder for heat treatment through the vertical frame portion. Thereby, the heat treatment of the object to be processed can be performed more uniformly.

According to the present invention, when heat-treating an object to be treated such as a metal ring member, it is possible to reduce variations in heat treatment quality and to heat-treat more objects at once.

FIG. 3 is a schematic cross-sectional view of the heat treatment apparatus according to the embodiment of the present invention, showing a state in which the heat treatment apparatus is viewed in plan. FIG. 3 is a schematic cross-sectional view of the heat treatment apparatus, showing a state in which the heat treatment apparatus is viewed from the side. It is the figure which expanded the holder and to-be-processed object in the heat processing apparatus of FIG. It is the figure which expanded the holder and to-be-processed object in the heat processing apparatus of FIG. It is a schematic diagram for demonstrating the relationship between a holder and a to-be-processed object. It is a schematic diagram for explaining an inferior angle, and shows a case where the inferior angle is not zero. It is a flow chart for explaining an example of heat treatment operation in a heat treatment device. It is a graph which shows an example of temperature control of the to-be-processed object in a heat processing apparatus. FIG. 3 is a schematic equilibrium state diagram of a Fe—C alloy for explaining the state of the object to be heat treated by the heat treatment apparatus. It is a typical top view of a holder and a heater unit with which a heat treatment equipment concerning a 2nd embodiment of the present invention is equipped. FIG. 3 is a schematic side view of a main part showing a holder and an object to be processed held by the holder. FIG. 3 is a schematic front view of a main part showing a holder and an object to be processed held by the holder. It is a schematic plan view of the principal part which shows the holder with which the heat treatment apparatus which concerns on 2nd Embodiment of this invention is equipped, and the to-be-processed object hold|maintained at the said holder. It is a typical side view of the principal part for demonstrating one of the modifications. FIG. 15 is a schematic side view of a main portion for explaining a modification different from the modification shown in FIG. 14. It is a graph for demonstrating the thermal strain according to the kind of placement of a to-be-processed object. It is a graph for demonstrating the relationship between the inferior angle which an axial direction of a to-be-processed object and the main radiation direction make, and thermal strain. It is a graph for explaining the relationship between the carbon potential of the atmosphere in the furnace and the thermal strain.

Embodiments for carrying out the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic cross-sectional view of a heat treatment apparatus 1 according to an embodiment of the present invention, showing a state in which the heat treatment apparatus 1 is viewed in a plan view. FIG. 2 is a schematic cross-sectional view of the heat treatment apparatus 1, showing the heat treatment apparatus 1 in a side view. It is a side view. FIG. 3 is an enlarged view of the holder 2 and the object 100 to be processed in the heat treatment apparatus 1 of FIG. FIG. 4 is an enlarged view of the holder 2 and the object 100 to be processed in the heat treatment apparatus 1 of FIG. In FIG. 4, a part of the object to be processed 100 is not shown.

Referring to FIGS. 1 and 2, heat treatment apparatus 1 is provided for heat treating object 100 to be processed. Examples of this heat treatment include carburizing treatment such as vacuum carburizing, carbonitriding and carburizing and quenching, quenching treatment, tempering treatment, and annealing treatment. In this embodiment, a case where the heat treatment apparatus 1 is a gas carburizing furnace will be described as an example.

The object to be processed 100 is a metal member formed in a circular shape. In this case, the “circular shape” includes a cylindrical shape having a through hole formed therein, a disk shape having no through hole formed therein, and a shape having an outer shape having a circular envelope. An example of the member having a circular outer shape envelope is a gear having teeth formed on its outer peripheral portion. In the present embodiment, the object to be processed 100 is a ring-shaped metal part. The object to be processed 100 is formed in a substantially circular cylinder shape, and the strain amount is substantially zero in a state before the heat treatment by the heat treatment apparatus 1 is performed. The strain in this case refers to elliptic strain, and refers to the difference or ratio between the largest diameter portion and the smallest diameter portion of the object 100 to be processed.

Examples of the object 100 to be processed include race members such as outer and inner rings of rolling bearings, gears such as spur gears, rollers of rolling bearings, shafts and washers. It should be noted that the object to be processed 100 may be a metal part formed in a circular shape and subjected to heat treatment. The workpiece 100 is, for example, carbon steel having a carbon content (carbon potential) of about 0.2%. The carbon content of the object 100 to be processed may be 0.15% to 0.2%. In the present embodiment, the object to be processed 100 is formed in a ring shape having a thickness of about several mm in the axial direction D1 of the object to be processed 100. Therefore, the inner peripheral surface and the outer peripheral surface of the object to be processed 100 are cylindrical shapes concentric with each other.

The heat treatment apparatus 1 has a heat treatment unit 3 and a control unit 4.

The heat treatment unit 3 includes a holder 2, a heat treatment furnace 5, a heater unit 6, a pedestal 7, a stirrer 8, and an atmosphere gas supply unit 9.

The heat treatment furnace 5 is formed in a hollow box shape. The heat treatment furnace 5 forms an accommodation chamber for accommodating the object 100 to be processed. An inlet door 10 and an outlet door 11 are formed on a pair of side walls of the heat treatment furnace 5 which face each other and are arranged substantially parallel to each other. The object 100 to be processed is carried into the heat treatment furnace 5 from the outside of the heat treatment furnace 5 with the entrance door 10 opened. Further, the object 100 to be processed is carried out of the heat treatment furnace 5 to the outside of the heat treatment furnace 5 with the outlet door 11 opened. Further, the inlet door 10 and the outlet door 11 are closed while the workpiece 100 is being heat-treated. In this embodiment, the direction from the entrance door 10 to the exit door 11 is defined as the traveling direction X1.

The heat treatment furnace 5 is provided with a temperature sensor 12 for detecting the furnace temperature T as the temperature in the heat treatment furnace 5. The temperature detection result of the temperature sensor 12 is given to the control unit 4. Further, the heat treatment furnace 5 is provided with an oxygen sensor 13 for measuring the carbon potential in the heat treatment furnace 5. The result of oxygen concentration detection by the oxygen sensor 13 is given to the control unit 4. A heater unit 6 is arranged in the heat treatment furnace 5.

The heater unit 6 is provided to raise the temperature in the heat treatment furnace 5 to a temperature required for heat treatment of the object to be treated 100. The heater unit 6 is arranged in the heat treatment furnace 5 along the traveling direction X1. The heater unit 6 is arranged at a position apart from each of the four side walls of the heat treatment furnace 5 in a plan view.

The heater unit 6 has a plurality of first heaters 14 and a plurality of second heaters 15.

Each of the heaters 14 and 15 has a heating element (electric heating element) configured to convert electric power supplied from a power source (not shown) into heat. Each of the heaters 14 and 15 is configured to heat the atmosphere in the heat treatment furnace 5 by performing a heating operation by the heating element. A plurality of first heaters 14 (six in the present embodiment) are arranged at substantially equal intervals along the traveling direction X1. Similarly, the plurality of second heaters 15 are arranged at substantially equal intervals along the traveling direction X1. In the present embodiment, the number of first heaters 14 and the number of second heaters 15 are set to be the same.

Further, in the traveling direction X1, the position of each first heater 14 is aligned with the position of one corresponding second heater 15. As a result, the pair of first heater 14 and second heater 15 whose positions in the traveling direction X1 are aligned face each other in a state of being separated in a direction orthogonal to the traveling direction X1 in a plan view.

The first heater 14 and the second heater 15 have the same configuration. More specifically, the first heater 14 and the second heater 15 are formed in the same shape and have the same heating performance.

Each heater 14, 15 has a tube 16.

The tube 16 is provided to transfer the heat generated by energizing the electric heating element arranged in the tube 16 to the space inside the heat treatment furnace 5. The heat treatment furnace 5 is heated by the heat generated from the electric heating element in the tube 16, and the object 100 to be processed in the heat treatment furnace 5 is heated. The tube 16 is formed in the heat treatment furnace 5 in a cylindrical shape extending downward from the top wall 5a of the heat treatment furnace 5, and has a vertically straight shape. The diameter of each tube 16 is set to a predetermined value. Each tube 16 extends from the top wall 5 a of the heat treatment furnace 5 to a position below the position of the upper surface of the pedestal 7. Each tube 16 radiates heat radially to the circumference of the tube 16.

The main radiation direction D2 is defined in the heater unit 6 having the above configuration. The main radiation direction D2 is a direction in which the amount of heat supplied from the heater unit 6 per unit time is the largest. In other words, the heater unit 6 is configured to radiate the heat in the main radiation direction D2. In the present embodiment, the main radiation direction D2 is a direction in which the pair of heaters 14 and 15 having the same position in the traveling direction X1 face each other. More specifically, the main radiation direction D2 is a direction orthogonal to the traveling direction X1 in a plan view. In this embodiment, the heater unit 6 radiates heat in the direction orthogonal to the traveling direction X1. Further, in the present embodiment, the main radiation direction D2 is along the horizontal direction. It can be said that the main radiation direction D2 is the direction in which the combined value of the vectors is maximum when the heat radiation amounts from the heaters 14 and 15 are displayed as a vector. When the heater as the heat source is only one heater 14 or one heater 15, the main radiation direction D2 is the direction in which the normal line at any point of the cylindrical portion of the tube 16 extends, and It can also be defined as a direction passing through the center point of the processing object 100.

The pedestal 7 is arranged between the heaters 14 and 15 having the above configuration. The pedestal 7 is provided to support the holder 2. The pedestal 7 is, for example, arranged between the second heater 14 and 15 from the entrance door 10 in the traveling direction X1, and is also arranged between the fifth heaters 14 and 15 from the entrance door 10. The pedestal 7 includes, for example, a plurality of columns 7a to 7f. Each of the columns 7a to 7f extends vertically. For example, six columns 7a to 7f are provided, and four columns 7a, 7b, 7e, and 7f support the four corners of the holder 2, and two columns 7c and 7d support the middle portion of the holder 2. Is configured to.

In the present embodiment, the three columns 7a, 7c, 7e are arranged between the second heaters 14, 15 from the entrance door 10 in the traveling direction X1, and these three columns 7a, 7c, 7e are the main radiations. They are arranged at equal intervals in the direction D2. Further, two of these three columns 7a, 7c, 7e are adjacent to the corresponding heaters 14, 15. Further, the remaining three columns 7b, 7d, 7f are arranged between the fifth heaters 14, 15 from the entrance door 10, and these three columns 7b, 7d, 7f are equally spaced in the main radiation direction D2. It is located in. Further, two of these three columns 7b, 7d, 7f are adjacent to the corresponding heaters 14, 15.

The holder 2 is used to carry in and carry out one or more objects 100 to be processed into the heat treatment furnace 5. The holder 2 is used to hold the object to be processed 100 when the object to be processed 100 is heat-treated. The holder 2 is made of metal in the present embodiment. The holder 2 is formed in a rectangular box shape with an open top. The four side surfaces and one bottom surface of the holder 2 are formed in a mesh shape, and are configured to pass a fluid such as gas.

FIG. 5 is a schematic diagram for explaining the relationship between the holder 2 and the object 100 to be processed. 1 to 5, the holder 2 has a bottom frame portion 21, four vertical frame portions 22 to 25, and a receiving portion 26 attached to the bottom frame portion 21.

The bottom frame portion 21 is formed, for example, by combining metal rods in a rectangular shape. Four vertical frame portions 22 to 25 extend from the four side portions of the bottom frame portion 21.

The vertical frame portions 22 and 23 are formed as a pair of frame portions arranged so as to sandwich the object 100 to be processed in the front and rear (main radiation direction D2). The vertical frame portions 22 and 23 extend upward from both ends of the bottom frame portion 21 in the predetermined first arrangement direction E1 and are arranged so as to sandwich the plurality of workpieces 100 held by the receiving portion 26. ing. The vertical frame portion 22 is provided as a front frame portion and is arranged, for example, so as to be adjacent to the heater 14. The vertical frame portion 22 is provided as a rear frame portion and is arranged, for example, so as to be adjacent to the heater 15.

The vertical frame portions 24 and 25 are formed as a pair of frame portions arranged so as to sandwich the object 100 to be processed on the left and right sides (the traveling direction X1). The vertical frame portion 24 is provided as a left frame portion, and the vertical frame portion 25 is provided as a right frame portion. The vertical frame portions 24 and 25 are arranged between the heaters 14 and 15 so that, for example, the heaters 14 and 15 extend in the facing direction.

Each of the vertical frame portions 22 to 25 is formed in a mesh shape, and is configured to pass gas. In the bottom frame portion 21 supporting the vertical frame portions 22 to 25, the receiving portion 26 extends between two side portions separated in the main radiation direction D2 described later.

The receiving portion 26 is provided to support the plurality of objects to be processed 100. The receiving portion 26 extends along the predetermined first arrangement direction E1. The first arrangement direction E1 is along the axial direction D1 of the workpiece 100 held by the receiving portion 26. Further, the first arranging direction E1 is along the direction in which the vertical frame portions 24 and 25 extend in plan view. The receiving portion 26 has a plurality of supporting members 27.

The support members 27 are arranged in pairs at a predetermined pitch along a second arrangement direction E2 that is orthogonal to the first arrangement direction E1 in a plan view. Then, a plurality of pairs of support members 27, 27 are provided along the second arrangement direction E2. In the present embodiment, both the first arrangement direction E1 and the second arrangement direction E2 are substantially horizontal directions, and the inclination angle with respect to the horizontal plane is set to about 0 to several degrees. Then, the pair of adjacent support members 27, 27 supports the object to be processed 100.

The pair of support members 27, 27 is configured to dispose the object 100 to be processed in the heat treatment furnace 5 in an upright posture. The axial direction D1 of the object 100 to be processed is along the horizontal direction. "Along the horizontal direction" in this case can be exemplified as an angle formed by the axial direction D1 and the horizontal plane being in the range of about zero degrees to several degrees. In addition, in the present embodiment, the pair of support members 27, 27 support the outer peripheral surface 100a of the object 100 to be processed from below the outer peripheral surface 100a.

Further, the pair of support members 27, 27 is configured to support the workpiece 100 at two points. More specifically, the pair of support members 27, 27 is configured to support the object 100 to be processed at two points in the circumferential direction of the object 100 to be processed. In this way, the pair of support members 27, 27 includes the outer peripheral surface 100a of the object to be processed 100, which is separated from the outer peripheral surface 100a in the circumferential direction of the outer peripheral surface 100a at two positions (specifically, a first supporting portion 31 and a first supporting portion 31 described later). It is configured to be supported by the two support portions 32).

Each support member 27 is formed using, for example, a metal rod having a circular cross section, and in the present embodiment, extends in parallel to the main radiation direction D2. In the present embodiment, each support member 27 extends in the first arranging direction E1 so as to be in linear contact with the object 100 to be processed and support the object 100 to be processed.

More specifically, each support member 27 has a facing surface 28 that faces the workpiece 100 to be supported. The facing surface 28 extends straight along the first arrangement direction E1. The portion of the facing surface 28 that is in contact with the object 100 to be processed forms the support portion 31 or the support portion 32. In this way, the first support portion 31 formed on the one support member 27 of the pair of support portions 27, 27 and the second support portion 32 formed on the other support member 27 are present. Becomes In the present embodiment, the first support portion 31 and the second support portion 32 are linear portions extending in the first alignment direction E1 (main radiation direction D2). The outer peripheral surface 100a of the object to be processed 100 is supported by supporting portions 31 and 32 that are spaced apart from each other in the circumferential direction of the outer peripheral surface 100a.

Further, the object 100 to be processed is arranged in the holder 2 such that an inferior angle θ1 formed by the axial direction D1 of the object 100 to be processed and the main radiation direction D2 is 45° or less (including zero).

FIG. 6 is a schematic diagram for explaining the inferior angle θ1 and shows a case where the inferior angle θ1 is not zero. 1 to 4 show a case where the inferior angle θ1 is zero. With reference to FIG. 6, in the present embodiment, the inferior angle θ1 is defined as follows, for example. The inferior angle θ1 is defined by a plane including two straight lines, that is, a central axis B3 of the object to be processed 100 extending in the axial direction D1 and a reference line B4 extending along the main radiation direction D2, that is, a plane shown in FIG. 6. .. The inferior angle θ1 has a first half line B5 formed by a part of the central axis line B3 and a second half line B6 formed by a part of the reference line B4 with an origin O at an intersection point where these two lines B3, B4 intersect. The smaller one of the two conjugate angles formed.

The inferior angle θ1 may be defined by using an angle formed by a virtual orthogonal plane orthogonal to the reference line B4 (main radiation direction D2) and the central axis B3 (axial direction D1). In this case, the inferior angle θ1 when the imaginary orthogonal plane is orthogonal to the central axis B3 is zero. Then, the inclination angle of the central axis B3 with respect to the central axis B3 (reference central axis) when the virtual orthogonal plane and the central axis B3 are orthogonal to each other is the inferior angle θ1.

In the present embodiment, the axial direction D1 and the main radiation direction D2 of the object to be processed 100 extend along the horizontal direction. Therefore, in this embodiment, the inferior angle θ1 is an angle formed by the axial direction D1 and the main radiation direction D2 on the virtual horizontal plane.

With reference to FIGS. 1 to 6, by setting the inferior angle θ1 to 45° or less, it is possible to more reliably suppress the uneven transfer of heat in the outer peripheral portion of the object to be processed 100. That is, by setting the inferior angle θ1 to 1/2 or less of 90°, which is a right angle, the heat from the heaters 14 and 15 is evenly transferred to the entire surface of the object 100 to be processed. This makes it possible to further reduce the deviation in the timing of starting transformation (hereinafter, also simply referred to as transformation timing) in each part of the object to be processed 100 while the object to be processed 100 is being heat-treated. As a result, it is possible to further reduce the occurrence of transformation stress (that is, stress due to the shift of transformation timing) in the object 100 to be processed. As a result, the thermal strain of the object to be processed 100 due to the internal stress of the object to be processed 100 can be further reduced. In particular, it is possible to further reduce the elliptic distortion in which the ring-shaped object to be processed 100 having a substantially perfect circle is distorted into an elliptical shape.

If the inferior angle θ1 exceeds 45°, the degree to which the distribution of heat transmitted to the object to be processed 100 along the main radiation direction D2 becomes nonuniform within the object to be processed 100 increases. As a result, when the object 100 to be processed is being heat-treated, the transformation timing shift in the object 100 to be processed becomes large. As a result, the transformation stress in the object to be processed 100 increases. Therefore, the thermal strain of the object to be processed 100 due to the internal stress of the object to be processed 100 becomes larger.

In addition, the inferior angle θ1 is more preferably 30° or less. If the inferior angle θ1 is 30° or less, which is ⅔ of 45°, the degree of heat received by the inner peripheral surface 100a and the outer peripheral surface 100b of the ring-shaped workpiece 100 can be made more uniform. As a result, the thermal strain of the object to be processed 100 due to the internal stress of the object to be processed 100 becomes smaller. The inferior angle θ1 is more preferably 15° or less, which is ½ of 30°. The most preferable value of the inferior angle θ1 is zero.

The inferior angle θ1 is adjusted, for example, by changing the orientation of the holder 2 with respect to the heaters 14 and 15 in a plan view. In addition, the inferior angle θ1 can be adjusted by changing the direction in which the support member 27 extends with respect to the bottom frame portion 21 of the holder 2 in plan view.

In this way, the holder 2 makes the object to be processed 100 and the heater unit 6 face each other, and the inferior angle θ1 formed by the axial direction D1 of the object to be processed 100 and the main radiation direction D2 is 45° or less (zero is set). The object 100 to be processed is arranged so as to be (including).

As shown in FIG. 5, when viewed in the first alignment direction E1, the first support portion 31 and the second support portion 32 are in point contact with the outer peripheral surface 100a of the object 100 to be processed. The bottom portion 100e of the object 100 to be processed is arranged between the first support portion 31 and the second support portion 32. In the present embodiment, the height positions of the first support portion 31 and the second support portion 32 are aligned, and they are symmetrically located in the second alignment direction E2.

The first support portion 31 and the second support portion 32 have a predetermined angular interval θ2. In other words, when the first support portion 31 and the second support portion 32 when the object 100 to be processed is placed are seen in the axial direction D1 of the object 100 to be processed, the first support portion 31 and the second support portion 31. 32 has a predetermined angular interval θ2.

More specifically, the first line when the first support portion 31 and the second support portion 32 when the workpiece 100 is placed on the support member 27 is viewed in the axial direction D1 of the workpiece 100. An inferior angle formed by the segment B1 and the second line segment B2 is defined as an angular interval θ2. The first line segment B1 is a line segment connecting the central axis line B3 of the object 100 to be processed and the first support portion 31. The second line segment B2 is a line segment that connects the central axis B3 of the object 100 to be processed and the second support portion 32. It can be said that the angular interval θ2 is the interval between the first support portion 31 and the second support portion 32 around the central axis B3 of the object to be processed 100.

The angular interval θ2 is preferably set in the range of 20° to 60°. By setting the angular interval θ2 to 20° or more, the compressive stress acting on each part of the object to be processed 100 supported by these supporting parts 31 and 32 can be made more uniform. Therefore, the thermal strain of the object 100 to be processed can be further reduced. Further, by setting the angular interval to 60° or less, when the object 100 to be processed thermally expands due to the heat treatment, the object 100 to be processed is sandwiched between the two support portions 31 and 32 due to expansion. Can be suppressed. As a result, it is possible to prevent the workpiece 100 from being deformed so as to bite into the two support portions 31 and 32.

Note that, of the facing surface 28 of each support member 27, the portion forming the first support portion 31 and the second support portion 32 may have a projection shape. In this case, the 1st support part 31 and the 2nd support part 32 support the to-be-processed object 100 in the state of being in point contact.

A plurality of workpieces 100 are arranged on the pair of support members 27, 27 at substantially equal intervals along the first arrangement direction E1 (main radiation direction D2 in the present embodiment). Further, a plurality of pairs of the first support portion 31 and the second support portion 32 are arranged along the second arrangement direction E2 that is orthogonal to the first arrangement direction E1 in plan view. Thereby, the objects 100 to be processed can be arranged in a plurality of rows in the traveling direction X1. In the present embodiment, the workpieces 100 in each row adjacent to the traveling direction X1 are completely separated from each other in the traveling direction X1, and are arranged so that their positions in the traveling direction X1 do not overlap.

In this embodiment, a lower holder 2aa, a middle holder 2b, and an upper holder 2c are provided as a plurality (three in this embodiment) of holders 2.

In this embodiment, the lower holder 2a, the middle holder 2b, and the upper holder 2c are stacked in this order. In the lower holder 2a, the bottom frame portion 21 of the lower holder 2a is supported by the pedestal 7. The middle holder 2b is placed on the four vertical frame portions 22 to 25 of the lower holder 2a. The upper holder 2c is placed on the four vertical frame portions 22 to 25 of the middle holder 2b. In this way, by stacking the plurality of holders 2, a large number of objects 100 to be processed can be heat-treated collectively.

An airflow stirred by a stirring device 8 for stirring the gas in the heat treatment furnace 5 is applied to the object to be processed 100 arranged in the heat treatment furnace 5.

With reference to FIG. 1 and FIG. 2, stirring device 8 is provided to make temperature and gas components in heat treatment furnace 5 more uniform. The stirring device 8 has a stirring fan 33 that is rotationally driven by an electric motor or the like. The agitation fan 33 is, for example, a centrifugal fan, and is configured to generate a wind outward in the radial direction of the agitation fan 33. The stirring fan 33 is arranged in the upper part of the heat treatment furnace 5. In the present embodiment, the stirring fan 33 is arranged directly above the base 7 and the holder 2. The operation of the stirring device 8 is controlled by the control unit 4. Further, the atmospheric gas for heat treatment is supplied from the atmospheric gas supply unit 9 into the heat treatment furnace 5.

The atmosphere gas supply unit 9 is configured to supply an atmosphere gas, which is a heat treatment gas for performing a desired heat treatment to the object to be processed 100, to the heat treatment furnace 5. The atmospheric gas supply unit 9 has a pipe connected to the heat treatment furnace 5, and the pipe is connected to the pump 9a and a tank (not shown). The operation of the pump 9a of the atmospheric gas supply unit 9 is controlled by the control unit 4. As a result, the atmospheric gas stored in the tank is supplied into the heat treatment furnace 5 by the atmospheric gas supply unit 9.

In this embodiment, a gas containing carbon such as carbon monoxide (CO) gas is used as the heat treatment gas. The carbon potential (mass %) in this gas is set to be larger than the carbon content of the carbon steel that is the base material of the object 100 to be processed. Then, in the present embodiment, at the time of heating in the heat treatment apparatus 1, the object to be processed 100 is exposed to the atmospheric gas set to the carbon potential Cp in the range of 0.6% to 1.0%.

More specifically, the carbon potential Cp of the atmospheric gas in the heat treatment furnace 5 is set based on 0.77%, which is the carbon potential at the eutectoid point in the equilibrium diagram of the Fe—C alloy. By setting the carbon potential Cp in the range of 0.6% to 1.0%, the carbon content on the surface of the object to be processed 100 becomes close to 0.77% during the heat treatment of the object to be processed 100. .. This makes it possible to further shorten the time during which the object to be processed 100 is in the state of ferrite+austenite during the heat treatment of the object to be processed 100. Thereby, the transformation stress generated in the object to be processed 100 can be further reduced. In the present embodiment, the carbon potential Cp in the atmospheric gas is set to be three times or more than 0.2% which is the carbon potential of the base material of the object 100 to be processed.

In the present embodiment, more preferably, the carbon potential Cp of the atmospheric gas is 0.77%±0.1%, that is, 0.67% to 0.87%. By setting the carbon potential Cp of the atmospheric gas to 0.77%±0.1%, the carbon potential Cp of the atmospheric gas can be substantially set to the carbon potential at the eutectoid point. As a result, the carbon content on the surface of the object to be processed 100 becomes close to 0.77% during the heat treatment of the object to be processed 100, and the time when the object to be processed 100 is ferrite+austenite can be further shortened. .. Thereby, the transformation stress in the object to be processed 100 can be further reduced.

In the heat treatment furnace 5, the heat treatment operation of the workpiece 100 is controlled by the control unit 4. The control unit 4 has a configuration of outputting a predetermined output signal based on a predetermined input signal, and can be formed using, for example, a safety programmable controller or the like. The safety programmable controller refers to a publicly certified programmable controller having a safety function of SIL2 or SIL3 of JIS (Japanese Industrial Standard) C0508-1. The control unit 4 may be formed using a computer including a CPU (Central Processing Unit), a RAM (Random Access Memory), and a ROM (Read Only Memory).

The control unit 4 is configured to calculate the carbon potential Cp of the atmospheric gas in the heat treatment furnace 5 based on the oxygen concentration detection result from the oxygen sensor 13. Further, the control unit 4 controls the pump 9a (not shown) of the atmospheric gas supply unit 9 based on the detected carbon potential Cp and the like to control the flow rate of the atmospheric gas supplied to the heat treatment furnace 5 and the like. Is configured. Thereby, the control unit 4 controls the carbon potential Cp of the atmospheric gas in the heat treatment furnace 5. The control unit 4 is also configured to be able to control the flow rate of the combustion gas supplied to each of the heaters 14 and 15. Thereby, the control unit 4 can control the temperature in the heat treatment furnace 5 based on the temperature detection result detected by the temperature sensor 12.

Next, an example of the heat treatment operation in the heat treatment apparatus 1 will be described. FIG. 7 is a flow chart for explaining an example of the heat treatment operation in heat treatment apparatus 1. FIG. 8 is a graph showing an example of temperature control of the object 100 to be processed in the heat treatment apparatus 1. FIG. 9 is a schematic equilibrium state diagram of the Fe—C alloy for explaining the state of the object 100 to be heat-treated in the heat treatment apparatus 1. Note that, in the following, when the description is made with reference to the flowchart, the description will be given with appropriate reference to the drawings other than the flowchart.

In the heat treatment operation of the heat treatment apparatus 1, first, an operation of arranging the object 100 to be processed is performed by, for example, an operator or an automatic arrangement device (not shown) by a machine (step S1). Specifically, for example, a worker places the object 100 to be processed in each of the holders 2a, 2b, 2c. Then, the worker mounts the lower holder 2a on the pedestal 7. Further, the middle holder 2b is placed on the lower holder 2a. Further, the upper holder 2c is placed on the middle holder 2b. The holders 2a, 2b, 2c may be moved by a transfer device (not shown).

As a result, the holder 2 is arranged in the heat treatment furnace 5 in the above-described mode described with reference to FIGS. That is, in the state where the object to be processed 100 and the heater unit 6 face each other, the inferior angle θ1 formed by the axial direction D1 of each object to be processed 100 and the main radiation direction D2 of the heater unit 6 is 45° or less (zero is set). Object 100 to be treated is arranged in the heat treatment furnace 5.

Next, the workpiece 100 in the heat treatment furnace 5 is heated by using the heater unit 6 (step S2). Specifically, the control unit 4 controls the heating operation of the heater unit 6 and also controls the supply amount of the atmospheric gas supplied from the atmospheric gas supply unit 9, so that the atmospheric temperature and carbon in the heat treatment furnace 5 are controlled. Control the potential Cp. Thereby, the control unit 4 controls the heat treatment operation of the object 100 to be processed. More specifically, the control unit 4 controls the heating operation of the heater unit 6 so that the relationship between time and the temperature of the object to be processed 100 shown in FIG. 8 is realized.

In the following, unless otherwise specified, the term “temperature” refers to the temperature of the atmospheric gas in the heat treatment furnace 5. In step S2, the control unit 4 first heats the atmospheric gas in the heat treatment furnace 5 to the A1 transformation point. The A1 transformation point may be in the range of 727°C to 810°C, for example. The A1 transformation point may be in the range of 750°C to 850°C.

After the temperature rises to the A1 transformation point, this temperature is maintained for a predetermined time until a predetermined timing T1. As a result, the entire object 100 including the inside thereof is heated to the A1 transformation point. Next, the control unit 4 increases the temperature in the heat treatment furnace 5 from the A1 transformation point to the A3 transformation point by performing control to increase the electric power supplied to the heater unit 6 (timings T1 to T2, for example). ).

Between the A1 transformation point and the A3 transformation point, the atmospheric gas and the object to be treated 100 are heated at a temperature rising rate (temperature rising rate) within a range of 0.5° C./min to 10° C./min. When the temperature increase rate of the object to be processed 100 is equal to or higher than the above lower limit value, the time required to transform the object to be processed 100 from the A1 transformation point to the A3 transformation point can be further shortened. Further, since the temperature rising rate of the object to be processed 100 is equal to or lower than the above upper limit value, when the object to be processed 100 is transformed from the A1 transformation point to the A3 transformation point, the object to be treated is treated from the outer surface of the object 100 to be treated. When heat is transferred to the inside of the object 100, the temperature difference between the outer surface and the inside of the object 100 to be processed can be made sufficiently small. Thereby, the transformation stress inside the object 100 to be processed can be further reduced. Therefore, the thermal strain of the object 100 to be processed can be further reduced. In other words, when each part of the object to be processed undergoes austenite transformation, unevenness in transformation timing (that is, nonuniformity of transformation timing) can be further reduced.

It is more preferable that the atmosphere gas and the object to be processed 100 are heated at a temperature rising rate within the range of 0.5° C./min to 1.0° C./min between the A1 transformation point and the A3 transformation point. .. Accordingly, when heat is transferred from the outer surface of the object 100 to be processed to the inside of the object 100, the temperature difference between the outer surface and the inside of the object 100 can be significantly reduced.

Further, the object 100 to be processed is heated to the A3 transformation point or higher in the atmosphere gas of the carbon potential Cp described above. At this time, the carbon potential inside the object to be processed 100 does not substantially change. On the other hand, the carbon potential of the outer surface of the object to be treated 100 increases due to the heat treatment.

More specifically, the inside of the object 100 to be processed is heated to a temperature higher than the A3 transformation point by following the course defined by the line L1 in FIG. At this time, the inside of the object to be processed 100 is in a state of ferrite+cementite at a temperature below the A1 transformation point. Then, the inside of the object to be processed 100 is transformed into a state of ferrite+austenite when exceeding the A1 transformation point, as indicated by the line L1. When the temperature of the object to be processed 100 further rises and the internal temperature of the object to be processed 100 exceeds the A3 transformation point, ferrite disappears and the object is transformed into an austenite state. The carbon potential inside the object to be processed 100 does not change even when heated to a temperature exceeding the A3 transformation point.

Here, in the heat treatment, the temperature of the outer surface of the object to be treated 100 first rises, and then the temperature of the inner portion thereof rises. Therefore, in the present embodiment, the state of the atmospheric gas in the heat treatment furnace 5 is controlled so as to be in the state near the eutectoid point (for example, 727° C., carbon potential Cp=0.77%). Thereby, the effect of reducing the distortion of the object to be processed 100 can be further enhanced.

In the present embodiment, the outer surface of the object 100 to be processed follows the course indicated by the line L2 (for example, L21, L22, L23) in FIG. It converges to the carbon potential Cp of the atmospheric gas. The line L21 indicates the case where the carbon potential Cp of the atmospheric gas is at the lower limit (Cp=0.6%) of the above range. The line L22 shows the case where the carbon potential Cp of the atmospheric gas is equal to the carbon potential at the eutectoid point (Cp=0.77%). The line L23 shows the case where the carbon potential Cp in the atmosphere gas is at the upper limit (Cp=1.0%) of the above range.

The outer surface of the object 100 to be processed reacts with carbon in the atmospheric gas as the temperature of the atmospheric gas in the heat treatment furnace 5 rises. As a result, the carbon potential of the outer surface of the object to be processed 100 increases. In particular, the carbon potential of the outer surface of the object to be treated 100 rises in a manner substantially proportional to the temperature rise until reaching the A1 transformation point. Then, when the temperature of the outer surface of the object to be processed 100 becomes close to the A1 transformation point, the carbon potential of the outer surface of the object to be processed 100 becomes substantially constant while slightly increasing as the temperature of the outer surface of the object to be processed 100 increases. Become. Then, as compared with the inside of the object 100 to be processed, the temperature of the outer surface of the object 100 to be processed is lower until it is transformed into an austenite state.

For example, when the carbon potential Cp of the atmospheric gas in the heat treatment furnace 5 is set to the above lower limit, as shown by the line L21, when the outer surface of the object 100 to be processed reaches the A1 transformation point, ferrite+cementite. The state is transformed into a ferrite + austenite state. The temperature difference Δt21 from the outer surface of the object to be processed 100 reaching the A3 transformation point to the A1 transformation point is calculated from the temperature difference Δt1 from the inside of the object 100 to the A3 transformation point to the A3 transformation point. Is also small. Therefore, on the outer surface of the object 100 to be processed, the transformation stress can be further reduced from the A1 transformation point to the A3 transformation point. As a result, the thermal strain on the outer surface of the object to be processed 100 can be further reduced.

On the other hand, for example, when the carbon potential Cp of the atmospheric gas in the heat treatment furnace 5 is set to 0.77% which is the carbon potential at the eutectoid point, the outer surface of the object 100 to be treated is When the A1 transformation point is reached, the ferrite+cementite state is transformed into the austenite state substantially immediately. In this case, the temperature difference until the outer surface of the object 100 to be processed reaches the A3 transformation point from the A1 transformation point is substantially zero. Therefore, on the outer surface of the object 100 to be processed, the transformation stress can be further reduced from the A1 transformation point to the A3 transformation point. As a result, the thermal strain on the outer surface of the object to be processed 100 can be further reduced.

Further, for example, when the carbon potential Cp of the atmospheric gas in the heat treatment furnace 5 is set to the above upper limit, as shown by the line L23, when the outer surface of the object 100 to be processed reaches the A1 transformation point, ferrite Transform from + cementite state to austenite + cementite state. The temperature difference Δt23 from when the outer surface of the object to be processed 100 reaches the Acm transformation point to the A1 transformation point is calculated from the temperature difference Δt1 from when the inside of the object to be treated 100 reaches the A3 transformation point from the A1 transformation point. Is also small. Therefore, on the outer surface of the object 100 to be processed, the transformation stress can be further reduced from the A1 transformation point to the Acm transformation point. As a result, the thermal strain on the outer surface of the object to be processed 100 can be further reduced. In this way, even if any of the lines L21, L22, and L23 is followed, the strain on the outer surface of the object 100 to be processed can be further reduced.

As described above, in the heating step (step S2), the entire object 100 to be processed is heated beyond the A1 transformation point to the A3 transformation point. The control unit 4 performs control for maintaining the temperature of the atmospheric gas in the heat treatment furnace 5 at the same temperature as the A3 transformation point for a predetermined period (timing T2 to T3). As a result, the entire temperature of the object to be processed 100 becomes the A3 transformation point. After that, the control unit 4 causes the heater unit 6 to perform the heating operation so as to further raise the atmospheric gas temperature in the heat treatment furnace 5 to the maximum temperature tmax during the heat treatment (timing T3 to T4).

It should be noted that the maximum temperature tmax is a temperature set for causing the object 100 to be carburized in the present embodiment. This maximum temperature tmax is set to a temperature required for a target heat treatment such as diffusion treatment when subjecting the object to be processed 100 to another heat treatment such as diffusion treatment. The maximum temperature tmax is set to, for example, about 800°C to 960°C. In addition, the control unit 4 sets the temperature rising rate when heating the inside of the object to be processed 100 from the A3 transformation point to the maximum temperature tmax to the heating rate when heating the inside of the object to be treated 100 from the A1 transformation point to the A3 transformation point. Set higher than the temperature rising rate.

The control unit 4 heat-treats the workpiece 100 by maintaining the temperature of the atmospheric gas in the heat treatment furnace 5 at the maximum temperature tmax for a predetermined period. After that, the control unit 4 lowers the temperature of the object to be processed 100 by, for example, stopping the heating operation by the heater unit 6 (step S3). After that, the object 100 to be processed is carried out from the heat treatment furnace 5, and then subjected to other processing such as quenching. As described above, the tube 16 of the heater unit 6 is arranged perpendicular to the ceiling wall 5a of the heat treatment furnace 5 from the viewpoint of durability and the like.

Conventionally, from the viewpoint of heat treatment distortion, in consideration of the temperature distribution in one object to be processed, it is not necessary to arrange the object to be processed in an upright posture and to support the object to be treated from below, The object to be processed was in a lying position. Further, conventionally, a bar configured to receive the inner peripheral surface of a ring-shaped object is used to suspend the object to be processed in a heat treatment furnace and subject the object to heat treatment. There was also.

On the other hand, in the present embodiment, in each of the circular object 100 to be processed, in order to suppress the temperature difference in the circumferential direction of the object 100 to be processed, the axial direction D1 and the main radiation direction D2 are combined. The inferior angle θ1 formed is set to 45° or less. In addition, in the present embodiment, the outer peripheral surface 100a of the object to be processed 100 is configured to support a downward position, and the angular interval θ2 between the first support portion 31 and the second support portion 32 is 20. It is set within the range of 60°. Accordingly, the holder 2 can support the object to be processed 100 in a posture in which tensile stress is unlikely to occur in the object to be processed 100. Thereby, the thermal strain generated in the object 100 to be processed can be significantly reduced.

Further, in the present embodiment, the atmospheric gas supply is controlled with reference to the carbon potential at the eutectoid point in the equilibrium diagram of the Fe—C alloy. As a result, the thermal strain of the object to be processed 100 during austenite transformation becomes smaller. Furthermore, by setting the temperature rising rate of the object to be processed 100 to the value described above, the temperature difference in the object to be processed 100 when the object to be processed 100 undergoes austenite transformation can be made smaller. Thereby, the thermal strain of the object to be processed 100 becomes smaller. As a result, it is possible to heat-treat a large number of objects 100 to be processed by the heat treatment apparatus 1 in a short time while suppressing thermal strain of the objects 100 to be processed.

As described above, according to the present embodiment, the inferior angle θ1 formed by the axial direction D1 of each workpiece 100 and the main radiation direction D2 of the heater unit 6 is 45° or less (including zero). The processed material 100 is arranged. With this configuration, the heat from the heater unit 6 is evenly transferred to each part of the object 100 to be processed. This makes it possible to reduce the temperature difference inside the object to be processed 100 when the object to be processed 100 is heated by the heater unit 6. More specifically, the temperature difference of the object to be processed 100 in the circumferential direction of the object to be processed 100 can be further reduced. In particular, when the axial direction D1 and the main radiation direction D2 coincide with each other, that is, when the inferior angle θ1 is zero, the temperature difference in the object 100 to be processed in the circumferential direction of the object 100 can be significantly reduced. As a result, it is possible to suppress the occurrence of stress imbalance in the object to be processed 100. In particular, in one object 100 to be processed, the timings at which the respective parts undergo austenite transformation can be made more uniform. Further, as a result of suppressing the occurrence of stress imbalance in the object 100 to be processed, the object 100 to be processed can be heat-treated in a shorter time. This makes it possible to further reduce the distortion due to the heat treatment of the circular object 100 to be processed, which is made of metal, and further shorten the heat treatment time of the object 100 to be processed. More specifically, the elliptic distortion in which the object to be processed 100 is distorted in an elliptical shape can be further reduced. Further, when the object to be processed 100 is heated to the A1 transformation point or higher, the temperature of each part in the object to be treated 100 can pass through the A1 transformation point more uniformly. As a result, it is possible to suppress the occurrence of transformation stress in the object to be processed 100.

Further, according to the present embodiment, when the object 100 to be processed is placed in the heat treatment furnace 5 (step S1), the plurality of objects 100 to be processed are arranged along the main radiation direction D2. According to this configuration, it is possible to collectively heat-treat the plurality of objects to be processed 100 while reducing thermal strain.

Further, according to the present embodiment, each of the processed objects 100 is arranged in an upright posture, and the axial direction D1 of each of the processed objects 100 is along the horizontal direction. With this configuration, it is possible to suppress the tensile stress from being generated in the object to be processed 100. As a result, the thermal strain caused by the stress of the object to be processed 100 can be significantly reduced.

Further, according to the present embodiment, when the object 100 to be processed is placed in the heat treatment furnace 5 (step S1), the holder 2 supports the outer peripheral surface of the object 100 to be processed from below. With this configuration, it is possible to suppress the tensile stress from being generated in the object to be processed 100. As a result, the thermal strain caused by the stress of the object to be processed 100 can be significantly reduced.

In addition, according to the present embodiment, the support portions 31 and 32 of the holder 2 support the workpiece 100 in line contact or point contact. According to this configuration, the holder 2 can support the object to be processed 100 in a state in which the expansion and contraction of the object to be processed 100 during the heat treatment of the object to be processed 100 are suppressed. As a result, the strain of the object 100 to be processed due to the heat treatment can be further reduced.

Further, according to the present embodiment, the angular interval θ2 between the first support portion 31 and the second support portion 32 around the central axis B3 of the object to be processed 100 is set in the range of 20° to 60°. According to this configuration, by setting the angular interval θ2 between the first support portion 31 and the second support portion 32 to be 20° or more, it acts on each portion of the object to be processed 100 supported by these support portions 31 and 32. The stress applied can be made more uniform. Therefore, the thermal strain of the object 100 to be processed can be further reduced. Further, by setting the angular interval θ2 between the first support portion 31 and the second support portion 32 to be 60° or less, when the workpiece 100 is thermally expanded by the heat treatment, the two support portions 31, 32 are expanded by the expansion. It can suppress that the to-be-processed object 100 is pinched between them. As a result, it is possible to prevent the workpiece 100 from being deformed so as to bite into the two support portions 31 and 32.

Further, according to the present embodiment, when each of the objects to be processed 100 is heated (step S2), the objects to be processed 100 are the atmospheric gas set to the carbon potential in the range of 0.6% to 1.0%. Heated in. According to this configuration, when heating the object to be processed 100, the time required for each part of the surface of the object to be processed 100 to shift from the area of ferrite+cementite to the area of austenite can be further shortened. As a result, the object 100 to be processed can be transformed into austenite more uniformly.

Further, according to the present embodiment, when heating the object 100 to be processed (step S2), the heater unit 6 heats the object 100 to be processed at least between the A1 transformation point and the A3 transformation point. According to this configuration, each part of the object to be processed 100 can undergo austenite transformation more uniformly.

In addition, according to the present embodiment, when each of the objects to be processed 100 is heated (step S2), the objects to be processed 100 undergo A1 transformation at a temperature rising rate in the range of 0.5° C./min to 10° C./min. It is heated from the point to the A3 transformation point. According to this configuration, since the temperature increase rate of the object to be processed 100 is equal to or higher than the above lower limit value, the time required to transform the object to be processed 100 from the A1 transformation point to the A3 transformation point can be further shortened. Further, since the temperature rising rate of the object to be processed 100 is equal to or lower than the above upper limit value, when the object to be processed 100 is transformed from the A1 transformation point to the A3 transformation point, the object to be treated is treated from the outer surface of the object 100 to be treated. When heat is transferred to the inside of the object 100, the temperature difference between the outer surface and the inside of the object 100 to be processed can be made sufficiently small. Thereby, the transformation stress inside the object 100 to be processed can be further reduced. Therefore, the thermal strain of the object 100 to be processed can be further reduced. In other words, when each part of the object to be processed 100 undergoes austenite transformation, it is possible to further reduce unevenness in transformation timing (that is, nonuniformity of transformation timing).

Further, according to the present embodiment, the object to be processed 100 is formed in a ring shape. With this configuration, in the ring-shaped object to be processed 100, the degree of temperature change in each part can be made more uniform. As a result, it is possible to form a metal component having small thermal strain such as elliptic strain.

Further, when the object 100 to be processed is a bearing race or gear, a bearing or gear with high dimensional accuracy can be manufactured.

<Second Embodiment>
Next, a second embodiment of the present invention will be described. In the following, points different from the above-described embodiment will be mainly described, and configurations similar to those in the above-described embodiment may be denoted by the same reference numerals in the drawings and description thereof may be omitted.

FIG. 10 is a schematic plan view of a holder 2A and a heater unit 6 included in the heat treatment apparatus 1 according to the second embodiment of the present invention. FIG. 11 is a schematic side view of a main part showing the holder 2A and the object to be processed 100 held by the holder 2A. FIG. 12 is a schematic front view of the main part showing the holder 2A and the object to be processed 100 held by the holder 2A. FIG. 13 is a schematic plan view of the main part showing the holder 2A provided in the heat treatment apparatus 1 according to the second embodiment of the present invention and the object 100 to be processed held by the holder 2A. 11 and 13, the object 100 to be processed in the second link row 42, which will be described later, is cross-hatched in order to make the object 100 easier to see.

With reference to FIGS. 10 to 13, the holder 2A of the present embodiment is suitable for holding a plurality of circular object 100 to be heat-treated, and in particular, holding the ring-shaped object 100. Suitable for The holder 2A has a configuration for suppressing a difference between the supply mode of the atmospheric gas to the inner peripheral portion and the supply mode of the atmospheric gas to the outer peripheral portion for each of the workpieces 100. Further, the holder 2A of the present embodiment has a configuration for increasing the number of objects to be processed 100 that can be held at one time as much as possible. The object 100 to be processed is arranged with the holder 2A in a manner described later (step S1), and then subjected to a heating process (step S2) and a cooling process (step S3). Hereinafter, the holder 2A will be described more specifically.

The receiving portion 26A of the holder 2A extends along the first arranging direction E1 and is configured to receive the plurality of objects to be processed 100. As described above, the first alignment direction E1 is along the axial direction D1 of the object 100 to be processed held by the receiving portion 26A. In addition, the receiving portion 26A arranges a plurality of the objects 100 to be processed in a state of standing upright so that the openings 100c of the objects 100 to be processed are horizontal and the openings 100c face the first arranging direction E1 side. Is configured. In addition, the receiving member 26A is configured to dispose the two objects to be processed 100 adjacent to each other in the first arrangement direction E1 while being offset from each other in the second arrangement direction E2 orthogonal to the first arrangement direction E1.

More specifically, each support member 27A of the receiving portion 26A extends along the first alignment direction E1 and supports the lower part of the outer peripheral surface of the object 100 to be processed, including the downward surface. It is arranged. Also in this embodiment, the first support portion 31A and the second support portion 32A of the support member 27A are formed in a linear shape, and the workpiece 100 and the support member 27A are in line contact with each other. The object 100 to be processed and the support member 27A preferably have a small contact area, and may be point contact, line contact, or surface contact.

Both ends of each support member 27A are received by the upper portion of the bottom frame portion 21A of the holder 2A. Further, a reinforcing beam 35 extending along the second arrangement direction E2 and fixed to the bottom frame portion 21A is provided. The reinforcing beams 35 are arranged at, for example, two positions in the first arrangement direction E1. Both ends of each reinforcing beam 35 are fixed to the bottom frame portion 21A. Then, each support member 27A is arranged on these reinforcing beams 35.

The support members 27A are arranged at equal pitches at a predetermined pitch P1 in the second arrangement direction E2. The facing surface 28 of each support member 27A extends straight along the first alignment direction E1. Then, the pair of support members 27A, 27A adjacent to the second arrangement direction E2 are configured to support one workpiece 100.

In the present embodiment, among the plurality of support members 27A, the support members 27A arranged at both ends in the second arrangement direction E2 support the workpiece 100 of one ring row 41. On the other hand, among the plurality of support members 27A, the support members 27A arranged at other than both ends in the second alignment direction E2 support the object 100 to be processed of the two ring rows 41 and 42. The ring row 41 includes a plurality of objects to be processed 100 arranged in the first arrangement direction E1 in a state where the positions in the second arrangement direction E2 are aligned. Similarly, the ring row 42 includes a plurality of objects 100 to be processed that are aligned in the first arrangement direction E1 with the positions in the second arrangement direction E2 being aligned.

In this embodiment, many ring rows 41 and many ring rows 42 are formed. The ring rows 41 and 42 each include a plurality of objects 100 to be processed that are arranged along the first arrangement direction E1. Ring rows 41 and ring rows 42 are alternately formed along the second arrangement direction E2. The ring rows 41, 42 other than the ring rows 41 at both ends in the second arrangement direction E2 share one support member 27A with the ring row 41 or the ring row 42 adjacent to the second arrangement direction E2. Therefore, of the plurality of support members 27A, the facing surfaces 28 of the support members 27A that are arranged at other than both ends in the second alignment direction E2 are in contact with the two objects 100 to be processed at two locations. The facing surface 28 is in contact with the object 100 to be processed of one ring row 41 or ring row 42 at the first support portion 31A, and is in contact with the object 100 to be processed of another ring row 41 or ring row 42 to the second side. It is in contact with the support portion 32A. Each support member 27A may be configured to support the object 100 to be processed in only one ring row 41 or one ring row 42.

In the present embodiment, a first ring row 41 and a second ring row 42 are formed as ring rows adjacent to each other in the second arrangement direction E2. Each object 100 to be processed of the second ring row 42 and each object 100 to be processed of the first ring row 41 which are adjacent to the second arrangement direction E2 are in the first position with their positions displaced in the second arrangement direction E2. They are lined up along the line direction E1. In the present embodiment, one object 100 to be processed in the first ring row 41 and one object 100 to be processed in the second ring row 42 are alternately arranged when proceeding in the first arrangement direction E1. With such a configuration, one object 100 to be processed in the first ring row 41 and one object 100 to be processed in the second ring row 42 are arranged in a zigzag shape.

Further, the two objects to be processed 100 adjacent to each other in the first arrangement direction E1 are arranged such that the end surfaces 100d facing each other are in contact with each other. That is, the one end surface 100d of the workpiece 100 of the first ring row 41 is in contact with the corresponding one end surface 100d of the corresponding workpiece 100 of the second ring row 42. Therefore, in the first ring row 41, the pair of end surfaces 100d and 100d of the object 100 to be processed arranged in the middle portion in the first alignment direction E1 correspond to the two object 100 to be processed in the second ring row 42. It is sandwiched by one end surface 100d. Similarly, in the second ring row 42, the pair of end surfaces 100d and 100d of the object 100 to be processed, which are arranged in the middle portion in the first arrangement direction E1, are the two object 100 to be processed of the first ring row 41. It is sandwiched between the corresponding one end faces 100d.

In the present embodiment, the first ring row 41 and the second ring row 42 are arranged alternately in the second arrangement direction E2. That is, the first ring row 41, the second ring row 42, the first ring row 41, the second ring row 42,... Are arranged in this order along the second arrangement direction E2. As described above, in the present embodiment, a large number of ring rows are formed by the two types of ring rows 41 and 42.

With the above configuration, one ring row is opened and the same ring row (first ring row 41 or second ring row 42) is arranged in the second arrangement direction E2.

As shown in FIG. 12, when the ring row 41 or the ring row 42 is viewed from the first arranging direction E1, each object 100 to be processed of the ring row is adjacent to the ring row 42 or the ring row 41. An area having a length equal to or smaller than half the outer diameter DR1 of the object to be processed 100 is arranged to overlap with the object to be processed 100 in the second alignment direction E2. For example, three ring rows 41a, 42a, 41b arranged in the second arrangement direction E2 will be described. Of these three ring rows 41a, 42a, 41b, the object 100 to be processed in the middle ring row 42a is a first virtual plane PL1 that extends vertically through the central axis B3 of the object 100 to be processed in one ring row 41a. , A second virtual plane PL2 that extends vertically through the central axis B3 of the object 100 to be processed in the other ring row 41b, and is arranged in a space sandwiched between the second virtual plane PL2 and

By arranging the objects 100 to be processed on the holder 2A in the above-described manner, a large number of objects 100 to be processed can be placed on the holder 2A. For example, the holder 2A has the same length, width and height as the holder 2 in the first embodiment. On the other hand, the number of objects to be processed 100 that can be placed on the holder 2A at a time can be approximately 125% of the number of objects to be processed 100 that can be placed on the holder 2 at a time.

With reference to FIGS. 10 to 13, the vertical frame portions 22A and 23A as the front frame portion and the rear frame portion of the holder 2A respectively include a plurality of columns arranged at a predetermined pitch in the second alignment direction E2, It has a beam portion connecting the upper ends of these columns. The vertical frame portions 24A and 25A as a pair of horizontal frame portions of the holder 2A respectively include a plurality of pillars arranged at a predetermined pitch in the first alignment direction E1 and a beam portion connecting the upper end portions of these pillars. And have. The vertical frame portions 22A to 25A are formed in a mesh shape with such a configuration.

Further, L-shaped stoppers 43 are provided at the four corners of the upper portion of the holder 2A, respectively. Each stopper 43 projects upward from the upper ends of the four vertical frame portions 22A, 23A, 24A, 25A of the holder 2A. When another holder 2A is stacked above the holder 2A, the four stoppers 43 face the four corners of the bottom frame portion 21A of the another holder 2A. As a result, it is possible to prevent the position of the other holder 2A from deviating from the position of the holder 2A.

As described above, according to the present embodiment, the object to be processed 100 as the ring member is in a state in which the opening 100c of the object to be processed 100 is erected sideways and the opening 100c has the first opening. Plural pieces are arranged so as to face the arrangement direction E1 side. Further, the positions of the two objects to be processed 100 adjacent to the first arrangement direction E1 are displaced from each other in the second arrangement direction E2. With this configuration, the fluid can more smoothly pass through the space surrounded by the inner peripheral surface 100b of each of the objects to be processed 100. Therefore, for example, a medium (fluid) for heat treatment, such as carburizing gas in the carburizing process and oil and nitrogen gas in the quenching process, can be more smoothly supplied to the space on the inner peripheral side of the object 100 to be processed. can do. Further, in each of the objects to be processed 100, it is possible to suppress variations in the supply degree of the medium at the inner peripheral portion and the outer peripheral portion. As a result, it is possible to further reduce the degree of variation in heat treatment of each object 100 to be processed. Further, it is possible to further reduce the degree of variation in heat treatment among the plurality of objects to be processed 100. Therefore, the heat treatment qualities such as the surface hardness and the internal hardness of each object 100 can be made more uniform. Further, the medium for heat treatment is not smoothly supplied to the inner peripheral side of the object to be processed 100 by increasing the interval between the objects to be processed 100 in the first arrangement direction E1. Therefore, the space required for heat-treating the object to be processed 100 can be further reduced. As a result, more objects to be processed 100 can be placed in the holder 2A placed in the heat treatment furnace 5 at once. Therefore, more objects 100 to be processed can be heat-treated at once. As described above, when heat-treating the object 100 to be processed made of metal, it is possible to reduce variations in heat treatment quality, and it is possible to heat-treat more objects 100 to be processed at once.

Further, according to the present embodiment, both the first arrangement direction E1 and the second arrangement direction E2 are horizontal directions. According to this configuration, the space occupied by each of the objects to be processed 100 vertically can be made narrower. Therefore, more objects to be processed 100 can be arranged at once in the limited space for heat treatment.

Further, according to the present embodiment, the two processing objects 100 adjacent to each other in the first arrangement direction E1 are arranged such that the end surfaces 100d, 100d facing each other are in contact with each other. According to this configuration, each object to be processed 100 can function as a spacer that defines the position of the object to be processed 100. For example, in the three processed objects 100 arranged in the first arrangement direction E1, the first processed object 100 and the third processed object 100 in the first arranged direction E1 sandwich the second processed object 100. It will be. With such a configuration, the second processed object 100 can set the interval between the first processed object 100 and the third processed object 100 to be the same as the thickness of the second processed object 100. .. As a result, a large number of objects to be processed 100 can be arranged more evenly along the first arrangement direction E1. In addition, since the plurality of objects to be processed 100 can be erected while being in contact with each other, these objects to be processed 100 can be autonomously erected. Therefore, it is not necessary to separately provide a support member for supporting the object 100 to be processed so as not to fall. This allows the objects to be processed 100 to be arranged at a higher density. Therefore, more objects to be processed 100 can be arranged at once in a limited space.

Further, according to the present embodiment, the objects to be processed 100 of the first ring row 41 and the objects to be processed 100 of the second ring row 42 are alternately arranged in the first arrangement direction E1. With this configuration, the objects to be processed 100 can be arranged in a zigzag pattern. Accordingly, even when the space for arranging the object 100 to be processed is small, the medium can be more evenly distributed to the inner peripheral portion and the outer peripheral portion of each object 100 to be processed. Further, the object to be processed 100 can be arranged more efficiently. As a result, more objects to be processed 100 can be heat-treated more uniformly at once in a limited space.

Further, according to the present embodiment, when the ring rows 41 and 42 are viewed from the first arrangement direction E1, each of the processed objects 100 is different from the processed object 100 of the adjacent ring row in the second arranged direction E2. Areas having a length not more than half the outer diameter of the object to be processed 100 are arranged so as to overlap each other. According to this configuration, when viewed from the first arrangement direction E1, both the one object to be processed 100 and the two object to be processed 100 that are adjacent to both sides of the one object to be processed 100 in the second arrangement direction E2. And can be overlaid. Thereby, the object 100 to be processed can be more efficiently arranged in the limited space for arranging the object 100 to be processed. As a result, more objects 100 to be processed can be heat treated at once in a limited space.

Further, according to the present embodiment, the support members 27A of the receiving portions 26A of the holder 2A are arranged so as to be arranged at the predetermined pitch P1 in the second arrangement direction E2. In addition, the workpiece 100 is configured to be supported by the pair of support members 27A and 27A that are adjacent to each other in the second arrangement direction E2. With this configuration, it is possible to realize a configuration in which the object 100 to be processed is stably supported without falling down with a simple configuration in which the pair of support members 27A and 27A support the object 100 to be processed. Further, since the object to be processed 100 is not hung, it is possible to suppress tensile stress from being generated in the object to be processed 100 during the heat treatment of the object to be processed 100. As a result, it is possible to prevent tensile stress from occurring in the object to be processed 100 as residual stress. Therefore, the mechanical strength of the object to be processed 100 can be further increased.

Moreover, according to this embodiment. The pair of vertical frame portions 22A and 23A of the holder 2A are each formed in a mesh shape. According to this configuration, since the vertical frame portions 22A and 23A can receive the object 100 to be processed, it is possible to prevent the object 100 to be processed from falling. Further, since the vertical frame portions 22A to 25A are formed in a mesh shape, the medium for heat treatment can be smoothly introduced from the outer side to the inner side of the holder 2A through the vertical frame portions 22A to 25A. Thereby, the heat treatment of the object to be processed 100 can be performed more uniformly.

Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment. The present invention can be variously modified within the scope of the claims.

(1) In the above embodiment, the heater unit 6 has been described as an example in which the object to be processed 100 is heated at least between the A1 transformation point and the A3 transformation point. In this regard, the heater unit 6 may heat the object 100 to be processed not only between the A1 transformation point and the A3 transformation point but also in another temperature range.

(2) Further, in the above-described embodiment, the mode in which the electrothermal heater unit is used as the heat source has been described as an example. However, this need not be the case. For example, a gas type tube burner, an electric resistance heating type heater having a structure in which a heating element is embedded in the wall may be used as the heat source.

(3) Moreover, in the above-described embodiment, the holders 2 and 2A hold the object to be processed 100 in a state where the axial direction D1 of the object to be processed 100 is horizontal. .. However, this need not be the case. For example, as shown in each of the modified examples of FIGS. 14 and 15, the object to be processed 100 is arranged in an upright posture, and the axial direction D1 and the first arrangement direction E1 are directions inclined with respect to the horizontal plane. May be arranged so that

In the modified example shown in FIG. 14, the holder 2 is provided with an inclined posture support portion 29. The inclined posture support portion 29 is a rod-shaped member whose both ends are supported by the left and right vertical frame portions 24 and 25 of the holder 2. The object 100 to be processed is received by the tilted posture support portion 29 in a posture tilted with respect to the horizontal plane. More specifically, the lower part of the object to be processed 100 is received by the support member 27, and the position of the upper part of the object to be processed 100 is inclined with respect to the position of the lower part of the object to be processed 100 in the main radiation direction D2. The object to be processed 100 is arranged in a state of being brought close to the support portion 29 side. At this time, in a plan view, that is, when the holder 2 is viewed from above, the axial direction D1 and the main radiation direction D2 may coincide with each other or may be inclined with respect to each other.

When the holder 2 is viewed from above, when the axial direction D1 and the main radiation direction D2 match, the inferior angle formed by the axial direction D1 and the main radiation direction D2 is the inferior angle θ1 in a side view. ..

Further, when the holder 2 is viewed from above, when the axial direction D1 is inclined with respect to the main radiation direction D2, in plan view (more accurately, in plan view from a direction orthogonal to the axial direction D1). The inferior angle formed by the axial direction D1 and the main radiation direction D2 is the first inferior angle θ1. Furthermore, in side view, the inferior angle formed by the axial direction D1 and the main radiation direction D2 is the second inferior angle θ1. In this case, both the first inferior angle θ1 and the second inferior angle θ1 are set to be 45° or less (including zero).

In the modification shown in FIG. 15, the entire holder 2 is arranged so as to be inclined with respect to the horizontal direction. In this case, the holder 2 is maintained in the inclined posture by being received by the block-shaped inclined posture support member 30 fixed to the pedestal 7.

Note that the same configuration as the configuration of the holder 2 shown in FIGS. 14 and 15, that is, the configuration in which the workpiece 100 in the standing posture is arranged in an inclined posture with respect to the horizontal direction may be adopted for the holder 2A. ..

According to the modified examples shown in FIGS. 14 and 15 described above, the axial direction D1 of the object to be processed 100 is a direction inclined with respect to the horizontal direction. According to this configuration, the plurality of objects to be processed 100 can be more appropriately arranged in a state in which the weight balance of the plurality of objects to be processed 100 as a whole is taken into consideration.

(4) In addition, in the above-described embodiment, the case where the corresponding support members 27 and 27A of the holders 2 and 2A are fixed to the corresponding bottom frame portions 21 and 21A has been described as an example. However, this need not be the case. For example, in each of the holders 2 and 2A, the support members 27 and 27A may be configured to be rotatable with respect to the bottom frame portions 21 and 21A. In this case, the support members 27, 27A are configured to be rotatable about the central axis of the support members 27, 27A. As a result, the workpiece 100 placed on the support members 27, 27A can be rotated around the central axis B3 of the workpiece 100. Thereby, the stress generated in each part of the object to be processed 100 can be made more uniform, so that the thermal strain generated in the object to be processed 100 can be further reduced. Further, the degree of exposure of the inner peripheral portion and the outer peripheral portion of the object 100 to the medium can be made more uniform, so that the heat treatment quality can be made more uniform.

(5) Further, in each of the above-described embodiments, the configuration in which the subordinary angle θ1 formed by the axial direction D1 and the main radiation direction D2 is defined has been described. It is possible to arbitrarily combine configurations other than this inferior angle.

(5) In addition, in the above-described second embodiment, an example has been described in which the first ring row 41 and the second ring row 42 are alternately arranged in the second alignment direction E2. However, this need not be the case. In the second embodiment, the two objects to be processed 100 that are adjacent to each other in the first arrangement direction E1 may be displaced from each other in the second arrangement direction E2, and the arrangement of the objects to be processed 100 that is illustrated is not necessary. Good.

<Regarding thermal strain by type of placement of object to be processed>
Example 1 and Comparative Example 1 were produced by carburizing a ring-shaped metal workpiece using a heat treatment apparatus having the same configuration as the heat treatment apparatus 1 described in the first embodiment. The manufacturing conditions of Example 1 and Comparative Example 1 are different in the following points.

Example 1: The inferior angle formed by the axial direction of the object to be processed and the main radiation direction was set to zero. That is, Example 1 was the object to be heat-treated in the state where the axial direction of the object to be processed and the main radiation direction were the same.
Comparative Example 1: The inferior angle formed by the axial direction and the main radiation direction was set to 90°. More specifically, Comparative Example 1 was obtained by performing heat treatment in a state in which the object to be processed was placed horizontally so that the axial direction of the object to be processed was oriented in the vertical direction. Note that, except for the inferior angle, Example 1 and Comparative Example 1 are heat-treated under the same conditions.

140 pieces of Example 1 and 120 pieces of Comparative Example 1 were produced, respectively. Then, with respect to Example 1 and Comparative Example 1, the elliptic strain (elliptic strain) was measured. Specifically, for each of Example 1 and Comparative Example 1, the difference between the diameter at the location with the largest diameter and the diameter at the location with the smallest diameter is calculated as the elliptic strain amount. Was measured as. Then, the average value of the elliptic strain amounts in the plurality of comparative examples 1 was defined as the reference strain amount. Then, the ratio of the strain amount to the reference strain amount is defined as the elliptic strain ratio. The results are shown in Fig. 16. The vertical axis of FIG. 16 represents the elliptic distortion ratio.

As shown in FIG. 16, in the plurality of comparative examples 1, when the elliptic strain amount was the largest, the elliptic strain ratio as the ratio of the strain amount to the reference strain amount reached 200%. On the other hand, the average value of the elliptic strain amounts in the plurality of Examples 1 was only about 60% of the reference strain amount. In addition, the elliptic distortion ratio was only about 110% even when the elliptic distortion amount was the largest among the plurality of Examples 1. That is, Example 1 was able to reduce the elliptic distortion to about half as compared with Comparative Example 1. As described above, it was proved that Example 1 can make the elliptic distortion extremely small.

<Relationship between thermal distortion and the inferior angle formed by the axial direction of the object to be processed and the main radiation direction>
In addition to Example 1, Example 2, Example 3, and Comparative Example 2 were prepared. In addition, Example 1, Example 2, Example 3, and Comparative Example 2 have the same configuration except that the inferior angle formed by the axial direction of the object to be processed and the main radiation direction during heat treatment is different. Have In each of the example 1, the example 2, the example 3, and the comparative example 2, the heat treatment is performed in a vertical posture (a standing posture). Specifically, it is as follows.
Example 1: Inferior angle=0°
Example 2: Inferior angle=30°
Example 3: Inferior angle=45°
Comparative Example 2: Inferior angle=60°

Five pieces of Example 2, five pieces of Example 3, and five pieces of Comparative Example 2 were produced. Then, the elliptic strain was measured for each of Example 2, Example 3, and Comparative Example 2. Results are shown in FIG. The display method of the elliptic distortion is the same as the display method shown in FIG. The vertical axis of FIG. 17 indicates the elliptic distortion ratio, as with the vertical axis of FIG. In addition, about Example 1, the same result as the result shown in FIG. 16 is shown.

As shown in FIG. 17, among the plurality of comparative examples 2, when the elliptic strain amount was the largest, the elliptic strain ratio reached about 180%. Moreover, the elliptic strain ratio was about 90% with respect to the average value of the elliptic strains in Comparative Examples 2. On the other hand, with respect to the maximum value of the elliptic strain amount in the plurality of Examples 3, the elliptic strain ratio was only about 130%. Further, the elliptic strain ratio was only about 80% with respect to the average value of the elliptic strain amounts in the plurality of Examples 3. Further, with respect to the maximum value of the elliptic strain amount in the plurality of Examples 2, the elliptic strain ratio was only about 120%. In addition, the elliptic strain ratio was only about 70% with respect to the average value of the elliptic strain amounts in the plurality of Examples 2. In addition, as described above, the elliptic strain ratio was only about 110% with respect to the maximum value of the elliptic strain amount in the plurality of Examples 1. Further, the elliptic strain ratio was only about 60% with respect to the average value of the elliptic strain amounts in the plurality of Examples 1.

As described above, it was proved that the elliptic distortion decreases as the inferior angle formed by the axial direction of the object to be processed and the main radiation direction decreases. In addition, when the straight line F1 passing through the maximum elliptic strain ratio in each of Examples 1 to 3 is drawn in FIG. 17, the maximum value of the elliptic strain ratio in Comparative Example 2 is located far above the straight line F1. Become. That is, it was proved that Examples 1 to 3 in which the inferior angle formed by the axial direction of the object to be processed and the main radiation direction was 45° or less had an extremely small elliptic distortion.

<Relationship between carbon potential of furnace atmosphere and thermal strain>
Examples 4 to 6 and Comparative Example 3 were produced by varying the carbon potential in the atmospheric gas during the heat treatment of the object to be treated. The heat treatment conditions for Examples 4 to 6 and Comparative Example 3 were the same except for the carbon potential. Specifically, the carbon potentials during the heat treatments of Examples 4 to 6 and Comparative Example 3 are as follows.

Example 4: 0.6%
Example 5: 0.8%
Example 6: 1.0%
Comparative Example 3: 1.4%

Ten pieces of Example 4, ten pieces of Example 5, ten pieces of Example 6, and ten pieces of Comparative Example 4 were produced. Then, the elliptic distortion was measured for each of Example 4, Example 5, Example 6, and Comparative Example 3. The results are shown in Fig. 18. The display method of the elliptic distortion is the same as the display method shown in FIG. The vertical axis in FIG. 18 represents the elliptic distortion ratio, as in the vertical axis in FIG.

As shown in FIG. 18, among the plurality of comparative examples 3, when the elliptic strain amount was the largest, the elliptic strain ratio reached about 110%. On the other hand, regarding the average value of the elliptic strain amounts in the plurality of Examples 6, the elliptic strain ratio was only about 50%. In addition, the elliptic strain ratio was only about 90% even when the amount of elliptic strain was the largest among the plurality of Examples 6. In addition, the elliptic strain ratio was only about 40% with respect to the average value of the elliptic strain amounts in the plurality of Examples 5. Further, even in the case where the elliptic strain amount was the largest among the plurality of Examples 5, the elliptic strain ratio was only about 80%. In addition, the elliptic strain ratio was only about 55% with respect to the average value of the elliptic strain amounts in the plurality of Examples 4. In addition, the elliptic strain ratio was only about 95% even when the amount of elliptic strain was the largest among the plurality of Examples 4.

As described above, in Examples 4 to 6 in which the carbon potential during the heat treatment is in the range of 0.6% to 1.0%, the elliptic strain ratio is less than 100% at the maximum, and the elliptic strain is extremely small. Was demonstrated. Particularly, it was demonstrated that the elliptic strain was extremely small in Example 5 in which the carbon potential during the heat treatment was set to 0.8% which was substantially equal to 0.77% which was the carbon potential at the eutectoid point.

INDUSTRIAL APPLICABILITY The present invention can be widely applied as a method for manufacturing a metal part and a holder for heat treatment.

2,2A holder (heat treatment holder)
6 Heater unit (heat source)
21,21A Bottom frame part 22,23 Pair of vertical frame parts 22A,23A Pair of vertical frame parts 26,26A Receiving part 27,27A Supporting member 28 Opposing surface 31,31A First supporting part 32,32A Second supporting part 41 First ring row (first row)
42 Second Ring Row (Second Row)
100 Processed object 100a Outer peripheral surface 100d End surface (one end surface)
B3 Central axis of object to be processed DR1 Outer diameter D2 Main radiation direction E1 First arrangement direction E2 Second arrangement direction P1 Pitch θ1 Inferior angle θ2 Angle interval

Claims (20)

A circular object to be processed and a heat source that radiates heat in a predetermined main radiation direction are opposed to each other, and an inferior angle formed by the axial direction of the object and the main radiation direction. An arrangement step of arranging a plurality of the objects to be processed so that the angle is 45° or less (including zero),
A heat treatment step of subjecting the plurality of objects to be heat treated,
In the arranging step, the object to be processed is in a state of being erected such that one end surface in the axial direction of the object to be processed is laterally oriented, and the one end surface is directed to a predetermined first array direction side. More than one,
The method for manufacturing a metal component, wherein the two objects to be processed adjacent to each other in the first arrangement direction are displaced from each other in a second arrangement direction orthogonal to the first arrangement direction. A method of manufacturing a metal component according to claim 1, wherein
The method for manufacturing a metal component, wherein the two objects to be processed that are adjacent to each other in the first arrangement direction are arranged such that end surfaces facing each other are in contact with each other. A method of manufacturing a metal component according to claim 1 or 2, wherein
In the placement step,
A first row including a plurality of the objects to be processed arranged along the first arrangement direction;
A second row, which includes a plurality of the objects to be processed that are arranged along the first arrangement direction in a state in which the positions of the objects to be processed in the first row are displaced from each other,
Is formed,
The method for manufacturing a metal component, wherein the objects to be processed in the first row and the objects to be processed in the second row are alternately arranged in the first arranging direction. A method of manufacturing a metal component according to claim 3,
A plurality of the first rows and a plurality of the second rows are arranged alternately in the second arrangement direction,
When each of the rows is viewed from the first arrangement direction, each of the objects to be treated is equal to or less than half the outer diameter of the object to be treated in the second arrangement direction with respect to the objects to be treated in the adjacent row. A method for manufacturing a metal component, wherein the length regions are arranged so as to overlap each other. A method for manufacturing the metal component according to any one of claims 1 to 4, comprising:
In the arranging step, a plurality of the objects to be processed are arranged along the main radiation direction, a method for manufacturing a metal component. A method for manufacturing the metal component according to any one of claims 1 to 5, comprising:
A method for manufacturing a metal component, wherein both the first arrangement direction and the second arrangement direction are horizontal directions. A method for manufacturing the metal component according to any one of claims 1 to 5, comprising:
A method of manufacturing a metal component, wherein the axial direction is a direction inclined with respect to a horizontal direction. A method for manufacturing the metal component according to any one of claims 1 to 7, comprising:
In the arranging step, a predetermined holder is configured to support an outer peripheral surface of the object to be processed from below, and a method for manufacturing a metal component. A method of manufacturing a metal component according to claim 8,
The said holder is comprised so that the said to-be-processed object may be supported in the state of line contact or point contact, The manufacturing method of the metal components characterized by the above-mentioned. A method of manufacturing a metal component according to claim 9,
The holder supports the outer peripheral surface of the object to be processed by a first supporting portion and a second supporting portion that are separated in the circumferential direction of the outer peripheral surface,
A method for manufacturing a metal component, wherein an angular interval between the first support portion and the second support portion around the central axis of the object to be processed is set in a range of 20° to 60°. A holder for heat treatment, for holding a plurality of objects to be processed made of metal, which are formed in a circular shape and subjected to heat treatment,
The holder opposes the object to be processed and a heat source that radiates heat in a predetermined main radiation direction, and an inferior angle formed by the axial direction of the object to be processed and the main radiation direction is 45° or less. It is configured to hold the object to be processed (including zero),
The holder includes a receiving portion that extends along a predetermined first arrangement direction and receives the object to be processed,
The receiving section arranges a plurality of the objects to be processed in a state of being erected such that one end surface in the axial direction of the object to be processed is laterally oriented and the one end surface faces the first arrangement direction side. And the two objects to be processed which are adjacent to each other in the first arrangement direction are arranged to be displaced from each other in the second arrangement direction orthogonal to the first arrangement direction. Characteristic holder for heat treatment. The holder for heat treatment according to claim 11,
The heat treatment holder, wherein the receiving portion is configured to receive the plurality of objects to be processed in an array along the main radiation direction. The holder for heat treatment according to claim 11 or claim 12,
A holder for heat treatment, wherein the receiving portion is arranged so that the axial direction is a horizontal direction or a direction inclined with respect to the horizontal direction. The holder for heat treatment according to any one of claims 11 to 13,
A holder for heat treatment, wherein the holder is configured to support an outer peripheral surface of the object to be processed from below. The heat treatment holder according to claim 14,
The holder for heat treatment, wherein the holder is configured to support the object to be processed in line contact or point contact. The holder for heat treatment according to claim 15,
The holder is configured to support the outer peripheral surface of the object to be processed by a first supporting portion and a second supporting portion that are separated in the circumferential direction of the outer peripheral surface,
The heat treatment holder, wherein an angular interval between the first support portion and the second support portion around the central axis of the object to be processed is set in a range of 20° to 60°. The heat treatment holder according to any one of claims 11 to 15 ,
The receiving portion includes a plurality of support members extending along the first arrangement direction for supporting a lower portion of the object to be processed,
The support members are arranged so as to be arranged at a predetermined pitch in the second arrangement direction,
A holder for heat treatment, wherein the pair of support members adjacent to each other in the second arrangement direction are configured to support the object to be processed. The holder for heat treatment according to claim 17,
Each of the support members has a facing surface as a surface facing the object to be processed,
The heat treatment holder, wherein the facing surface extends linearly along the first arrangement direction. The holder for heat treatment according to any one of claims 11 to 18,
A bottom frame part to which the receiving part is attached,
A pair of vertical frame portions extending upward from both ends of the bottom frame portion in the first arrangement direction and arranged to sandwich the plurality of objects to be processed held by the receiving portion,
Further equipped with,
A holder for heat treatment, wherein each of the vertical frame portions is formed in a mesh shape. The heat treatment holder according to claim 16,
The receiving portion includes a plurality of support members extending along the first arrangement direction for supporting a lower portion of the object to be processed,
The support members are arranged so as to be arranged at a predetermined pitch in the second arrangement direction,
The pair of support members adjacent to each other in the second array direction is configured to support the object to be processed,
The first supporting portion is formed on one of the supporting members of the pair of supporting members, and the second supporting portion is formed on the other supporting member of the pair of supporting members. A holder for heat treatment, characterized by

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