JP6786296B2 - Manufacturing method of metal parts and heat treatment equipment - Google Patents

Description

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

It is known that a steel ring member is heat-treated by a heating device, and then the ring member is cooled to heat-treat the ring member (see, for example, Patent Document 1).

JP-A-2007-297664

When heat-treating a ring member, it is required to reduce the thermal strain in the ring member as much as possible. For example, ring members used in a high load environment, such as inner and outer rings of tapered roller bearings, are heat treated, such as by charcoal burning. However, in this heat treatment, distortion that distorts the roundness of the ring member, so-called elliptical distortion, occurs. Elliptical distortion is a phenomenon in which a perfectly circular steel part is distorted into an elliptical shape. Then, in order to correct such elliptical distortion, for example, a multi-step method of curing the ring member by heating and then turning it is adopted, which is inefficient.

Further, in the heat treatment of the ring member, the temperature difference of each part of the ring member can be suppressed by slowing the temperature change, so that the thermal strain can be suppressed. However, in this case, it takes time to heat-treat the ring member.

The present invention, by view of the above circumstances, such as a ring member, with respect to circular metal of the workpiece, it is possible to further reduce the distortion due to heat treatment, and can shorten the heat treatment time of the workpiece , A method for manufacturing a metal part, and a heat treatment apparatus.

Conventionally, in order to suppress the distortion of the object to be treated during the heat treatment, it has been common to pay attention to the cooling process after heating the object to be processed and to suppress the distortion by devising the cooling process. On the other hand, the inventor of the present application paid attention to the temperature raising step (temperature raising step) of the object to be processed, and further conceived an unprecedented arrangement method of the object to be processed in this temperature raising step. This makes it possible to significantly reduce the elliptical strain of the object to be treated in the heat treatment.

(1) Based on the above findings, the method for manufacturing a metal part according to a certain aspect of the present invention comprises a circularly formed metal object to be treated and a heat source that radiates heat in a predetermined main radiation direction. The heat source is arranged outside the object to be processed while facing each other, and the inferior angle between the axial direction of the object to be processed and the main radiation direction is 45 ° or less (including zero). a placement step of placing an object to be processed, a heating step of heating the object to be processed by using the heat source, viewed including the, in the arrangement step, a predetermined holder from below the outer peripheral surface of the object to be processed Support .

According to this configuration, the heat from the heat source is transferred more evenly to each part of the object to be processed. Thereby, when the object to be processed is heated by the heat source, the temperature difference in the object to be processed can be made smaller. More specifically, the temperature difference of the object to be processed in the circumferential direction of the object to be processed can be made smaller. In particular, when the axial direction and the main radiation direction coincide with each other, that is, when the inferior angle is zero, the temperature difference in the object to be processed in the circumferential direction of the object to be processed can be remarkably reduced. As a result, it is possible to suppress the occurrence of stress imbalance in the object to be treated. For example, the timing of austenite transformation of each part in one object to be processed can be made more equal. Further, as a result of suppressing 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, with respect to the metal object to be processed formed in a circular shape, the strain caused by the heat treatment can be made smaller, and the heat treatment time of the object to be processed can be made shorter. More specifically, the elliptical distortion in which the object to be processed is distorted in an elliptical shape can be made smaller. For example, when the object to be processed is heated above the A1 transformation point, the timing at which the temperature of each part in the object to be processed passes through the A1 transformation point can be made more uniform. As a result, it is possible to suppress the generation of transformation stress in the object to be treated. Further, in the arrangement step, a predetermined holder supports the outer peripheral surface of the object to be processed from below. Therefore, according to this configuration, it is possible to suppress 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 remarkably reduced.

(2) In the arrangement step, a plurality of the objects to be processed may be arranged along the main radiation direction.

According to this configuration, a plurality of objects to be treated can be collectively heat-treated while reducing thermal strain.

The object to be processed is arranged in an upright posture, and the axial direction may be along the horizontal direction.

According to this configuration, it is possible to suppress the occurrence of tensile stress in the object to be treated. As a result, the thermal strain caused by the stress of the object to be processed can be remarkably reduced.

The object to be processed is arranged in an upright posture, and the axial direction may be an inclined direction with respect to the horizontal direction.

According to this configuration, a plurality of objects to be processed can be arranged more appropriately in consideration of the weight balance of the plurality of objects to be processed as a whole.

( 3 ) The holder may support the object to be processed in a state of line contact or point contact.

According to this configuration, the holder can support the object to be processed in a state where it is suppressed from hindering the expansion and contraction of the object to be processed during the heat treatment of the object to be processed. As a result, the distortion of the object to be treated due to the heat treatment can be further reduced.

( 4 ) The holder supports the outer peripheral surface of the object to be processed by a first support portion and a second support portion separated in the circumferential direction of the outer peripheral surface, and is said to be around the central axis of the object to be processed. The angular distance 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 even. .. Therefore, the thermal strain of the object to be processed can be made smaller. Further, 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 is thermally expanded by heat treatment, the object to be processed is sandwiched between the two support portions due to the expansion. It is possible to prevent the condition from becoming a heat treatment. As a result, it is possible to prevent the object to be processed from being deformed so as to bite into the two support portions.

( 5 ) In the heating step, the object to be treated may be heated in an atmospheric gas set to a carbon potential in the range of 0.6% to 1.0%.

According to this configuration, when the object to be processed is heated, the time required for each part of the surface of the object to be processed to move from the region of ferrite + cementite to the region of austenite can be shortened. As a result, the object to be treated can be transformed into austenite more uniformly.

( 6 ) The heating step may be performed at least between the A1 transformation point and the A3 transformation point of the object to be treated.

According to this configuration, each part of the object to be treated can be transformed into austenite more evenly.

( 7 ) In the heating step, the object to be treated may be heated from the A1 transformation point to the A3 transformation point at a temperature rise rate in the range of 0.5 ° C./min to 10 ° C./min.

According to this configuration, when the temperature rise rate (temperature rise rate) of the object to be processed is equal to or higher than the above lower limit value, the time required to transform the object to be processed from the A1 transformation point to the A3 transformation point is increased. Can be shortened. Further, when the temperature rise rate of the object to be processed is equal to or less than the above upper limit value, when the object to be processed is transformed from the A1 transformation point to the A3 transformation point, the inside of the object to be processed is transferred from the outer surface of the object to be processed. The temperature difference between the outer surface and the inside of the object to be processed when heat is transferred to the surface can be sufficiently reduced. Thereby, the transformation stress inside the object to be treated can be made smaller. Therefore, the thermal strain of the object to be processed can be made smaller. In other words, when each part of the object to be processed undergoes austenitic transformation, the unevenness of the transformation timing (that is, the non-uniformity of the transformation timing) can be made smaller.

( 8 ) The object to be treated may be formed in a ring shape.

According to this configuration, the degree of temperature change of each part can be made more uniform in the ring-shaped object to be processed. As a result, it is possible to form a metal component having a small thermal strain such as an elliptical strain.

( 9 ) The object to be processed may include a race or a gear of a bearing.

According to this configuration, bearings or gears with high dimensional accuracy can be manufactured.

( 10 ) Further, the heat treatment apparatus according to a certain aspect of the present invention includes a heat source configured to radiate heat in a predetermined main radiation direction, a metal object to be processed formed in a circular shape, and the heat source. The heat source is arranged outside the object to be processed, and the inferior angle between the axial direction of the object to be processed and the main radiation direction is 45 ° or less (including zero). ) , The holder is provided with a holder for arranging the object to be processed, and the holder supports the outer peripheral surface of the object to be processed from below .

According to this configuration, the heat from the heat source is transferred more evenly to each part of the object to be processed. Thereby, when the object to be processed is heated by the heat source, the temperature difference in the object to be processed can be made smaller. More specifically, the temperature difference of the object to be processed in the circumferential direction of the object to be processed can be made smaller. In particular, when the axial direction and the main radiation direction coincide with each other, that is, when the inferior angle is zero, the temperature difference in the object to be processed in the circumferential direction of the object to be processed can be remarkably reduced. As a result, it is possible to suppress the occurrence of stress imbalance in the object to be treated. For example, the timing of austenite transformation of each part in one object to be processed can be made more equal. Further, as a result of suppressing 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, with respect to the metal object to be processed formed in a circular shape, the strain caused by the heat treatment can be made smaller, and the heat treatment time of the object to be processed can be made shorter. More specifically, the elliptical distortion in which the object to be processed is distorted in an elliptical shape can be made smaller. For example, when the object to be processed is heated above the A1 transformation point, the timing at which the temperature of each part in the object to be processed passes through the A1 transformation point can be made more uniform. As a result, it is possible to suppress the generation of transformation stress in the object to be treated. Further, the holder supports the outer peripheral surface of the object to be processed from below. Therefore, according to this configuration, it is possible to suppress 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 remarkably reduced.

According to the present invention, with respect to a circular metal object to be processed such as a ring member, the strain due to heat treatment can be made smaller, and the heat treatment time of the object to be processed can be shortened.

It is a schematic cross-sectional view of the heat treatment apparatus which concerns on embodiment of this invention, and shows the state which the heat treatment apparatus is viewed in a plan view. It is a schematic cross-sectional view of a heat treatment apparatus, and shows the state which looked at the heat treatment apparatus from the side. It is an enlarged view of the holder and the object to be processed in the heat treatment apparatus of FIG. It is an enlarged view of the holder and the object to be processed in the heat treatment apparatus of FIG. It is a schematic diagram for demonstrating the relationship between a holder and an object to be processed. It is a schematic diagram for explaining the inferior angle, and shows the case where the inferior angle is not zero. It is a flowchart for demonstrating an example of a heat treatment operation in a heat treatment apparatus. It is a graph which shows an example of temperature control of the object to be processed in a heat treatment apparatus. It is a typical equilibrium state diagram of the Fe—C alloy for explaining the state of the object to be heat-treated by the heat treatment apparatus. It is a schematic plan view of the holder and the heater unit provided in the heat treatment apparatus which concerns on 2nd Embodiment of this invention. It is a schematic side view of the main part which shows the holder and the object to be processed held in the holder. It is a schematic front view of the main part which shows the holder and the object to be processed held in the holder. It is a schematic plan view of the main part which shows the holder provided in the heat treatment apparatus which concerns on 2nd Embodiment of this invention, and the object to be processed held by the holder. It is a schematic side view of the main part for demonstrating one of the modification. It is a schematic side view of the main part for demonstrating the modification different from the modification shown in FIG. It is a graph for demonstrating the thermal strain for each type of placement of an object to be processed. It is a graph for demonstrating the relationship between the inferior angle formed by the axial direction and the main radiation direction of an object to be processed, and thermal strain. It is a graph for demonstrating the relationship between the carbon potential of the atmosphere in a furnace, and thermal strain.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

FIG. 1 is a schematic cross-sectional view of the heat treatment apparatus 1 according to the 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 a side view of the heat treatment apparatus 1. It is a side view. FIG. 3 is an enlarged view of the holder 2 and the object to be processed 100 in the heat treatment apparatus 1 of FIG. FIG. 4 is an enlarged view of the holder 2 and the object to be processed 100 in the heat treatment apparatus 1 of FIG. In FIG. 4, the illustration of a part of the object to be processed 100 is omitted.

With reference to FIGS. 1 and 2, the heat treatment apparatus 1 is provided for heat-treating the object to be treated 100. Examples of this heat treatment include carburizing treatments such as vacuum carburizing, carburizing nitriding and carburizing quenching, quenching treatments, tempering treatments, annealing treatments and the like. In the present embodiment, the 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. The "circular shape" in this case includes a cylindrical shape in which a through hole is formed, a disk shape in which a through hole is not formed, a shape in which the envelope of the outer shape is circular, and the like. As a member having a circular envelope having an outer shape, a gear having teeth formed on the outer peripheral portion can be exemplified. 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 perfect circular cylinder shape, and the amount of strain 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 elliptical strain, and refers to the difference or ratio between the portion having the largest diameter and the portion having the smallest diameter in 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, shafts and washers of rolling bearings. The object to be treated 100 may be a metal part formed in a circular shape and subjected to heat treatment. The object to be treated 100 is, for example, carbon steel having a carbon content (carbon potential) of about 0.2%. The carbon content of the object to be treated 100 can be exemplified as 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 concentric cylinders.

The heat treatment apparatus 1 includes 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 stirring device 8, and an atmospheric gas supply unit 9.

The heat treatment furnace 5 is formed in a hollow box shape. The heat treatment furnace 5 forms a storage chamber for housing the object to be processed 100. 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. With the entrance door 10 open, the object to be processed 100 is carried into the heat treatment furnace 5 from the outside of the heat treatment furnace 5. Further, with the outlet door 11 open, the object to be processed 100 is carried out of the heat treatment furnace 5 from the inside of the heat treatment furnace 5. Further, the entrance door 10 and the exit door 11 are closed while the object 100 to be treated is heat-treated. In the present 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 temperature T in the furnace as the temperature inside the heat treatment furnace 5. The temperature detection result of the temperature sensor 12 is given to the control unit 4. Further, in the heat treatment furnace 5, an oxygen sensor 13 for measuring the carbon potential in the heat treatment furnace 5 is arranged. The oxygen concentration detection result 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 100 to be processed. 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 separated 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 this embodiment) are arranged at substantially equal intervals along the traveling direction X1. Similarly, a plurality of second heaters 15 are arranged at substantially equal intervals along the traveling direction X1. In the present embodiment, the number of the first heater 14 and the number of the second heater 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 heaters 14 and second heaters 15 whose positions in the traveling direction X1 are aligned face each other 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 of the heaters 14 and 15 has a tube 16.

The tube 16 is provided to transfer the heat generated by energizing the electric heating body arranged in the tube 16 to the space in the heat treatment furnace 5. The heat treatment furnace 5 is heated by the heat generated from the electric heating body in the tube 16, and the object 100 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 straight shape in the vertical direction. The diameter of each tube 16 is set to a predetermined value. Each tube 16 extends from the top wall 5a 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 around the tube 16.

The main radiation direction D2 is defined for the heater unit 6 having the above configuration. The main radiation direction D2 is the 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 heat toward the main radiation direction D2. In the present embodiment, the main radiation direction D2 is a direction in which a 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 the present embodiment, the heater unit 6 radiates heat in a direction orthogonal to the traveling direction X1. Further, in the present embodiment, the main radiation direction D2 is along the horizontal direction. The main radiation direction D2 can be said to be the direction in which the combined value of each vector is the maximum when the amount of heat radiation from the heaters 14 and 15 is 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 at an arbitrary point of the cylindrical portion of the tube 16 extends and is covered. It can also be defined as the direction passing through the center point of the processed object 100.

A 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 arranged, for example, between the inlet doors 10 and the second heaters 14 and 15 in the traveling direction X1 and between the inlet doors 10 and the fifth heaters 14 and 15. The pedestal 7 includes, for example, a plurality of columns 7a to 7f. The columns 7a to 7f extend 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 intermediate portion of the holder 2. It is configured to do.

In the present embodiment, the three columns 7a, 7c, 7e are arranged between the inlet door 10 and the second heaters 14, 15 in the traveling direction X1, and these three columns 7a, 7c, 7e are the main radiation. They are evenly spaced in 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 and 15 from the entrance door 10, and these three columns 7b, 7d, 7f are evenly 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 one or more objects 100 to be processed into and out of the heat treatment furnace 5. Further, 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 this embodiment. The holder 2 is formed in a rectangular box shape with an open upper part. The four side surfaces and one bottom surface of the holder 2 are formed in a mesh shape and are configured to allow a fluid such as gas to pass through.

FIG. 5 is a schematic view for explaining the relationship between the holder 2 and the object to be processed 100. With reference to FIGS. 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 to be processed 100 in the front-rear direction (main radiation direction D2). These vertical frame portions 22 and 23 are arranged so as to extend upward from both ends of the predetermined first alignment direction E1 of the bottom frame portions 21 and to sandwich a plurality of objects to be processed 100 held by the receiving portion 26. ing. The vertical frame portion 22 is provided as a front frame portion, and is arranged so as to be adjacent to the heater 14, for example. The vertical frame portion 22 is provided as a rear frame portion, and is arranged so as to be adjacent to the heater 15, for example.

The vertical frame portions 24 and 25 are formed as a pair of frame portions arranged so as to sandwich the object to be processed 100 on the left and right (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 the heaters 14 and 15 extend in opposite directions, for example.

Each of the vertical frame portions 22 to 25 is formed in a mesh shape and is configured to allow gas to pass through. Of the bottom frame portions 21 that support the vertical frame portions 22 to 25, the receiving portion 26 extends between two side portions that are separated from each other in the main radiation direction D2, which will be described later.

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

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

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

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

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

More specifically, each support member 27 has an facing surface 28 facing the object to be processed 100 to be supported. The facing surface 28 extends straight along the first alignment direction E1. The portion of the facing surface 28 that is in contact with the object to be processed 100 forms the support portion 31 or the support portion 32. As described above, the first support portion 31 formed on one of the support members 27 of the pair of support portions 27, 27 and the second support portion 32 formed on the other support member 27 are present. It 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 support portions 31 and 32 separated in the circumferential direction of the outer peripheral surface 100a.

Further, the object to be processed 100 is arranged in the holder 2 so that 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 (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. Note that FIGS. 1 to 4 show a case where the inferior angle θ1 = 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 of the central axis B3 of the object to be processed 100 extending in the axial direction D1 and the reference line B4 extending along the main radiation direction D2, that is, the plane shown in FIG. .. The inferior angle θ1 includes a first half line B5 formed of a part of the central axis B3 and a two half line B6 formed of a part of the reference line B4 with the intersection of these two lines B3 and B4 as the origin O. The smaller of the two conjugate angles.

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 virtual orthogonal plane and the central axis B3 are orthogonal to each other becomes 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 the present 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.

By setting the inferior angle θ1 to 45 ° or less with reference to FIGS. 1 to 6, it is possible to more reliably suppress the bias of heat transfer 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 transferred more evenly to the entire surface of the object to be processed 100. As a result, when the object to be processed 100 is heat-treated, the deviation of the timing at which transformation starts (hereinafter, also simply referred to as simply transformation timing) in each portion of the object to be processed 100 can be made smaller. As a result, the generation of transformation stress (that is, stress due to the deviation of transformation timing) in the object to be processed 100 can be further reduced. 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 made smaller. In particular, the ring-shaped object 100, which is substantially circular, is distorted in an elliptical shape, and the elliptical distortion can be further reduced.

When the inferior angle θ1 exceeds 45 °, the degree to which the distribution of heat transferred to the object to be processed 100 along the main radiation direction D2 becomes non-uniform within the object to be processed 100 increases. As a result, when the object to be processed 100 is heat-treated, the deviation of the transformation timing in the object to be processed 100 becomes large. As a result, the transformation stress in the object to be processed 100 becomes large. 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.

The inferior angle θ1 is more preferably 30 ° or less. When the inferior angle θ1 is 30 ° or less, which is 2/3 of 45 °, the degree of heat reception on the inner peripheral surface 100a and the outer peripheral surface 100b of the ring-shaped object 100 can be made more even. 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 1/2 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. Further, in a plan view, 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 this way, the holder 2 faces the object to be processed 100 and the heater unit 6 with each other, and the inferior angle θ1 formed by the axial direction D1 and the main radiation direction D2 of the object to be processed 100 is 45 ° or less (zero). The object to be processed 100 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 to be processed 100. The bottommost portion 100e of the object to be processed 100 is arranged between the first support portion 31 and the second support portion 32. In the present embodiment, the first support portion 31 and the second support portion 32 are aligned in height and are positioned symmetrically with respect to 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 to be processed 100 is placed are viewed in the axial direction D1 of the object to be processed 100, the first support portion 31 and the second support portion 31 and the second support portion are viewed. 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 object to be processed 100 is placed on the support member 27 are viewed in the axial direction D1 of the object to be processed 100. The inferior angle formed by the minute B1 and the second line segment B2 is defined as the angle interval θ2. The first line segment B1 is a line segment connecting the central axis B3 of the object to be processed 100 and the first support portion 31. The second line segment B2 is a line segment connecting the central axis B3 of the object to be processed 100 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 angle interval θ2 is preferably set in the range of 20 ° to 60 °. By setting the angle interval θ2 to 20 ° or more, the compressive stress acting on each part of the object to be processed 100 supported by these support parts 31 and 32 can be made more even. Therefore, the thermal strain of the object to be processed 100 can be made smaller. Further, by setting the angle interval to 60 ° or less, when the object to be processed 100 is thermally expanded by heat treatment, the object to be processed 100 is sandwiched between the two support portions 31 and 32 due to the expansion. Can be suppressed. As a result, it is possible to prevent the object to be processed 100 from being deformed so as to bite into the two support portions 31 and 32.

Of the facing surfaces 28 of each support member 27, the portions forming the first support portion 31 and the second support portion 32 may be convex. In this case, the first support portion 31 and the second support portion 32 support the object to be processed 100 in a point contact state.

On the pair of support members 27, 27, a plurality of objects 100 to be processed are arranged at substantially equal intervals along the first alignment 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 alignment direction E2 orthogonal to the first alignment direction E1 in a plan view. As a result, the objects to be processed 100 can be arranged in a plurality of rows in the traveling direction X1. In the present embodiment, the objects 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 the present embodiment, a lower holder 2aa, a middle holder 2b, and an upper holder 2c are provided as a plurality of (three in the present embodiment) 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. Further, the upper holder 2c is placed on the four vertical frame portions 22 to 25 of the middle holder 2b. By stacking the plurality of holders 2 in this way, a large number of objects 100 to be treated can be heat-treated at once.

The object to be processed 100 arranged in the heat treatment furnace 5 is provided with an air stream stirred by the stirring device 8 for stirring the gas in the heat treatment furnace 5.

With reference to FIGS. 1 and 2, the stirring device 8 is provided to make the air temperature and gas components in the 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 stirring fan 33 is, for example, a centrifugal fan, and is configured to generate an outward wind in the radial direction of the stirring fan 33. The stirring fan 33 is arranged above the heat treatment furnace 5. In this embodiment, the stirring fan 33 is arranged directly above the pedestal 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 the atmosphere gas, which is a heat treatment gas for performing a desired heat treatment on the object 100 to be processed, 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 a 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 the present 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 which is the base material of the object to be treated 100. Then, in the present embodiment, during heating in the heat treatment apparatus 1, the object to be treated 100 is exposed to an atmospheric gas set to a 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 phase diagram of the Fe—C alloy. By setting the carbon potential Cp in the above range of 0.6% to 1.0%, the carbon content on the surface of the object to be treated 100 becomes close to 0.77% during the heat treatment of the object to be treated 100. .. As a result, when the object to be treated 100 is heat-treated, the time in which the object to be processed 100 is in a ferrite + austenite state can be shortened. As a result, the transformation stress generated in the object to be processed 100 can be made smaller. In the present embodiment, the carbon potential Cp in the atmospheric gas is set to be 3 times or more of 0.2%, which is the carbon potential of the base material of the object to be treated 100.

In the present embodiment, the carbon potential Cp of the atmospheric gas is more preferably 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, during the heat treatment of the object to be treated 100, the carbon content on the surface of the object to be treated 100 becomes close to 0.77%, and the time in which the object to be treated 100 is in a ferrite + austenite state can be shortened. .. As a result, the transformation stress in the object to be processed 100 can be made smaller.

In the heat treatment furnace 5, the heat treatment operation of the object to be processed 100 is controlled by the control unit 4. The control unit 4 has a configuration for outputting a predetermined output signal based on a predetermined input signal, and can be formed by using, for example, a safety programmable controller or the like. The safety programmable controller means a publicly certified programmable controller having the safety function of SIL2 or SIL3 of JIS (Japanese Industrial Standards) C 0508-1. The control unit 4 may be formed by 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 flow rate of the atmospheric gas supplied to the heat treatment furnace 5 by controlling the pump 9a and the like (not shown) of the atmospheric gas supply unit 9 based on the detected carbon potential Cp and the like. It is configured as follows. As a result, the control unit 4 controls the carbon potential Cp of the atmospheric gas in the heat treatment furnace 5. Further, the control unit 4 is configured to be able to control the flow rate of the combustion gas supplied to each of the heaters 14 and 15. As a result, the control unit 4 can control the temperature inside 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 flowchart for explaining an example of the heat treatment operation in the heat treatment apparatus 1. FIG. 8 is a graph showing an example of temperature control of the object to be processed 100 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 to be treated 100 to be heat-treated by the heat treatment apparatus 1. In the following, when the explanation is made with reference to the flowchart, the drawings other than the flowchart will be referred to as appropriate.

In the heat treatment operation in the heat treatment apparatus 1, first, for example, an operation of arranging the object to be processed 100 is performed by a worker or an automatic arranging apparatus (not shown) by a machine (step S1). Specifically, for example, a worker arranges an object 100 to be processed in each of the holders 2a, 2b, and 2c. Then, the lower holder 2a is placed on the pedestal 7 by the worker. 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, and 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 manner with reference to FIGS. 1 to 4. That is, with the object to be processed 100 and the heater unit 6 facing 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). The object to be processed 100 is arranged in the heat treatment furnace 5 so as to be (including).

Next, the object 100 to be processed 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 controls the supply amount of the atmospheric gas supplied from the atmospheric gas supply unit 9, thereby controlling the atmospheric temperature and carbon in the heat treatment furnace 5. Control the potential Cp. As a result, the control unit 4 controls the heat treatment operation of the object to be processed 100. More specifically, the control unit 4 controls the heating operation of the heater unit 6 so that the relationship between the 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, for example, 727 ° C to 810 ° C. Further, 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 body including the inside of the object to be treated 100 is heated to the A1 transformation point. Next, the control unit 4 raises the temperature in the heat treatment furnace 5 from the A1 transformation point to the A3 transformation point by, for example, controlling to increase the electric power supplied to the heater unit 6 (timings T1 to T2). ).

Between the A1 transformation point and the A3 transformation point, the atmospheric gas and the object to be treated 100 are heated at a heating rate (temperature rising rate) within the range of 0.5 ° C./min to 10 ° C./min. When the rate of temperature rise 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, when the temperature rise rate of the object to be processed 100 is equal to or less 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 processed is treated from the outer surface of the object 100. 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 sufficiently reduced. As a result, the transformation stress inside the object to be processed 100 can be made smaller. Therefore, the thermal strain of the object to be processed 100 can be made smaller. In other words, when each part of the object to be processed undergoes austenitic transformation, the unevenness of the transformation timing (that is, the non-uniformity of the transformation timing) can be made smaller.

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

Further, the object to be treated 100 is heated to the A3 transformation point or higher in the above-mentioned atmospheric gas having carbon potential Cp. At this time, the carbon potential inside the object to be treated 100 does not substantially change. On the other hand, the carbon potential of the outer surface of the object to be treated 100 is increased by the heat treatment.

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

Here, at the time of heat treatment, the temperature of the outer surface of the object 100 to be treated first rises, and then the temperature of the inside rises. Therefore, in the present embodiment, the state of the atmospheric gas in the heat treatment furnace 5 is controlled so as to be 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 to be treated 100 has an increased carbon potential by following the process shown by the line L2 (for example, L21, L22, L23) in FIG. 9, and is generally in the heat treatment furnace 5. It converges on the carbon potential Cp of the atmospheric gas. The line L21 shows the case where the carbon potential Cp of the atmospheric gas is within the lower limit (Cp = 0.6%) of the above-mentioned range. Further, the line L22 shows the case where the carbon potential Cp of the atmospheric gas is equal to the carbon potential (Cp = 0.77%) at the eutectoid point. Further, the line L23 shows the case where the carbon potential Cp in the atmospheric gas is within the upper limit (Cp = 1.0%) of the above-mentioned range.

The outer surface of the object to be treated 100 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 on the outer surface of the object to be treated 100 increases. In particular, the carbon potential of the outer surface of the object to be treated 100 increases in a manner substantially proportional to the temperature increase until it reaches the A1 transformation point. Then, when the temperature of the outer surface of the object to be treated 100 approaches the A1 transformation point, the carbon potential of the outer surface of the object to be treated 100 becomes substantially constant, albeit slightly increasing as the temperature of the outer surface of the object to be treated rises. Become. The temperature of the outer surface of the object to be treated 100 is lower than that of the inside of the object to be treated 100 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 line L21, when the outer surface of the object to be treated 100 reaches the A1 transformation point, ferrite + cementite It transforms from the state to the ferrite + austenite state. The temperature difference Δt21 from the A1 transformation point to the A3 transformation point on the outer surface of the object 100 to be processed is the temperature difference Δt1 from the A1 transformation point to the A3 transformation point inside the object 100 to be processed. Is also small. Therefore, on the outer surface of the object to be treated 100, the transformation stress between the A1 transformation point and the A3 transformation point can be made smaller. As a result, the thermal strain on the outer surface of the object to be treated 100 can be made smaller.

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 to be treated 100 is as shown in L22. 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 from the A1 transformation point to the A3 transformation point on the outer surface of the object 100 to be treated is substantially zero. Therefore, on the outer surface of the object to be treated 100, the transformation stress between the A1 transformation point and the A3 transformation point can be made smaller. As a result, the thermal strain on the outer surface of the object to be treated 100 can be made smaller.

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 line L23, when the outer surface of the object to be treated 100 reaches the A1 transformation point, ferrite is formed. It transforms from the + cementite state to the austenite + cementite state. The temperature difference Δt23 from the A1 transformation point to the Acm transformation point on the outer surface of the object 100 to be processed is the temperature difference Δt1 from the A1 transformation point to the A3 transformation point inside the object 100 to be processed. Is also small. Therefore, on the outer surface of the object to be treated 100, the transformation stress from the A1 transformation point to the arrival at the Acm transformation point can be made smaller. As a result, the thermal strain on the outer surface of the object to be treated 100 can be made smaller. In this way, even if any of the lines L21, L22, and L23 is followed, the distortion of the outer surface of the object to be processed 100 can be made smaller.

As described above, in the heating step (step S2), the entire object 100 to be processed is heated beyond the A1 transformation point and further to the A3 transformation point. The control unit 4 controls to maintain 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 overall 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 a heating operation so as to further raise the atmospheric gas temperature in the heat treatment furnace 5 to the maximum temperature tmax at the time of heat treatment (timing T3 to T4).

In the present embodiment, the maximum temperature tmax is a temperature set for causing the object 100 to be carburized. This maximum temperature tmax is set to a temperature required for the target heat treatment such as diffusion treatment when the object 100 to be treated is subjected to other heat treatment such as diffusion treatment. The maximum temperature tmax is set to, for example, about 800 ° C. to 960 ° C. Further, the control unit 4 sets the heating rate when heating the inside of the object to be processed 100 from the A3 transformation point to the maximum temperature tmax, and when heating the inside of the object to be processed 100 from the A1 transformation point to the A3 transformation point. Set higher than the temperature rise rate.

The control unit 4 heat-treats the object to be treated 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 stopping the heating operation by the heater unit 6 (step S3). After that, the object to be processed 100 is carried out from the heat treatment furnace 5 and then subjected to other treatments such as quenching treatment. As described above, the tube 16 of the heater unit 6 is arranged perpendicular to the top wall 5a of the heat treatment furnace 5 from the viewpoint of durability and the like.

Conventionally, from the viewpoint of heat treatment strain, in consideration of the temperature distribution in one object to be processed, the object to be processed is not arranged in an upright posture and the object to be processed is supported from below. The object to be treated was laid down. Further, conventionally, the object to be processed is subjected to heat treatment by suspending the object to be processed in a heat treatment furnace using a bar configured to receive the inner peripheral surface of the ring-shaped object to be processed. There was also.

On the other hand, in the present embodiment, in order to suppress the occurrence of a temperature difference in the circumferential direction of the object to be processed 100 in each of the circular objects to be processed 100, the axial direction D1 and the main radiation direction D2 are used. The inferior angle θ1 is set to 45 ° or less. In addition, in the present embodiment, it is configured to support a downward portion of the outer peripheral surface 100a of the object to be processed 100, and the angle distance θ2 between the first support portion 31 and the second support portion 32 is 20. It is set within the range of ° to 60 °. As a result, 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. As a result, the thermal strain generated in the object to be processed 100 can be remarkably reduced.

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

As described above, according to the present embodiment, 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 (including zero). The processed object 100 is arranged. According to this configuration, the heat from the heater unit 6 is more evenly transferred to each part of the object to be processed 100. As a result, when the object to be processed 100 is heated by the heater unit 6, the temperature difference in the object to be processed 100 can be made smaller. 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 made smaller. 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 to be processed 100 in the circumferential direction of the object to be processed 100 can be remarkably reduced. As a result, it is possible to suppress the occurrence of stress imbalance in the object to be processed 100. In particular, the timing of austenite transformation of each part in one object 100 can be made more equal. Further, as a result of suppressing the occurrence of stress imbalance in the object to be processed 100, the object to be processed 100 can be heat-treated in a shorter time. As a result, with respect to the metal object 100 formed in a circular shape, the strain caused by the heat treatment can be made smaller, and the heat treatment time of the object 100 to be processed can be shortened. More specifically, the elliptical distortion in which the object to be processed 100 is distorted in an elliptical shape can be made smaller. Further, when the object to be processed 100 is heated to the A1 transformation point or higher, the timing at which the temperature of each part in the object to be processed 100 passes through the A1 transformation point can be made more uniform. As a result, it is possible to suppress the generation of transformation stress in the object to be processed 100.

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

Further, according to the present embodiment, each object to be processed 100 is arranged in an upright posture, and the axial direction D1 of each object to be processed 100 is along the horizontal direction. According to this configuration, it is possible to suppress the occurrence of tensile stress 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 remarkably reduced.

Further, according to the present embodiment, when the object to be processed 100 is arranged in the heat treatment furnace 5 (step S1), the holder 2 supports the outer peripheral surface of the object to be processed 100 from below. According to this configuration, it is possible to suppress the occurrence of tensile stress 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 remarkably reduced.

Further, according to the present embodiment, the support portions 31 and 32 of the holder 2 support the object to be processed 100 in a state of line contact or point contact. According to this configuration, the holder 2 can support the object to be processed 100 in a state where it is suppressed from hindering the expansion and contraction of the object to be processed 100 during the heat treatment of the object to be processed 100. As a result, the strain of the object to be treated 100 due to the heat treatment can be further reduced.

Further, according to the present embodiment, the angular distance 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 distance θ2 between the first support portion 31 and the second support portion 32 to 20 ° or more, it acts on each part of the object to be processed 100 supported by these support portions 31 and 32. The stress to be applied can be made more even. Therefore, the thermal strain of the object to be processed 100 can be made smaller. Further, by setting the angle distance θ2 between the first support portion 31 and the second support portion 32 to 60 ° or less, when the object to be treated 100 is thermally expanded by heat treatment, the support portions 31, 32 at two locations are expanded due to the expansion. It is possible to prevent the object to be treated 100 from being sandwiched between them. As a result, it is possible to prevent the object to be processed 100 from being deformed so as to bite into the two support portions 31 and 32.

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

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

Further, according to the present embodiment, when each object to be processed 100 is heated (step S2), the object to be processed 100 undergoes A1 transformation at a temperature rise 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, when the heating 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, when the temperature rise rate of the object to be processed 100 is equal to or less 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 processed is treated from the outer surface of the object 100 to be processed. 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 sufficiently reduced. As a result, the transformation stress inside the object to be processed 100 can be made smaller. Therefore, the thermal strain of the object to be processed 100 can be made smaller. In other words, when each part of the object to be treated 100 undergoes austenite transformation, the unevenness of the transformation timing (that is, the non-uniformity of the transformation timing) can be made smaller.

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

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

<Second Embodiment>
Next, the second embodiment of the present invention will be described. In the following, the points different from the above-described embodiment will be mainly described, and the same components as those in the above-described embodiment may be designated by the same reference numerals and the description thereof may be omitted.

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

With reference to FIGS. 10 to 13, the holder 2A of the present embodiment is suitable for holding a plurality of circular objects to be processed 100 to be heat-treated, and in particular, holding a ring-shaped object to be processed 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 of each object 100 to be processed. 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 the manner described later (step S1), and then subjected to a heat treatment (step S2) and a cooling treatment (step S3). Hereinafter, the holder 2A will be described more specifically.

The receiving portion 26A of the holder 2A extends along the first alignment direction E1 and is configured to receive a plurality of objects 100 to be processed. As described above, the first alignment direction E1 is along the axial direction D1 of the object to be processed 100 held by the receiving portion 26A. Further, the receiving portion 26A arranges a plurality of objects 100 to be processed so that the openings 100c of the objects 100 to be processed are erected sideways and the openings 100c face the first alignment direction E1 side. It is configured as follows. Further, the receiving member 26A is configured so that two objects 100 to be processed adjacent to the first alignment direction E1 are arranged so as to be offset from each other in the second alignment direction E2 orthogonal to the first alignment direction E1.

More specifically, each support member 27A of the receiving portion 26A extends along the first alignment direction E1 and supports the lower portion of the outer peripheral surface of the object to be processed 100 including the downward surface. Have been placed. 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 object to be processed 100 and the support member 27A are in line contact with each other. The contact area between the object to be treated 100 and the support member 27A is preferably small, 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 alignment direction E2 and fixed to the bottom frame portion 21A is provided. The reinforcing beams 35 are arranged at, for example, two locations in the first alignment direction E1. Both ends of each reinforcing beam 35 are fixed to the bottom frame portion 21A. 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. A pair of support members 27A, 27A adjacent to the second alignment direction E2 are configured to support one object 100 to be processed.

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

In this embodiment, a large number of ring rows 41 and a large number of ring rows 42 are formed. Each of the ring rows 41 and 42 contains a plurality of objects 100 to be processed, which are arranged along the first arrangement direction E1. Ring rows 41 and ring rows 42 are alternately formed along the second alignment direction E2. The ring rows 41 and 42 other than the ring rows 41 at both ends of the second alignment direction E2 share one support member 27A with the ring row 41 or the ring row 42 adjacent to the second alignment direction E2. Therefore, of the plurality of support members 27A, the facing surfaces 28 of the support members 27A arranged at other than both ends in the second alignment direction E2 are in contact with the two objects to be processed 100 at two points. The facing surface 28 is in contact with the object 100 of one ring row 41 or the ring row 42 at the first support portion 31A, and is in contact with the object 100 of another ring row 41 or the ring row 42 and the second object 100. They are 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, the first ring row 41 and the second ring row 42 are formed as the ring rows adjacent to the second alignment direction E2. Each object 100 in the second ring row 42 adjacent to the second alignment direction E2 and each object 100 in the first ring row 41 are first in a state of being displaced in the second alignment direction E2. They are lined up along the line-up direction E1. In the present embodiment, when proceeding along the first alignment direction E1, one object to be processed 100 in the first ring row 41 and one object to be processed 100 in the second ring row 42 are alternately arranged. With such a configuration, one object to be processed 100 in the first ring row 41 and one object to be processed 100 in the second ring row 42 are arranged in a zigzag shape.

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

In the present embodiment, the first ring row 41 and the second ring row 42 are alternately arranged in the second alignment direction E2. That is, they are arranged in the order of the first ring row 41, the second ring row 42, the first ring row 41, the second ring row 42, ..., Along the second alignment 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.

According to the above configuration, the same ring row (first ring row 41 or second ring row 42) is arranged with one ring row open 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 alignment direction E1, each object 100 of the ring row is covered with the adjacent ring row 42 or the ring row 41. With respect to the second alignment direction E2, the processed object 100 is arranged so that regions having a length of half or less of the outer diameter DR1 of the object to be processed 100 overlap. 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 extending vertically through the central axis B3 of the object 100 to be processed in one ring row 41a. , The other ring row 41b is arranged in the space sandwiched between the second virtual plane PL2 extending vertically through the central axis B3 of the object 100 to be processed.

By arranging the objects to be processed 100 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 one time can be about 125% of the number of objects 100 to be processed that can be placed on the holder 2 at one time.

With reference to FIGS. 10 to 13, the front frame portion and the vertical frame portions 22A and 23A as the rear frame portion of the holder 2A are each a plurality of pillars arranged at a predetermined pitch in the second alignment direction E2. It has a beam portion that connects the upper ends of these columns. Further, the vertical frame portions 24A and 25A as a pair of horizontal frame portions of the holder 2A each have a plurality of pillars arranged at a predetermined pitch in the first alignment direction E1 and a beam portion connecting the upper ends 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 upper corners of the holder 2A, respectively. Each stopper 43 projects upward from the upper ends of the four vertical frame portions 22A, 23A, 24A, and 25A of the holder 2A. Then, 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 other holder 2A. As a result, it is possible to prevent the position of the other holder 2A from being displaced with respect to the position of the holder 2A.

As described above, according to the present embodiment, the object to be processed 100 as a ring member is in a state where the opening 100c of the object to be processed 100 is erected so as to be sideways, and the opening 100c is the first. A plurality of arrangements are arranged so as to face the E1 side. Further, the positions of the two objects 100 to be processed adjacent to the first alignment direction E1 are shifted from each other in the second alignment direction E2. According to this configuration, the fluid can be passed more smoothly into the space surrounded by the inner peripheral surface 100b of each object to be processed 100. Therefore, for example, a medium (fluid) for heat treatment, such as carburized gas in the carburizing step and oil and nitrogen gas in the quenching step, is more smoothly supplied to the space on the inner peripheral side of the object to be treated 100. can do. Further, in each object to be processed 100, it is possible to suppress variations in the degree of supply of the medium in each of the inner peripheral portion and the outer peripheral portion. As a result, the degree of variation in the heat treatment of each object to be treated 100 can be made smaller. In addition, the degree of variation in heat treatment among the plurality of objects to be treated 100 can be further reduced. Therefore, the heat treatment quality such as the surface hardness and the internal hardness of each object to be treated can be made more uniform. Further, by increasing the interval between the objects to be processed 100 in the first alignment direction E1, the medium for heat treatment is not smoothly supplied to the inner peripheral portion side of the object to be processed 100. Therefore, the space required for heat-treating the object to be treated 100 can be made smaller. As a result, more objects 100 to be processed can be arranged at one time in the holder 2A arranged in the heat treatment furnace 5. Therefore, more objects 100 to be treated can be heat-treated at one time. Based on the above, when the metal object to be treated 100 is heat-treated, the variation in heat treatment quality can be reduced, and more objects 100 to be processed can be heat-treated at one time.

Further, according to the present embodiment, both the first alignment direction E1 and the second alignment direction E2 are horizontal directions. According to this configuration, the space occupied by each object to be processed 100 as a whole can be narrowed. Therefore, more objects 100 to be processed can be arranged at one time in the limited space for heat treatment.

Further, according to the present embodiment, the two objects to be processed 100 adjacent to the first alignment direction E1 are arranged so that the end faces 100d and 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 objects to be processed 100 arranged in the first arrangement direction E1, the first object to be processed 100 and the third object to be processed 100 in the first arrangement direction E1 sandwich the second object to be processed 100. It will be. With such a configuration, the second object to be processed 100 can set the distance between the first object to be processed 100 and the third object to be processed 100 to be the same as the thickness of the second object to be processed 100. .. As a result, a large number of objects to be processed 100 can be arranged more evenly along the first alignment direction E1. Further, since a plurality of objects to be processed 100 can be erected in a state of being in contact with each other, these objects to be processed 100 can be erected autonomously. Therefore, it is not necessary to separately provide a support member for supporting the object to be processed 100 so that it does not fall over. As a result, the objects to be processed 100 can be arranged at a higher density. Therefore, more objects 100 to be processed can be arranged at one time in a limited space.

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

Further, according to the present embodiment, when the ring rows 41 and 42 are viewed from the first alignment direction E1, each object 100 to be processed is different from the object 100 to be processed in the adjacent ring row with respect to the second alignment direction E2. , Regions having a length of less 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 alignment direction E1, the one object to be processed 100 and the one object to be processed 100 are both the two objects to be processed 100 adjacent to both sides of the second arrangement direction E2. And can be superimposed. As a result, the object to be processed 100 can be arranged more efficiently in the limited space for arranging the object to be processed 100. As a result, more objects 100 to be treated can be heat-treated at one time in a limited space.

Further, according to the present embodiment, the support members 27A of the receiving portion 26A of the holder 2A are arranged so as to be arranged at a predetermined pitch P1 in the second arrangement direction E2. Further, the pair of support members 27A and 27A adjacent to the second alignment direction E2 are configured to support the object 100 to be processed. According to this configuration, it is possible to realize a configuration in which the object to be processed 100 is stably supported without falling by a simple configuration in which the pair of support members 27A, 27A support the object to be processed 100. Further, since the object to be processed 100 is not suspended, it is possible to suppress the occurrence of tensile stress 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 being generated as residual stress in the object to be treated 100. Therefore, the mechanical strength of the object to be processed 100 can be further increased.

Also, 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, the vertical frame portions 22A and 23A can receive the object to be processed 100, so that the object to be processed 100 can be prevented 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 outside to the inside of the holder 2A through the vertical frame portions 22A to 25A. As a result, the heat treatment of the object to be treated 100 can be performed more evenly.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments. The present invention can be modified in various ways as long as it is described in the claims.

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

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

(3) Further, in the above-described embodiment, the embodiment in which 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 in the horizontal direction has been described as an example. .. However, this does not have to be the case. For example, as shown in 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 alignment direction E1 are inclined with respect to the horizontal plane. It may be arranged so as to be.

In the modified example shown in FIG. 14, the holder 2 is provided with the inclined posture support portion 29. The inclined posture support portion 29 is a rod-shaped member supported at both ends by the left and right vertical frame portions 24 and 25 of the holder 2. The object to be processed 100 is received by the inclined posture support portion 29 in an inclined posture 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 an inclined posture in the main radiation direction D2 with respect to the position of the lower part of the object to be processed 100. The object to be processed 100 is arranged in a state of being brought closer 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 to each other.

When the holder 2 is viewed from above, when the axial direction D1 and the main radiation direction D2 coincide with each other, the inferior angle formed by the axial direction D1 and the main radiation direction D2 is the inferior angle θ1 in the 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 a plan view (more accurately, a 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. Further, in the side view, the inferior angle formed by the axial direction D1 and the main radiation direction D2 becomes 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 modified example 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 tilted posture by being received by the block-shaped tilted posture support member 30 fixed to the pedestal 7.

Note that a configuration similar to the configuration of the holder 2 shown in FIGS. 14 and 15, that is, a configuration in which the object 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 inclined with respect to the horizontal direction. According to this configuration, the plurality of objects to be processed 100 can be arranged more appropriately in consideration of the weight balance of the plurality of objects to be processed 100 as a whole.

(4) Further, in the above-described embodiment, the embodiment in which the corresponding support members 27 and 27A of the holders 2 and 2A are fixed to the corresponding bottom frame portions 21 and 21A will be described as an example. However, this does not have to 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 rotate around the central axis of the support members 27, 27A. As a result, the object to be processed 100 mounted on the support members 27 and 27A can be rotated around the central axis B3 of the object to be processed 100. As a result, the stress generated in each part of the object to be processed 100 can be made more even, so that the thermal strain generated in the object to be processed 100 can be further reduced. Further, since the degree of exposure of the inner peripheral portion and the outer peripheral portion of the object to be treated 100 to the medium can be made more uniform, the heat treatment quality can be made more uniform.

(5) Further, in each of the above-described embodiments, the configuration in which the inferior angle θ1 formed by the axial direction D1 and the main radiation direction D2 is defined has been described. Any combination can be made for configurations other than this inferior angle.

(5) Further, in the above-described second embodiment, a mode in which the first ring row 41 and the second ring row 42 are alternately arranged in the second alignment direction E2 has been described as an example. However, this does not have to be the case. In the second embodiment, the two objects to be processed 100 adjacent to the first arrangement direction E1 need only be displaced from each other in the second arrangement direction E2, and the arrangement of the objects to be processed 100 may not be exemplified. Good.

<About thermal strain by type of placement of the object to be processed>
Example 1 and Comparative Example 1 were produced by carburizing a ring-shaped metal object to be treated using a heat treatment apparatus having the same configuration as that of the heat treatment apparatus 1 described in the first embodiment. The production 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 is set to zero. That is, the object to be treated, which was heat-treated in a state where the axial direction of the object to be processed and the main radiation direction coincided with each other, was designated as Example 1.
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 the heat treatment in a state where the object to be processed was arranged horizontally so that the axial direction of the object to be processed faces the vertical direction. Except for the inferior angle, Example 1 and Comparative Example 1 are heat-treated under the same conditions.

140 Examples 1 and 120 Comparative Example 1 were prepared. Then, elliptical strain (elliptical strain) was measured for each of Example 1 and Comparative Example 1. Specifically, for each of Example 1 and Comparative Example 1, the difference between the diameter at the largest diameter portion and the diameter at the smallest diameter portion is set as the amount of elliptical strain. Was measured as. Then, the average value of the elliptical strain amount in the plurality of Comparative Example 1 was defined as the reference strain amount. Then, the ratio of the strain amount to the reference strain amount was defined as the elliptical strain ratio. The results are shown in FIG. The vertical axis of FIG. 16 shows the elliptical strain ratio.

As shown in FIG. 16, in the plurality of Comparative Examples 1, when the elliptical strain amount was the largest, the elliptical strain ratio as the ratio of the strain amount to the reference strain amount reached as much as 200%. On the other hand, the average value of the elliptical strain amount in the plurality of Examples 1 was only about 60% of the reference strain amount. Further, among the plurality of Examples 1, even when the amount of elliptical strain was the largest, the elliptical strain ratio was only about 110%. That is, in Example 1, the elliptical distortion could be reduced to about half as compared with Comparative Example 1. As described above, it was demonstrated that Example 1 can make the elliptical strain extremely small.

<Relationship between the inferior angle between the axial direction and the main radiation direction of the object to be processed and the thermal strain>
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 and the main radiation direction of the object to be treated at the time of heat treatment is different. Have. Example 1, Example 2, Example 3, and Comparative Example 2 are all heat-treated in a vertical posture (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 °

5 Examples 2 were prepared, 5 Examples 3 were prepared, and 5 Comparative Example 2 were prepared. Then, the elliptical strain was measured for each of Example 2, Example 3, and Comparative Example 2. The results are shown in FIG. The display method of the elliptical distortion is the same as the display method shown in FIG. The vertical axis of FIG. 17 shows the elliptical strain ratio as in 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, when the amount of elliptical strain was the largest among the plurality of Comparative Examples 2, the elliptical strain ratio reached about 180%. Further, regarding the average value of the elliptical strain in the plurality of Comparative Examples 2, the elliptical strain ratio was about 90%. On the other hand, with respect to the maximum value of the amount of elliptical strain in the plurality of Examples 3, the elliptical strain ratio was only about 130%. Further, with respect to the average value of the amount of elliptical strain in the plurality of Examples 3, the elliptical strain ratio was only about 80%. Further, the elliptical strain ratio was only about 120% with respect to the maximum value of the elliptical strain amount in the plurality of Examples 2. Further, with respect to the average value of the amount of elliptical strain in the plurality of Examples 2, the elliptical strain ratio was only about 70%. Further, as described above, the elliptical strain ratio was only about 110% with respect to the maximum value of the elliptical strain amount in the plurality of Examples 1. Further, with respect to the average value of the amount of elliptical strain in the plurality of Examples 1, the elliptical strain ratio was only about 60%.

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

<Relationship between carbon potential and thermal strain in the furnace atmosphere>
Examples 4 to 6 and Comparative Example 3 were prepared by making the carbon potentials in the atmospheric gas different during the heat treatment of the object to be treated. The heat treatment conditions other than the carbon potential are the same for Examples 4 to 6 and Comparative Example 3. Specifically, the carbon potentials of Examples 4 to 6 and Comparative Example 3 at the time of heat treatment are as follows.

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

10 Examples 4 were prepared, 10 Examples 5 were prepared, 10 Examples 6 were prepared, and 10 Comparative Example 4 were prepared. Then, the elliptical strain was measured for each of Example 4, Example 5, Example 6, and Comparative Example 3. The results are shown in FIG. The display method of the elliptical distortion is the same as the display method shown in FIG. The vertical axis of FIG. 18 shows the elliptical strain ratio as in the vertical axis of FIG.

As shown in FIG. 18, when the amount of elliptical strain was the largest among the plurality of Comparative Examples 3, the elliptical strain ratio reached about 110%. On the other hand, with respect to the average value of the amount of elliptical strain in the plurality of Examples 6, the elliptical strain ratio was only about 50%. Further, among the plurality of Examples 6, even when the amount of elliptical strain was the largest, the elliptical strain ratio was only about 90%. Further, with respect to the average value of the amount of elliptical strain in the plurality of Examples 5, the elliptical strain ratio was only about 40%. Further, among the plurality of Examples 5, even when the amount of elliptical strain was the largest, the elliptical strain ratio was only about 80%. Further, with respect to the average value of the amount of elliptical strain in the plurality of Examples 4, the elliptical strain ratio was only about 55%. Further, among the plurality of Examples 4, even when the amount of elliptical strain was the largest, the elliptical strain ratio was only about 95%.

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

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

1 Heat treatment device 2, 2A holder 6 Heater unit (heat source)
31,31A 1st support 32,32A 2nd support 100 Object to be processed (metal parts)
100a Outer surface of the object to be treated B3 Central axis of the object to be processed Cp Carbon potential D1 Axial direction of the object to be processed D2 Main radiation direction θ1 Inferior angle θ2 Angle interval

Claims (10)

A metal object to be processed formed in a circular shape and a heat source for radiating heat in a predetermined main radiation direction face each other, and the heat source is arranged outside the object to be processed, and the object to be processed is provided. The arrangement step of arranging the object to be processed so that the inferior angle formed by the axial direction of the above and the main radiation direction is 45 ° or less (including zero).
A heating step of heating the object to be processed using the heat source,
Only including,
A method for manufacturing a metal part, characterized in that, in the arrangement step, a predetermined holder supports the outer peripheral surface of the object to be processed from below . The method for manufacturing a metal part according to claim 1.
A method for manufacturing a metal part, characterized in that, in the arrangement step, a plurality of the objects to be processed are arranged along the main radiation direction. The method for manufacturing a metal part according to claim 1 or 2 .
A method for manufacturing a metal part, wherein the holder supports the object to be processed in a state of line contact or point contact. The method for manufacturing a metal part according to claim 3 .
The holder supports the outer peripheral surface of the object to be processed by a first support portion and a second support portion separated in the circumferential direction of the outer peripheral surface.
A method for manufacturing a metal part, characterized in that the angular distance between the first support portion and the second support portion around the central axis of the object to be processed is set in the range of 20 ° to 60 °. The method for manufacturing a metal part according to any one of claims 1 to 4 .
A method for manufacturing a metal part, wherein in the heating step, the object to be treated is heated in an atmospheric gas set to a carbon potential in the range of 0.6% to 1.0%. The method for manufacturing a metal part according to any one of claims 1 to 5 .
The method for manufacturing a metal part, characterized in that the heating step is performed at least between the A1 transformation point and the A3 transformation point of the object to be processed. The method for manufacturing a metal part according to any one of claims 1 to 6 .
In the heating step, the object to be processed is heated from the A1 transformation point to the A3 transformation point at a temperature rise rate in the range of 0.5 ° C./min to 10 ° C./min. Method. The method for manufacturing a metal part according to any one of claims 1 to 7 .
A method for manufacturing a metal part, wherein the object to be treated is formed in a ring shape. The method for manufacturing a metal part according to claim 8 .
A method for manufacturing a metal part, wherein the object to be processed includes a race or a gear of a bearing. A heat source configured to radiate heat in a predetermined main radiation direction,
The circularly formed metal object to be processed and the heat source face each other, the heat source is arranged outside the object to be processed, and the axial direction of the object to be processed and the main A holder for arranging the object to be processed so that the inferior angle formed by the radiation direction is 45 ° or less (including zero).
Equipped with a,
The holder is a heat treatment apparatus that supports the outer peripheral surface of the object to be processed from below .

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