JP7807191B2 - Molding device and molding method - Google Patents

Description

The present invention relates to a molding device and a molding method.

Conventionally, molding devices for molding heated metal materials are known. For example, Patent Document 1 below discloses a molding device equipped with a mold having a pair of lower and upper molds, a gas supply unit that supplies gas into the metal pipe material held between the molds, and a heating unit that heats the metal pipe material by electrical heating. This molding device also includes a cooling unit that flows water through a flow path formed in the mold to cool the heated metal pipe during molding. This allows the molding device to perform quench molding by bringing the cooled mold into contact with the metal pipe material.

Japanese Patent Application Laid-Open No. 2009-220141

In a molding device like the above-mentioned conventional technology, once the quench-forming of a heated metal material is completed, a new heated metal material is quench-formed. In this way, the molding device repeatedly quenches and forms the heated metal material. In other words, the mold repeatedly comes into contact with the high-temperature metal material. However, in the past, when a cooling unit cooled the mold, no consideration was given to the possibility of repeated molding. In this case, heat gradually accumulates in the mold, which can reduce the hardenability of the metal material. This creates the problem of reduced stability in the quality of the molded product, including its hardenability and formability, when repeated molding is performed.

The present invention was made to solve these problems, and its object is to provide a molding device and molding method that can improve the stability of the quality of molded products when repeated molding is performed.

One aspect of the present invention is a molding device for molding heated metal material, and includes a mold that performs hardening by contacting the metal material, and a cooling unit that cools the mold. The cooling unit suppresses a decrease in the hardenability of the metal material due to heat accumulation in the mold caused by repeated molding.

This type of forming device has a mold that performs hardening by coming into contact with the metal material. When the mold and heated metal material come into contact with each other, the temperature of the mold rises. In response to this, the cooling unit cools the mold, enabling the mold to be in a state where hardening can be performed. Furthermore, the cooling unit suppresses the deterioration of the hardenability of the metal material due to heat accumulation in the mold from repeated forming. Therefore, even if the mold receives repeated heat input from the metal material through repeated forming, the mold can perform repeated hardening without reducing its hardenability. As a result, the forming device can improve the stability of the quality of formed products when performing repeated forming.

The cooling unit may keep the mold temperature within a predetermined range. In this case, the cooling unit can make the mold temperature change pattern during molding more constant. Therefore, the molding device can improve the stability of the quality of molded products.

The cooling capacity of the cooling section may be increased as the number of molding cycles of the mold increases. The more molding cycles of the mold, the more likely heat will accumulate in the mold. Therefore, by increasing the cooling capacity of the cooling section as the number of molding cycles of the mold increases, heat accumulation in the mold can be suppressed.

The cooling capacity of the cooling section may be increased as the molding time of the mold becomes longer. The longer the molding time of the mold, the more likely heat will accumulate in the mold. Therefore, by increasing the cooling capacity of the cooling section as the molding time of the mold becomes longer, heat accumulation in the mold can be suppressed.

The molding device may be equipped with a temperature sensor that detects the temperature of the mold, and the cooling unit may adjust its cooling capacity based on the detection results of the temperature sensor. In this case, the cooling unit can adjust the mold to an appropriate temperature depending on the mold temperature.

One embodiment of the present invention relates to a forming device for forming heated metal material, and includes a mold that performs quench forming by contacting the metal material, and a cooling unit that cools the mold, with the cooling unit removing a greater amount of heat from the mold than the amount of heat input from the metal material to the mold.

This type of molding device has a mold that performs hardening by coming into contact with the metal material. When the mold and heated metal material come into contact with each other, the temperature of the mold tends to rise. In response to this, the cooling unit cools the mold, bringing the mold into a state where hardening is possible. Furthermore, the cooling unit makes the amount of heat removed from the mold greater than the amount of heat input from the metal material to the mold. In this case, the cooling unit can prevent the mold temperature from rising or lower the mold temperature that has risen. This makes it possible to prevent changes in hardenability caused by the mold temperature becoming too high when repeated molding is performed. As a result, the molding device can improve the stability of the quality of molded products when repeated molding is performed.

One embodiment of the forming method of the present invention is a forming method for forming a heated metal material, and includes a forming step in which the metal material is brought into contact with a mold to perform quench forming, and a cooling step in which the mold is cooled. The cooling step may suppress a decrease in the hardenability of the metal material due to heat accumulation in the mold caused by repeated forming.

This molding method achieves the same effects and benefits as the molding device described above.

One embodiment of the forming method of the present invention is a method for forming a heated metal material, and includes a forming step in which the metal material is brought into contact with a mold to perform quench forming, and a cooling step in which the mold is cooled. In the cooling step, the amount of heat removed from the mold is set to be greater than the amount of heat input from the metal material to the mold.

This molding method achieves the same effects and benefits as the molding device described above.

The present invention provides a molding device that can improve the stability of molded product quality when performing repeated molding.

1 is a schematic diagram of a molding device according to an embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view showing the state of the metal pipe material and the mold during blow molding. FIG. FIG. 10 is a plan view of the mold showing a state in which the first member has been removed. FIG. 4 is a cross-sectional view taken along line VV shown in FIG. FIG. 6 is a cross-sectional view taken along line VI-VI shown in FIG. 5. FIG. 10 is a graph showing the relationship between time and the temperature change of the mold. 10 is a graph showing the relationship between time and the temperature change of the mold. FIG. 10 is a cross-sectional view showing a mold of a molding device according to a modified example.

A preferred embodiment of the present invention will now be described with reference to the drawings. Note that identical or equivalent parts in each drawing will be designated by the same reference numerals, and duplicate explanations will be omitted.

Figure 1 is a schematic diagram of a molding apparatus 1 according to this embodiment. As shown in Figure 1, the molding apparatus 1 is an apparatus for molding a hollow metal pipe by blow molding. In this embodiment, the molding apparatus 1 is installed on a horizontal surface. The molding apparatus 1 includes a molding die 2, a drive mechanism 3, a holding unit 4, a heating unit 5, a fluid supply unit 6, a cooling unit 7, and a control unit 8. Note that in this specification, a metal pipe refers to a hollow article after molding in the molding apparatus 1 is completed, and a metal pipe material 40 (metal material) refers to a hollow article before molding in the molding apparatus 1 is completed. The metal pipe material 40 is a pipe material made of a steel type that can be hardened. Furthermore, among the horizontal directions, the direction in which the metal pipe material 40 extends during molding is sometimes referred to as the "longitudinal direction," and the direction perpendicular to the longitudinal direction is sometimes referred to as the "width direction."

The forming die 2 is a die used to form the metal pipe material 40 into a metal pipe, and includes a lower die 11 and an upper die 12 that face each other in the vertical direction. The lower die 11 and the upper die 12 are constructed from steel blocks. Each of the lower die 11 and the upper die 12 has a recess that accommodates the metal pipe material 40. When the lower die 11 and the upper die 12 are in close contact with each other (closed state), each recess forms a space of the target shape into which the metal pipe material is to be formed. Therefore, the surface of each recess becomes the forming surface of the forming die 2. The lower die 11 is fixed to the base 13 via a die holder or the like. The upper die 12 is fixed to the slide of the drive mechanism 3 via a die holder or the like.

The drive mechanism 3 is a mechanism that moves at least one of the lower mold 11 and the upper mold 12. In Figure 1, the drive mechanism 3 is configured to move only the upper mold 12. The drive mechanism 3 includes a slide 21 that moves the upper mold 12 so that the lower mold 11 and the upper mold 12 mate with each other, a pullback cylinder 22 that serves as an actuator that generates a force to pull the slide 21 upward, a main cylinder 23 that serves as a drive source that pressurizes the slide 21 downward, and a drive source 24 that applies a drive force to the main cylinder 23.

The holding unit 4 is a mechanism for holding the metal pipe material 40 disposed between the lower mold 11 and the upper mold 12. The holding unit 4 includes a lower electrode 26 and an upper electrode 27 that hold the metal pipe material 40 at one longitudinal end of the molding die 2, and a lower electrode 26 and an upper electrode 27 that hold the metal pipe material 40 at the other longitudinal end of the molding die 2. The lower electrode 26 and the upper electrode 27 on both longitudinal sides hold the metal pipe material 40 by sandwiching the ends of the metal pipe material 40 from above and below. Grooves having a shape corresponding to the outer peripheral surface of the metal pipe material 40 are formed on the upper surface of the lower electrode 26 and the lower surface of the upper electrode 27. The lower electrode 26 and the upper electrode 27 are provided with drive mechanisms (not shown) that allow them to move independently in the vertical direction.

The heating unit 5 heats the metal pipe material 40. The heating unit 5 is a mechanism that heats the metal pipe material 40 by passing electricity through the metal pipe material 40. The heating unit 5 heats the metal pipe material 40 between the lower mold 11 and the upper mold 12, while the metal pipe material 40 is separated from the lower mold 11 and the upper mold 12. The heating unit 5 includes the lower electrode 26 and upper electrode 27 on both sides of the longitudinal direction, as described above, and a power source 28 that applies current to the metal pipe material via these electrodes 26, 27. The heating unit may also be arranged in a process upstream of the molding device 1 and heat externally.

The fluid supply unit 6 is a mechanism for supplying high-pressure fluid into the metal pipe material 40 held between the lower mold 11 and the upper mold 12. The fluid supply unit 6 supplies high-pressure fluid to the metal pipe material 40, which has been heated in the heating unit 5 to a high temperature, thereby expanding the metal pipe material 40. The fluid supply unit 6 is provided on both longitudinal ends of the molding die 2. The fluid supply unit 6 includes a nozzle 31 that supplies fluid into the interior of the metal pipe material 40 from an opening at the end of the metal pipe material 40, a drive mechanism 32 that moves the nozzle 31 toward and away from the opening of the metal pipe material 40, and a supply source 33 that supplies high-pressure fluid into the metal pipe material 40 through the nozzle 31. The drive mechanism 32 tightly contacts the nozzle 31 with the end of the metal pipe material 40 while maintaining a seal during fluid supply and exhaust, and separates the nozzle 31 from the end of the metal pipe material 40 at other times. The fluid supply unit 6 may supply a gas such as high-pressure air or an inert gas as the fluid. The fluid supply unit 6 may also be integrated into the same device as the holding unit 4, which has a mechanism for moving the metal pipe material 40 in the vertical direction, and the heating unit 5.

The cooling unit 7 is a mechanism for cooling the molding die 2. By cooling the molding die 2, the cooling unit 7 is able to rapidly cool the expanded metal pipe material 40 when it comes into contact with the molding surface of the molding die 2. The cooling unit 7 includes flow paths 36 formed inside the lower die 11 and upper die 12, and a circulation mechanism 37 that supplies a cooling medium to the flow paths 36 and circulates it.

The control unit 8 is a device that controls the entire molding device 1. The control unit 8 controls the drive mechanism 3, holding unit 4, heating unit 5, fluid supply unit 6, and cooling unit 7. The control unit 8 repeatedly performs the operation of molding the metal pipe material 40 in the molding die 2.

Specifically, the control unit 8 controls the timing of transfer from a transfer device such as a robot arm to place the metal pipe material 40 between the open lower and upper dies 11 and 12. Alternatively, the control unit 8 may wait for an operator to manually place the metal pipe material 40 between the lower and upper dies 11 and 12. The control unit 8 also controls the actuators of the holding unit 4 to support the metal pipe material 40 with the lower electrodes 26 on both longitudinal sides, and then lower the upper electrode 27 to sandwich the metal pipe material 40. The control unit 8 also controls the heating unit 5 to electrically heat the metal pipe material 40. As a result, an axial current flows through the metal pipe material 40, and the metal pipe material 40 itself generates heat through Joule heat due to its own electrical resistance.

The control unit 8 controls the drive mechanism 3 to lower the upper die 12 and bring it close to the lower die 11, thereby closing the molding die 2. Meanwhile, the control unit 8 controls the fluid supply unit 6 to seal the openings at both ends of the metal pipe material 40 with the nozzle 31 and supply fluid. This causes the heated, softened metal pipe material 40 to expand and come into contact with the molding surface of the molding die 2. The metal pipe material 40 is then molded to conform to the shape of the molding surface of the molding die 2. When forming a metal pipe with a flange, a portion of the metal pipe material 40 is inserted into the gap between the lower die 11 and the upper die 12, and then the mold is closed to crush the inserted portion and form a flange. Once the metal pipe material 40 contacts the molding surface, it is rapidly cooled by the molding die 2, which is cooled by the cooling unit 7, thereby quenching the metal pipe material 40. This cooling method is called mold contact cooling or mold cooling. Immediately after quenching, austenite transforms into martensite (hereinafter, the transformation of austenite into martensite is referred to as martensitic transformation). In the latter half of the cooling process, the cooling rate slows down, and the martensite transforms into a different structure (troostite, sorbite, etc.) due to reheating. Therefore, a separate tempering process is not necessary. The control of the cooling unit 7 by the control unit 8 will be described later.

The molding procedure of the molding apparatus 1 will be described with reference to Figure 2. As shown in Figure 2(a), the control unit 8 closes the molding die 2 and supplies fluid to the metal pipe material 40 using the fluid supply unit 6, thereby performing blow molding (primary blow). In the primary blow, the control unit 8 molds the pipe portion 43 in the main cavity portion MC and causes the portion corresponding to the flange portion 44 to enter the sub-cavity portion SC. Then, as shown in Figure 2(b), the control unit 8 further closes the molding die 2, further crushing the portion that has entered the sub-cavity portion SC, thereby forming the flange portion 44. Next, the control unit 8 lifts the upper die 12 away from the metal pipe material 40, thereby performing mold opening. This results in the formation of the metal pipe 41.

Next, the detailed configuration of the mold 11 will be described with reference to Figures 3 to 6. Note that in the following explanation, the lower mold 11 will be described, but the same explanation applies to the upper mold 12, so the explanation will be omitted. Figure 3 is a plan view of the mold 11. Figure 4 is a plan view of the mold 11 showing the state with the first member 50 removed. Figure 5 is a cross-sectional view taken along line V-V shown in Figure 3. Figure 6 is a cross-sectional view taken along line VI-VI shown in Figure 5.

In this embodiment, the molding device 1 can mold two metal pipe materials 40 simultaneously. Therefore, as shown in FIG. 3, the mold 11 has a molding surface 47 for molding two metal pipe materials 40 arranged in parallel with each other (see also FIG. 2). The number of metal pipe materials 40 arranged is not limited and may be one, three, or more. The molding surface 47 has a shape that extends along the longitudinal direction of the metal pipe material 40 to correspond to the longitudinal direction of the metal pipe material 40. In the following description, the longitudinal direction of the molding surface 47 may be referred to as the X-axis direction, the horizontal direction perpendicular to the longitudinal direction as the Y-axis direction, and the up-down direction as the Z-axis direction. Furthermore, one side in the longitudinal direction is referred to as the positive side in the X-axis direction, one side in the direction perpendicular to the longitudinal direction as the positive side in the Y-axis direction, and the upper side as the positive side in the Z-axis direction.

As shown in Figures 4 and 5, the mold 11 is divided into three units U1, U2, and U3 in the X-axis direction, starting from the positive side. Unit U2 is the unit corresponding to the center position of the mold 11 in the X-axis direction. Units U1 and U3 are units on both ends in the X-axis direction. Each unit U1, U2, and U3 has a cooling area E1 (first area), a cooling area E2 (second area), and a cooling area E3 (third area). Each cooling area E1, E2, and E3 is surrounded on its entire periphery in plan view by a seal groove 90 in which an O-ring is disposed. The same description applies to units U1, U2, and U3 and cooling areas E1, E2, and E3 unless otherwise specified. In this embodiment, the mold 11 is divided into three units U1, U2, and U3. However, to achieve uniform cooling, including the cooling areas, the mold 11 may be treated as a single unit.

As shown in Figures 4 to 6, a flow path 60 for circulating a cooling medium (water) is formed inside the mold 11. The flow path 60 includes multiple cooling sections 61 (slit-shaped flow paths), a supply jacket section 62, a recovery jacket section 63, a supply communication section 64 (see Figures 5 and 6), and a discharge communication section 66 (see Figure 6). The die holder 91 supporting the mold 11 also includes a supply section 67 (see Figures 5 and 6) and discharge sections 68 and 69 (see Figure 6). The multiple cooling sections 61, supply jacket section 62, recovery jacket section 63, supply communication section 64, and discharge communication section 66 are provided as individual flow paths for units U1, U2, and U3 and cooling zones E1, E2, and E3. Meanwhile, the supply section 67 and discharge sections 68 and 69 are provided as common flow paths for units U1, U2, and U3 and cooling zones E1, E2, and E3.

The cooling section 61 is a section that primarily functions to cool the mold 11. The cooling section 61 is formed to extend in the Y-axis direction. Multiple cooling sections 61 are arranged side by side in the X-axis direction. The supply jacket section 62 is a section that supplies cooling medium to each cooling section 61. The supply jacket section 62 extends in the X-axis direction so as to be connected to the negative end of each cooling section 61 in the Y-axis direction. The recovery jacket section 63 is a section that recovers cooling medium from each cooling section 61 (see Figures 4 and 6). The recovery jacket section 63 extends in the X-axis direction so as to be connected to the positive end of each cooling section 61 in the Y-axis direction.

The supply communication section 64 connects the supply jacket section 62 and the supply section 67, thereby supplying cooling medium from the supply section 67 to the supply jacket section 62. One or more supply communication sections 64 are provided for the supply jacket section 62, and extend toward the negative side in the Z-axis direction. The discharge communication section 66 connects the recovery jacket section 63 and the discharge section 68, thereby discharging cooling medium from the recovery jacket section 63 to the discharge section 68 (see Figures 4 and 6). One or more discharge communication sections 66 are provided for the recovery jacket section 63, and extend toward the negative side in the Z-axis direction.

The supply unit 67 extends in the X-axis direction at the die holder 91 (see Figures 5 and 6). The positive end of the supply unit 67 in the X-axis direction opens from the die holder 91. A nozzle (not shown) that supplies cooling medium is inserted into this opening. The supply unit 67 distributes cooling medium to the supply communication units 64 of each unit U1, U2, and U3. The discharge unit 68 extends in the X-axis direction at the die holder 91 (see Figure 6). The discharge unit 69 extends from the positive end of the discharge unit 68 in the X-axis direction to the positive side in the Y-axis direction and opens from the die holder 91. A nozzle (not shown) that discharges cooling medium is inserted into this opening. The discharge units 68 and 69 commonly discharge cooling medium from the discharge communication units 66 of each unit U1, U2, and U3.

The mold 11 is divided into a first member 50 having a molding surface 47 that molds the metal pipe material 40, and a second member 51 that supports the first member 50 on the side opposite the molding surface 47. The first member 50 has a parting surface 50a on the negative side of the Z-axis direction. The second member 51 has a parting surface 51a on the positive side of the Z-axis direction. The first member 50 and the second member 51 are joined by bolts (or screws) while overlapping each other so that their parting surfaces 50a, 51a are in contact. The first member 50 can be removed from the second member 51 by removing the bolts (or screws) (see Figure 7). In this embodiment, the parting surfaces 50a, 51a are formed by planes extending parallel to the XY plane.

The thickness of the first member 50 is thinner than the thickness of the second member 51. Here, the thickness refers to the dimension on the negative side in the Z-axis direction. The surface on the positive side in the Z-axis direction of the first member 50 is formed to be curved according to the shape of the molding surface 47. Therefore, the thickness of the first member 50 varies depending on the location. The molding surface 47 is recessed furthest toward the negative side in the Z-axis direction at the position of unit U2, so the dividing surface 50a of unit U2 is positioned on the negative side in the Z-axis direction relative to the dividing surfaces 50a of the other units U1 and U3.

The material of the first member 50 is more durable against molding than the material of the second member 51. The material of the first member 50 is made of a higher-quality material that is harder and more wear-resistant than the material of the second member 51.

The second member 51 has a slit 53 that extends along the dividing surface 51a and opens at the dividing surface 51a. By joining the first member 50 and the second member 51, the slit 53 forms the cooling section 61, which is part of the flow path 60. The dividing surface 50a of the first member 50 is formed as a smooth surface without any slits. As a result, the slit 53 defines the bottom surface 61a and side surface 61b of the cooling section 61, and the dividing surface 50a of the first member 50 defines the top surface 61c of the cooling section 61 (see Figure 7(b)). In other words, by blocking the opening of the slit 53 with the first member 50, the cooling section 61, which is a flow path with a rectangular cross section, is formed.

The second member 51 has a jacket groove 54 that extends along the dividing surface 51a and opens at the dividing surface 51a. By joining the first member 50 and the second member 51, the jacket groove 54 forms the supply jacket portion 62 and the recovery jacket portion 63, which are part of the flow path 60. The dividing surface 50a of the first member 50 is formed as a smooth surface without any slits. As a result, the jacket groove 54 defines the bottom surface 62a and side surface 62b of the supply jacket portion 62, and the dividing surface 50a of the first member 50 defines the top surface 62c of the supply jacket portion 62 (see Figure 7(a)). In other words, by blocking the opening of the jacket groove 54 with the first member 50, the supply jacket portion 62, which is a flow path with a rectangular cross section, is formed. The same applies to the recovery jacket portion 63.

As shown in Figure 4, the arrangement of the slits 53 and jacket grooves 54 is similar to the arrangement of the cooling section 61, supply jacket section 62, and recovery jacket section 63 described above. That is, the slits 53 extend in the Y-axis direction, and multiple slits 53 are arranged in the X-axis direction. At both ends of the multiple slits 53 in the Y-axis direction, a jacket groove 54 for the supply jacket section 62 and a jacket groove 54 for the recovery jacket section 63 are formed for each slit 53. The slits 53 and jacket grooves 54 formed in each unit U1, U2, and U3 are positioned within the range of the seal groove section 90 surrounding each cooling region E1, E2, and E3.

The mold 11 has cooling regions E1, E2, and E3 at different positions in the X-axis direction. In cooling regions E1 and E3, multiple slits 53 are arranged at a first pitch P1. In cooling region E2, multiple slits 53 are arranged at a second pitch P2 that is shorter than the first pitch P1. As a result, the slits 53 in cooling region E2 are formed more densely than the slits 53 in cooling regions E1 and E3.

The cross-sectional area of the cooling section 61, defined by the slit 53, is smaller than the cross-sectional area of the supply jacket section 62 and the recovery jacket section 63 defined by the jacket groove 54. Specifically, as shown in Figure 7, the width W1 of the slit 53 is narrower than the width W2 of the jacket groove 54. Furthermore, the height H1 of the slit 53 is smaller than the height H2 of the jacket groove 54.

Next, with reference to Figures 5 and 8, the control of the cooling unit 7 by the control unit 8 will be described in detail. Note that while the following explanation focuses on cooling of the mold 11, the same explanation also applies to cooling of the mold 12. As shown in Figure 5, the circulation mechanism 37 of the cooling unit 7 supplies cooling medium to the supply unit 67. The circulation mechanism 37 is connected to the inlet of the supply unit 67 via piping 101. The circulation mechanism 37 also recovers the cooling medium discharged from the discharge unit 69. The circulation mechanism 37 cools the recovered cooling medium using a cooling device and supplies the cooling medium at a predetermined temperature to the supply unit 67.

The molding device 1 is equipped with a temperature sensor 100 that detects the temperature of the mold 11. The temperature sensor 100 transmits the detected temperature to the control unit 8. In Figure 5, the temperature sensor 100 is located inside the mold 11, close to the molding surface. However, the temperature sensor 100 may be located anywhere relative to the mold 11. For example, the temperature sensor 100 may be located inside the mold 11 at a position different from that shown in Figure 5, or it may be located on the surface of the mold 11.

The control unit 8 controls the cooling capacity of the cooling unit 7. Specifically, the control unit 8 controls the cooling capacity by adjusting the flow rate of the cooling medium supplied by the circulation mechanism 37. That is, the control unit 8 reduces the flow rate of the cooling medium to decrease the cooling capacity, and increases the flow rate of the cooling medium to increase the cooling capacity. However, the control unit 8 may adjust the cooling capacity not only by adjusting the amount of water but also by adjusting the temperature of the cooling medium. However, the flow rate is easier to adjust than the temperature.

Here, referring to Figure 8, we will explain how the temperature of the mold 11 changes when the molding apparatus 1 repeatedly molds to produce a large number of metal pipes. Figures 8(a) and (b) are graphs showing the relationship between time and temperature change of the mold 11. The horizontal coordinate axis in Figures 8(a) and (b) represents time from the start of molding. Solid line graphs TG1 and TG2 are graphs showing temperature change of the mold 11. The vertical coordinate axis (vertical axis on the left side of the page) represents the temperature of the mold 11 for graphs TG1 and TG2. Note that the temperature of the mold 11 can be measured at any location, whether on the molding surface or inside the mold. Two-dot chain line graphs FG1 and FG2 are graphs showing the flow rate of the cooling medium. The vertical coordinate axis (vertical axis on the right side of the page) represents the flow rate of the cooling medium for graphs FG1 and FG2.

8(a), when the molding device 1 performs the first molding, the heated metal pipe material 40 comes into contact with the mold 11. At this time, the heat contained in the metal pipe material 40 is input to the mold 11. Therefore, the temperature of the mold 11 rises (see part "A" in the figure). The minimum temperature point at the start of the first molding is designated "P1a." After the hardening of the metal pipe material 40 is completed and the metal pipe is removed from the mold 11, cooling by the cooling unit 7 is performed without heat input to the mold 11. Therefore, the temperature of the mold 11 drops (see part "B" in the figure). The maximum temperature point during the first molding is designated "P1b." Next, the molding device 1 performs the second molding before the temperature of the mold 11 returns to the temperature at the start of molding. This causes the temperature of the mold 11 to rise again (see part "C" in the figure). The minimum temperature point at the start of the second molding is designated "P2a." The maximum point in the second molding run is designated "P2b." At this time, the temperature of the minimum point P2a in the second molding run is higher than the temperature of the minimum point P1a in the first molding run. Furthermore, the temperature of the maximum point P2b in the second molding run is higher than the temperature of the maximum point P1b in the first molding run. In this way, from the start of molding to the specified number of molding runs, the temperatures of the minimum and maximum points gradually increase with each molding run.

After a certain number of molding cycles, the temperature rise in the mold 11 reaches saturation. When this state is reached, the temperatures of the minimum point Pma and the maximum point Pmb in a given molding cycle no longer change from the temperatures of the minimum point Pna and the maximum point Pnb in the previous molding cycle. Thereafter, molding is repeated with the temperatures of the minimum point and the maximum point remaining constant. In the following explanation, this state may be referred to as the "stable state."

Graph La is set, which passes through the minimum points in each molding, and graph Lb is set, which passes through the maximum points in each molding. Because graph FG1 shows the temperature change described above, graphs La and Lb curve upward toward the stable temperature for a certain period after molding begins, and then take on an asymptote-like shape that becomes a horizontal straight line once the stable state is reached.

In response to this, the control unit 8 controls the cooling unit 7 to suppress a decrease in the hardenability of the metal pipe material 40 due to heat accumulation in the mold 11 caused by repeated molding. For example, to achieve good hardening, it is preferable to set the temperature of the mold 11 to temperature T1 or below. The control unit 8 controls the cooling unit 7 so that the temperature of the mold 11 in a stable state is temperature T1 or below. In other words, to prevent the cooling capacity from being too low and the temperature of the mold 11 in a stable state from rising above temperature T1, the control unit 8 maintains the flow rate of the cooling medium at a high constant value (see graph FG1). The control unit 8 controls the temperature so that at least the minimum temperature in the saturated state is temperature T1 or below. Note that temperature T1 is a value that is appropriately set depending on the material and size of the mold 11 and the metal pipe material 40. For example, when setting temperature T1, the durability of the mold 11 should also be taken into consideration; if durability is low, temperature T1 may be kept low. For example, if the temperature of the mold 11 becomes too high, there is a risk that the strength of the mold will decrease due to tempering, etc., and that wear will be accelerated; however, by setting the temperature T1 in consideration of the durability of the mold 11, such risks can be reduced.

The control unit 8 also controls the cooling unit 7 so that the temperature of the mold 11 falls within a predetermined range. As described above, in a stable state, the graph TG1 shown in FIG. 8(a) falls within the range of the graph La consisting of constant minimum values and the graph La consisting of constant maximum values. However, even in a stable state, the maximum and minimum values in each molding may fluctuate slightly. In this case, the graphs La and Lb will have a shape that is distorted from the straight line shown in FIG. 8(a). However, even in this case, it is preferable that the fluctuations in the maximum and minimum values fall within a predetermined error range, as long as the stability of the hardenability of the metal pipe is not compromised.

The control unit 8 may increase the cooling capacity of the cooling unit 7 as the number of molding operations using the mold 11 increases. Furthermore, the control unit 8 may increase the cooling capacity of the cooling unit 7 as the molding time using the mold 11 increases. For example, the control unit 8 may control the flow rate of the cooling medium so that it follows the curve FG2 shown in FIG. 8(b). In this case, the control unit 8 keeps the flow rate of the cooling medium low at the start of molding and gradually increases it over time. In this case, the control unit 8 increases the flow rate of the cooling medium as the number of molding operations and the molding time increase. Note that the "molding time" here does not refer to the time required for one molding operation (the time corresponding to one peak in curve TG2), but rather refers to the total time for each molding operation when multiple molding operations are performed. Once a stable state is reached, the control unit 8 controls the flow rate of the cooling medium to remain constant.

In the control method of Figure 8(b), the control unit 8 intentionally reduces the cooling capacity of the cooling unit 7 at the start of molding. This allows the control unit 8 to quickly stabilize the temperature change of the mold 11. Specifically, at the start of molding, the temperature rise of graph TG2 is greater than the temperature rise of graph TG1. The time at which graph TG2 reaches a stable state is "t1," but the temperature of graph TG1 is still rising at "t1." Graph TG1 reaches a stable state a predetermined time after "t1." In other words, the control method of Figure 8(b) allows the mold 11 to quickly reach a stable state and quickly stabilize the quality of the molded product.

The control unit 8 may adjust the cooling capacity of the cooling unit 7 based on the detection results of the temperature sensor 100. For example, in the control of FIG. 8(b), the control unit 8 may detect that a stable state has been reached from the detection results of the temperature sensor 100. This allows the control unit 8 to maintain a constant flow rate of cooling medium at an appropriate timing. Furthermore, if the temperature of the mold 11 drops from the stable state temperature due to a temporary pause in the molding cycle, the control unit 8 may recognize this temperature drop based on the detection results of the temperature sensor 100. In this case, the control unit 8 may reduce the amount of cooling medium to increase the temperature of the mold 11 so that the temperature reaches a stable state.

Next, we will explain the operation and effects of the molding device 1 according to this embodiment.

The molding apparatus 1 according to this embodiment has molds 11 and 12 that perform quench forming by coming into contact with the metal material. The temperature of the molds 11 and 12 rises as the molds 11 and 12 come into contact with the heated metal material. In response to this, the cooling unit 7 cools the molds 11 and 12, thereby enabling the molds 11 and 12 to be in a state where quench forming is possible. Furthermore, the cooling unit 7 suppresses a decrease in the hardenability of the metal material due to heat accumulation in the molds 11 and 12 caused by repeated molding. Therefore, even if the molds 11 and 12 receive repeated heat input from the metal material during repeated molding, the molds 11 and 12 can repeatedly perform quench forming without a decrease in their hardenability. As a result, the molding apparatus 1 can improve the stability of the quality of molded products when performing repeated molding.

The cooling unit 7 may keep the temperature of the dies 11, 12 within a predetermined range. In this case, the cooling unit 7 can keep the temperature change pattern of the dies 11, 12 during molding closer to a constant pattern. Therefore, the molding device 1 can improve the stability of the quality of the molded product. That is, the temperature change pattern of the die 11 during the first molding in Figure 8(a) is different from the temperature change pattern of the die 11 during the fifth molding. Therefore, there is a difference in hardenability between the metal pipe produced by the first molding and the metal pipe produced by the fifth molding. In contrast, during molding under stable conditions, the dies 11, 12 can be molded with a constant temperature change pattern regardless of the number of moldings. This stabilizes the quality of the molded product.

The cooling capacity of the cooling unit 7 may be increased as the number of molding cycles of the molds 11 and 12 increases. The more molding cycles of the molds 11 and 12, the more likely heat will accumulate in the molds 11 and 12. Therefore, by increasing the cooling capacity of the cooling unit 7 as the number of molding cycles of the molds 11 and 12 increases, heat accumulation in the molds 11 and 12 can be suppressed.

The cooling capacity of the cooling unit 7 may be increased as the molding time of the molds 11, 12 becomes longer. The longer the molding time of the molds 11, 12, the more easily heat accumulates in the molds 11, 12. Therefore, by increasing the cooling capacity of the cooling unit 7 as the molding time of the molds 11, 12 becomes longer, heat accumulation in the molds 11, 12 can be suppressed.

The molding device 1 is equipped with a temperature sensor 100 that detects the temperature of the molds 11, 12, and the cooling unit 7 may adjust its cooling capacity based on the detection results of the temperature sensor 100. In this case, the cooling unit 7 can adjust the molds 11, 12 to an appropriate temperature depending on the temperature of the molds 11, 12.

The forming method according to this embodiment is a forming method for forming a heated metal material, and includes a forming step in which the metal material is brought into contact with a mold to perform quench forming, and a cooling step in which the mold is cooled. The cooling step may suppress a decrease in the hardenability of the metal material due to heat accumulation in the mold caused by repeated forming.

This molding method achieves the same effects and benefits as the molding device 1 described above.

The present invention is not limited to the above-described embodiments.

The pattern of the cooling medium flow paths formed in the mold is not limited to the above-described embodiment, and may be modified as appropriate as long as the pattern can effectively cool the mold.

The manner in which the control unit controls the cooling capacity is not limited to that shown in the above-described embodiment. For example, a control pattern such as that shown in Figure 9 may be adopted. Note that Figure 9 only shows graph La, which shows the change in the minimum value, and graph Lb, which shows the change in the maximum value, and does not include the temperature change graph. The temperature change graph will have a wave-like shape within the range of graphs La and Lb.

In Figure 9(a), the control unit 8 adjusts the cooling capacity so that it is very high. The flow rate in graph FG3 is higher than that in graph TG1 shown in Figure 8(a). In this case, the amount of heat removed from the molds 11, 12 by the cooling unit 7 during one molding operation is greater than the amount of heat input from the metal material to the molds 11, 12. In the control pattern of Figure 8, the molds 11, 12 were stable at a high temperature, but in the control pattern of Figure 9, they are stable at a low temperature.

In Figure 9(b), the control unit 8 adjusts the cooling capacity to allow the temperature of the molds 11 and 12 to rise, and then lowers the temperature once it reaches a predetermined temperature. As shown in graph FG4, at the start of molding, the control unit 8 limits the flow rate of the cooling medium to a low value, allowing a certain degree of temperature rise in the molds 11 and 12. When the control unit 8 determines, based on the detection results of the temperature sensor 100, that the temperature of the molds 11 and 12 has reached a predetermined temperature, it temporarily increases the flow rate of the cooling medium. As a result, the control unit 8 lowers the temperature of the molds 11 and 12 by increasing the amount of heat removed by the cooling unit 7 compared to the amount of heat input to the molds 11 and 12. When the control unit 8 determines, based on the detection results of the temperature sensor 100, that the temperature of the molds 11 and 12 has returned to approximately the initial stage, it reduces the flow rate of the cooling medium. Here, the control unit 8 sets the temperature range W of the molds 11 and 12 to a value large enough to prevent excessive changes in the quality of the molded product. As a result, the control unit 8 allows fluctuations in the temperature change patterns of the molds 11 and 12, but by limiting the extent of these fluctuations, it is possible to suppress variations in the quality of the molded product.

As described above, the cooling unit 7 removes more heat from the dies 11, 12 than the amount of heat input from the metal material to the dies 11, 12. In this case, the cooling unit 7 can prevent the temperature of the dies 11, 12 from rising, or can lower the temperature of the dies 11, 12 that has risen. This makes it possible to prevent changes in hardenability caused by the temperature of the dies 11, 12 becoming too high when repeated molding is performed. As a result, the molding device can improve the stability of the quality of molded products when repeated molding is performed.

The forming method according to this modified example is a method for forming a heated metal material, and includes a forming process in which the metal material is brought into contact with a mold to perform quenching, and a cooling process in which the mold is cooled. In the cooling process, the amount of heat removed from the mold is set to be greater than the amount of heat input from the metal material to the mold.

This molding method achieves the same effects and benefits as the molding device according to the modified example described above.

A mold 110 as shown in FIG. 10 may also be employed. The mold 110 shown in FIG. 10 comprises a lower mold 111, an upper mold 112, and a nested mold 113. The nested mold 113 is connected to the upper mold 112 via a damper 135. The lower mold 111, the upper mold 112, and the nested mold 113 have flow paths 131, 132, and 133 for circulating a cooling medium. The nested mold 113 has a protrusion 113a for molding complex shapes. With this mold 110, as shown in FIG. 10(a), when the upper mold 112 is lowered and closed, the nested mold 113 first comes into close proximity with the metal pipe material 300. As a result, when high-pressure fluid is supplied to the metal pipe material 300, a shape corresponding to the nested mold 113 is first molded. Then, when the upper die 112 is lowered, the final flanged molded product 301 is formed by the lower die 111, upper die 112, and nested die 113, as shown in Figure 10(b).

As mentioned above, when molding a complex part with a concave-convex shape, it is desirable to start molding at as high a temperature as possible. Therefore, by using the nested mold 113 as described above, the mold contact area in the concave-convex shape can be minimized. Therefore, expansion molding can be performed before the temperature of the metal pipe material 300 drops. Here, with the nested mold structure described above, it is believed that there is almost no heat transfer at the sliding area between the upper mold 112 and the nested mold 113. Therefore, the upper mold 112 and the nested mold 113 must be cooled independently of each other. If the mold temperatures differ, this can cause internal distortion in the molded product 301, affecting molding accuracy. Therefore, it is necessary to adjust the mold temperature by controlling the cooling medium flowing through the flow paths 131, 132, and 133 to minimize mold temperature differences between the lower mold 111, upper mold 112, and nested mold 113.

1...molding device, 7...cooling unit, 8...control unit, 11, 12...mold, 40, 300...metal pipe material (metal material), 100...temperature sensor, 111...lower mold (mold), 112...upper mold (mold), 113...nested mold (mold), 131, 132, 133...flow path (cooling unit).

Claims (3)

A forming apparatus for forming a heated metal material,
a mold that performs quench forming by contacting the metal material;
a cooling unit provided inside the mold and configured to cool the mold,
A molding device in which the cooling section increases its cooling capacity as the number of molding operations using the mold increases or the molding time becomes longer, and makes the cooling capacity constant when the temperature rise of the mold reaches saturation. Further provided is a temperature sensor for detecting the temperature of the mold;
The molding apparatus according to claim 1 , wherein the cooling unit adjusts a cooling capacity based on a detection result of the temperature sensor. A forming method for forming a heated metal material, comprising:
a forming step of performing quench forming by bringing the metal material into contact with a mold;
a cooling step of cooling the mold by a cooling section provided inside the mold,
A molding method in which, in the cooling step, the cooling capacity is increased as the number of moldings using the mold increases or the molding time becomes longer, and the cooling capacity is made constant when the temperature rise of the mold reaches saturation.