JP2015199075A - Cooling structure and metal mold cooling device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the cooling effect of a casting metal mold and a steel material during molding and reduce a cooling temperature difference thereby preventing cracks, distortion, and deformation caused by heat stress.SOLUTION: A metal mold cooling device 10 includes: a metal mold 11; a heat conduction member 13; and a refrigerant supply part 20. An attachment seat 12 is provided on an upper surface of a female mold 11A of the metal mold 11. A hole part 16 is formed from a bottom part 15A of the attachment hole 15 of the attachment seat 12 toward the lower side. The heat conduction member 13 is made of graphite and fills the hole part 16. The refrigerant supply part 20 is attached to the opening side of the hole part 16 and supplies a coolant to an exposed surface 13B of the heat conduction member 13, which is exposed from the hole part 16, in a circulation manner.

Description

  The present invention relates to a cooling structure for cooling a cooling target such as a casting mold, and a mold cooling apparatus.

  2. Description of the Related Art Conventionally, an element that uses graphite having a structure in which graphene sheets are stacked is known as an element that dissipates heat by moving heat of a heat storage body that is a cooling target. For example, Patent Document 1 discloses a heat conductor in which a metal having a thermal conductivity lower than that of graphite is provided as a heat receiving portion that receives heat from an object to be cooled, and the metal is embedded in a part of graphite.

  Conventionally, as a method of cooling a steel material such as a mold, cooling water is circulated and supplied to a hole formed in the steel material to cool the steel material, or cooling water is inserted into a copper pipe inserted in the hole. There is known a method for cooling the steel material by flowing a gas (see Patent Document 2).

JP 2008-28283 A JP 2007-136512 A

  However, since graphite is generally brittle in composition and has a property of being easily broken, the thermal conductor of Patent Document 1 has a problem that the contact portion with the metal is easily broken and the lifetime as the thermal conductor is short. In addition, since a metal having a lower thermal conductivity than graphite is interposed as the heat receiving portion, it is not possible to realize efficient heat conduction compared to a heat conductor using graphite as the heat receiving portion.

  In addition, in the method of cooling the mold by supplying a coolant such as cooling water to the hole, the heat of the part up to the deep part of the hole is absorbed by the cooling water, so the cooling effect in the deep part of the hole is effective. There is a problem that it is low. In particular, in a casting mold for molding molten metal, it is necessary to cool the cavity in order to prevent adhesion between the molded product and the mold, and therefore the hole is formed to the vicinity of the cavity. Nevertheless, since the cooling effect in the deep part of the hole is low, the cavity is not sufficiently cooled, and adhesion between the molded product and the mold cannot be reliably prevented. Moreover, in the conventional cooling method, since parts other than the deep part of the hole are rapidly cooled first after molding, an excessive temperature difference is generated between the deep part and the other part. This excessive temperature difference causes excessive thermal stress in the mold. For this reason, there exists a possibility that a crack, distortion, and a deformation | transformation may arise in a metal mold | die with the said thermal stress. In particular, when a molten metal molded product is continuously formed using a mold, cracking, distortion, and deformation due to thermal stress are likely to occur because the mold is repeatedly heated and cooled.

  Therefore, the present invention has been made in view of the above circumstances, and its purpose is to increase the cooling effect of the steel material to be heated and the casting mold at the time of molding, and to suppress the cooling temperature difference and to crack and strain due to thermal stress. Another object of the present invention is to provide a cooling structure capable of preventing deformation and a casting mold.

  The cooling structure of the present invention includes a hole, a heat conducting member, and a refrigerant supply unit. The hole is formed from the surface of the casting mold to be cooled toward the inside. The heat conducting member is made of graphite and fills the hole. The refrigerant supply unit is mounted on the opening side of the hole and circulates and supplies the refrigerant to the exposed surface of the heat conducting member exposed from the hole.

  The cooling structure of the present invention is attached to a hole formed from the surface of a steel material to be cooled toward the inside, a heat conductive member made of graphite filled in the hole, and an opening side of the hole. And a refrigerant supply part that circulates and supplies the refrigerant to the exposed part of the heat conducting member exposed from the hole part.

  The mold cooling apparatus of this invention is equipped with a metal mold | die, a heat conductive member, and a refrigerant | coolant supply part. The mold has a hole formed from the surface toward the inside. The heat conducting member is made of graphite and fills the hole. The refrigerant supply unit is mounted on the opening side of the hole and circulates and supplies the refrigerant to the exposed surface of the heat conducting member exposed from the hole.

  Since the cooling structure is configured in this way, the heat in the deep part of the hole is efficiently transferred to the refrigerant supply part through the heat conducting member. And the heat is heat-exchanged by the refrigerant | coolant supplied by circulation in a refrigerant | coolant supply part. Thereby, the deep part of a hole can be cooled efficiently.

  In the cooling structure and the mold cooling apparatus, the heat conducting member is preferably a layer structure in which graphene sheets are stacked in a direction perpendicular to the depth direction of the hole.

  If it is this structure, absorption of the heat | fever until it reaches a deep part in a hole is suppressed, and the heat of the deep part of a hole is efficiently heat-transferred to a refrigerant | coolant supply part by a heat conductive member. This makes it difficult for an excessive temperature difference to occur in the mold and suppresses thermal stress, thereby preventing cracks, distortion, and deformation due to thermal stress.

  Moreover, in the cooling structure and the mold cooling apparatus, it is preferable that the heat conducting member is filled in the hole portion in close contact with the inner surface of the hole portion.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to raise the cooling effect of the casting metal mold | die at the time of shaping | molding, and to suppress a cooling temperature difference and to prevent the crack, distortion, and deformation | transformation by a thermal stress.

FIG. 1 is a perspective view showing a configuration of a mold cooling apparatus according to an embodiment of the present invention. FIG. 2 is a central sectional view of the mold cooling apparatus in FIG. FIG. 3 is a diagram for explaining a cooling effect confirmation test method for the mold of the mold cooling apparatus in FIG. 1. FIG. 4 is a graph showing a change in temperature after the cooling effect confirmation test for the mold in FIG.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. The embodiment described below is merely an example embodying the present invention, and the embodiment of the present invention can be changed as appropriate without departing from the scope of the present invention.

  The mold cooling apparatus 10 (refer FIG. 1) which concerns on embodiment of this invention is an apparatus for cooling the metal mold | die 11 for casting used in order to shape | mold the molded product of a molten metal continuously. As shown in FIG. 1, the mold cooling apparatus 10 includes a mold 11, a heat conducting member 13, and a refrigerant supply unit 20.

  The mold 11 is made of a steel material (steel material) such as SKD steel. The mold 11 has a female mold 11A and a male mold 11B. Each of the female mold 11A and the male mold 11B is formed with a recess, and the cavity 14 (see FIG. 2) is formed by each recess by joining the female mold 11A and the male mold 11B up and down. The cavity 14 is formed in a shape corresponding to the molded product. The molten metal (molten metal) is poured directly into the cavity 14, and then cooled and hardened to form a metal molded product. 1 and 2, a mold cooling device 10 having a cylindrical mold 11 is shown, but this is schematically shown for convenience of explanation, and the present invention. The mold cooling apparatus 10 is not limited to such a shape.

  A mounting seat 12 for mounting the coolant supply unit 20 is provided on the upper surface of the female mold 11A of the mold 11. The mounting seat 12 is provided at the center of the upper surface of the female die 11A, and is integrally formed with the female die 11A. As shown in FIG. 2, a mounting hole 15 is formed in the center of the upper surface of the mounting seat 12. The attachment hole 15 is for attaching the refrigerant supply unit 20 to the mold 11, and the bottom in the depth direction reaches the vicinity of the upper surface of the female die 11 </ b> A. Further, a hole 16 is formed downward from the bottom 15A of the attachment hole 15. The hole 16 is long in the vertical direction and has a smaller diameter than the mounting hole 13. The hole portion 16 is a vertical hole that extends downward from the bottom portion 15 </ b> A and has a lower end portion (deep portion) 16 </ b> A reaching the vicinity of the cavity 14. The hole 16 is formed in a cylindrical shape with a circular cross section, and its lower end 16A is formed in a hemispherical shape. The hole 16 is used for cooling the mold 11. The shape of the hole 16 is not limited to a circular cylindrical shape, and may be, for example, a quadrangular prism shape that is long in the vertical direction.

  In the mold 11 used for casting, the temperature change of the surface (the inner surface of the cavity 14) in contact with the molten metal is large. Moreover, heating and cooling are repeated frequently by forming a molded article continuously. For this reason, cracks due to thermal fatigue called heat tracks may occur on the inner surface of the cavity 14, or the inner surface of the cavity 14 and the molded product may adhere. Further, during molding, the temperature difference in the entire mold 11 becomes excessive, and thermal stress due to the temperature difference is generated, and the mold 11 may be cracked, distorted, or deformed by the thermal stress. Therefore, in this embodiment, the hole 16 is filled with the heat conducting member 13.

  The heat conducting member 13 is made of graphite and fills the hole 16 as described above. The heat conducting member 13 has a shape corresponding to the shape of the hole 16, that is, the cross section is circular, and its lower end 13A is formed in a hemispherical shape. For this reason, when the heat conducting member 13 is mounted in the hole 16, the heat conducting member 13 is filled in the hole 16 in a state of being in close contact with the inner surface of the hole 16. When the gap between the inner surface of the hole portion 16 and the heat conducting member 13 is not in close contact, a high heat conductive filler is attached to the inner surface of the rear portion 16, and then the heat conducting member 13 is removed. It may be attached to the part 16.

  The heat conducting member 13 is a layered structure in which graphene sheets are laminated in a direction perpendicular to the depth direction of the hole 16 (left and right direction in FIG. 2). The heat conducting member 13 is made of graphite having a crystal structure in which a plurality of graphene sheets formed by covalently bonding six-membered rings are stacked along one direction. Since the layers of each graphene sheet are bonded by van der Waals force, the graphene sheet has a property of being easily peeled off. On the other hand, the thermal conductivity in the direction along the layer surface of the graphene sheet (the vertical direction in FIG. 2) is extremely larger than the thermal conductivity in the direction orthogonal to the layer surface of the graphene sheet. Therefore, by adopting a layer structure in which graphene sheets are laminated in a direction orthogonal to the depth direction of the hole portion 16, the heat conducting member 13 has a portion from the upper opening to the lower end portion 16 </ b> A in the hole portion 16. It has a structure that hardly absorbs heat, and heat at the lower end 16A of the hole 16 can be efficiently conducted to the outside of the hole 16.

  In the present embodiment, highly oriented pyrolytic graphite having higher thermal conductivity than general graphite is employed as the material of the heat conducting member 13. Specifically, the heat conducting member 13 is manufactured by US MINTEQ International Inc. The product name “PYROID HT” is manufactured. In this highly oriented pyrolytic graphite, the thermal conductivity in the direction along the layer surface is much higher than the thermal conductivity in the direction orthogonal to the layer surface of the graphene sheet. Specifically, the thermal conductivity in the direction along the layer surface is 1500 W. The thermal conductivity in the direction perpendicular to the layer surface is 5 to 10 W / mk.

  The refrigerant supply unit 20 is mounted on the opening side of the hole 16 and circulates and supplies cooling water (refrigerant) to the exposed surface 13B of the heat conducting member 13 exposed from the hole 16. Specifically, the refrigerant supply unit 20 includes a first joint 21 that is attached to the attachment hole 15 of the attachment seat 12 and a second joint 22 that is attached to the upper end of the first joint 21. Furthermore, a pipe 29 for passing cooling water is provided inside the refrigerant supply unit 20. A water supply port 27 is formed on the side surface of the first joint 21, and a drain port 28 is formed on the side surface of the second joint 22. The second joint 22 is formed with a through hole 22 </ b> A continuous from the water supply port 27, and the upper end of the pipe 29 is attached to the outlet side of the through hole 22 (lower end in FIG. 2). The first joint 21 is formed with a through hole 21 </ b> A having a size into which the pipe 29 can be inserted. A drain port 28 communicates with the through hole 21A.

  The second joint 22 is connected to the first joint 21 such that the pipe 29 is inserted into the through hole 21A. In a state where the first joint 21 and the second joint 22 are connected, the inner hole of the pipe 29 constitutes a water supply path 33 (see FIG. 1) from the water supply port 27 to the exposed surface 13B. Further, a gap between the outer peripheral surface of the pipe 29 and the inner surface of the through-hole 21A is a drainage channel 34 (see FIG. 1) that guides the cooling water heat-exchanged from the opening 29A below the pipe 29 through the exposed surface 13A to the drainage port 28. Reference). As shown in FIG. 1, a water supply pipe 25 is connected to the water supply port 27 by a shaft coupling 23, and a drainage pipe 26 is connected to the drainage port 28 by a shaft coupling 24.

  In the mold cooling apparatus 10 configured as described above, when the mold 11 is cooled, cooling water is supplied from the water supply pipe 25. The supplied cooling water is conveyed to the bottom 15A of the mounting hole 15 through the water supply channel 33, and exchanges heat with the exposed surface 13B while being in contact with the exposed surface 13B of the heat conducting member 13. Thereafter, the cooling water warmed by heat exchange is conveyed to the drain outlet 28 through the drainage channel 34 and discharged from the drainage pipe 26.

  As described above, in the present embodiment, unlike the conventional configuration in which the cooling water is circulated and supplied to the hole 16, the heat conductive member 13 made of graphite is filled in the hole 16 and the exposed surface 13 </ b> B is filled. The cooling water is circulated and supplied. In addition, as described above, the heat conductive member 13 has a configuration in which the portion of the hole 16 extending to the lower end 16A has a low thermal conductivity and has a high thermal conductivity with respect to the heat at the lower end 16A of the hole 16. It has become. Therefore, when the cooling water is circulated and supplied to the exposed surface 13B of the heat conducting member 13, the heat of the lower end portion 16A of the hole 16 transmitted through the heat conducting member 13 is exchanged with the cooling water. Thereby, it is possible to efficiently cool only the heat in the vicinity of the lower end portion 16A of the hole 16 without extremely cooling the other portion of the mold 11. As a result, the cooling effect of the mold 11 at the time of molding can be enhanced by heat exchange with the cooling water, and the cooling temperature difference in the entire mold 11 is reduced, so that cracks, distortion, and deformation due to thermal stress are reduced. It becomes possible to prevent.

  Hereinafter, the cooling effect of the female mold 11A of the mold 11 during cooling by the mold cooling apparatus 10 will be described with reference to FIGS. FIG. 3 is a view for explaining a cooling effect confirmation test method for the female die 11A. FIG. 4A is a graph showing a temperature change at the position P1 of the female die 11A. FIG. 4B is a graph showing a temperature change at the position P2 of the female die 11A. In FIG. 3, the refrigerant supply unit 20 is not shown for convenience of explanation.

  As shown in FIG. 3, in the cooling effect confirmation test, first, the bottom surface of the female die 11 </ b> A of the mold 11 is directly heated by the heater 35 of 600 degrees. When the temperature of the bottom surface of the female die 11A reaches 470 degrees, the heater 35 is turned off, the heater 35 is removed from the female die 11A, the cooling water flow is started, and the cooling water is circulated and supplied for 60 seconds. The above test is performed on each of the female die 11A in which the hole 16 is not filled with the heat conducting member 13 and the female die 11A in which the heat conducting member 13 is filled in the hole 16, and the temperature of the female die 11A in each of them. Changes were measured. The measurement locations were two locations: a position P1 directly below the lower end portion 16A of the hole portion 16 and a position P2 slightly above the center portion in the vertical direction of the hole portion 16. A horizontal hole was formed from the side surface of the female die 11A to each position P1, P2, and a thermocouple was provided at each of the positions P1, P2 to measure the temperature.

  4A and 4B, a graph 41 indicated by a dotted line shows a temperature change of the female die 11A in which the heat conductive member 13 is filled in the hole 16 and the cooling water is circulated and supplied to the exposed surface 13B. A graph 42 indicated by a solid line shows a temperature change of the female die 11A in which the cooling water is circulated and supplied to the hole 16 without being filled with the heat conducting member 13. As shown in FIG. 4A, in each of the graphs 41 and 42, the temperature at the position P1 was 500 degrees before the start of cooling, but the temperature gradually decreased after the start of cooling. After cooling, the graph 41 decreases to 400 degrees and the graph 42 decreases to 350 degrees. There is a difference of about 50 degrees in the temperature of the position P1 after the test, and the cooling effect is slightly lower in the female die 11A filled with the heat conducting member 13, but both the temperatures are lowered at substantially the same reduction rate. It can be said that.

  On the other hand, as shown in FIG. 4B, in the graph 41, the temperature at the position P2 was 500 degrees before the start of cooling, but the temperature gradually decreased after the start of cooling, and the cooling for 60 seconds. After that, it drops to 400 degrees. In the heat conductive member 13, it means that the cooling of the heat | fever of the position P2 is suppressed. On the other hand, regarding the graph 42, the temperature at the position P2 was 600 degrees before the start of cooling, but it was rapidly cooled after the start of cooling, and decreased to 310 degrees after 10 seconds of cooling, and after 30 seconds of cooling. The temperature decreases to 200 degrees, the temperature gradually decreases from there, and decreases to 180 degrees after 60 seconds of cooling. This indicates that the heat at the position P2 is rapidly cooled by the cooling water that has passed through the hole 16.

  As can be understood from FIGS. 4A and 4B, in the case of the female die 11A not filled with the heat conducting member 13, the temperature difference in the female die 11A is caused by cooling the hole 16 with cooling water. Since there is 170 degrees, excessive thermal stress is likely to be generated in the female die 11A, and the thermal stress may cause cracking, distortion, and deformation in the female die 11A. However, in the case of the female die 11A filled with the heat conducting member 13, the heat around the hole 16 is absorbed by the heat conducting member 13 and heat exchange is performed by the cooling water from the exposed surface 13B. There is almost no temperature difference between them, so that no thermal stress is generated in the female die 11A, and problems such as cracking, distortion and deformation of the female die 11A due to the thermal stress do not occur.

  In the above description, the mold cooling device 10 is illustrated and described as an embodiment of the present invention. However, the present invention may be understood as a cooling structure including the hole 16, the heat conduction member 13, and the refrigerant supply unit 20. it can. Further, the cooling structure is not limited to the cooling of the mold 11 and can also be applied to the cooling of a heated steel material.

10: Mold cooling device 11: Mold 12: Mounting seat 13: Heat conduction member 14: Cavity 16: Hole 20: Refrigerant supply unit

Claims (7)

A hole formed from the surface of the casting mold to be cooled toward the inside;
A heat conducting member made of graphite filled in the hole;
A cooling structure comprising: a refrigerant supply unit that is mounted on the opening side of the hole and that circulates and supplies the refrigerant to the exposed surface of the heat conducting member exposed from the hole.   The cooling structure according to claim 1, wherein the heat conducting member is a layered structure in which graphene sheets are laminated in a direction orthogonal to the depth direction of the hole.   The cooling structure according to claim 1, wherein the heat conducting member is filled in the hole in a state of being in close contact with the inner surface of the hole. A hole formed from the surface of the steel material to be cooled toward the inside;
A heat conducting member made of graphite filled in the hole;
A cooling structure comprising: a refrigerant supply unit that is attached to the opening of the hole part and circulates and supplies the refrigerant to the exposed part of the heat conducting member that is exposed from the hole part. A mold having a hole formed from the surface toward the inside;
A heat conducting member made of graphite filled in the hole;
A mold cooling device, comprising: a refrigerant supply unit that is mounted on the opening side of the hole and that circulates and supplies the refrigerant to the exposed surface of the heat conducting member exposed from the hole.   The mold cooling apparatus according to claim 5, wherein the heat conducting member is a layer structure in which graphene sheets are laminated in a direction orthogonal to the depth direction of the hole.   The mold cooling device according to claim 5 or 6, wherein the heat conducting member is filled in the hole in a state of being in close contact with an inner surface of the hole.