JP6630586B2 - Hot forging method and hot forging product manufacturing method - Google Patents

Description

  The present invention relates to a hot forging method for a metal material and a method for manufacturing a hot forged product, and more particularly, to a hot forging method used for hot forging a difficult-to-work metal material such as a titanium alloy or a nickel-based alloy. The present invention relates to a method and a method for manufacturing a hot forged product using the hot forging method.

  Generally, titanium alloys, nickel-based alloys, and the like have excellent mechanical properties and heat resistance, and are therefore used for engine members and structural members of transportation equipment such as aircraft and vehicles. A hot forging method using a hot forging die apparatus is used as a method for forging the above-described various members using a work material made of a difficult-to-work metal material such as a titanium alloy. The hot forging method is such that a heated work material is charged into a mold formed in advance to imitate a product shape, and the work material is stretched to a shape along the mold while maintaining the work material at a high temperature state. It is forged while deforming. By using the hot forging method, a metal flow that conforms to the product shape can be obtained during deformation during forging, so that a forged product that is more tenacious than other processing methods and has excellent mechanical properties such as impact fracture resistance is obtained. be able to.

  Examples of such a hot forging method are disclosed in Patent Documents 1 to 3 below. For example, in Patent Document 1 below, as a hot forging method of a titanium alloy or a nickel-based alloy, a glass lubricant is applied to a surface of a work material such as a titanium alloy to form a film of the glass lubricant on the surface. A glass lubricant application step, a release agent application step of applying a release agent containing a solid lubricant to the molding surface of the mold, and heating the workpiece on which the glass lubricant film is formed to a forging temperature. And a hot forging step of forging using a mold in the above state. The application of the glass lubricant (formation of the coating) is performed for the purpose of reducing the friction generated between the workpiece and the mold in the hot forging step, and obtaining the effect of keeping the workpiece warm. The release agent is applied for the purpose of, for example, preventing the glass lubricant coated on the surface of the workpiece from adhering to the mold and deteriorating the releasability.

JP 2014-213365 A JP 2013-208632 A JP 2013-530047 A

  In Patent Document 1, a mold release agent in a liquid state in which a solid lubricating component such as graphite or boron nitride is dispersed in a solvent such as water or mineral oil is applied to a mold. Here, the present inventors have found that when the temperature of the mold rises to 600 ° C. or higher, the Leidenfrost phenomenon occurs, the release agent does not adhere to the mold, and even if it adheres, the solid lubricating component evaporates in a short time. We paid attention to the point that it would do. That is, when a liquid release agent is applied to a high-temperature mold, a liquid layer in contact with the mold evaporates to form a vapor layer between the liquid and the mold. Is inhibited. For this reason, in the above-mentioned Patent Document 1, the release agent cannot be sufficiently adhered to the mold, and the glass lubricant coated on the workpiece adheres to the mold, and the releasability deteriorates. There is a fear.

  The present invention has been made in view of the above problems, and an object of the present invention is to improve the releasability in hot forging in which a workpiece coated with a glass lubricant is forged with a mold at 600 ° C. or higher. An object of the present invention is to provide a hot forging method and a method of manufacturing a hot forged product using the hot forging method.

The hot forging method according to one aspect of the present invention includes disposing a heated work material between a first mold and a second mold having at least one temperature of 600 ° C. or more, Is a hot forging method in which forging is performed so as to be stretched into a shape along the first molding surface of the first mold and the second molding surface of the second mold while maintaining the heating state. The hot forging method includes a step of coating the surface of the workpiece with a glass lubricant, and the workpiece coated with the glass lubricant between the first mold and the second mold. Disposing the workpiece and moving the first mold and the second mold relatively to each other so as to approach each other, so that the workpiece is stretched along the first molding surface and the second molding surface. Forging step. In the step of forging the workpiece, the sheet-like release material containing at least one solid lubricating component selected from the group consisting of graphite, carbon fiber, boron nitride, molybdenum disulfide and tungsten disulfide is used as the first material. Interposed between the molding surface and the glass lubricant and between the second molding surface and the glass lubricant. The release material includes a sheet-shaped first release material and a second release material containing at least one solid lubricating component selected from the group consisting of graphite, carbon fiber, boron nitride, molybdenum disulfide and tungsten disulfide. I have. The step of arranging the workpiece is a step of arranging the first release material on the second molding surface, and the step of arranging the workpiece coated with the glass lubricant on the first release material. And a step of disposing the second release material on a portion of the workpiece opposite to a portion disposed on the first release material. In the step of forging the workpiece, the second mold release material is interposed between the first molding surface and the glass lubricant, and the second molding material is interposed between the second molding surface and the glass lubricant. A first release material is interposed. The workpiece has a concave portion. The step of arranging the second release material, a step of arranging a first release sheet having an area in plan view before forging larger than the recess and smaller than the entire workpiece, covering the recess. Arranging a second release sheet having an area in plan view before forging larger than the entire workpiece to be processed on the first release sheet.

In the hot forging method, the surface of the workpiece is coated with a glass lubricant, and hot forging of the workpiece is performed in a state where a release material is interposed between the glass lubricant and a molding surface of a mold. Is The release material contains a high-melting point material such as graphite, carbon fiber, boron nitride, molybdenum disulfide, and tungsten disulfide as a solid lubricating component, and is formed in a sheet shape. For this reason, unlike the case where the solid lubricating component is applied to the mold in a state in which the solid lubricating component is dispersed in a liquid, the solid lubricating component volatilizes before forging even when the mold is heated to a high temperature of 600 ° C. or higher. It is possible to reliably exist between the glass lubricant and the molding surface of the mold without the need. Therefore, according to the hot forging method, it is possible to prevent the glass lubricant coated on the workpiece from attaching to the mold, and to improve the releasability of the forged product from the mold. it can. Further, by using two sheet-like release materials, it becomes easy to arrange the release material between the molding surfaces of the two molds and the glass lubricant coated on the workpiece. Therefore, it is possible to more reliably prevent the glass lubricant from adhering to the molding surface of the mold. Further, according to the above configuration, the first release sheet can be bent so as to enter the recess during forging. For this reason, even if the second release sheet is torn, it is possible to prevent the portion near the concave portion from being exposed to the mold.

  In the hot forging method, the first forming surface and the second forming surface may each be a continuous surface having no through-hole. Thereby, it becomes easy to arrange | position the sheet-shaped 1st release material and 2nd release material along the 1st molding surface and the 2nd molding surface.

  In the hot forging method, when the step of forging the workpiece is completed, the first release material covers the entire second molding surface, and the second release material covers the entire first molding surface. May be covered. This makes it possible to more reliably prevent the glass lubricant coated on the workpiece from adhering to the first molding surface and the second molding surface.

  In the hot forging method, at least one of the first release material and the second release material may have elasticity to expand and contract in a specific direction. Thus, the release material can be deformed following the deformation of the workpiece during forging. As a result, it is possible to prevent the glass lubricant coated on the workpiece from being exposed to the mold, and to more reliably prevent the glass lubricant from adhering to the molding surface.

  In the hot forging method, at least one of the first release material and the second release material may be arranged by stacking a plurality of release sheets. Thereby, even when a part of the release sheet is broken during forging, it is possible to prevent the glass lubricant from being exposed to the molding surface of the mold by another release sheet. As a result, it is possible to more reliably prevent the glass lubricant from adhering to the molding surface.

  In the hot forging method, each of the plurality of release sheets may have elasticity to expand and contract in a specific direction, and may be stacked so that the directions of expansion and contraction are different from each other. Thereby, even when the workpiece is deformed in multiple directions during forging, it is possible to follow the release sheets by expanding and contracting the release sheets in different directions. For this reason, it is possible to more reliably prevent the glass lubricant from being exposed to the mold and adhering to the molding surface of the mold.

  A method for manufacturing a hot forged product according to another aspect of the present invention is a method for manufacturing a forged product using the hot forging method. By using the above hot forging method, adhesion of the glass lubricant to the mold can be suppressed, and the releasability can be improved. As a result, a forged product can be manufactured efficiently.

  According to the present invention, a hot forging method in which releasability is improved in hot forging in which a workpiece coated with a glass lubricant is forged with a mold at 600 ° C. or higher, and the hot forging method are used. A method for manufacturing a hot forged product can be provided.

It is a flowchart which shows the flow of the hot forging method in Embodiment 1 of this invention, and the manufacturing method of a hot forged product. It is a schematic diagram which shows the cross-section of a workpiece. It is a schematic diagram which shows a mode that a to-be-processed material is heated in a furnace. It is a schematic diagram which shows the state which the surface of the to-be-processed material was covered with the glass lubricant. FIG. 4 is a schematic diagram showing a state in which a workpiece is disposed between an upper mold and a lower mold. It is a schematic diagram which shows the state where the hot forging of the workpiece was completed. FIG. 9 is a schematic diagram illustrating a state in which a release sheet is stacked on an upper surface of a workpiece in Embodiment 2 of the present invention. FIG. 13 is a schematic diagram illustrating a state in which a workpiece is arranged between an upper mold and a lower mold in Embodiment 3 of the present invention. FIG. 11 is a schematic diagram illustrating a state in which release sheets having different sizes are stacked on the upper surface of a workpiece in Embodiment 3 of the present invention. It is a mimetic diagram for explaining the hot forging method in other embodiments of the present invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
First, a hot forging method according to the first embodiment of the present invention and a method for manufacturing a hot forged product for manufacturing a forged product using the hot forging method will be described with reference to the flowchart of FIG. 1 and FIGS. . The flowchart of FIG. 1 shows the flow of each step in the hot forging method, and FIGS. 2 to 6 show the state of each step.

  First, as step S10, a step of preparing the workpiece 10 is performed. In this step S10, as shown in FIG. 2, a workpiece 10 having, for example, a column shape or a rectangular column shape having a rectangular cross section is prepared. The workpiece 10 includes an upper surface 10B, a lower surface 10A, and a side surface 10C connecting these. The workpiece 10 is made of a difficult-to-work metal material such as a titanium alloy, a nickel-based alloy, or stainless steel. As titanium alloys, Ti-10V-2Fe-3Al, Ti-6Al-4V, Ti-6Al-2Sn-4Zr-6Mo, Ti-5Al-2Sn-2Zr-4Mo-4Cr, Ti-5Al-5V-5Mo-3Cr , Ti-6Al-2Sn-4Zr-2Mo and the like. Then, as shown in FIG. 3, the workpiece 10 is placed in the heating furnace 2, and is heated until the whole reaches a forging temperature of about 700 to 1000 ° C. In addition, during the heat treatment of the workpiece 10 in this manner, the molds 3 and 4 (FIG. 5) for hot forging the workpiece 10 are provided by a built-in heater (not shown) or the like as necessary. It is heated to a temperature of about 1000 ° C.

Next, a step S20 of covering the surface of the workpiece 10 with the glass lubricant 11 is performed. In this step S20, as shown in FIG. 4, a glass lubricant 11 is applied so as to cover the entire surface (upper surface 10B, lower surface 10A, and side surface 10C) of the workpiece 10 after being heated. Is formed. The glass lubricant 11 is glass particles such as silicon oxide (SiO ₂ ) and boron oxide (B ₂ O ₃ ) having a particle diameter of several μm to several tens μm, and a binder component (resin component). , Water, and a liquid lubricant. By forming the film of the glass lubricant 11 in this manner, a warming effect of the workpiece 10 can be obtained, and the workpiece 10 can be maintained in a state heated to the forging temperature.

  Next, as step S30, a step of disposing the workpiece 10 between the molds is performed. In this step S30, by performing steps S31 to S33 described below in order, the workpiece 10 heated to the forging temperature and covered with the glass lubricant 11 is hot forged as shown in FIG. The device 1 is arranged between an upper mold 3 (first mold) and a lower mold 4 (second mold).

  Here, the configuration of the hot forging apparatus 1 will be described. The hot forging apparatus 1 includes an upper die 3, a lower die 4 vertically opposed to the upper die 3, a driving unit (not shown) for bringing the upper die 3 and the lower die 4 closer to each other. , Is provided. The upper die 3 presses the upper surface 10B of the workpiece 10 in the forging process, and has an upper molding surface 3A (first molding surface) on which irregularities imitating a product shape are formed. For example, the upper molding surface 3A is provided with an upper flat surface 3B located at the center and an annular upper bottom surface 3C surrounding the upper flat surface 3B.

  On the other hand, the lower mold 4 presses the lower surface 10A of the workpiece 10 in the forging process, and the lower molding surface 4A (second molding surface) on which irregularities simulating the product shape are formed similarly to the upper molding surface 3A. Molding surface). As shown in FIG. 5, the lower molding surface 4A has a vertically symmetric shape with respect to the upper molding surface 3A, and faces the lower flat surface 4B facing the upper flat surface 3B and the upper bottom surface 3C. And an annular lower bottom surface 4C. Each of the upper molding surface 3A and the lower molding surface 4A is formed of a continuous surface on which no through hole is formed.

  Next, a procedure for disposing the workpiece 10 between the upper mold 3 and the lower mold 4 will be described. First, in step S31, a first release material 22 made of a sheet material having a rectangular shape in plan view is disposed on the lower molding surface 4A of the lower mold 4. Since the first release material 22 is a flexible sheet material, the first release material 22 is arranged in a bent state along the uneven shape of the lower molding surface 4A as shown in FIG. The first release material 22 has a length substantially the same as the length along the uneven surface of the lower molding surface 4A, and is disposed so as to cover substantially the entire lower molding surface 4A. In addition, the first release material 22 may have elasticity that expands and contracts in a specific direction, for example, a rectangular diagonal direction, and in that case, the expansion ratio is 1% or more. The first release member 22 may have a shape other than a rectangular shape in plan view, and may be, for example, a circular sheet material, and is not particularly limited.

  The first release material 22 is a sheet material containing at least one solid lubricating component selected from the group consisting of graphite, carbon fiber, boron nitride, molybdenum disulfide and tungsten disulfide. Since these solid lubricating components have a melting point higher than the forging temperature, they function in a solid state during forging. More specifically, the first release material 22 is a woven fabric formed by combining a large number of carbon fibers in the vertical direction and the horizontal direction, and is a mesh-like carbon sheet in which carbon fibers are woven or twill-woven.

  The first release material 22 is adjusted in sheet thickness, weaving method, gaps between carbon fibers, and the like so as to suppress the seeping out of the semi-molten glass lubricant 11 during forging. Regarding the sheet thickness, the exudation amount of the glass lubricant 11 at the time of forging is large at 0.3 mm, and the exudation amount is small at 0.6 mm. Therefore, the sheet thickness of the first release material 22 is 0.6 mm or more. Has become. Regarding the weaving method, a plain weave made of carbon fibers is less likely to form a gap between the fibers than a twill weave of carbon fibers, and the bleeding of the glass lubricant 11 during forging is suppressed. It is preferably a woven fabric in which carbon fibers are plain woven. Further, the first release material 22 is not limited to a woven fabric, and may be a nonwoven fabric containing carbon fibers. Further, the first release material 22 may be a sheet material made of another solid lubricating component such as graphite, boron nitride, molybdenum disulfide or tungsten disulfide.

  Next, in step S32, the workpiece 10 covered with the glass lubricant 11 is disposed on the first release material 22. Specifically, as shown in FIG. 5, the workpiece 10 is heated on the lower molding surface 4A (the lower flat surface 4B) via the first release material 22 on the lower surface 10A in a state heated to the forging temperature. Be placed. As described above, since the first release material 22 is interposed between the workpiece 10 and the lower molding surface 4A, the glass lubricant 11 coated on the workpiece 10 directly contacts the lower molding surface 4A. Can be prevented.

  Next, in step S33, the second release material 21 is disposed on the upper surface 10B of the workpiece 10 (the portion opposite to the portion disposed on the first release material 22). The second release material 21 is a rectangular sheet material in a plan view similarly to the first release material 22, and has substantially the same size as the first release material 22. The second release material 21 is a flexible sheet, and has a length longer than the width W1 of the workpiece 10 and substantially the same as the length along the uneven surface of the upper molding surface 3A. For this reason, as shown in FIG. 5, the second release member 21 has a sheet central portion 21A covering the upper surface 10B of the workpiece 10 and a sheet end portion 21B closer to the end portion than the sheet central portion 21A due to gravity. It hangs down and covers the upper half of the side surface 10C of the workpiece 10. The sheet end portion 21B is a surplus portion when covering the upper surface 10B of the workpiece 10; however, by leaving the sheet end portion 21B, the entire upper molding surface 3A can be covered with the second release material 21 during forging. Can be. Similarly to the first release material 22, the second release material 21 is a sheet material containing at least one solid lubricating component selected from the group consisting of graphite, carbon fiber, boron nitride, molybdenum disulfide and tungsten disulfide. In addition, the glass lubricant 11 which is in a semi-molten state during forging can be prevented from seeping out. In addition, the second release material 21 may have elasticity that expands and contracts in a specific direction such as a rectangular diagonal direction, and in that case, the elasticity is 1% or more. The first release material 22 and the second release material 21 may be sheet materials of the same material or different sheet materials.

  Next, as step S40, step S40 of forging the workpiece 10 is performed. In this step S40, the drive unit (not shown) provided in the hot forging apparatus 1 lowers the upper mold 3 so as to approach the lower mold 4. Thereby, the upper molding surface 3A (the upper flat surface 3B) comes into contact with the second release material 21 (the sheet central portion 21A). By further lowering the upper mold 3 in this state, the workpiece 10 held in the heated state is pressed vertically by the upper molding surface 3A and the lower molding surface 4A, whereby the workpiece 10 is moved upward. It is deformed so as to be stretched along the molding surface 3A and the lower molding surface 4A. As a result, as shown in FIG. 6, a hot forged product 50 having a shape along the shape of the cavity 51 surrounded by the upper molding surface 3A and the lower molding surface 4A is obtained. In this process, the first and second release members 22 and 21 may extend so as to follow the deformation of the workpiece 10. Then, as shown in FIG. 6, at the time of completion of the forging step S40, the first release material 22 covers the entire lower molding surface 4A along the uneven surface of the lower molding surface 4A, and The release material 21 covers the entire upper molding surface 3A along the uneven surface of the upper molding surface 3A. Thereafter, the upper mold 3 is raised, and the hot forged product 50 is taken out of the lower mold 4.

  In the forging step S40, the second release material 21 is always interposed between the upper molding surface 3A and the glass lubricant 11 coated on the upper surface 10B of the workpiece 10, and the lower molding surface 4A is covered with the second molding material 21. The first release material 22 is always interposed between the processing material 10 and the glass lubricant 11 coated on the lower surface 10A. For this reason, the glass lubricant 11 coated on the workpiece 10 can be prevented from directly contacting the upper molding surface 3A and the lower molding surface 4A. In addition, since the first and second release materials 22 and 21 are sheet materials capable of suppressing the exudation of the glass lubricant 11, the first and second glass lubricants 11 which are in a semi-molten state during forging are formed. It is also possible to prevent the bleeding from passing through the mold release materials 22 and 21 to the upper and lower molding surfaces 4A and 3A.

  Therefore, in the present embodiment, the glass lubricant 11 coated on the workpiece 10 can be prevented from adhering to the upper and lower molding surfaces 4A and 3A. Therefore, the releasability of the hot forged product 50 is improved, and the hot forged product 50 can be easily separated from the dies 3 and 4 and taken out. Moreover, since the first and second release materials 22 and 21 adhere to the glass lubricant 11 during forging, the first and second release materials 22 and 21 are also removed when the hot forged product 50 is taken out of the dies 3 and 4. Can be taken out at the same time. For this reason, there is no need to perform the operation of removing the first and second mold release members 22 and 21 every time forging is completed separately from the operation of taking out the hot forged product 50, and the forged product can be efficiently and continuously produced. When the production efficiency is increased in this manner, the first and second release materials 22 and 21 are preferably formed of one sheet as in the present embodiment in order to easily stick to the glass lubricant 11. .

  Next, the features and effects of the hot forging method according to the present embodiment will be described.

  In the hot forging method, the heated workpiece 10 is arranged between the upper mold 3 and the lower mold 4 at a temperature of 600 ° C. or higher, and the upper mold is held while the workpiece 10 is kept in a heated state. In this method, forging is performed so as to extend the shape along the upper molding surface 3A and the lower molding surface 4A of the lower mold 4. The hot forging method includes a step S20 of coating the surfaces 10A to 10C of the workpiece 10 with the glass lubricant 11, and a step of coating the glass lubricant 11 between the upper mold 3 and the lower mold 4. A step S30 of disposing the workpiece 10 and a step of forging the workpiece 10 so that the upper mold 3 and the lower mold 4 are brought closer to each other to be stretched along the upper molding surface 3A and the lower molding surface 4A. S40. In the step S40 of forging the workpiece 10, sheet-like release materials 21 and 22 containing at least one solid lubricating component selected from the group consisting of graphite, carbon fiber, boron nitride, molybdenum disulfide and tungsten disulfide are formed. , Between the upper molding surface 3A and the glass lubricant 11, and between the lower molding surface 4A and the glass lubricant 11.

  In the hot forging method, the surfaces 10A to 10C of the workpiece 10 are covered with the glass lubricant 11, and the mold release materials 21 and 4 are provided between the glass lubricant 11 and the molding surfaces 3A and 4A of the molds 3 and 4. Hot forging of the workpiece 10 is performed in a state where the workpiece 22 is interposed. The release materials 21 and 22 include a material having a high melting point such as graphite, carbon fiber, boron nitride, molybdenum disulfide and tungsten disulfide as a solid lubricating component, and are formed in a sheet shape. Therefore, unlike the case where the solid lubricating component is applied to the molds 3 and 4 in a state where the solid lubricating component is dispersed in the liquid as in the related art, even when the molds 3 and 4 are heated to a high temperature of 600 ° C. or more, the glass lubricant 11 The solid lubricating component can be reliably present between the molds 3 and 4 and the molding surfaces 3A and 4A. Therefore, according to the hot forging method, it is possible to prevent the glass lubricant 11 coated on the workpiece 10 from adhering to the molds 3 and 4, and the releasability of the forged product from the mold. Can be improved.

  In the hot forging method, the step S30 of disposing the workpiece 10 includes, on the lower molding surface 4A, at least one selected from the group consisting of graphite, carbon fiber, boron nitride, molybdenum disulfide and tungsten disulfide. A step S31 of disposing a sheet-shaped first release material 22 containing two solid lubricating components, a step S32 of disposing the workpiece 10 covered with the glass lubricant 11 on the first release material 22, A step S33 of disposing a sheet-shaped second release material 21 containing at least one solid lubricating component selected from the group consisting of graphite, carbon fiber, boron nitride, molybdenum disulfide and tungsten disulfide on the upper surface 10B of the substrate 10; ,including. In the step S40 of forging the workpiece 10, the second release material 21 is interposed between the upper molding surface 3A and the glass lubricant 11, and the second release material 21 is interposed between the lower molding surface 4A and the glass lubricant 11. 1 Release material 22 is interposed. As described above, by using the two sheet-like release materials 21 and 22, the gap between the molding surfaces 3 </ b> A and 4 </ b> A of the two molds 3 and 4 and the glass lubricant 11 coated on the workpiece 10 is obtained. It is easy to arrange the release members 21 and 22. Therefore, it is possible to more reliably prevent the glass lubricant 11 from adhering to the molding surfaces 3A and 4A of the dies 3 and 4.

  In the hot forging method, the upper forming surface 3A and the lower forming surface 4A are formed by continuous surfaces having no through holes. This makes it easier to arrange the sheet-like release materials 21 and 22 along the molding surfaces 3A and 4A.

  In the above hot forging method, at the completion of the step S40 of forging the workpiece 10, the first release material 22 covers the entire lower molding surface 4A, and the second release material 21 covers the upper molding surface 3A. It is in a state of covering the whole. This makes it possible to more reliably prevent the glass lubricant 11 coated on the workpiece 10 from adhering to the upper molding surface 3A and the lower molding surface 4A.

  In the hot forging method, both or one of the first release material 22 and the second release material 21 has elasticity to expand and contract in a specific direction (for example, a diagonal direction). Thereby, the release materials 21 and 22 can be deformed following the deformation of the workpiece 10 during forging. As a result, the glass lubricant 11 coated on the workpiece 10 is prevented from being exposed to the molds 3 and 4, and the glass lubricant 11 is more reliably prevented from adhering to the molding surfaces 3A and 4A. can do.

(Embodiment 2)
Next, a hot forging method according to Embodiment 2 of the present invention will be described with reference to FIG. In the second embodiment, in the step S33 of arranging the second release material 25 on the upper surface 10B of the workpiece 10, the second release material 25 is arranged by stacking a plurality of release sheets 23 and 24, and It differs from the first embodiment in that each of the release sheets 23 and 24 has elasticity to expand and contract in a specific direction and is laminated so that the directions of expansion and contraction are different from each other. In the second embodiment, only the step S33 that is different from the first embodiment will be described. FIG. 7 shows a state in which the upper surface 10B of the workpiece 10 is viewed in plan. FIG. 7 shows a state where the release sheets 23 and 24 are unfolded in the horizontal direction.

  First, the lower release sheet 23 is arranged so as to cover the entire upper surface 10B of the workpiece 10. As shown in FIG. 7, the lower release sheet 23 is a rectangular sheet material having an area larger than the upper surface 10B in plan view, and has the same material and sheet structure as the second release material 21 of the first embodiment. It has. The lower release sheet 23 has elasticity to expand and contract in diagonal directions D1 and D2 (expansion and contraction directions). The expansion and contraction rate of the sheet in the expansion and contraction directions D1 and D2 is 1% or more. The lower release sheet 23 may have a stretching direction in a direction other than the diagonal directions D1 and D2, or may have a certain degree of stretching in directions other than the diagonal directions D1 and D2. Good. Further, the lower release sheet 23 is not limited to a rectangular shape, and may be a shape other than a rectangular shape such as a circular shape.

  Next, the upper release sheet 24 is laminated on the lower release sheet 23. The upper release sheet 24 is a rectangular sheet material having substantially the same size as the lower release sheet 23, and has the same material and sheet structure as the second release material 21 of the first embodiment. . The upper release sheet 24 also has elasticity to expand and contract in diagonal directions D3 and D4 (extending and contracting directions). The expansion ratio in the expansion directions D3 and D4 is 1% or more. Note that the upper release sheet 24 may also have a stretching direction in a direction other than the diagonal directions D3 and D4, or may have a certain degree of stretching in directions other than the diagonal directions D3 and D4. . Further, the upper release sheet 24 is not limited to a rectangular shape, and may be a shape other than a rectangular shape such as a circular shape.

  Here, the upper release sheet 24 is stacked such that the expansion and contraction directions D3 and D4 are different from the expansion and contraction directions D1 and D2 of the lower release sheet 23. That is, the upper and lower release sheets 23 and 24 are stacked so that the directions of expansion and contraction are different from each other. As shown in FIG. 7, in the present embodiment, the upper and lower release sheets 23 and 24 are shifted from each other by 45 ° about the center axis C of the concave portion 10D formed at the center of the workpiece 10. It is laminated. That is, the stretching direction D3 is shifted to form an angle of 45 ° with respect to the stretching directions D1 and D2, and the stretching direction D4 is also shifted so as to form an angle of 45 ° to the stretching directions D1 and D2. I have.

  As described above, in the second embodiment, by disposing the second release material 25 in which the plurality of release sheets 23 and 24 are stacked on the upper surface 10B of the workpiece 10, a part of the release sheet is broken during forging. In this case, the upper surface 10B can be covered with another release sheet, and the glass lubricant 11 can be prevented from being exposed to the upper molding surface 3A of the upper mold 3. As a result, it is possible to more reliably prevent the glass lubricant 11 from adhering to the upper molding surface 3A. In addition, the heat insulating property of the workpiece 10 is improved, and the workpiece 10 can be more easily deformed during forging, and the molding accuracy can be improved.

  Further, since the plurality of release sheets 23 and 24 have elasticity to expand and contract in a specific direction (diagonal direction) and are stacked so that the expansion and contraction directions D1 to D4 are different from each other, the workpiece 10 is formed during forging. Even in the case of deformation in a plurality of directions, it is possible to follow the release sheets 23 and 24 by expanding and contracting them in different directions. That is, even if the direction of expansion and contraction of the release sheets 23 and 24 is limited to a specific direction, the release sheets 23 and 24 can be deformed by following the deformation of the workpiece 10. Can be. Therefore, it is possible to prevent the workpiece 10 from being exposed to the upper mold 3.

  Further, in the present embodiment, the case where the two release sheets 23 and 24 are laminated has been described. However, the present invention is not limited to this, and three or more release sheets may be laminated so that the directions of expansion and contraction are different from each other. Similarly, the first release material covering the lower surface 10A of the workpiece 10 may be formed by laminating a plurality of release sheets so that the directions of expansion and contraction are different from each other.

(Embodiment 3)
Next, a hot forging method according to Embodiment 3 of the present invention will be described with reference to FIGS. The third embodiment differs from the first embodiment in that a plurality of release sheets 27 and 28 having different sizes are stacked in step S33 of disposing the second release material 26 on the upper surface 10B of the workpiece 10. I have. In the third embodiment, only the step S33 different from the first embodiment will be described. FIG. 8 shows a state where the workpiece 10 is disposed between the upper mold 3 and the lower mold 4. FIG. 9 shows a state in which the upper surface 10B of the workpiece 10 is viewed in plan. FIG. 9 shows a state in which the release sheets 27 and 28 are expanded in the horizontal direction.

  As shown in FIGS. 8 and 9, a concave portion 10 </ b> D recessed toward the lower surface 10 </ b> A is formed in the center of the upper surface 10 </ b> B of the workpiece 10. The concave portion 10D has a side wall surface 10E along the height direction and a bottom wall surface 10F, and has a depth at which the bottom wall surface 10F is located closer to the upper surface 10B than the center of the workpiece 10 in the height direction. Is formed. The concave portion 10D has a circular shape in plan view, but is not limited thereto. For example, the concave portion 10D may have a shape other than a circular shape such as a rectangular shape.

  First, the first release sheet 27 is arranged on the upper surface 10B so as to cover the recess 10D. As shown in FIG. 9, the first release sheet 27 is a rectangular sheet material having an area in plan view before forging larger than the concave portion 10D and smaller than the entire upper surface 10B of the workpiece 10. It has the same material and sheet structure as the second release material 21 of the first embodiment. Therefore, in a state where the first release sheet 27 is disposed, a part of the upper surface 10B of the workpiece 10 is exposed.

  Next, the second release sheet 28 is stacked on the first release sheet 27. The second release sheet 28 is a rectangular sheet material whose area in plan view before forging is larger than the entire upper surface 10B of the workpiece 10, and is made of the same material and material as the second release material 21 of the first embodiment. It has a sheet structure. Therefore, the second release sheet 28 is disposed so as to cover the entire upper surface 10B of the workpiece 10. As shown in FIG. 8, a portion of the second release sheet 28 that extends outside the upper surface 10 </ b> B hangs down due to gravity and covers the side surface 10 </ b> C of the workpiece 10.

  As described above, when the workpiece 10 has the concave portion 10D, a strong force is applied to the sheet portion near the concave portion 10D during forging, and the sheet may be broken. On the other hand, in the present embodiment, the first release sheet 27 having a smaller area than the upper surface 10B can be bent so as to enter the recess 10D during forging. Therefore, even if the second release sheet 28 is torn during the forging, the portion near the concave portion 10D can be prevented from being exposed to the upper mold 3 by the first release sheet 27. .

  In the third embodiment, the case where one concave portion 10D is formed in the workpiece 10 has been described. However, the present invention is not limited to this, and can be similarly applied to a workpiece in which a plurality of concave portions are formed. Further, the present invention is not limited to the concave portion 10D formed at the center of the workpiece 10, and may be applied to a notched concave portion formed at the outer edge of the workpiece 10. Also, in the third embodiment, similarly to the second embodiment, the first and second release sheets 27 and 28 have elasticity that expands and contracts in a specific direction, and are laminated so that the directions of expansion and contraction are different from each other. May be.

(Other embodiments)
Finally, other embodiments of the present invention will be described.

  In the first embodiment, the case where the adhesion of the glass lubricant 11 to the molding surfaces 3A and 4A is suppressed using the two sheet-like release materials 21 and 22 has been described, but the invention is not limited to this. For example, as shown in FIG. 10, one sheet-like release material 29 is arranged so as to cover the entire surface of the workpiece 10, and the glass lubricant 11 covering the upper surface 10B is directly on the upper molding surface 3A during forging. The glass lubricant 11 that does not contact and that covers the lower surface 10A may not directly contact the lower molding surface 4A. Also in this case, similarly to the first to third embodiments, it is possible to prevent the glass lubricant 11 from adhering to the molding surfaces 3A and 4A and deteriorating the releasability.

  In the first embodiment, the case where the upper mold 3 is lowered toward the lower mold 4 has been described. However, the present invention is not limited to this, and the lower mold 4 may be moved toward the upper mold 3. The molds 3 and 4 are not limited to being moved in the vertical direction, but may be moved in the horizontal direction, or may be moved in an oblique direction with respect to the vertical direction and the horizontal direction.

  In the above embodiment, as the release material, not only a material having elasticity in a specific direction but also a material having elasticity (ductility) in a plurality of directions or all directions may be used. Thereby, cracks (or cuts) of the release material are more reliably prevented.

  The embodiments disclosed this time are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

3 Upper mold (first mold)
3A Upper molding surface (first molding surface)
4 Lower mold (second mold)
4A Lower molding surface (second molding surface)
DESCRIPTION OF SYMBOLS 10 Work material 10D recessed part 11 Glass lubricant 21, 25, 26 2nd release material (release material)
22 1st release material (release material)
23 Lower release sheet (release sheet)
24 Upper release sheet (release sheet)
27 1st release sheet 28 2nd release sheet D1, D2, D3, D4 Expansion direction

Claims (7)

A heated workpiece is disposed between a first mold and a second mold having at least one temperature of 600 ° C. or higher, and the first mold is held while the workpiece is being heated. A hot forging method for forging so as to stretch to a shape along a first molding surface and a second molding surface of the second mold,
Coating the surface of the workpiece with a glass lubricant,
Disposing the workpiece coated with the glass lubricant between the first mold and the second mold;
Forging the workpiece so as to stretch along the first molding surface and the second molding surface by relatively moving the first mold and the second mold and approaching each other. Prepare,
In the step of forging the workpiece, the sheet-like release material containing at least one solid lubricating component selected from the group consisting of graphite, carbon fiber, boron nitride, molybdenum disulfide and tungsten disulfide is used as the first material. Interposed between the molding surface and the glass lubricant and between the second molding surface and the glass lubricant ,
The release material includes a sheet-shaped first release material and a second release material containing at least one solid lubricating component selected from the group consisting of graphite, carbon fiber, boron nitride, molybdenum disulfide and tungsten disulfide,
The step of arranging the workpiece,
Arranging the first release material on the second molding surface;
Placing the workpiece coated with the glass lubricant on the first release material;
Arranging the second release material on a portion of the workpiece opposite to a portion arranged on the first release material,
In the step of forging the workpiece, the second mold release material is interposed between the first molding surface and the glass lubricant, and the second molding material and the glass lubricant are interposed between the second molding surface and the glass lubricant. The first release material is interposed,
The workpiece has a concave portion,
The step of arranging the second release material includes:
A step of arranging a first release sheet having an area in plan view before forging larger than the recess and smaller than the entire workpiece, covering the recess.
Arranging, on the first release sheet, a second release sheet having a larger area in plan view before forging than the entire workpiece . The hot forging method according to claim 1 , wherein the first forming surface and the second forming surface are each formed of a continuous surface having no through hole. Wherein at the completion of the process of forging a workpiece, the first release material covers the entire second molding surface, and the second release material covers the entire first molding surface, according to claim 1 or 2 The hot forging method according to 1. The hot forging method according to any one of claims 1 to 3 , wherein at least one of the first release material and the second release material has elasticity. The hot forging method according to any one of claims 1 to 4 , wherein at least one of the first release material and the second release material is arranged by stacking a plurality of release sheets. The hot forging method according to claim 5 , wherein each of the plurality of release sheets has elasticity to expand and contract in a specific direction, and is stacked so that the directions of expansion and contraction are different from each other. A method for manufacturing a hot forged product, comprising manufacturing a forged product using the hot forging method according to any one of claims 1 to 6 .

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