Method for manufacturing metal member

Abstract

Provided is a manufacturing method capable of ensuring the quality of a metal member manufactured by hot extrusion. A material (1) includes a tip surface (11), an outer peripheral surface (12), and a chamfered surface (13). At the start of extrusion, in a vertical cross-sectional view in a state in which a glass disk (4) and the material (1) are loaded into a container (2), an outer diameter Db of the tip surface (11) of the material (1) satisfies formula (1) in relation to a maximum dimension Dd in the radial direction of a die hole (31) and an inner diameter Dc of the container (2); when a virtual straight line (L1) connecting a connection point (P1) between the tip surface (11) and the chamfered surface (13) and a connection point (P2) between the chamfered surface (13) and the outer peripheral surface (12) is defined, an inclination angle θb of the virtual straight line (L1) with respect to a perpendicular line (VL) of an axial center (CL) of the container (2) satisfies formula (2); and the inclination angle θb, the outer diameter Db, the maximum dimension Dd, and the inner diameter Dc satisfy formula (3). (1): Dd ≤ Db ≤ Dd + 0.8 × (Dc - Dd), (2): 45° ≤ θb ≤ 65°

Description

Manufacturing method of metal member

[0001] The present disclosure relates to a method for producing a metal component by hot extrusion.

[0002] Hot extrusion is used to manufacture metal parts with a uniform cross-sectional shape in the longitudinal direction, such as seamless metal pipes, steel sections, and steel bars. In hot extrusion, a glass disk, which serves as a front lubricant, is placed in a container, and the heated raw material for the metal part is placed in the container. The raw material in the container is pressed against a die and extruded through the die hole. The shape of the die hole corresponds to the cross-sectional shape of the metal part to be produced. The raw material is extruded through the die hole to produce the metal part.

[0003] During hot extrusion, the glass disk softens when it comes into contact with the heated material. As the material is pressed toward the die, the softened glass fills the area around the die in the container, and the molten glass flows into the die hole along with the raw material. The molten glass that flows into the die hole acts as a lubricant, providing glass lubrication between the material and the die.

[0004] In hot extrusion, the higher the extrusion ratio (the ratio of the cross-sectional area of ​​the raw material to the cross-sectional area of ​​the metal component), the higher the extrusion load required, which increases the load on the die. Even with glass lubrication, excessive load on the die can easily cause seizure in the die. Die seizure causes deterioration of the surface quality and irregular shapes in the manufactured metal component (product). Die seizure also reduces the lifespan of the die itself.

[0005] For example, Japanese Patent Laid-Open Publication No. 2020-15057 (Patent Document 1) proposes a technology for reducing the load on a die by reducing the peak extrusion load that occurs at the beginning of extrusion. In this technology, the edge of a billet (material) on the die side is tapered, and the relationship between the taper half angle θB (°) of the billet and the die half angle θD (°) of the die is (θD - θB) = 5 to 20°. In a billet, the taper half angle θB is the inclination angle of the tapered surface formed on the edge of the billet on the die side relative to the axis. In a die, the die half angle θD is the inclination angle of the inlet side of the die relative to the axis. Patent Document 1 states that if the relationship between the taper half angle θB of the billet and the die half angle θD is within the above range, the load applied to the die during extrusion can be reduced when glass lubricated extrusion is applied.

[0006] Japanese Patent Application Laid-Open No. 2020-15057

[0007] The technology of Patent Document 1 focuses on the peak extrusion load that occurs at the beginning of extrusion, and specifies the relationship between the taper half angle θB of the billet (material) and the die half angle θD of the die. However, simply specifying this relationship may result in insufficient glass lubrication during periods other than the beginning of extrusion. This may cause the die to seize, resulting in a deterioration in the quality of the manufactured metal part.

[0008] An object of the present disclosure is to provide a method for manufacturing a metal component that can ensure the quality of the metal component manufactured by hot extrusion.

[0009] A manufacturing method according to the present disclosure is a method for manufacturing a metal component by hot extrusion. The manufacturing method includes a material preparation step, a heating step, a glass disk loading step, a material loading step, and an extrusion step. The material preparation step involves preparing a cylindrical material. The heating step involves heating the material. The glass disk loading step involves loading a glass disk into a cylindrical container. The material loading step involves loading the material into the container with the glass disk loaded. The extrusion step involves pressing the material loaded into the container toward a die having a die hole, and extruding the material through the die hole to produce a metal component.

[0010] The material charged into the container in the material charging step includes a leading edge surface disposed on the die side, an outer peripheral surface, and a chamfered surface connecting the leading edge surface and the outer peripheral surface. At the start of the extrusion step, in a vertical cross-sectional view with the glass disk and material charged into the container, the outer diameter Db of the leading edge surface of the material satisfies formula (1) in relation to the maximum radial dimension Dd of the die hole and the inner diameter Dc of the container. When a virtual line connecting the connection point between the leading edge surface and the chamfered surface and the connection point between the chamfered surface and the outer peripheral surface is defined, the inclination angle θb of the virtual line with respect to a perpendicular to the axis of the container satisfies formula (2). Furthermore, the inclination angle θb of the virtual line, the outer diameter Db of the leading edge surface of the material, the maximum dimension Dd of the die hole, and the inner diameter Dc of the container satisfy formula (3). Dd≦Db≦Dd+0.8×(Dc−Dd) (1) 45°≦θb≦65° (2)

[0011] According to the method for manufacturing a metal component according to the present disclosure, the quality of the metal component manufactured by hot extrusion can be ensured.

[0012] FIG. 1 is a schematic diagram showing an FEM analysis simulating hot extrusion. FIG. 2 is a longitudinal sectional view showing a state in which a glass disk and a raw material are loaded into a container. FIG. 3 is a diagram showing an image of the left side of formula (3). FIG. 4 is a diagram showing an image of the right side of formula (3). FIG. 5 is a flow diagram showing a method for manufacturing a metal member according to this embodiment. FIG. 6 is a longitudinal sectional view showing a state in which a glass disk and a raw material are loaded into a container in a method for manufacturing a metal member according to a second embodiment. FIG. 7 is a longitudinal sectional view showing a state in which a glass disk and a raw material are loaded into a container in a method for manufacturing a metal member according to a third embodiment. FIG. 8 is a longitudinal sectional view showing a state in which a glass disk and a raw material are loaded into a container in a method for manufacturing a metal member according to a fourth embodiment.

[0013] In order to solve the above problems, the present inventors conducted an FEM analysis simulating hot extrusion and investigated the behavior of the raw material during extrusion (metal flow). Based on the results of this investigation, they conducted extensive research and obtained the following findings.

[0014] FIG. 1 is a schematic diagram illustrating an FEM analysis simulating hot extrusion. In FIG. 1, the flow velocity distribution of the raw material 10 during extrusion is shown by contours in a longitudinal cross-sectional view of a cylindrical raw material 1, a cylindrical container 2, and a die 3. In this specification, the longitudinal cross-section refers to a cross-section including the axial center CL2 of the container 2. Similarly, the longitudinal cross-section of the raw material 1 and the die 3 also refers to a cross-section including the axial centers CL1 and CL3 of the raw material 1 and the die 3, respectively. When the raw material 1 is loaded into the container 2, the axial centers CL1, CL2, and CL3 of the raw material 1, the container 2, and the die 3 substantially coincide. Hereinafter, the axial centers CL1, CL2, and CL3 are collectively referred to as the axial center CL. In hot extrusion, a horizontal press is used. The axial center CL extends substantially horizontally.

[0015] Referring to Figure 1, a raw material 1 placed in a container 2 is pressed toward a die 3 by a dummy block 6 connected to a stem (not shown). This causes the raw material 10 to flow into a die hole 31 (see the arrow in Figure 1) and be extruded from the die hole 31. The extruded raw material 10 becomes a metal member 5. The metal member 5 shown in Figure 1 is a seamless metal pipe, and in this case, the raw material 1 is a hollow billet, with a mandrel 7 as an inner surface regulating tool protruding from the dummy block 6.

[0016] During extrusion, the flow rate of the raw material 10 in the container 2 is essentially zero at the corners 20 (shown cross-hatched in FIG. 1 ) formed between the die 3 and the container 2. That is, dead metal of the raw material 10 is generated at the corners 20 of the container 2 during extrusion. In this case, even if softened glass originating from the glass disk is present between the raw material 10 and the die 3, the dead metal hinders the flow of molten glass into the die hole 31. This is because the dead metal does not easily flow into the die hole 31. For this reason, glass lubrication between the raw material 10 and the die 3 may be insufficient during periods other than the initial stage of extrusion, i.e., the middle and final stages of extrusion. Insufficient glass lubrication can cause the die 3 to seize, resulting in a deterioration in the quality of the resulting metal component 5.

[0017] From the above, we found that sufficient glass lubrication can be ensured by suppressing the generation of dead metal. Therefore, we investigated a method to suppress the generation of dead metal. To suppress the generation of dead metal, we simply filled the corners of the container with softened glass originating from glass disks instead of dead metal.

[0018] A simple solution would be to make the outer diameter of the entire material significantly smaller than the inner diameter of the container. In this case, at the beginning of extrusion, the softened glass flows into the space between the outer peripheral surface of the material on the die side and the inner peripheral surface of the container. As a result, the softened glass fills the corners of the container. However, if the outer diameter of the entire material is significantly smaller than the inner diameter of the container, the material must be enlarged in length to ensure the length of the metal component that will be the product, and as a result, the container must be enlarged in length. Therefore, it is not appropriate to make the outer diameter of the entire material significantly smaller than the inner diameter of the container.

[0019] Therefore, a method was investigated for filling the corners of the container with softened glass originating from glass disks while suppressing the expansion of the overall length of the material. This method involves forming a chamfered surface connecting the leading end surface and the outer circumferential surface of the material. In a longitudinal cross-sectional view of the material loaded in the container, the chamfered surface may be formed on the material side relative to the interface between the material flowing during extrusion and the dead metal, so as to substantially follow the flow line of the material during extrusion. In a typical example, the chamfered surface is a straight line in the longitudinal cross-sectional view of the material. Alternatively, the chamfered surface may be a convex arc in the longitudinal cross-sectional view of the material.

[0020] In this case, at the beginning of extrusion, the softened glass flows into the generally closed space between the chamfered surface of the material and the inner surface of the container. As a result, the softened glass fills the corners of the container. Moreover, because the outer diameter of the material as a whole is not made smaller than the inner diameter of the container, the increase in the overall length of the material is suppressed.

[0021] This configuration will be described in detail below. Fig. 2 is a longitudinal cross-sectional view showing the state in which the glass disk 4 and the raw material 1 are loaded into the container 2. Fig. 2 shows one half of the raw material 1 in the radial direction with respect to the axis CL. The other half is symmetrical to the one half shown in Fig. 2. Referring to Fig. 2, the raw material 1 includes a leading edge surface 11, an outer peripheral surface 12, and a chamfered surface 13. The leading edge surface 11 is disposed on the die 3 side. The chamfered surface 13 connects the leading edge surface 11 and the outer peripheral surface 12. In other words, the leading edge surface 11, the chamfered surface 13, and the outer peripheral surface 12 are continuous in this order.

[0022] At the start of extrusion, when the glass disk 4 and the raw material 1 are loaded into the container 2, the outer diameter Db of the tip end surface 11, as viewed in vertical cross section, may satisfy the following relationship with the maximum radial dimension Dd of the die hole 31 and the inner diameter Dc of the container 2: Dd≦Db≦Dd+0.8×(Dc−Dd) (1). When manufacturing a metal member having a circular cross section, such as a seamless metal pipe or a steel bar, the die hole 31 is circular, so the diameter of the die hole 31 corresponds to the maximum dimension Dd of the die hole 31. On the other hand, when manufacturing a metal member having a non-circular cross section, such as a structural steel, the die hole 31 is non-circular, so the diameter of a circle centered on the axis CL of the die hole 31 and passing through the outermost periphery of the die hole 31 corresponds to the maximum dimension Dd of the die hole 31. Dd≦Db≦Dd+0.8×(Dc−Dd) (1)

[0023] From the relationship between the left and middle sides of equation (1), the outer diameter Db of the leading end surface 11 is equal to or greater than the maximum dimension Dd of the die hole 31. If the outer diameter Db of the leading end surface 11 is smaller than the maximum dimension Dd of the die hole 31, the manufactured metal member will have irregular shapes and dimensions at the leading end portion corresponding to the initial stage of extrusion. This leading end portion cannot be used as a product, resulting in a decrease in product yield. Therefore, the lower limit of the outer diameter Db of the leading end surface 11 is the maximum dimension Dd of the die hole 31. The outer diameter Db of the leading end surface 11 is preferably larger than the maximum dimension Dd of the die hole 31.

[0024] From the relationship between the middle and right sides of equation (1), the outer diameter Db of the tip end surface 11 is equal to or less than "Dd + 0.8 × (Dc - Dd)". Within the container 2, dead metal may occur in a region exceeding "Dd + 0.8 × (Dc - Dd)", depending on the extrusion ratio. If the outer diameter Db of the tip end surface 11 is greater than "Dd + 0.8 × (Dc - Dd)", the occurrence of dead metal cannot be completely suppressed. Therefore, the upper limit of the outer diameter Db of the tip end surface 11 is "Dd + 0.8 × (Dc - Dd)".

[0025] At the start of extrusion, in a vertical cross-sectional view with the glass disk 4 and the raw material 1 loaded in the container 2, an imaginary line L1 is further defined, connecting a connection point P1 between the leading end surface 11 and the chamfered surface 13 and a connection point P2 between the chamfered surface 13 and the outer circumferential surface 12. When the imaginary line L1 is defined in this manner, the inclination angle θb of the imaginary line L1 with respect to a perpendicular line VL to the axis center CL of the container 2 only needs to satisfy formula (2). When the chamfered surface 13 is configured as a straight line, this imaginary line L1 is on the chamfered surface 13. When the chamfered surface 13 is configured as a convex arc, the imaginary line L1 is approximately on the chamfered surface 13, and the inclination angle θb is 45°. 45°≦θb≦65° (2)

[0026] That is, the inclination angle θb of the virtual straight line L1 is 45° or more and 65° or less. At the corners of the container 2, the angle of the streamline of the raw material 10 relative to the perpendicular VL to the axis CL of the container 2 falls within the range of 45° to 65°. If the inclination angle θb is less than 45°, dead metal may be generated. If the inclination angle θb is greater than 65°, the chamfered surface 13 of the raw material 10 deforms radially at the start of extrusion, resulting in the inclination angle θb being 65° or less. In other words, even if the inclination angle θb is greater than 65° before extrusion, the situation at the start of extrusion is the same as when the inclination angle θb is 65° or less. In fact, if the inclination angle θb is greater than 65°, the processing allowance required to form the chamfered surface 13 on the raw material 1 increases, resulting in a decrease in yield. Therefore, the lower limit of the inclination angle θb is 45°, and the upper limit of the inclination angle θb is 65°. The inclination angle θb is preferably greater than 45°, and more preferably equal to or greater than 50°.

[0027] At the start of extrusion, in a vertical cross-sectional view of the glass disk 4 and the raw material 1 loaded in the container 2, the inclination angle θb of the virtual straight line L1, the outer diameter Db of the tip surface 11 of the raw material 1, the maximum dimension Dd of the die hole 31, and the inner diameter Dc of the container 2 may further satisfy formula (3).

[0028]

[0029] The middle side of equation (3) represents a value A obtained by non-dimensionalizing the area of ​​the region surrounded by the imaginary line L1, the extension line L2 of the imaginary line L1, the inner circumferential surface 21 of the container 2, and the extension line L3 on the tip end surface 11 when the inclination angle of the imaginary line L1 is θb, using the inner diameter Dc of the container 2. This value A is an index of the size of the approximately closed space between the chamfered surface 13 of the raw material 1 and the inner circumferential surface 21 of the container 2 at the start of extrusion. In this specification, this value may be referred to as the size A of the closed space based on the inclination angle θb.

[0030] The left side of equation (3) represents a value A1 obtained by non-dimensionalizing the area of ​​a region surrounded by the imaginary line L1, the extension L2 of the imaginary line L1, the inner circumferential surface 21 of the container 2, and the extension L3 on the front end surface 11 with the inner diameter Dc of the container 2 when the outer diameter Db of the front end surface 11 is at the above-mentioned upper limit and the inclination angle θb of the imaginary line L1 is at the above-mentioned upper limit of 65°. In other words, the left side of equation (3) represents the size A1 of the enclosed space when the outer diameter Db of the front end surface 11 and the inclination angle θb of the imaginary line L1 are each at the above-mentioned upper limits. Figure 3 shows an image of the left side of equation (3).

[0031] From the relationship between the left side and the middle side of Equation (3), the size A of the enclosed space based on the inclination angle θb is equal to or greater than the size A1 of the enclosed space when the outer diameter Db of the tip end surface 11 and the inclination angle θb of the virtual line L1 are at their respective upper limits. The conditions of Equations (1) and (2) are satisfied and the size A of the enclosed space is smaller than A1 when the outer diameter Db of the tip end surface 11 is at its upper limit (Dd + 0.8 × (Dc - Dd)) and the inclination angle θb of the virtual line L1 is smaller than its upper limit (65°). In this case, the size A of the enclosed space is too small, which may result in dead metal. Therefore, the lower limit of the size A of the enclosed space based on the inclination angle θb is the size A1 of the enclosed space when the outer diameter Db of the tip end surface 11 and the inclination angle θb of the virtual line L1 are at their respective upper limits.

[0032] The right side of equation (3) represents a value A2 obtained by non-dimensionalizing the area of ​​a region surrounded by the imaginary line L1, the extension line L2 of the imaginary line L1, the inner circumferential surface 21 of the container 2, and the extension line L3 on the front end surface 11 with the inner diameter Dc of the container 2 when the outer diameter Db of the front end surface 11 is at the above-mentioned lower limit and the inclination angle θb of the imaginary line L1 is at the above-mentioned lower limit of 45 degrees. In other words, the right side of equation (3) represents the size A2 of the enclosed space when the outer diameter Db of the front end surface 11 and the inclination angle θb of the imaginary line L1 are each at their lower limits. Figure 4 shows an image of the right side of equation (3).

[0033] From the relationship between the middle and right sides of Equation (3), the size A of the enclosed space based on the inclination angle θb is equal to or smaller than the size A2 of the enclosed space when the outer diameter Db of the leading end surface 11 and the inclination angle θb of the virtual line L1 are at their respective lower limits. The conditions of Equations (1) and (2) are satisfied, and the size A of the enclosed space is greater than A2, when the outer diameter Db of the leading end surface 11 is at its lower limit (Dd) and the inclination angle θb of the virtual line L1 is greater than its lower limit (45°). In this case, the glass tends to flow out of the die hole 31 at the initial stage of extrusion, and shape irregularities due to excessive glass deposition may occur in the tip portion of the manufactured metal component corresponding to the initial stage of extrusion. This tip portion cannot be used as a product, resulting in reduced product yield. Therefore, the upper limit of the size A of the enclosed space based on the inclination angle θb is the size A2 of the enclosed space when the outer diameter Db of the leading end surface 11 and the inclination angle θb of the virtual line L1 are at their respective lower limits.

[0034] In this way, if all of the formulas (1) to (3) are satisfied, the generation of dead metal can be suppressed without reducing the product yield.

[0035] The method for manufacturing a metal member according to an embodiment of the present disclosure has been completed based on the above findings.

[0036] The manufacturing method according to this embodiment is a method for manufacturing a metal component by hot extrusion (first configuration). The manufacturing method includes a material preparation step, a heating step, a glass disk loading step, a material loading step, and an extrusion step. The material preparation step involves preparing a cylindrical material. The heating step involves heating the material. The glass disk loading step involves loading a glass disk into a cylindrical container. The material loading step involves loading the material into the container with the glass disk loaded. The extrusion step involves pressing the material loaded into the container toward a die having a die hole, and extruding the material through the die hole to produce a metal component.

[0037] The material charged into the container in the material charging step includes a leading edge surface disposed on the die side, an outer peripheral surface, and a chamfered surface connecting the leading edge surface and the outer peripheral surface. At the start of the extrusion step, in a vertical cross-sectional view with the glass disk and material charged into the container, the outer diameter Db of the leading edge surface of the material satisfies formula (1) in relation to the maximum radial dimension Dd of the die hole and the inner diameter Dc of the container. When a virtual line connecting the connection point between the leading edge surface and the chamfered surface and the connection point between the chamfered surface and the outer peripheral surface is defined, the inclination angle θb of the virtual line with respect to a perpendicular to the axis of the container satisfies formula (2). Furthermore, the inclination angle θb of the virtual line, the outer diameter Db of the leading edge surface of the material, the maximum dimension Dd of the die hole, and the inner diameter Dc of the container satisfy formula (3). Dd≦Db≦Dd+0.8×(Dc−Dd) (1) 45°≦θb≦65° (2)

[0038] In the manufacturing method according to the first aspect, the blank material charged into the container during the blank material charging step includes a leading edge, an outer peripheral surface, and a chamfered surface. Furthermore, at the start of the extrusion step, in a longitudinal cross-sectional view with the glass disk and blank material loaded into the container, the outer diameter Db of the leading edge of the blank material, the maximum radial dimension Dd of the die hole, and the inner diameter Dc of the container satisfy formula (1) described in the above-mentioned findings. Furthermore, when a virtual line is defined connecting the connection point between the leading edge and the chamfered surface and the connection point between the chamfered surface and the outer peripheral surface, the inclination angle θb of the virtual line with respect to a perpendicular to the axis of the container satisfies formula (2) described in the above-mentioned findings. Furthermore, the inclination angle θb of the virtual line, the outer diameter Db of the leading edge of the blank material, the maximum dimension Dd of the die hole, and the inner diameter Dc of the container satisfy formula (3) described in the above-mentioned findings. Therefore, as described in the above-mentioned findings, the generation of dead metal can be suppressed. Without dead metal, the molten glass flows into the die hole together with the blank material, ensuring sufficient glass lubrication. Therefore, according to the manufacturing method of the first configuration, it is possible to suppress seizure of the die, and as a result, it is possible to ensure the quality of the manufactured metal parts.

[0039] In the above manufacturing method, the chamfered surface of the material is preferably configured as a straight line when viewed in vertical cross section (second configuration).

[0040] In the manufacturing method according to the first aspect, the chamfered surface of the blank may be configured as a convex arc in a vertical cross section (third aspect).

[0041] In the above manufacturing method, the inlet surface of the die may be perpendicular to the axis in a longitudinal cross section (fourth configuration). In this case, softened glass is likely to accumulate on the inlet surface of the die, and the flow of molten glass into the die hole is appropriately suppressed. Therefore, sufficient glass lubrication can be achieved even at the end of extrusion.

[0042] The manufacturing method according to any one of the first to third configurations may also include the following configuration. The inlet side of the die is inclined relative to a perpendicular to the axis so as to move away from the axis as it approaches the blank, in a longitudinal cross-sectional view, and the inclination angle θd of the inlet side is greater than 0° and less than 20° (fifth configuration). In this case, because the inlet side of the die is inclined toward the die hole, the blank material easily flows into the die hole. This further reduces the generation of dead metal. Furthermore, because the inclination angle θd of the inlet side is limited to 20° or less, softened glass is appropriately accumulated on the inlet side of the die, appropriately suppressing the flow of molten glass into the die hole. Therefore, sufficient glass lubrication can be achieved even at the end of the extrusion process.

[0043] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In each drawing, the same or equivalent components are designated by the same reference numerals, and redundant description will not be repeated.

[0044] <First embodiment> [Method of manufacturing a metal member] A method of manufacturing a metal member according to a first embodiment will be described with reference to Figures 1 to 5. Figure 5 is a flow diagram showing the manufacturing method of this embodiment. Referring to Figure 5, the manufacturing method of this embodiment is a method of manufacturing a metal member by hot extrusion, and includes a material preparation step (#5), a heating step (#10), a glass disk loading step (#15), a material loading step (#20), and an extrusion step (#25).

[0045] In this embodiment, the manufacturing method uses hot extrusion to produce a seamless metal pipe as a metal component. In the blank preparation step (#5), a cylindrical blank is prepared. In this embodiment, the blank is a hollow billet to produce a seamless metal pipe. Referring to FIGS. 2 to 4 , the blank 1 includes a leading end surface 11, an outer peripheral surface 12, and a chamfered surface 13 connecting the leading end surface 11 and the outer peripheral surface 12. The chamfered surface 13 is formed by cutting. The blank 1 has a central hole along the axis CL. Examples of materials that can be used for the blank 1 include carbon steel, stainless steel, a nickel alloy, and an aluminum alloy. The dimensions of the blank 1 will be described later.

[0046] In the heating step (#10), the raw material 1 is heated. The heating temperature varies depending on the material of the raw material 1, but for example, in the case of stainless steel, it is in the range of 1000 to 1200°C. As a heating method, a well-known heating method using a batch-type heating furnace, a walking beam-type continuous heating furnace, a high-frequency heating furnace, or the like can be applied.

[0047] In the glass disk loading step (#15), a glass disk 4 is loaded into the cylindrical container 2. The glass disk 4 is an annular compact containing powdered glass as a main component. For example, the glass disk 4 can be obtained by mixing powdered glass with water glass as a binder, molding the mixture into an annular shape, and drying it. The glass disk 4 loaded into the container 2 is positioned so as to overlap the die 3 in the axial direction.

[0048] In the raw material charging step (#20), the heated raw material 1 is charged into the container 2 in which the glass disk 4 has been charged. The raw material 1 is positioned so that the leading end surface 11 faces the die 3. Therefore, the chamfered surface 13 also faces the die 3. Before charging the raw material 1 into the container 2, powdered glass for external lubrication may be applied to the outer peripheral surface 12 of the raw material 1. Powdered glass for internal lubrication may be applied to the inner peripheral surface of the raw material 1.

[0049] In the extrusion process (#25), the blank 1 placed in the container 2 is pressed toward a die 3 having a die hole 31, and the blank 1 is extruded through the die hole 31 to produce a metal member 5. Specifically, referring to FIG. 1 , a dummy block 6 connected to a stem (not shown) advances. Note that the glass disk 4, its softened glass, and its molten glass are not shown in FIG. 1 . The advancing dummy block 6 presses the blank 1 toward the die 3 within the container 2. As a result, the blank material 10 flows into the die hole 31 and is extruded through the die hole 31. The extruded blank material 10 becomes the metal member 5. In this embodiment, a mandrel 7 serving as an inner surface regulating tool protrudes from the dummy block 6 and penetrates the center hole of the blank 1. In this manner, a seamless metal tube is produced as the metal member 5.

[0050] During extrusion, the raw material 1 is pressed toward the die 3, and the glass disk 4 comes into contact with the heated raw material 1 and softens. The softened glass fills the vicinity of the die 3 in the container 2, and the molten glass flows into the die hole 31 together with the raw material 10. The molten glass flowing into the die hole 31 provides glass lubrication between the raw material 1 and the die 3.

[0051] 2 , the raw material 1 charged into the container 2 in the raw material charging step (#20) includes a leading edge surface 11 disposed on the die 3 side, an outer peripheral surface 12, and a chamfered surface 13 connecting the leading edge surface 11 and the outer peripheral surface 12. The container 2 is cylindrical and includes an inner peripheral surface 21. The diameter of the inner peripheral surface 21 is the inner diameter Dc of the container 2.

[0052] The die 3 includes a die hole 31 and an inlet surface 32. The die hole 31 has a maximum radial dimension Dd. In this specification, the maximum dimension Dd refers to the diameter of a circle that passes through the outermost periphery of the die hole 31 and is centered on the axis CL of the die hole 31. In this embodiment, the die hole 31 is circular. In this case, the maximum dimension Dd of the die hole 31 is the diameter of the die hole 31. The inlet surface 32 is perpendicular to the axis CL.

[0053] With respect to the raw material 1, the tip surface 11 is a surface perpendicular to the axis CL. The tip surface 11 has a circular outer contour and an outer diameter Db. The outer peripheral surface 12 is a cylindrical surface. The diameter of the outer peripheral surface 12 is the outer diameter of the raw material 1. The diameter of the outer peripheral surface 12 is constant throughout the axial direction. The outer diameter of the raw material 1 is slightly smaller than the inner diameter Dc of the container 2. The chamfered surface 13 is formed by straight lines in a vertical cross-sectional view of the raw material 1. That is, the chamfered surface 13 in this embodiment is a so-called angular chamfered surface. For example, the chamfered surface 13 may be a C-chamfered surface.

[0054] At the start of the extrusion step (#25), the dimensions of the raw material 1 satisfy the following conditions (Equations (1) to (3)) when viewed in vertical cross section with the glass disk 4 and raw material 1 loaded in the container 2. In other words, the raw material 1 having dimensions that satisfy the following conditions is prepared in the raw material preparation step (#5).

[0055] The outer diameter Db of the front end surface 11 satisfies the above-described formula (1) in relation to the maximum dimension Dd of the die hole 31 and the inner diameter Dc of the container 2. Furthermore, when an imaginary line L1 is defined that connects a connection point P1 between the front end surface 11 and the chamfered surface 13 and a connection point P2 between the chamfered surface 13 and the outer peripheral surface 12, the inclination angle θb of the imaginary line L1 with respect to a perpendicular line VL to the axis CL of the container 2 satisfies the above-described formula (2). This imaginary line L1 is on the chamfered surface 13. Furthermore, the inclination angle θb of the imaginary line L1, the outer diameter Db of the front end surface 11 of the blank 1, the maximum dimension Dd of the die hole 31, and the inner diameter Dc of the container 2 satisfy formula (3).

[0056] [Effects] In the manufacturing method of a metal component according to the first embodiment, all of the conditions of formulas (1) to (3) are satisfied at the start of the extrusion step (#25). This suppresses the generation of dead metal, as described above. In this case, at the start of extrusion, the corners 20 of the container 2 can be filled with softened glass originating from the glass disks 4 instead of dead metal. Without dead metal, the molten glass flows into the die hole 31 together with the raw material, ensuring sufficient glass lubrication. Therefore, according to the manufacturing method of the first embodiment, seizure of the die 3 can be suppressed, thereby ensuring the quality of the manufactured metal component 5.

[0057] In this embodiment, the inlet side 32 of the die 3 is perpendicular to the axis CL. In this case, softened glass is likely to accumulate on the inlet side 32 of the die 3. This appropriately suppresses the flow of molten glass into the die hole 31. This allows for more sufficient glass lubrication even at the end of the extrusion process.

[0058] Second Embodiment A method for manufacturing a metal member according to a second embodiment will be described with reference to Fig. 6. Fig. 6 is a longitudinal cross-sectional view showing a state in which a glass disk 4 and a raw material 1A are loaded into a container 2. The raw material 1A differs from the raw material 1 in the manufacturing method of the first embodiment in that it does not have a center hole.

[0059] In the manufacturing method of the second embodiment, a metal component, such as a steel bar, is manufactured by hot extrusion. The manufactured metal component may be a steel section. A mandrel is not required during extrusion. The manufacturing method of the second embodiment also satisfies all of the conditions of formulas (1) to (3) at the start of the extrusion step (#25), and therefore provides the same effects as the first embodiment.

[0060] Third Embodiment A method for manufacturing a metal member according to a third embodiment will be described with reference to Fig. 7. Fig. 7 is a longitudinal cross-sectional view showing a state in which a glass disk 4 and a raw material 1 are loaded into a container 2. In the third embodiment, the configuration of a die 3A differs from the die 3 in the manufacturing method according to the first embodiment.

[0061] In the die 3A, the entry side 32A is inclined with respect to a perpendicular VL to the axis CL so as to move away from the axis CL toward the raw material 1 in a vertical cross-sectional view. That is, the entry side 32A of the die 3A is inclined toward the die hole 31. In this case, the inclination angle θd of the entry side 32A is preferably greater than 0° and equal to or less than 20°.

[0062] In the manufacturing method of the third embodiment, the inlet side 32A of the die 3A is inclined toward the die hole 31, so that the blank material 10 flows more easily into the die hole 31 during extrusion. This further reduces the generation of dead metal. Furthermore, if the inclination angle θd of the inlet side 32A is limited to 20° or less, softened glass is appropriately accumulated on the inlet side 32A of the die 3A, and the flow of molten glass into the die hole 31 is appropriately suppressed. Therefore, sufficient glass lubrication can be achieved even in the final stage of extrusion.

[0063] The manufacturing method of the third embodiment also satisfies all of the conditions of formulas (1) to (3) at the start of the extrusion step (#25), and therefore has the same effects as the first embodiment. The die 3A in the third embodiment may be applied to the manufacturing method of the second embodiment.

[0064] Fourth Embodiment A method for manufacturing a metal member according to a fourth embodiment will be described with reference to Fig. 8. Fig. 8 is a longitudinal cross-sectional view showing a state in which a glass disk 4 and a raw material 1 are loaded into a container 2. In the fourth embodiment, the configuration of a chamfered surface 13A of the raw material 1 differs from that of the chamfered surface 13 in the manufacturing method according to the first embodiment.

[0065] The chamfered surface 13A is configured as a convex arc in a vertical cross-sectional view of the raw material 1. This arc has a constant radius of curvature R. That is, the chamfered surface 13A of this embodiment is a so-called R-chamfered surface. In this case, the inclination angle θb of the imaginary straight line L1 is 45°.

[0066] The manufacturing method of the fourth embodiment also satisfies all of the conditions of formulas (1) to (3) at the start of the extrusion step (#25), and therefore has the same effects as the first embodiment. The chamfered surface 13A in the fourth embodiment may be applied to the manufacturing method of the second or third embodiment.

[0067] The present disclosure will be described in more detail below with reference to examples, although the present disclosure is not limited to the following examples.

[0068] To confirm the effects of the present disclosure, a rigid-plastic finite element analysis of a two-dimensional axisymmetric model was performed using the static implicit method using the general-purpose code DEFORM manufactured by SFTC. The tools (die, mandrel, container, etc.) were treated as rigid bodies, and the workpiece (raw material) and glass (glass disk) were modeled using quadrilateral elements. The friction coefficient between the tool and the workpiece was set to Coulomb friction coefficient μ = 0.3, and the friction coefficient between the glass and the workpiece, and between the glass and the tool was set to Coulomb friction coefficient μ = 0.05. The stress-strain diagram of the workpiece was calculated using a temperature of 1000 to 1200°C and a strain rate of 1 to 10 sec. －１ The tensile test results for the above experiment were entered as table values ​​and linear interpolated. Because glass softens when it comes into contact with a high-temperature workpiece, it was assumed that the deformation resistance of the glass was one-third that of the workpiece. Strictly speaking, glass that is far from the workpiece is not easily softened, as the powder is simply compressed. However, in this numerical analysis, the entire glass was softened as an accelerated test condition to simulate glass outflow in the latter stages of extrusion, and the relative difference with the reference conditions for which there is actual extrusion experience was evaluated.

[0069] After the blank material was extruded through the die hole to an arbitrary length, the glass thickness was measured at a position on the inlet side of the die closest to the die hole. Specifically, the measurement position was 1 / 4 of the die width from the die hole (the position "Dd / 2 + 1 / 4 × (Dc / 2 - Dd / 2)" from the axis). The measured glass thickness was judged according to the following criteria. The shape and dimensions of the tip portion corresponding to the initial stage of extrusion were also confirmed. ○ (Excellent): The glass thickness remained at 10% or more of the thickness before extrusion. △ (Good): The glass thickness remained at more than 0% to less than 10% of the thickness before extrusion. × (Fail): The glass film disappeared and nothing remained. ● (Fail): There was irregularity in the shape and dimensions of the tip portion corresponding to the initial stage of extrusion.

[0070] The set conditions and results are shown in Tables 1A and 1B below.

[0071]

[0072]

[0073] In Nos. 1 to 12, the raw material was a hollow round billet and the metal member was a seamless metal pipe. In Nos. 13 to 26, the raw material was a solid round billet and the metal member was a round steel bar. When the metal member was a seamless metal pipe, the diameter of the mandrel was the same as the inner diameter of the metal member. The chamfered surfaces of Nos. 20 to 22 and 24 to 26 were R-chamfered surfaces. For example, R30 in No. 20 means that the radius of curvature R of the R-chamfered surface was 30 mm. Nos. 3, 4, 10 to 12, 15 to 17, 21, 22, and 25 satisfied all of the conditions of formulas (1) to (3) defined in this disclosure, and therefore achieved good results. Among these, No. 1, in which the inclination angle θd of the inlet surface of the die was 20° or less, achieved good results. Nos. 3, 10-12, 15, 17, 21, 22, and 25 showed particularly good results.

[0074] The above describes the embodiments of the present disclosure. However, the above-described embodiments are merely examples for implementing the present disclosure. Therefore, the present disclosure is not limited to the above-described embodiments, and the above-described embodiments can be appropriately modified within the scope of the present disclosure. For example, the chamfered surface 13 of the raw material 1 may be configured in a stepped shape when viewed in vertical cross section of the raw material 1.

[0075] 1, 1A: Blank 10: Raw material 11: Tip face 12: Outer periphery 13, 13A: Chamfered surface 2: Container 20: Corner 21: Inner periphery 3, 3A: Die 31: Die hole 32, 32A: Entry side 4: Glass disk 5: Metal member CL, CL1, CL2, CL3: Axis center VL: Perpendicular line P1, P2: Connection point L1: Imaginary line L2: Extension line of imaginary line L3: Extension line on tip face θb: Inclination angle of imaginary line Db: Outer diameter of tip face of blank Dc: Inner diameter of container Dd: Maximum dimension of die hole θd: Inclination angle of entry side of die

Claims

1. A method for manufacturing a metal component by hot extrusion, comprising: a material preparation step of preparing a cylindrical material; a heating step of heating the material; a glass disk charging step of charging a glass disk into a cylindrical container; a material charging step of charging the material into the container with the glass disk charged; and an extrusion step of pressing the material charged into the container toward a die having a die hole and extruding the material through the die hole to manufacture the metal component, wherein the material charged into the container in the material charging step includes a tip surface disposed on the die side, an outer peripheral surface, and a chamfered surface connecting the tip surface and the outer peripheral surface, and at the start of the extrusion step, in a vertical cross-sectional view with the glass disk and the material charged in the container, an outer diameter Db of the tip surface of the material satisfies formula (1) in relation to a maximum dimension Dd in the radial direction of the die hole and an inner diameter Dc of the container, A method for manufacturing a metal member, wherein, when a virtual line connecting a connection point between the front end surface and the chamfered surface and a connection point between the chamfered surface and the outer circumferential surface is defined, an inclination angle θb of the virtual line with respect to a perpendicular to the axis of the container satisfies formula (2), and the inclination angle θb of the virtual line, the outer diameter Db of the front end surface of the blank, the maximum dimension Dd of the die hole, and the inner diameter Dc of the container satisfy formula (3): Dd≦Db≦Dd+0.8×(Dc−Dd) (1) 45°≦θb≦65° (2) 2. A method for manufacturing a metal component according to claim 1, wherein the chamfered surface of the material is configured as a straight line when viewed in vertical cross section.

3. A method for manufacturing a metal component according to claim 1, wherein the chamfered surface of the material is configured as a convex arc when viewed in vertical cross section.

4. A method for manufacturing a metal component according to any one of claims 1 to 3, wherein the inlet surface of the die is perpendicular to the axis when viewed in vertical cross section.

5. A method for manufacturing a metal component according to any one of claims 1 to 3, wherein the entry surface of the die is inclined with respect to the perpendicular to the axis so as to move away from the axis as it approaches the material in a longitudinal cross-sectional view, and the inclination angle θd of the entry surface is greater than 0° and not greater than 20°.

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