Manufacturing method of metal member

Abstract

The present invention provides a manufacturing method for a metal part manufactured by hot extrusion that can ensure the quality of the metal part. The material (1) includes a tip surface (11), an outer peripheral surface (12), and a chamfered surface (13). When the glass disk 4 and the raw material 1 are loaded into the container 2 at the start of extrusion, as viewed in vertical cross section, the outer diameter Db of the leading end surface 11 of the raw material 1 satisfies formula (1) in relation to the maximum radial dimension Dd of the die hole 31 and the inner diameter Dc of the container 2. When an imaginary line (L1) is 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 peripheral surface 12, 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 satisfies formula (2). Furthermore, the inclination angle θb, the outer diameter Db, the maximum dimension Dd, and the inner diameter Dc satisfy formula (3). Dd≦Db≦Dd+0.8×(Dc-Dd) (1) 45°≦θb≦65° (2) [Equation 1] TIFF0007755226000007.tif37157

Description

[Technical Field]

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

[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 places a greater strain on the die. Even with glass lubrication, excessive strain on the die can easily cause seizure in the die. Die seizure can cause 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) facing the die is tapered, and the relationship between the billet's taper half angle θB (°) 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 billet's edge facing the die 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 when glass-lubricated extrusion is applied, the load on the die during extrusion can be reduced if the relationship between the billet's taper half angle θB and the die half angle θD is within the above range. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2020-15057 Summary of the Invention [Problem to be solved by the invention]

[0007] The technology of Patent Document 1 focuses on the peak extrusion load that occurs in the early stage 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 early stage 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. [Means for solving the problem]

[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 is defined connecting the junction of the leading edge surface and the chamfered surface and the junction of 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). Furthermore, the inclination angle θb of the virtual line, the outer diameter Db of the leading edge surface of the material, the maximum radial 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)

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[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. [Brief explanation of the drawings]

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

[0013] In order to solve the above problems, the 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, a longitudinal cross-section refers to a cross-section including the axial center CL2 of the container 2. Similarly, a cross-section including the axial centers CL1 and CL3 of the raw material 1 and the die 3 is also referred to as a longitudinal cross-section. 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 are substantially aligned. 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. Note that 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 1 and the die 3 can 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 glass disk 4 and the raw material 1 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. That is, 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, is required to satisfy formula (1) in relation to the maximum radial dimension Dd of the die hole 31 and the inner diameter Dc of the container 2. When producing a metal member having a circular cross section, such as a seamless metal pipe or a steel bar, the die hole 31 is circular, and therefore the diameter of the die hole 31 corresponds to the maximum dimension Dd of the die hole 31. On the other hand, when producing a metal member having a non-circular cross section, such as a structural steel, the die hole 31 is non-circular, and therefore 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 front 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 front end surface 11 is smaller than the maximum dimension Dd of the die hole 31, the shape and dimensions of the front end portion of the manufactured metal member corresponding to the initial stage of extrusion will be irregular. This front end portion cannot be used as a product, resulting in a reduced product yield. Therefore, the lower limit of the outer diameter Db of the front end surface 11 is the maximum dimension Dd of the die hole 31. The outer diameter Db of the front 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 smaller than "Dd + 0.8 × (Dc - Dd)". Within the container 2, dead metal may occur in an area exceeding "Dd + 0.8 × (Dc - Dd)", depending on the extrusion ratio. If the outer diameter Db of the tip end surface 11 is larger than "Dd + 0.8 × (Dc - Dd)", the occurrence of dead metal cannot be 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 into the container 2, an imaginary line L1 is further defined that connects 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 CL of the container 2 only needs to satisfy formula (2). When the chamfered surface 13 is formed as a straight line, this imaginary line L1 lies on the chamfered surface 13. When the chamfered surface 13 is formed as a convex arc, the imaginary line L1 lies 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 flow line of the raw material 10 relative to the perpendicular line VL to the axis CL of the container 2 is 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 so as to bulge radially at the start of extrusion, and the inclination angle θb becomes 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 all satisfy formula (3).

[0028]

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[0029] The middle side of equation (3) represents a value A obtained by non-dimensionally calculating the area of ​​the 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 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 ​​the 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 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. FIG. 3 shows an image of the left side of equation (3).

[0031] From the relationship between the left and middle sides 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 ​​the 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 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°. 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 respective lower limits. FIG. 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 in the early 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 early stage of extrusion. This tip portion cannot be used as a product, resulting in a 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 process, a heating process, a glass disk loading process, a material loading process, and an extrusion process. The material preparation process prepares a cylindrical material. The heating process heats the material. The glass disk loading process loads a glass disk into a cylindrical container. The material loading process loads the material into the container with the glass disk loaded. The extrusion process presses the material loaded into the container toward a die having a die hole, and extrudes the material through the die hole to manufacture 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 is defined connecting the junction of the leading edge surface and the chamfered surface and the junction of 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). Furthermore, the inclination angle θb of the virtual line, the outer diameter Db of the leading edge surface of the material, the maximum radial 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)

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[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 surface, an outer peripheral surface, and a chamfered surface. Furthermore, at the start of the extrusion step, in a longitudinal cross-sectional view of the container with the glass disk and blank material loaded, the outer diameter Db of the leading edge surface 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 above. Furthermore, when a virtual line is defined 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, the inclination angle θb of the virtual line with respect to a perpendicular to the axis of the container satisfies formula (2) described above. Furthermore, the inclination angle θb of the virtual line, the outer diameter Db of the leading edge surface of the blank material, the maximum dimension Dd of the die hole, and the inner diameter Dc of the container satisfy formula (3) described above. Therefore, as described above, 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 member.

[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 configuration, the chamfered surface of the blank may be configured as a convex arc in a vertical cross section (third configuration).

[0041] In the above manufacturing method, the inlet surface of the die may be perpendicular to the axis in a longitudinal cross-sectional view (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 moderately suppressed. Therefore, sufficient glass lubrication can be achieved even in the final stage of extrusion.

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

[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 [Metal component manufacturing method] A method for manufacturing a metal component 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 for manufacturing a metal component 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 the manufacturing method of this embodiment, a seamless metal pipe is manufactured as a metal member by hot extrusion. In the material preparation step (#5), a cylindrical material is prepared. In this embodiment, the material is a hollow billet to manufacture a seamless metal pipe. With reference to FIGS. 2 to 4, the material 1 includes a front end surface 11, an outer circumferential surface 12, and a chamfered surface 13 connecting the front end surface 11 and the outer circumferential surface 12. The chamfered surface 13 is formed by cutting. The material 1 has a center hole along the axis CL. Examples of materials that can be used for the material 1 include carbon steel, stainless steel, nickel alloy, and aluminum alloy. Dimensions of the material 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 1, but for example, in the case of stainless steel, it is in the range of 1000 to 1200°C. As the 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 the 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 that it overlaps the die 3 in the axial direction.

[0048] In the raw material charging step (#20), a 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 its leading edge 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 control tool protrudes from the dummy block 6 and penetrates the center hole of the blank 1. As a result, a seamless metal pipe is produced as the metal member 5.

[0050] During extrusion, the raw material 1 is pressed toward the die 3, causing the glass disk 4 to come into contact with the heated raw material 1 and soften. The softened glass fills the vicinity of the die 3 within 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] [Material 1 and dimensions related to material 1] 2, the raw material 1 charged into the container 2 in the raw material charging step (#20) includes a leading end surface 11 disposed on the die 3 side, an outer peripheral surface 12, and a chamfered surface 13 connecting the leading end 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 side 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 side 32 is perpendicular to the axis CL.

[0053] The leading end surface 11 of the raw material 1 is a surface perpendicular to the axis CL. The leading end 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 of this embodiment is a so-called square-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 disc 4 and raw material 1 loaded into 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 leading edge surface 11 satisfies the above-mentioned 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 leading edge 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-mentioned formula (2). This imaginary line L1 is located on the chamfered surface 13. Furthermore, the inclination angle θb of the imaginary line L1, the outer diameter Db of the leading edge 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] [effect] In the manufacturing method for 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), thereby suppressing the generation of dead metal, as described above. In this case, at the start of extrusion, softened glass originating from the glass disks 4 can be filled in the corners 20 of the container 2 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 according to the first embodiment, seizure of the die 3 can be suppressed, and as a result, the quality of the manufactured metal component 5 can be ensured.

[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 the second embodiment will be described with reference to Fig. 6. Fig. 6 is a vertical cross-sectional view showing a state in which a glass disc 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 according to the first embodiment in that it does not have a center hole.

[0059] In the manufacturing method of the second embodiment, a metal part, for example, a steel bar, is manufactured by hot extrusion. The manufactured metal part may be a sectional steel. No mandrel is 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 has 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 vertical cross-sectional view showing a state in which a glass disc 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 entry side 32A of the die 3A is inclined toward the die hole 31, which facilitates the flow of the blank material 10 into the die hole 31 during extrusion. This further reduces the generation of dead metal. Furthermore, if the inclination angle θd of the entry side 32A is limited to 20° or less, an appropriate amount of softened glass accumulates on the entry side 32A of the die 3A, thereby appropriately suppressing the flow of molten glass into the die hole 31. This allows for sufficient glass lubrication even at the end of the extrusion process.

[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 vertical 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 virtual 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. [Example]

[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 this 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 workpiece was set to Coulomb friction coefficient μ = 0.3, and the friction coefficient between the glass and workpiece, and between the glass and the tool was set to Coulomb friction coefficient μ = 0.05. The stress-strain curve 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 from the previous study 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 away from the workpiece is less likely to soften as the powder is simply compressed, but this numerical analysis softened the entire glass as an accelerated test condition to simulate glass outflow in the latter stages of extrusion, and evaluated the relative difference with the reference conditions for which there is actual extrusion experience.

[0069] After the blank material was extruded through the die hole to a desired 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 (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): Glass thickness remains at 10% or more of pre-extrusion thickness △ (Good): Glass thickness remains between 0% and 10% of pre-extrusion thickness × (Not acceptable): The glass film has disappeared and no longer remains. ·● (Not allowed): The tip part corresponding to the initial stage of extrusion has irregularities in shape and dimensions.

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

[0071] [Table 1A]

[0072] [Table 1B]

[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 the conditions of Equations (1) to (3) defined in this disclosure, and therefore achieved good results. Among these, Nos. 3, 10 to 12, 15, 17, 21, 22, and 25, in which the inclination angle θd of the inlet side of the die was 20° or less, achieved 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. [Explanation of symbols]

[0075] 1,1A:Material 10: Materials 11: Tip surface 12: Outer surface 13, 13A: Chamfered surface 2: Container 20: Corner 21: Inner surface 3,3A: Dice 31: Die hole 32,32A:Entry side 4: Glass disc 5: Metal parts CL, CL1, CL2, CL3: Axial center VL: Perpendicular P1, P2: Connection points L1: Virtual line L2: Extension of the virtual line L3: Extension line on the tip surface θb: Inclination angle of the virtual line Db: Outer diameter of the tip surface of the material Dc: Inner diameter of container Dd: Maximum dimension of die hole θd: Inclination angle of the entry side of the die

Claims

1. A method for manufacturing a metal member by hot extrusion, a material preparation process for preparing a cylindrical material; a heating step of heating the material; a glass disk loading step of loading glass disks into a cylindrical container; a material charging step of charging the material into the container in which the glass disk has been charged; an extrusion process of pressing the material charged in the container toward a die having a die hole and extruding the material through the die hole to produce the metal member, The material charged into the container in the material charging step includes a leading end surface disposed on the die side, an outer peripheral surface, and a chamfered surface connecting the leading end surface and the outer peripheral surface, At the start of the extrusion process, the glass disk and the material are loaded into the container as viewed in vertical section, an outer diameter Db of the front end surface of the blank satisfies formula (1) in relation to a maximum dimension Dd of the die hole in the radial direction and an inner diameter Dc of the container, When a virtual line connecting the connection point between the tip surface and the chamfered surface and the connection point between the chamfered surface and the outer circumferential surface is defined, the inclination angle θb of the virtual line with respect to the perpendicular to the axis of the container satisfies formula (2), and a manufacturing method of a metal member, wherein the inclination angle θb of the virtual straight line, the outer diameter Db of the tip 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) [Equation 1]

2. The method for manufacturing a metal member according to claim 1, A method for manufacturing a metal component, wherein the chamfered surface of the material is configured as a straight line when viewed in vertical cross section.

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

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

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

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