Method for manufacturing piping components and piping components

Abstract

The objective is to provide a method for manufacturing piping components that have sufficient hardness. [Solution] A method for manufacturing piping parts is employed, comprising: a first step of obtaining a first preformed product by cold upsetting a round metal bar-shaped material with a first die and a first punch; a second step of obtaining a second preformed product by cold upsetting the first preformed product with a second die and a second punch; and a third step of obtaining a piping part by cold backward extruding the second preformed product with a third die and a third punch.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing pipe components and pipe components.

Background Art

[0002] Conventionally, pipe components for flowing high-pressure fluids such as high-pressure fuel are known. Such pipe components are generally manufactured by forming a steel material used as a raw material by forging.

[0003] For example, Patent Document 1 discloses a preparation step of arranging a solid bar-shaped base material extending in the longitudinal direction in a forging die, and a step of applying a load to the die to forge the base material, which includes a forging step of simultaneously forging a plurality of forged products from one base material, and a drilling step of drilling a central flow path and branch flow paths in the forged products. The central pipe portion and branch pipe portion of the first forged product among the plurality of forged products are defined as the first central pipe portion and the first branch pipe portion, and the central pipe portion and branch pipe portion of the second forged product among the plurality of forged products are defined as the second central pipe portion and the second branch pipe portion. In the forging step, the first central pipe portion and the second central pipe portion are positioned parallel to both sides of the base material, and the first branch pipe portion is positioned on the opposite side of the second central pipe portion with respect to the first central pipe portion, and the second branch pipe portion is positioned on the opposite side of the first central pipe portion with respect to the second central pipe portion. A method for manufacturing a pipe component is described.

[0004] Further, Patent Document 2 discloses a preparation step of arranging a solid bar-shaped base material extending in the longitudinal direction in a forging die, and a forging step of applying a load to the die to forge the base material to form a forged product having a central forging portion corresponding to the central pipe portion and a branch forging portion corresponding to the branch pipe portion, and a drilling step of drilling the forged product to form a central flow path and branch flow paths. In the forging step, the forging is performed such that a dummy forging provided on the forged product is positioned on the opposite side of the branch forging portion with respect to the central forging portion that protrudes from the central forging portion intersecting the longitudinal direction. After the forging step, a removal step of removing the dummy forging portion is further provided. A method for manufacturing a pipe component is described.

Prior Art Documents

[0005] [Patent Document 1] Japanese Patent Publication No. 2018-158372 [Patent Document 2] Japanese Patent Publication No. 2018-158373 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] However, when manufacturing piping components for high-pressure fluids from rod-shaped materials through a forging process, extrusion is required during the forging process, but there is a problem in that it is difficult to introduce strain into the extruded portion.

[0007] Furthermore, forging includes hot forging, in which the material is heated to over 1000°C before processing, and cold forging, in which the material is processed without heating. In hot forging, heating reduces the deformation resistance of the material, making it possible to form with relatively low loads. However, this results in rough surface finishes and poor dimensional accuracy of the processed product, increasing the burden on subsequent processes such as machining. In addition, it is difficult to introduce processing strain into the processed product, making it difficult to achieve sufficiently high hardness.

[0008] On the other hand, cold forging can reduce surface roughness and improve dimensional accuracy of processed parts, and by introducing processing strain, it can also increase the hardness of the processed parts, but it increases the forming load during processing. For example, when manufacturing complex-shaped piping parts made of stainless steel, forming by cold forging is considered difficult because stainless steel tends to have higher strength than ordinary steel.

[0009] The present invention has been made in view of the above circumstances, and aims to provide a method for manufacturing piping components having sufficient hardness. Furthermore, the present invention aims to provide a piping component having sufficient hardness. [Means for solving the problem]

[0010] To solve the above problems, the present invention adopts the following configuration. [1] A first step is to obtain a first preformed product by cold upsetting a round metal bar material using a first die and a first punch, A second step involves obtaining a second preformed product by cold upsetting the first preformed product using a second die and a second punch, The third step involves cold extruding the second preformed product backward using a third die and a third punch to obtain a piping component, The first step is to prepare a first die having a die groove on a flat die-working surface and a first punch having a punch groove on a flat punch-working surface, and to obtain the first preformed product by cold upsetting the material with the first die and the first punch brought relatively close together, while arranging the material so that its axial direction coincides with the groove length direction of the die groove and the punch groove. The first preformed product has a main body portion that is pressure-molded between the die groove portion and the punch groove portion, and a pair of bulge portions located on both sides of the main body portion in the width direction and having a thickness smaller than the thickness of the main body portion. The second step involves preparing a second die having a die recess and a second punch insertable into the die recess, arranging the first preformed product in the die recess of the second die so that the width direction of the main body of the first preformed product coincides with the insertion direction of the second punch, and then, while suppressing deformation in the thickness direction of the main body of the first preformed product by the vertical wall portion of the second die that divides the die recess, bringing the second die and the second punch closer together to cold upset the first preformed product to obtain the second preformed product. The second preformed product has a widthwise length that is smaller than the widthwise length of the first preformed product. The third step involves preparing a third die having a die recess and a third punch that can be inserted into the die recess and has at least one recess for backward extrusion provided on a flat punching surface. With the width direction of the main body portion of the second preform being aligned with the insertion direction of the third punch, while suppressing deformation of the main body portion of the second preform in the thickness direction by a vertical wall portion that partitions the die recess of the third die, the third die and the third punch are relatively moved closer to each other to perform cold backward extrusion on the second preform, thereby obtaining the pipe component. The pipe component has a pipe main body portion formed by the die recess of the third die and the punching surface of the third punch, and a protrusion portion formed by being extruded into the recess of the third punch. A method for manufacturing a pipe component. [2] For the first die and the first punch, the length A, which is half of the groove width of each of the die groove portion and the punch groove portion, satisfies D / 2 ≦ A ≦ 3D / 4 with respect to the diameter D of the material, and the groove depth h of each of the die groove portion and the punch groove portion satisfies 0.02D < A ≦ 0.06D. The indentation process in the first step is processed such that the thickness Tc1 of the main body portion of the first preform satisfies Tc1 ≦ 0.65D. The method for manufacturing a pipe component according to [1]. [3] The indentation process in the second step is processed such that when the length in the width direction of the first preform is Wc1 and the length in the width direction of the second preform is Wc2, it satisfies Wc2 ≦ 0.9Wc1. The method for manufacturing a pipe component according to [1]. [4] For the third punch, the depth Pd of the recess for backward extrusion satisfies D ≦ Pd, and the opening length PL of the recess for backward extrusion satisfies D ≦ PL. The backward extrusion process in the third step is processed such that when the length in the width direction of the second preform is Wc2 and the length in the insertion direction of the third punch of the pipe main body portion is H0, it satisfies 0.3 ≦ (Wc2 - H0) / Wc2. The method for manufacturing a pipe component according to [1]. [5] The first die and the first punch are such that the length A which is half of the groove width of each of the die groove portion and the punch groove portion satisfies D / 2 ≦ A ≦ 3D / 4 with respect to the diameter D of the material, and the groove depth h of each of the die groove portion and the punch groove portion satisfies 0.02D < A ≦ 0.06D. The third punch is such that the depth Pd of the recess for rear extrusion satisfies D ≦ Pd, and the opening length PL of the recess for rear extrusion satisfies D ≦ PL. In the indentation process in the first step, the indentation is performed so that the length Tc1 in the thickness direction of the main body portion of the first preformed product satisfies Tc1 ≦ 0.65D. In the indentation process in the second step, when the length in the width direction of the first preformed product is Wc1 and the length in the width direction of the second preformed product is Wc2, the indentation is performed so that Wc2 ≦ 0.9Wc1 is satisfied. In the rear extrusion process in the third step, when the length in the width direction of the second preformed product is Wc2 and the length in the insertion direction of the third punch of the pipe body portion is H0, the processing is performed so that 0.3 ≦ (Wc2 - H0) / Wc2 is satisfied, the manufacturing method of the pipe component according to [1]. [6] The material is austenitic stainless steel with a Vickers hardness of 100 HV or more and 160 HV or less, the manufacturing method of the pipe component according to any one of [1] to [5]. [7] The average Vickers hardness Hvb in a cross section parallel to the axial direction of the material, The ratio (Hvb / Hva) of the average Vickers hardness Hva in a cross section parallel to the axial direction of the pipe component obtained through the first step, the second step, and the third step satisfies 2.0 ≦ Hvb / Hva, the manufacturing method of the pipe component according to [1]. [8] It includes a pipe body portion and at least one or more protruding portions protruding from the pipe body portion. The protruding portion protrudes in a direction perpendicular to the axial direction of the pipe body portion. When the length in the protruding direction of the protruding portion of the pipe body portion is H0 and the length in the protruding direction of the protruding portion is H, 0.7 ≦ H / H0 is satisfied. A piping component that satisfies (Wmax - Wmin) ≤ 0.25, where Wmax is the maximum length of the main body of the piping and Wmin is the minimum length of the projections intersecting the main body and projections. [9] The piping component according to [8], wherein the average Vickers hardness Hva in a cross section parallel to the axial direction of the main body of the piping and the protruding direction of the projection is 220 Hv or more.

[10] Piping components as described in [8] or [9], made of austenitic stainless steel. [Effects of the Invention]

[0011] According to the present invention's method for manufacturing piping components, in the first step, a first preformed product having a pair of bulge portions is formed by using a first die provided with a die groove and a first punch provided with a punch groove. The widthwise length of the first preformed product (length perpendicular to the longitudinal direction of the material and the direction of pressure during molding) is longer than that of a comparative molded product obtained using a die and punch without grooves. Next, by applying pressure in a direction parallel to the widthwise direction to the first preformed product, whose widthwise length has been increased by a second die and a second punch, the amount of strain introduced into the first preformed product is increased compared to the comparative molded product, resulting in a second preformed product with increased overall strain. Then, by performing a back extrusion process on the second preformed product, a piping component with increased strain is obtained. Because the resulting piping component has significantly higher strain than the comparative product, its hardness is increased. Moreover, since all processes from the first to the third step are cold working processes, there is no risk of the accumulated strain decreasing. In this way, a piping component with high overall hardness can be obtained, which can be suitably used as a piping component for high-pressure fluids.

[0012] Next, according to the piping component of the present invention, the piping component comprises a main body and at least one projection, satisfies 0.7 ≤ H / H0 and (Wmax - Wmin) ≤ 0.25, and thus has a good shape and is a piping component with excellent dimensional accuracy. Further, according to the pipe fitting of the present invention, since the average Vickers hardness Hva in the cross-section parallel to the axial direction of the pipe main body portion and the protruding direction of the protruding portion is 220 Hv or more, it has a high hardness as a whole and can be suitably used as a pipe fitting for high-pressure fluids.

Brief Description of the Drawings

[0013] [Figure 1] It is a diagram for explaining a method of manufacturing a pipe fitting which is an embodiment of the present invention, and is a perspective schematic view showing a raw material. [Figure 2] It is a diagram for explaining a method of manufacturing a pipe fitting which is an embodiment of the present invention, and is a perspective view for explaining the first step. [Figure 3] It is a diagram for explaining a method of manufacturing a pipe fitting which is an embodiment of the present invention, and is an enlarged view showing a main part of FIG. 2. [Figure 4] It is a diagram for explaining a method of manufacturing a pipe fitting which is an embodiment of the present invention, and is a perspective schematic view for explaining the second step. [Figure 5] It is a diagram for explaining a method of manufacturing a pipe fitting which is an embodiment of the present invention, and is an enlarged view showing a main part of FIG. 4. [Figure 6] It is a diagram for explaining a method of manufacturing a pipe fitting which is an embodiment of the present invention, and is an enlarged view showing a main part of FIG. 4. [Figure 7] It is a diagram for explaining a method of manufacturing a pipe fitting which is an embodiment of the present invention, and is a perspective schematic view for explaining the third step. [Figure 8] It is a diagram for explaining a method of manufacturing a pipe fitting which is an embodiment of the present invention, and is an enlarged view showing a main part of FIG. 7. [Figure 9] It is a side schematic view of a pipe fitting which is an embodiment of the present invention. [Figure 10] It is a perspective schematic view of a pipe fitting which is an embodiment of the present invention.

Embodiments for Carrying Out the Invention

[0014] Hereinafter, a method of manufacturing a pipe fitting and a pipe fitting which are embodiments of the present invention will be described. The manufacturing method for the piping component of this embodiment includes a first step, a second step, and a third step. In the first step, a first preformed product is obtained by cold upsetting a round metal bar material using a first die and a first punch. In the second step, a second preformed product is obtained by cold upsetting the first preformed product using a second die and a second punch. In the third step, a piping component is obtained by cold backward extrusion of the second preformed product using a third die and a third punch. Each step will be described below.

[0015] (1st step) In the first step, a metal rod-shaped material is cold-upset. As shown in Figure 1, the shape of the material 1 is preferably a rod. There are no particular restrictions on the diameter D of the rod; for example, a rod with a diameter D of 15 to 60 mm can be used. In Figure 1, the direction of arrow M is perpendicular to the direction of the diameter of the material and is the axial direction of the material.

[0016] The material of Material 1 is not particularly limited as long as it is a metal, but austenitic stainless steel is preferred. When Material 1 is austenitic stainless steel, the average hardness Hvb of Material 1 is not particularly limited, but it is preferable that the Vickers hardness be 160 HV or less, more preferably 140 HV or less, and even more preferably 120 HV or less. A Vickers hardness of 160 HV or less makes it possible to perform the cold upsetting in the first and second processes and the cold back extrusion in the third process with a relatively low forming load. If the hardness of Material 1 is too low, the hardness of the piping component will decrease, so the lower limit of the hardness of Material 1 should be 100 HV or higher.

[0017] As shown in Figure 2, in the first step, a first die 2 and a first punch 3 are prepared. The first die 2 and the first punch 3 will be described below. Figure 2 shows the state in which the material 1 housed in the die recess 2d is upset by the relative proximity of the first die 2 and the first punch 3, resulting in the acquisition of the first preformed product 10.

[0018] The first die 2 has a flat die-machining surface 2a, and a die groove 2b is provided on the die-machining surface 2a. More specifically, the first die 2 is composed of a die body 2c. A die recess 2d is provided on the die body 2c. The die recess 2d has a rectangular shape when viewed from above (on the first punch 3 side) of the die body 2c. As a result, the bottom surface of the die recess 2d is also rectangular in plan view. The bottom surface of the die recess 2d, which is rectangular in plan view, is the die-machining surface 2a.

[0019] The size of the die-machined surface 2a in plan view is set to be large enough to allow sufficient upsetting on the material 1. In other words, the size of the die-machined surface 2a in plan view is set to be slightly larger than the size of the first preformed product 10.

[0020] A die groove 2b is provided on the die machining surface 2a. The die groove 2b extends along the longitudinal direction of the die machining surface 2a, which is rectangular in plan view.

[0021] The first punch 3 has a flat punching surface 3a, and a punch groove 3b is provided on the punching surface 3a. More specifically, the first punch 3 is composed of a punch body 3c. The punch body 3c is sized to be insertable into the die recess 2d of the first die 2. The bottom surface of the punch body 3c is the punching surface 3a. The punching surface 3a of the punch body 3c is positioned to face the die processing surface 2a parallel to it when the punch body 3c is inserted into the die recess 2d. Also, similar to the die processing surface 2a, the plan view shape of the punching surface 3a is rectangular. The size of the plan view shape of the punching surface 3a is approximately the same as the size of the plan view shape of the die processing surface 2a.

[0022] A punch groove 3b is provided on the punching surface 3a. The punch groove 3b extends along the longitudinal direction of the punching surface 3a, which is rectangular in plan view. The plan view shape of the punch groove 3b is approximately the same as the plan view shape of the die groove 2b.

[0023] In the first step, the material 1 is placed in the die recess 2d of the first die 2. At this time, the material 1 is positioned so that its axial direction M coincides with the groove length direction of the die groove 2b. As a result, the axial direction M of the material 1 also coincides with the groove length direction of the punch groove 3b.

[0024] Next, the first punch 3 is inserted into the die recess 2d of the first die 2, and the first die 2 and the first punch 3 are brought closer together to perform cold upsetting on the material 1. The bottom dead center of the first punch 3 is set so that the die-working surface 2a of the first die 2 and the punch-working surface 3a of the first punch 3 maintain a constant distance from each other. This yields the first preformed product 10 as shown in Figures 2 and 3.

[0025] As shown in Figure 2, the first pre-molded product 10 has a shape as if a round bar-shaped material 1 has been crushed from above and below. Hereafter, for convenience, the direction of the double-headed arrow X in Figures 2 and 3 will be called the width direction, the direction of the double-headed arrow Y will be called the longitudinal direction, and the direction of the double-headed arrow Z will be called the thickness direction.

[0026] As shown in Figures 2 and 3, the first preformed product 10 has a main body portion 10a and a pair of bulge portions 10b located on both sides of the main body portion 10a in the width direction and having a thickness smaller than the thickness of the main body portion 10a in the pressurized direction. The main body portion 10a is formed by the die groove portion 2b and the punch groove portion 3b when the material 1 is pressurized and crushed by the first die 2 and the first punch 3.

[0027] Furthermore, the bulge portion 10b is formed when the material 1 is crushed by the first die 2 and the first punch 3 to form the main body portion 10a, and the material constituting the material 1 is pushed out between the die-processing surface 2a and the punch-processing surface 3a.

[0028] Therefore, the molding load from the first die 2 and the first punch 3 is applied to the main body portion 10a, and strain accumulates inside it. On the other hand, less strain accumulates in the bulge portion 10b than in the main body portion 10a. Also, as shown in Figure 3, the length in the width direction at the center of the thickness direction of the first preformed product 10, that is, the maximum length in the width direction, is Wc1.

[0029] In the first step, the cold upsetting process is preferably performed such that the length Tc1 in the thickness direction of the main body portion 10a of the first preformed product 10 satisfies Tc1 ≤ 0.65D. If the length Tc1 in the thickness direction of the main body portion 10a is 0.65D or greater, sufficient strain is introduced into the main body portion 10a, improving the overall strain amount of the final product, the piping component, and increasing the hardness of the piping component. Note that the length Tc1 in the thickness direction of the main body portion 10a is the maximum thickness of the main body portion 10a, and may be, for example, the thickness at the center of the width direction of the main body portion 10a.

[0030] Furthermore, as shown in Figure 3, it is preferable that the length A of half the groove width of the die groove 2b and the punch groove 3b satisfies D / 2 ≤ A ≤ 3D / 4 with respect to the diameter D of the material 1. When length A is D / 2 or greater, the widthwise dimension of the main body 10a of the first preformed product 10 becomes sufficiently large, thereby allowing sufficient strain to be applied to the first preformed product in the second process, increasing the overall strain of the final product, the piping component, and improving the hardness of the piping component. Also, when length A is 3D / 4 or less, the widthwise dimension of the main body 10a of the first preformed product 10 does not become excessively large, thereby suppressing variations in the dimensions of the piping body of the final piping component. Specifically, in the piping component, as will be described later, (Wmax-Wmin) ≤ 0.25 is satisfied.

[0031] Furthermore, as shown in FIG. 3, it is preferable that the groove depth h of each of the die groove portion 2b and the punch groove portion 3b satisfies 0.02D < A ≤ 0.06D. When the groove depth h exceeds 0.02D, the length Tc1 of the main body portion 10a of the first preform 10 in the thickness direction becomes sufficiently larger than the length of the bulge portion 10b in the thickness direction. As a result, sufficient strain can be applied to the first preform 10 in the second step, increasing the overall strain amount of the final product, which is a pipe component, and enhancing the hardness of the pipe component. Also, when the depth h is 0.06D or less, the length Tc1 of the main body portion 10a of the first preform 10 in the thickness direction does not become excessively larger than the length of the bulge portion 10b in the thickness direction. Accordingly, variation in the dimensions of the pipe main body portion of the finally obtained pipe component is suppressed. Specifically, in the pipe component, as will be described later, (Wmax - Wmin) ≤ 0.25 is satisfied.

[0032] (Second step) As shown in FIG. 4, in the second step, cold pressing is performed on the first preform 10 obtained in the first step using the second die 22 and the second punch 23. FIG. 4 shows a state immediately before the processing is performed by relatively approaching the second die 22 and the second punch 23 with respect to the first preform 10 housed in the die recess 22d of the second die 22.

[0033] The pressing process in the second step is not performed by pressing from the thickness direction of the first preform 10, but as shown in FIG. 4, pressing is performed from the width direction of the first preform 10. That is, in the second step, the orientation of the workpiece (the first preform) with respect to the mold (die and punch) is rotated 90° with respect to the first step.

[0034] Hereinafter, the second die 22 and the second punch 23 will be described. In the second step, since the orientation of the workpiece (the first preform) with respect to the mold (die and punch) is rotated 90° with respect to the first step, the relationship between the thickness direction and the width direction is interchanged. However, in the description of the second step, the description of the first step is followed as it is.

[0035] The second die 22 consists of a die body portion 22c. The die body portion 22c is provided with a die recess 22d. The die recess 22d has a rectangular shape when viewed from above (on the second punch 23 side) of the die body portion 22c. As a result, the bottom surface of the die recess 22d is also rectangular when viewed from above. The bottom surface of the die recess 22d, which is rectangular when viewed from above, is the die processing surface 22a.

[0036] The size of the die recess 22d is such that upsetting can be performed on the first preformed product 10 while the main body portion 10a of the first preformed product 10 is restrained from both sides in the thickness direction. Specifically, in Figure 5, the distance Wd2 between the pair of vertical wall portions 22e of the die recess 22d is made approximately the same as the length Tc1 in the thickness direction of the main body portion 10a of the first preformed product 10. More specifically, the distance Wd2 is set to a range such that 1.000Tc1 ≤ Wd2 ≤ 1.010Tc1 holds true.

[0037] The second punch 23 consists of a punch body portion 23c. The punch body portion 23c is insertable into the die recess 22d of the second die 22. The bottom surface of the punch body portion 23c is the punching surface 23a. The punching surface 23a of the punch body portion 23c is positioned to face the die processing surface 22a parallel to it when the punch body portion 23c is inserted into the die recess 22d. Also, similar to the die processing surface 22a, the shape of the punching surface 23a in plan view is rectangular.

[0038] The size of the plan view shape of the punching surface 23a is approximately the same as the size of the plan view shape of the die processing surface 22a. Also, as shown in Figure 5, the width Wp2 of the punch body portion 23c is within the range where 1.000Tc1 ≤ Wp2 ≤ 1.010Tc1 holds true. However, in order for the second punch 23 to be insertable into the die recess 22d, Wp2 ≤ Wd2 is set.

[0039] In the second step, the first preformed product 10 is placed in the die recess 22d of the second die 22. At this time, the first preformed product 10 is placed in the die recess 22d of the second die 22 such that the width direction (direction of length Wc2) of the main body portion 10a of the first preformed product 10 coincides with the insertion direction of the second punch 23. As a result, the direction of pressure applied by the second die 22 and the second punch 23 substantially coincides with the width direction of the main body portion 10a of the first preformed product 10.

[0040] Next, the second punch 23 is inserted into the die recess 22d of the second die 22, and the second die 22 and the second punch 23 are brought closer together to perform cold upsetting on the first preformed product 10.

[0041] At this time, as shown in Figure 4, the vertical wall portion 22e that demarcates the die recess 22d of the second die 22 suppresses deformation of the main body portion 10a of the first preformed product 10 in the thickness direction. In the upsetting process of the second step, it is desirable to apply high strain to the first preformed product 10 by pressing it down in the width direction, but if deformation in the thickness direction is allowed, it will not be possible to sufficiently increase the strain. Specifically, in order to suppress deformation of the main body portion 10a of the first preformed product 10 in the thickness direction, the distance Wd2 between the pair of vertical wall portions 22e of the die recess 22d is restricted as described above. In this way, the second preformed product 20 as shown in Figure 6 is obtained. Note that deformation in the longitudinal direction of the first preformed product 10 does not need to be restricted.

[0042] As shown in Figure 6, the second premolded product 20 has a shape in which the first premolded product 10 has been compressed in the width direction. The widthwise length Wc2 of the second premolded product 20 is smaller than the widthwise length Wc1 of the first premolded product 10.

[0043] The second preformed product 20 has a main body portion 20a and a pair of bulge portions 20b located on both sides of the main body portion 20a in the width direction and having a thickness smaller than the thickness of the main body portion 20a in the pressurized direction. The main body portion 20a has almost the same shape as the main body portion 10a of the first preformed product 10, but further strain is introduced in its width direction by the upsetting process. On the other hand, the bulge portions 20b are flattened in shape relative to the bulge portion 10b of the first preformed product 10 by the upsetting process, and strain accumulates inside them. Thus, the second preformed product 20 obtained by the second process has strain introduced into both the main body portion 20a and the bulge portions 20b.

[0044] In the second step, the cold upsetting process is preferably performed such that the widthwise length Wc2 of the second preformed product 20 satisfies Wc2 ≤ 0.9Wc1 relative to the widthwise length Wc1 of the first preformed product 10. If the widthwise length Wc2 of the second preformed product 20 is 0.9Wc1 or less, sufficient strain is introduced throughout the second preformed product 20, improving the overall strain of the final product, the piping component, and increasing the hardness of the piping component. The lower limit of Wc2 can be set according to the dimensions of the final product, the piping component.

[0045] (3rd step) As shown in Figure 7, in the third step, the second preformed product 20 obtained in the second step is subjected to cold back extrusion using the third die 32 and the third punch 33. The back extrusion in the third step is performed by reducing the width direction of the second preformed product 20, as in the second step, as shown in Figure 7. Figure 7 shows the state just before processing is performed by bringing the third die 32 and the third punch 33 relatively close to the second preformed product 20 housed in the die recess 32d of the third die 32.

[0046] The third die 32 and the third punch 33 will be described below. In the third step, as in the second step, the orientation of the workpiece (second preformed product) relative to the mold (die and punch) is rotated by 90° compared to the first step, so the relationship between the thickness direction and the width direction is reversed. However, in the following description of the third step, the relationship between the thickness direction and the width direction will be the same as in the descriptions of the first and second steps.

[0047] The third die 32 consists of a die body 32c. The die body 32c is provided with a die recess 32d. The die recess 32d has a rectangular shape when viewed from above (towards the third punch 33) of the die body 32c. As a result, the bottom surface of the die recess 32d is also rectangular in plan view. The rectangular bottom surface of the die recess 32d is the die processing surface 32a.

[0048] The size of the die recess 32d is such that the main body portion 20a of the second preformed product 20 is restrained from both sides in the thickness direction, and that backward extrusion can be performed on the second preformed product 20. Specifically, in Figure 8, the distance Wd3 between the pair of vertical wall portions 32e of the die recess 32d is set to be approximately the same as the length Tc2 in the thickness direction of the main body portion 20a of the second preformed product 20. More specifically, the distance Wd3 is set to a range such that 1.000Tc2 ≤ Wd3 ≤ 1.010Tc2 holds true.

[0049] The third punch 33 consists of a punch body portion 33c. The punch body portion 33c is insertable into the die recess 32d of the third die 32. The bottom surface of the punch body portion 33c is the punching surface 33a. The punching surface 33a of the punch body portion 33c is positioned to face the die processing surface 32a parallel to it when the punch body portion 33c is inserted into the die recess 32d.

[0050] The punching surface 33a is provided with at least one recess 33f for backward extrusion. Figure 7 shows a state in which two recesses 33f are provided. Furthermore, the recesses 33f for backward extrusion are provided so as to be in communication with the entire width direction of the punch body 33c. As a result, the punching surface 33a is divided into multiple sections. The plan view shape of each divided punching surface 33a is rectangular.

[0051] Furthermore, as shown in Figure 8, the width Wp3 of the punch body 33c is set to a range where 1.000Tc2 ≤ Wp3 ≤ 1.010Tc2 is satisfied. However, in order for the third punch 33 to be insertable into the die recess 32d, Wp3 ≤ Wd3 is set.

[0052] In the third step, the second preformed product 20 is placed in the die recess 32d of the third die 32. At this time, the second preformed product 20 is placed in the die recess 32d of the third die 32 such that the width direction (direction of length Wc2) of the main body portion 20a of the second preformed product 20 coincides with the insertion direction of the third punch 33. As a result, the direction of pressure applied by the third die 32 and the third punch 33 substantially coincides with the width direction of the main body portion 20a of the second preformed product 20.

[0053] Then, the third punch 33 is inserted into the die recess 32d of the third die 32, and the third die 32 and the third punch 33 are brought closer together to perform cold back extrusion on the second preformed product 20. At this time, as shown in Figure 7, the vertical wall portion 32e that demarcates the die recess 32d of the third die 32 suppresses deformation of the main body portion 20a of the second preformed product 20 in the thickness direction. In the upsetting process of the third step, it is desirable to apply high strain to the second preformed product 20 by pressing it down in the width direction, but if deformation in the thickness direction is allowed, it will not be possible to sufficiently increase the strain. Specifically, in order to suppress deformation of the main body portion 20a of the second preformed product 20 in the thickness direction, the distance Wd3 between the pair of vertical wall portions 32e of the die recess 32d is restricted as described above. In this way, a piping component 40 as shown in Figures 9 and 10, as shown in Figure 8, is obtained. Furthermore, there is no need to restrict the longitudinal deformation of the second pre-molded product 20.

[0054] By performing a backward extrusion process, a molding load is applied to the second preformed product 20 by the die-processed surface 32a and the multiple punch-processed surfaces 33a separated by the recess 33f, causing the second preformed product 20 to deform. This forms the main body portion 41 of the piping component 40. At this time, a portion of the material constituting the second preformed product 20 flows into the backward extrusion recess 33f provided in the third punch 33. The material that flows into the recess 33f becomes the projection 42 of the piping component 40. In this way, the piping component 40 shown in Figures 9 and 10 is formed.

[0055] In the third step, the backward extrusion process is preferably performed such that 0.3 ≤ (Wc2 - H0) / Wc2 is satisfied, where Wc2 is the widthwise length of the second preformed product 20 and H0 is the insertion length of the third punch 33 in the pipe body portion 41 of the pipe component 40. By ensuring that (Wc2 - H0) / Tc2 is 0.3 or greater, the processing rate in the third step is secured, allowing for the formation of branch pipes of sufficient length in the pipe component and obtaining the required hardness.

[0056] To obtain the piping component 40, it is preferable that the depth Pd of the recess 33f for backward extrusion satisfies D ≤ Pd. Also, it is preferable that the opening length PL of the recess 33f for backward extrusion satisfies D ≤ PL. As shown in Figure 8, the depth Pd of the recess 33f is the distance from the punching surface 33a to the bottom of the recess 33f. The opening length PL of the recess 33f is the opening length on the punching surface 33a, and is the opening length in the longitudinal direction perpendicular to the width direction of the punch body 33c.

[0057] By ensuring that the depth Pd of the recess 33f satisfies D ≤ Pd, the length of the projection 42 of the piping component 40 in the protruding direction can be made sufficient. Furthermore, by ensuring that the opening length PL of the recess 33f satisfies D ≤ PL, excessive material flow into the projection 42 is prevented, thereby improving the average hardness of the piping component 40 and allowing the length of the projection 42 in the protruding direction to be made sufficient.

[0058] In the manufacturing method of the piping component of this embodiment, it is preferable that the ratio (Hvb / Hva) of the average Vickers hardness Hvb in a cross-section parallel to the axial direction of the material 1 and the average Vickers hardness Hva in a cross-section parallel to the axial direction of the piping component 40 obtained by going through the first, second, and third steps satisfies 2.0 ≤ Hvb / Hva. By satisfying this relationship, the material 1 before processing becomes soft and easy to process with little work hardening, while the piping component 40 after processing has high hardness. This makes it possible to reduce the molding load and mold load during processing in the first, second, and third steps.

[0059] The average Vickers hardness Hva of the piping component 40 is determined by exposing a cross section of the piping component 40 that is parallel to the longitudinal direction of the piping body 41 and parallel to the protruding direction of the projection 42. The cross section includes the central axis parallel to the longitudinal direction of the piping body 41. Multiple straight lines are drawn in a matrix pattern at intervals of 2.5 mm vertically and horizontally on the exposed cross section, and the Vickers hardness is measured at the intersection of each line. The measurement load for Vickers hardness is set to 0.1 kg. The average value is calculated from the measurements obtained at all measurement points, and this average value is taken as the average Vickers hardness Hva.

[0060] The average Vickers hardness Hvb of material 1 is determined by exposing a cross-section parallel to the axial direction of material 1. The cross-section should include the central axis parallel to the longitudinal direction of material 1. Multiple straight lines are drawn in a matrix pattern at intervals of 2.5 mm vertically and horizontally on the exposed cross-section, and the Vickers hardness is measured at the intersection of each line. The measurement load for Vickers hardness is set to 0.1 kg. The average value is calculated from the measurements obtained at all measurement points, and this average value is defined as the average Vickers hardness Hvb.

[0061] As shown in Figures 9 and 10, the piping component 40 comprises a pipe body portion 41 and at least one projection 42 protruding from the pipe body portion 41. The projection 42 protrudes perpendicular to the axial direction of the pipe body portion 41.

[0062] It is preferable to further perform surface grinding and polishing, and drilling, on the obtained piping component 40. The drilling should be performed along the longitudinal direction of the piping body 41 in the piping body 41 and along the protruding direction of the projection 42 in the projection 42 in the projection 42. This makes it possible to obtain a piping component having a main pipe made up of the piping body 41 and branch pipes made up of the projection 42.

[0063] When the length of the projection 42 of the main pipe body 41 in the protruding direction is H0, and the length of the projection 42 in the protruding direction is H, the condition 0.7 ≤ H / H0 must be satisfied. This makes it possible to form branch pipes with a certain length relative to the width of the main pipe body 41.

[0064] Furthermore, as shown in Figure 10, when Wmax is the maximum length in the longitudinal direction of the pipe body 41 and the direction intersecting the projection direction of the projection 42, and Wmin is the minimum length, it is necessary to satisfy (Wmax - Wmin) ≤ 0.25. This reduces the amount of processing required when post-processing the surface of the pipe component 40.

[0065] The average hardness of the piping component 40 is preferably 220 Hv or higher as an average Vickers hardness Hva. The average Vickers hardness Hva may be 260 Hv or higher, or 300 Hv or higher. The method for measuring the average Vickers hardness Hva of the piping component 40 is as described above.

[0066] As described above, according to the manufacturing method of the piping part of this embodiment, in the first step, a first preformed product 10 having a pair of bulge portions 10b is formed by using a first die 2 provided with a die groove portion 2b and a first punch 3 provided with a punch groove portion 3b. The widthwise length Wc1 of the first preformed product 10 (length in the direction perpendicular to the longitudinal direction of the material and the direction of pressure during molding) is longer than that of a comparative molded product obtained by a die and punch without grooves. Next, by performing an upsetting process on the first preformed product 10, whose widthwise length has been increased, using a second die 22 and a second punch 23, the amount of strain introduced into the first preformed product 10 is increased compared to that of a comparative molded product, thereby obtaining a second preformed product 20 with an overall increased amount of strain. Then, by performing a back extrusion process on the second preformed product 20, a piping part 40 with an increased amount of strain is obtained. The resulting piping component 40 exhibits significantly higher strain compared to the comparison object, thus increasing its hardness. Furthermore, since all processes from the first to the third stage are cold working, there is no risk of the accumulated strain decreasing. In this way, a piping component 40 with high overall hardness can be obtained, making it suitable for use as a piping component for high-pressure fluids.

[0067] Next, according to the piping component 40 of this embodiment, the piping component 40 comprises a main piping body 41 and at least one projection 42, satisfies 0.7 ≤ H / H0 and (Wmax - Wmin) ≤ 0.25, and thus has a good shape and is a piping component 40 with excellent dimensional accuracy.

[0068] Furthermore, according to the piping component of this embodiment, the average Vickers hardness Hva in a cross-section parallel to the axial direction of the pipe body 41 and the protruding direction of the projection 42 is 220 Hv or more, so the overall hardness is high and it can be suitably used as a piping component 40 for high-pressure fluids. [Examples]

[0069] The following describes embodiments of the present invention.

[0070] As the material, we prepared round bars made of austenitic steel having the chemical composition shown in Table 1 and an average Vickers hardness Hvb as shown in Table 2. The diameter D of each round bar was as shown in Table 2, and the axial length was 100 mm.

[0071] Furthermore, a first die, first punch, second die, second punch, third die, and third punch were prepared as shown in Figures 1 to 8. The dimensions of the dies and punches are as described in Tables 2 and 3.

[0072] Then, using these dies and punches, the first, second, and third steps were carried out in sequence to manufacture the piping components of the present invention examples A1 to A3.

[0073] Furthermore, the piping components of Comparative Examples B1 and B2 were manufactured in the same manner as the present invention example, except that the second step was omitted.

[0074] Furthermore, the piping component of Comparative Example B3 was manufactured in the same manner as the present invention example, except that the second and third steps were omitted.

[0075] For the obtained piping components A1-A3 and B1-B3, the average Vickers hardness Hva and hardness ratio (Hva / Hvb) were determined using the method described above. The results are shown in Table 4.

[0076] As shown in Table 4, Examples A1 to A3 of the present invention showed favorable average Vickers hardness Hva and hardness ratio (Hva / Hvb).

[0077] On the other hand, comparative examples B1 and B2, in which the second step was not performed, and comparative example B3, in which neither the second nor the third step was performed, showed average Vickers hardness Hva and hardness ratio (Hva / Hvb) outside the desirable values, and sufficient hardness was not obtained.

[0078] [Table 1]

[0079] [Table 2]

[0080] [Table 3]

[0081] [Table 4] [Explanation of symbols]

[0082] 1...Material, 2...First die, 2a...Die processing surface, 2b...Die groove, 3a...Punching surface, 3b...Punch groove, 3...First punch, 10...First preformed product, 10a...Main body, 10b...Bulge, 22...Second die, 22d...Die recess, 22e...Vertical wall, 23...Second punch, 20...Second preformed product, 20a...Main body, 32...Third die, 32d...Die recess, 32e...Vertical wall, 33...Third punch, 33a...Punching surface, 33f...Recess for rearward extrusion, 40...Piping component, 41...Piping main body, 42...Protrusion, M...Axial direction of the material.

Claims

1. The first step involves cold upsetting a round metal bar material using a first die and a first punch to obtain a first preformed product, A second step involves obtaining a second preformed product by cold upsetting the first preformed product using a second die and a second punch, The third step involves cold extruding the second preformed product backward using a third die and a third punch to obtain a piping component, The first step is to prepare a first die having a die groove on a flat die-working surface and a first punch having a punch groove on a flat punch-working surface, and to obtain the first preformed product by cold upsetting the material with the first die and the first punch brought relatively close together, while arranging the material so that its axial direction coincides with the groove length direction of the die groove and the punch groove. The first preformed product has a main body portion that is pressure-molded between the die groove portion and the punch groove portion, and a pair of bulge portions located on both sides of the main body portion in the width direction and having a thickness smaller than the thickness of the main body portion. The second step involves preparing a second die having a die recess and a second punch insertable into the die recess, and while the first preformed product is housed in the die recess of the second die so that the width direction of the main body of the first preformed product coincides with the insertion direction of the second punch, the second die and the second punch are brought relatively close to each other to perform cold upsetting of the first preformed product, thereby obtaining the second preformed product. The second preformed product has a widthwise length that is smaller than the widthwise length of the first preformed product. The third step is to obtain the piping component by preparing a third die having a die recess, a third punch that is insertable into the die recess and has a flat punching surface with at least one recess for backward extrusion, and placing the second preformed product in the die recess of the third die so that the width direction of the main body of the second preformed product coincides with the insertion direction of the third punch, and then bringing the third die and the third punch closer together to cold backward extrude the second preformed product while suppressing deformation in the thickness direction of the main body of the second preformed product with the vertical wall portion that divides the die recess of the third die, thereby obtaining the piping component. A method for manufacturing a piping component, wherein the piping component comprises a piping body formed by the die recess of the third die and the punched surface of the third punch, and a projection formed by being extruded into the recess of the third punch.

2. The first die and the first punch are such that the length A of half the groove width of the die groove and the punch groove satisfies D / 2 ≤ A ≤ 3D / 4 with respect to the diameter D of the material, and the groove depth h of the die groove and the punch groove satisfies 0.02D < A ≤ 0.06D. The method for manufacturing a piping component according to claim 1, wherein the upsetting process in the first step is performed such that the thickness Tc1 of the main body of the first preformed product satisfies Tc1 ≤ 0.65D.

3. The method for manufacturing a piping component according to claim 1, wherein the upsetting process in the second step is performed such that Wc2 ≤ 0.9Wc1 is satisfied when Wc1 is the widthwise length of the first preformed product and Wc2 is the widthwise length of the second preformed product.

4. The third punch is such that the depth Pd of the recess for rearward extrusion satisfies D ≤ Pd, and the opening length PL of the recess for rearward extrusion satisfies D ≤ PL. The method for manufacturing a piping component according to claim 1, wherein the backward extrusion process in the third step is performed such that 0.3 ≤ (Wc2 - H0) / Wc2 is satisfied when the widthwise length of the second preformed product is Wc2 and the length of the third punch in the insertion direction of the piping body is H0.

5. The first die and the first punch are such that the length A of half the groove width of the die groove and the punch groove satisfies D / 2 ≤ A ≤ 3D / 4 with respect to the diameter D of the material, and the groove depth h of the die groove and the punch groove satisfies 0.02D < A ≤ 0.06D. The third punch is such that the depth Pd of the recess for rearward extrusion satisfies D ≤ Pd, and the opening length PL of the recess for rearward extrusion satisfies D ≤ PL. The upsetting process in the first step is performed such that the length Tc1 in the thickness direction of the main body of the first preformed product satisfies Tc1 ≤ 0.65D. The upsetting process in the second step is performed such that, when the widthwise length of the first preformed product is Wc1 and the widthwise length of the second preformed product is Wc2, Wc2 ≤ 0.9Wc1. The method for manufacturing a piping component according to claim 1, wherein the backward extrusion process in the third step is performed such that 0.3 ≤ (Wc2 - H0) / Wc2 is satisfied when the widthwise length of the second preformed product is Wc2 and the insertion length of the third punch in the piping body is H0.

6. The method for manufacturing a piping component according to any one of claims 1 to 5, wherein the material is an austenitic stainless steel with a Vickers hardness of 100 HV or more and 160 HV or less.

7. The average Vickers hardness Hvb in a cross-section parallel to the axial direction of the aforementioned material, A method for manufacturing a piping component according to claim 1, wherein the ratio of the average Vickers hardness Hva in a cross-section parallel to the axial direction of the piping component obtained by going through the first, second, and third steps (Hvb / Hva) satisfies 2.0 ≤ Hvb / Hva.

8. The pipe comprises a main body and at least one projection extending from the main body, The aforementioned projection protrudes perpendicular to the axial direction of the main body of the pipe, When the length of the projection in the protruding direction of the main body of the piping is H0, and the length of the projection in the protruding direction is H, the condition 0.7 ≤ H / H0 is satisfied. A piping component that satisfies (Wmax - Wmin) ≤ 0.25, where Wmax is the maximum length in the direction intersecting the longitudinal direction of the main body of the piping and the protruding direction of the projection, and Wmin is the minimum length.

9. The piping component according to claim 8, wherein the average Vickers hardness Hva in a cross-section parallel to the axial direction of the main body of the piping and the protruding direction of the projection is 220 Hv or more.

10. The piping component according to claim 8 or claim 9, made of austenitic stainless steel.

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