Manufacturing method for tubular parts

Abstract

To provide a manufacturing method for a tubular component, by which the tubular component of a target shape can be accurately manufactured.SOLUTION: A manufacturing method for a tubular component includes a preparation step of preparing a plate blank having a hole penetrating therethrough, and a formation step of forming the blank into a tubular component by hole expansion drawing process. In the formation step, an outer diameter portion of the blank before the process becomes one end of the tubular component by the hole expansion drawing process. An inner diameter portion of the blank before the process becomes the other end of the tubular component by the hole expansion drawing process. In the preparation step, an outer-diameter-portion plate thickness (t0_out) of the blank before the process is set to have a first correlation with a target value of a wall thickness (a_up) of the one end of the tubular component. An inner-diameter-portion plate thickness (t0_in) of the blank before the process is set to have a second correlation with a target value of a wall thickness (a_down) of the other end of the tubular component.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a tubular component.

Background Art

[0002] For example, tubular components used for bearing raceways, gears, etc. are required to have a certain degree of shape accuracy. Conventionally, in order to obtain a tubular component with a desired shape, mechanical processing such as cutting is performed on an intermediate product after press forming. In mechanical processing, the yield of cutting and the loss of tact time are problems. As technologies for which an alternative to mechanical processing can be expected, the following technologies are disclosed.

[0003] For example, Japanese Patent Application Laid-Open No. 2002-239607 (Patent Document 1) describes forming a ring-shaped rolled member by ring rolling. In ring rolling, while detecting the diameter of the rolled material, the main roll and the mandrel perform thickness rolling in the radial direction of the rolled material, and the upper and lower conical edgers perform height rolling in the axial direction of the rolled material.

[0004] Further, Japanese Patent No. 6616027 (Patent Document 2) describes a method for obtaining a cylindrical rotating component by performing hole expanding and drawing on a donut-shaped metal disk. This method includes a step of obtaining a frustum-shaped intermediate formed product by pressing the entire surfaces of both sides of the donut-shaped metal disk between the tapered surfaces of a tapered punch and a die to perform hole expanding and drawing, and a step of obtaining a cylindrical rotating component by pressing the intermediate formed product with a punch and a die having a small taper angle to perform further hole expanding and drawing.

[0005] Further, Japanese Patent Application Laid-Open No. 2-227934 (Patent Document 3) describes a method for manufacturing a cathode cap for a cathode structure. This method includes a coining step in which the central portion of the blank is a thick portion and the peripheral portion is a thin portion, and a step of performing drawing and ironing of the side wall after blanking while leaving a slight amount of the thin portion.

Prior Art Documents

[0006] [Patent Document 1] Japanese Patent Publication No. 2002-239607 [Patent Document 2] Patent No. 6616027 [Patent Document 3] Japanese Patent Application Publication No. 2-227934 [Overview of the project] [Problems that the invention aims to solve]

[0007] The inventors investigated how to accurately manufacture tubular parts of a desired shape using a press molding method involving hole expansion and drawing. In conventional hole expansion and drawing, there is a large variation in thickness from the blank thickness before processing to the wall thickness of the tubular part after processing. Therefore, depending on the required precision, partial cutting may be necessary to adjust the shape of the molded product after processing.

[0008] Furthermore, the inventors considered a method to obtain a tubular part having a recess on its wall surface by pre-creating a recess in the blank before processing, and then performing a hole-expanding drawing process so that the pre-created recess becomes the desired recess in the tubular part after processing. Actual verification revealed that the position of the recess in the processed tubular part deviated from the target position. In hole-expanding drawing, both expansion flange deformation and contraction flange deformation occur within the material. The change in the material's thickness due to hole-expanding drawing is not uniform within the material. The position and shape of the recess after processing are affected by this non-uniform change. Therefore, it was found that predicting the position of the recess after processing is difficult.

[0009] Therefore, the present invention aims to provide a method for manufacturing tubular parts that can accurately produce tubular parts with a desired shape. [Means for solving the problem]

[0010] A method for manufacturing a tubular part in an embodiment of the present invention comprises a preparation step of preparing a plate-shaped blank having an upper surface, a lower surface, and a hole penetrating from the upper surface to the lower surface, and a forming step of forming the blank into a tubular part by hole-expanding drawing. In the forming step, the outer diameter portion, including the outer diameter surface of the blank before processing, becomes one end of the tubular part, including one end face in the axial direction, by the hole-expanding drawing. The inner diameter portion, including the inner diameter surface of the blank before processing, becomes the other end of the tubular part, including the other end face in the axial direction, by the hole-expanding drawing. In the preparation step, the outer diameter portion thickness (t0_out), which is the plate thickness of the outer diameter portion of the blank before processing, is set to have a first correlation with the target value of the wall thickness (a_up) of the one end of the tubular part. The inner diameter plate thickness (t0_in), which is the plate thickness of the inner diameter portion of the blank before processing, is set to have a second correlation with the target value of the wall thickness (a_down) at the other end of the tubular component. [Effects of the Invention]

[0011] According to the present invention, tubular parts with a desired shape can be manufactured with high precision. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 is a perspective view showing an example of a blank. [Figure 2] Figure 2 is a cross-sectional view of the blank shown in Figure 1. [Figure 3] Figure 3 is a perspective view showing an example of a tubular part obtained by enlarging and drawing the blank shown in Figure 1. [Figure 4] Figure 4 is a cross-sectional view of the tubular component shown in Figure 3. [Figure 5] Figure 5 is a diagram illustrating the deformation of a component during hole enlargement processing. [Figure 6] Figure 6 shows an example of a molding process using hole-expanding and drawing. [Figure 7] Figure 7 is a perspective view showing an example of a blank space. [Figure 8] Figure 8 is a cross-sectional view of the blank shown in Figure 7. [Figure 9] FIG. 9 is a perspective view showing an example of a tubular part obtained by performing hole expanding and drawing on the blank shown in FIG. 7. [Figure 10] FIG. 10 is a cross-sectional view of the tubular part shown in FIG. 9. [Figure 11] FIG. 11 is a cross-sectional view showing a modified example of the blank. [Figure 12] FIG. 12 is a cross-sectional view of a tubular part obtained by performing hole expanding and drawing on the blank shown in FIG. 11. [Figure 13] FIG. 13 is a diagram for explaining the dimensions in the model of the blank before processing used in the analysis. [Figure 14] FIG. 14 is a diagram for explaining the dimensions in the model of the tubular part after processing used in the analysis. [Figure 15] FIG. 15 is a diagram showing the conditions of the mold used in the calculation. [Figure 16] FIG. 16 is a graph showing the analysis result of the correlation between the plate thickness of the blank before processing and the wall thickness after processing. [Figure 17] FIG. 17 is a graph showing the analysis result of the correlation between the position of the depression of the blank before processing and the position of the recess after processing. [Figure 18] FIG. 18 is a diagram (left diagram) showing the dimensions of the blank in Example 1 and a photograph of the cross-section of the tubular part after processing (right diagram). [Figure 19] FIG. 19 is a diagram (left diagram) showing the dimensions of the blank in Example 2 and a photograph of the cross-section of the tubular part after processing (right diagram). [Figure 20] FIG. 20 is a diagram (left diagram) showing the dimensions of the blank in Example 3 and a photograph of the cross-section of the tubular part after processing (right diagram).

MODE FOR CARRYING OUT THE INVENTION

[0013] The inventors investigated a method for accurately manufacturing tubular parts of a desired shape by hole-expanding drawing. They performed drawing on a plate-shaped blank with a through hole under various conditions. They investigated the plate thickness on the inner and outer diameter sides of the blank, and the corresponding wall thicknesses at one axial end and the other end of the processed tubular part. As a result, they confirmed a correlation between the inner plate thickness before processing and the wall thickness at one end after processing, and between the outer plate thickness before processing and the wall thickness at the other end after processing, which could be expressed mathematically using linear functions. Furthermore, they found that the slopes of these linear functions remained within a constant range even when various processing conditions were changed. Using these correlations, it was found that the wall thickness at one end and the other end of the processed tubular part could be predicted from the inner and outer plate thicknesses of the blank. This can be used to estimate the inner and outer plate thicknesses of the blank required to obtain the desired wall thickness. For example, by calculating the blank plate thickness based on the correlation and reflecting it in the blank so that the thickness of the vertical wall after processing is the desired amount, it is possible to obtain a processed product with a uniform thickness. Based on this knowledge, we came up with the following embodiment.

[0014] A method for manufacturing a tubular part in an embodiment of the present invention comprises a preparation step of preparing a plate-shaped blank having an upper surface, a lower surface, and a hole penetrating from the upper surface to the lower surface, and a forming step of forming the blank into a tubular part by hole-expanding drawing. In the forming step, the outer diameter portion, including the outer diameter surface of the blank before processing, becomes one end of the tubular part, including one end face in the axial direction, by the hole-expanding drawing. The inner diameter portion, including the inner diameter surface of the blank before processing, becomes the other end of the tubular part, including the other end face in the axial direction, by the hole-expanding drawing. In the preparation step, the outer diameter portion thickness (t0_out), which is the plate thickness of the outer diameter portion of the blank before processing, is set to have a first correlation with the target value of the wall thickness (a_up) of the one end of the tubular part. The inner diameter plate thickness (t0_in), which is the plate thickness of the inner diameter portion of the blank before processing, is set to have a second correlation with the target value of the wall thickness (a_down) at the other end of the tubular component.

[0015] In the above manufacturing method, the outer diameter thickness (t0_out) of the blank before processing is set based on a first correlation with the target value of the wall thickness (a_up) at one end of the tubular part, and the inner diameter thickness (t0_in) of the blank before processing is set based on a second correlation with the target value of the wall thickness (a_down) at the other end of the tubular part. In other words, the outer diameter thickness (t0_out) and inner diameter thickness (t0_in) of the blank are each set independently based on their respective correlations with the target wall thickness. This makes it possible to set a thickness that takes into account the difference in stress and deformation between the inner and outer diameters during hole expansion and drawing. As a result, the wall thickness of the processed tubular part can be brought closer to the target. Consequently, tubular parts with the target shape can be manufactured with high precision.

[0016] The first and second correlations may be different from each other. Both the first and second correlations may be relationships in which the wall thickness after processing is expressed as a linear function of the plate thickness before processing. In this case, the slope of the linear function representing the first correlation may be greater than the slope of the linear function representing the second correlation.

[0017] In the blank before processing, the outer diameter plate thickness (t0_out) and the inner diameter plate thickness (t0_in) may be different. This allows the outer diameter plate thickness (t0_out) and the inner diameter plate thickness (t0_in) to be set to appropriate values ​​in relation to the target value of the corresponding wall thickness.

[0018] In the blank before processing, the thickness of the outer diameter portion (t0_out) may be thinner than the thickness of the inner diameter portion (t0_in). This makes it possible to reduce the difference between the wall thickness (a_up) at one end of the processed tubular part and the wall thickness (a_down) at the other end. As a result, the wall thickness of the processed tubular part can be made more uniform.

[0019] The outer diameter thickness (t0_out) of the blank before processing may be set thinner than the target value of the wall thickness (a_up) at one end of the tubular part. The inner diameter thickness (t0_in) of the blank may be set thicker than the target value of the wall thickness (a_down) at the other end of the tubular part. This makes it possible to reduce the difference between the wall thickness (a_up) at one end of the tubular part after processing and the wall thickness (a_down) at the other end. As a result, the wall thickness of the tubular part after processing can be made more uniform.

[0020] As the first correlation, the wall thickness (a_up) at one end of the tubular component may be expressed as a linear function of the outer diameter plate thickness (t0_out) of the blank, with a slope K1 of 1.19 ≤ K1 ≤ 1.55. As the second correlation, the wall thickness (a_down) at the other end of the tubular component may be expressed as a linear function of the inner diameter plate thickness (t0_in) of the blank, with a slope K2 of 0.63 ≤ K2 ≤ 0.83. This may also be the case. This allows for the use of more accurate correlations as the first and second correlations. As a result, tubular parts with the desired shape can be manufactured with greater precision.

[0021] The outer diameter thickness (t0_out) of the blank before processing may be set to have the first correlation with respect to the target value of the wall thickness (a_down) at one end of the tubular part, expressed by the formula t0_out(mm) = (a_up(mm) - 0.376) / K1. The inner diameter thickness (t0_in) of the blank before processing may be set to have the second correlation with respect to the target value of the wall thickness (a_up) at the other end of the tubular part, expressed by the formula t0_in(mm) = (a_down(mm) + 0.093) / K2. This allows for the use of more accurate correlations as the first and second correlations. As a result, tubular parts with the target shape can be manufactured with greater precision.

[0022] The inventors created a depression in the surface of a plate-shaped blank with a through hole and performed drawing under various conditions. They investigated the position of the depression on the blank's surface and the corresponding position of the recess on the wall surface of the processed tubular part. As a result, they conceived of a method in which a depression is formed on either the upper or lower surface of the plate-shaped blank, and this depression is drawn to form a recess on the inner surface of the tubular part after processing. The inventors found that in this processing method, there is a certain correlation between the position of the depression before processing and the position of the recess after processing. Furthermore, they found that by using this correlation, the position of the recess after processing can be controlled by the position of the depression before processing. The following embodiments are based on this finding.

[0023] A method for manufacturing a tubular part according to an embodiment of the present invention comprises a preparation step of preparing a plate-shaped blank having an upper surface, a lower surface, a hole penetrating from the upper surface to the lower surface, and a recess formed on one of the upper surface and the lower surface; and a forming step of forming the blank into a tubular part having a recess on its inner circumferential surface by a hole-expanding drawing process. In the forming step, the outer diameter portion of the blank before processing, including the outer diameter surface, becomes one end portion of the tubular part, including one end face in the axial direction, by the hole-expanding drawing process. The inner diameter portion of the blank before processing, including the inner diameter surface, becomes the other end portion of the tubular part, including the other end face in the axial direction, by the hole-expanding drawing process. One of the upper and lower surfaces of the blank before processing becomes the inner circumferential surface of the tubular part by the hole-expanding drawing process. The other of the upper and lower surfaces of the blank before processing becomes the outer circumferential surface of the tubular part by the hole-expanding drawing process. The recess in the blank before processing becomes a recess on the inner surface of the tubular part through the hole-expanding and drawing process.

[0024] In the above manufacturing method, a depression is formed on either the upper or lower surface of a plate-shaped blank having a through hole. Through hole-expanding and drawing, the outer diameter portion of the blank becomes one end of the processed tubular part, and the inner diameter portion of the blank becomes the other end of the processed tubular part. Furthermore, the hole-expanding and drawing process is performed so that the surface on which the depression is formed of the blank before processing becomes the inner circumferential surface of the processed tubular part. The hole-expanding and drawing process is performed so that the depression in the blank before processing forms a recess on the inner circumferential surface of the tubular part after processing. The inventors have found that there is a correlation between the position of the depression before processing and the position of the recess after processing in such processing. Therefore, in the above method, it is possible to control the position of the recess after processing by the position of the depression before processing. As a result, tubular parts of the desired shape can be manufactured with high precision.

[0025] Furthermore, the inventors attempted to formulate a mathematical equation for the relationship between the position of the indentation before processing and the position of the recess after processing. After diligent study, the following findings were obtained. The pre-processing ratio a0_out / a0_in was defined as the distance from the position of the indentation in the blank before processing to the inner diameter end, and the distance from the position of the indentation before processing to the outer diameter end, a0_out. The post-processing ratio h_up / h_down was defined as the distance from the recess of the tubular part after processing to one end face in the axial direction, h_up, and the distance from the position of the recess after processing to the other end face in the axial direction, h_down. It was found that the post-processing ratio h_up / h_down can be expressed as a linear function of the pre-processing ratio a0_out / a0_in. Furthermore, it was found that the slope of this linear function remains within a constant range even when various processing conditions are changed. By using this correlation, it becomes possible to determine the position of the indentation in the blank before processing necessary to obtain a tubular part with a recess in the desired position. Based on this finding, the following embodiment was conceived.

[0026] In the preparation step, the ratio (a0_out / a0_in) of the distance (a0_in) from the deepest point of the recess on one surface of the blank before processing to the inner diameter surface and the distance (a0_out) from the deepest point of the recess to the outer diameter surface of the blank may be set to have a third correlation with the target value of the ratio (h_up / h_down) of the distance (h_up) from the deepest point of the recess on the inner circumferential surface of the tubular part to one end surface and the distance (h_up) from the deepest point of the recess to the other end surface.

[0027] As a result, the ratio indicating the position of the recess in the radial direction of the blank (a0_out / a0_in) is set based on a third correlation with the target value of the ratio indicating the position of the recess in the axial direction of the tubular part (h_up / h_down). This allows for more precise control of the position of the recess after machining based on the position of the blank before machining. Therefore, tubular parts with the target shape can be manufactured with greater precision. Note that the third correlation may also be a relationship in which the ratio of the recess after machining (h_up / h_down) is expressed as a linear function of the ratio of the recess before machining (a0_out / a0_in).

[0028] The distance from the deepest point of the recess on one surface of the blank before processing to the inner diameter surface (a0_in) and the distance from the deepest point to the outer diameter surface (a0_out) may be different.

[0029] The distance (a0_out) from the deepest point of the recess on one of the blank surfaces to the outer diameter surface may be smaller than the distance (a0_in) from the deepest point of the recess to the inner diameter surface. This allows the position of the recess after machining to be brought closer to the axial center.

[0030] The ratio of the recess in the blank before processing (a0_out / a0_in) may differ from the ratio of the recess in the tubular part (h_up / h_down). This allows the position of the recess before processing to be appropriately set so that the position of the recess after processing is closer to the target position.

[0031] The ratio of the recess in the blank before processing (a0_out / a0_in) may be set to have a third correlation with respect to the target value of the ratio of the recess in the tubular part (h_up / h_down), expressed by the formula: (h_up / h_down) = K3 × (a0_out / a0_in) + B (1.05 ≤ K3 ≤ 1.29, B is a constant). This allows the use of a more accurate third correlation. As a result, tubular parts with the target shape can be manufactured with greater precision.

[0032] In the above manufacturing method, the setting of the outer diameter plate thickness (t0_out) of the blank based on a first correlation, the setting of the inner diameter plate thickness (t0_in) based on a second correlation, and the setting of the recess ratio (a0_out / a0_in) based on a second correlation may be combined. That is, in the preparation step, the outer diameter plate thickness (t0_out), which is the plate thickness of the outer diameter portion of the blank, may be set to have a first correlation with the target value of the wall thickness (a_up) at one end of the tubular part, the inner diameter plate thickness (t0_in), which is the plate thickness of the inner diameter portion of the blank, may be set to have a second correlation with the target value of the wall thickness (a_down) at the other end of the tubular part, and the recess ratio (a0_out / a0_in) of the blank may be set to have a third correlation with the target value of the recess ratio (h_up / h_down) of the tubular part.

[0033] The blank may be a metal disc with a through hole in the center. The through hole may be circular. In this case, the tubular part will be cylindrical. In this case, in the cross-section of the plane passing through the center of the blank and parallel to the thickness direction, the dimension in the thickness direction at the radially outer end is defined as the outer diameter thickness (t0_out), and the dimension in the thickness direction at the radially inner end is defined as the inner diameter thickness (t0_in). In the cross-section of the plane passing through the central axis of the tubular part, the radial dimension at one end face in the axial direction is defined as the wall thickness at one end (a_up), and the radial dimension at the other end face in the axial direction is defined as the wall thickness at the other end (a_down). If there is a recess on the upper or lower surface of the blank of the disc, in the cross-section of the plane passing through the center of the blank and parallel to the thickness direction, the radial distance from the deepest point of the recess to the inner diameter is defined as distance (a0_in), and the radial distance from the deepest point of the recess to the outer diameter is defined as distance (a0_out). Furthermore, the circular shape of blanks and tubular parts is not limited to a perfect circle; it may deviate from a perfect circle within the limits of the design.

[0034] The method for manufacturing tubular parts according to embodiments of the present invention will be described below with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and the description of those parts will not be repeated. Furthermore, the dimensions of the components in each drawing do not faithfully represent the dimensions of the actual components or the dimensional ratios of each component.

[0035] (Embodiment 1) This embodiment relates to a method for manufacturing a tubular part by enlarging and drawing a plate-shaped blank having a through hole. Figure 1 is a perspective view showing an example of a blank. Figure 2 is a cross-sectional view of the blank shown in Figure 1. Figure 3 is a perspective view showing an example of a tubular part obtained by enlarging and drawing the blank shown in Figure 1. Figure 4 is a cross-sectional view of the tubular part shown in Figure 3.

[0036] The blank 100 shown in Figures 1 and 2 is plate-shaped and has an upper surface 2, a lower surface 3, and a hole 1 that penetrates from the upper surface 2 to the lower surface 3. When viewed from above (viewed in the thickness direction), the blank 100 has a hole 1 in the center and a shape that radiates radially from the hole 1. The blank 100 has a donut shape. The outer surface of the blank 100 is the outer diameter surface 4, and the inner surface of the blank 100, i.e., the inner surface of the hole 1, is the inner diameter surface 5. By performing a hole-expanding drawing process on the blank 100, the tubular part 110 shown in Figure 3 is obtained.

[0037] In the examples in Figures 1 and 2, the z-axis is in the thickness direction, and the radial direction is the direction radiating from the central axis C1 in the xy-plane perpendicular to the z-axis. Figure 2 shows a cross-section of the machined blank on a plane parallel to the thickness direction, passing through the center of the through hole.

[0038] The tubular component 110 shown in Figures 3 and 4 is a hollow member formed by a wall that surrounds the entire circumference of an axis C2 in one direction. Both ends of the tubular component 110 in the axial direction are open. The wall forming the tubular component 110 has an outer circumferential surface 9, an inner circumferential surface 8, and one end face 6 and the other end face 7 in the axial direction. In the example of Figures 3 and 4, the z-axis is the axial direction.

[0039] The outer diameter surface 4 of the blank 100 becomes one end face 6 of the tubular part 110 after hole enlargement and drawing. The inner diameter surface 5 of the blank 100 becomes the other end face 6 of the tubular part 110 after hole enlargement and drawing. The upper surface 2 of the blank 100 becomes the inner circumferential surface 8 of the tubular part 110 after hole enlargement and drawing. The lower surface 3 of the blank 100 becomes the outer circumferential surface 9 of the tubular part 110 after hole enlargement and drawing.

[0040] The hole-expanding drawing process includes the step of placing a blank 100 between a punch and a die, and pressing the punch and die relatively close together. The punch has a convex portion with a diameter larger than the diameter of the hole 1. The die has a concave portion with a diameter smaller than the outer diameter of the blank 100. The convex portion of the punch presses against the upper surface 2 of the blank 100, and the concave portion of the die presses against the lower surface 3 of the blank 100. The blank 100 is deformed by being drawn between the punch and the die as the hole 1 is expanded by the punch.

[0041] The process of forming by hole-expanding drawing may include, as an example, an intermediate forming step of obtaining a frustoconical intermediate molded product by pressing the upper surface 2 and lower surface 3 of the blank 100 with the tapered surfaces of a punch and die having a predetermined taper and performing hole-expanding drawing; and a step of further performing hole-expanding drawing by pressing the intermediate molded product by inserting a punch from the larger diameter side of the intermediate molded product with a punch and die having a smaller taper angle than the punch and die used in the intermediate forming step, with the smaller diameter side of the intermediate molded product positioned towards the die. In the intermediate forming step, multiple drawing processes may be performed by changing the angle between the tapered surfaces of the punch and die and the processing direction. Specific examples of hole-expanding drawing will be described later.

[0042] The thickness t0_out of the outer diameter portion of blank 100 is smaller (thinner) than the thickness t0_in of the inner diameter portion. The thickness of blank 100 is thickest on the inner diameter surface 5, and decreases from the inner diameter surface 5 to the outer diameter surface 4. The top surface 2 is inclined with respect to the thickness direction. The bottom surface 3 is perpendicular to the thickness direction.

[0043] In the blank 100 shown in Figures 1 and 2, the plate thickness t0_out of the outer diameter portion including the outer diameter surface 4 is set based on a first correlation with the target value of the wall thickness a_up at one end of the tubular component 110, including one end face 6. The plate thickness t0_in of the inner diameter portion of the blank 100, including the inner diameter surface 5, is set based on a second correlation with the target value of the wall thickness a_down at the other end of the tubular component 110, including the other end face 7.

[0044] The first and second correlations are different from each other. The first correlation can be, for example, a relationship in which the wall thickness a_up at one end of the tubular component 110 is expressed by a linear function of the plate thickness t0_out at the outer diameter. The second correlation can be, for example, a relationship in which the wall thickness a_down at the other end of the tubular component 110 is expressed by a linear function of the plate thickness t0_in at the outer diameter. In this case, the slope of the linear function showing the first correlation is greater than the slope of the linear function showing the second correlation. These correlations were discovered by the inventors. These correlations are thought to be due to the following mechanism.

[0045] Figure 5 is a diagram illustrating the deformation of a component during hole enlargement processing. Figure 5 shows the shapes of the blank before processing, the intermediate molded product, and the final molded product, a tubular component. The blank shown in Figure 5 has a constant plate thickness; that is, the plate thickness of the inner diameter portion and the plate thickness of the outer diameter portion are the same. An intermediate molded product is formed by enlarging and drawing this blank. The top surface of the blank (line ab) becomes the outer surface (line ab) of the intermediate molded product. In this hole enlargement and drawing process, the portion of length X on the inner diameter side of the top surface of the blank is affected by elongation flange. The portion of length Y on the outer diameter side of the top surface of the blank is affected by shrinkage flange. As a result, the portion of length X on the top surface of the blank shrinks, and the portion of length Y expands. Also, the outer diameter surface of the blank (line bc) becomes one end face (line bc) of the intermediate molded product. The inner diameter surface of the blank (line ad) becomes the other end face (line ad) of the intermediate molded product. The wall thickness at one end face (line bc) is thicker than the wall thickness at the other end face (line ad).

[0046] The reason why the wall thickness of the end faces at both ends of the tube in the axial direction differs after hole-expanding and drawing is thought to be as follows: The outer diameter portion of the blank is compressed inward during processing, resulting in low material fluidity. Therefore, the wall thickness at one end corresponding to the outer diameter portion of the blank becomes thicker. Due to compression, the wall thickness at one end after processing becomes thicker than the plate thickness of the outer diameter portion of the blank. The end face corresponding to the outer diameter surface of the blank after processing can be called the compression surface. On the other hand, the inner diameter portion of the blank is stretched outward during processing, resulting in high material fluidity. Therefore, the wall thickness at the other end corresponding to the inner diameter portion of the blank after processing becomes thinner. Due to stretching, the wall thickness at the other end after processing becomes thinner than the plate thickness of the inner diameter portion of the blank. The other end face corresponding to the inner diameter surface of the blank after processing can be called the stretch surface. Due to this difference in material flow within the member, the radial center line CL (the boundary line between X and Y) on the top surface of the blank (line ab) is not located in the axial center after processing, but is shifted from the center towards the other end.

[0047] Thus, the outer diameter of the blank is compressed through shrinking flange deformation during the hole-expanding drawing process, becoming one end of the tubular component. The degree of this compression is represented by the first correlation. The inner diameter of the blank is stretched through elongating flange deformation during the hole-expanding drawing process, becoming one end of the tubular component. The degree of this stretching is represented by the second correlation.

[0048] The first and second correlations can be expressed, for example, by the following formulas. The relationship between the outer diameter thickness t0_out of the blank before processing and the wall thickness a_up at one end after processing can be expressed, for example, by the following formula. In the following formula, the units of t0_out and a_up are mm. a_up = 1.3735 × t0_out + 0.3763 In this case, the slope appears to vary within the range of 1.3735 ± 0.178. That is, the range of the correlation can be considered to be 1.19 × t0_out + 0.3763 ​​to 1.55 × t0_out + 0.3763. The outer diameter thickness t0_out of the blank before processing can be determined by substituting the target value of the wall thickness a_up at one end of the tubular part into a_up in the following formula. In the following formula, the intercept value 0.3763 ​​is rounded to 0.376 by rounding to the fourth decimal place. t0_out=(a_up-0.376) / K1 1.19 ≤ K1 ≤ 1.55

[0049] The relationship between the plate thickness t0_in of the inner diameter portion of the blank before processing and the wall thickness a_down of the other end portion after processing can be expressed, for example, by the following formula. In the following formula, the units of t0_in and a_down are mm. a_down = 0.7291 × t0_in - 0.0925 In this case, the slope appears to vary within the range of 0.7291 ± 0.102. That is, the range of the correlation can be defined as 0.63 × t0_in × 0.0925 ~ 0.83 × t0_out - 0.0925. The inner diameter thickness t0_in of the blank before processing can be determined by substituting the target value of the wall thickness a_up at the other end of the tubular part into a_down in the following formula. In the following formula, the intercept value 0.0925 is rounded to 0.093 by rounding to the fourth decimal place. t0_in=(a_down+0.093) / K2 0.63 ≤ K2 ≤ 0.83

[0050] <Example of a molding process using hole-expanding and drawing> Figure 6 shows an example of a forming process by hole-expanding drawing. As shown in Figure 6(a), in the first hole-expanding drawing process in the intermediate forming process, the entire surface of both sides of the metal disc blank 100 is pressed with a die consisting of a punch 10A1 and a die 20A1 that have a predetermined taper to perform hole-expanding drawing and obtain an intermediate molded product 100A1.

[0051] The tapered surfaces of punch 10A1 and die 20A1 have angles of θp1 and θd1, respectively, with respect to the machining direction. For example, θp1 = θd1 can be assumed.

[0052] As shown in Figure 6(b), in the second hole-expanding drawing process in the intermediate molding process, the entire surface of both sides of the intermediate molded product 100A1 is pressed with a die consisting of a punch 10A2 and a die 20A2 that have a predetermined taper to perform the hole-expanding drawing process and obtain the intermediate molded product 100A2.

[0053] The tapered surfaces of punch 10A2 and die 20A2 have angles of θp2 and θd2 with respect to the machining direction, respectively. For example, θp2 = θd2. The angles θp2 and θd2 of the tapered surfaces of punch 10A2 and die 20A2 used in the second hole-expanding drawing process are set to be smaller than the angles θp1 and θd1 ​​of the tapered surfaces of punch 10A1 and die 20A1 used in the first hole-expanding drawing process.

[0054] As shown in Figure 6(c), in the final molding process, the intermediate molded product 100A2 is further subjected to hole-expanding and drawing using a punch 10B and die 20B mold capable of forming a cylindrical rotating part of the desired shape to obtain the cylindrical rotating part 100B. In this embodiment, in order to obtain a tubular part with an inner diameter of D1' and an outer diameter of D2', the punch 10B has a cylindrical shape with an outer diameter of D1', and the die 20B has an annular shape with an inner diameter of D2'.

[0055] Note that the example of the forming process using hole-expanding and drawing is not limited to the example shown in Figure 6. In Figure 6, multiple sets of different dies and punches are used to perform multiple hole-expanding and drawing operations. The hole-expanding and drawing operation may be performed once or four or more times.

[0056] According to this embodiment, by using the first and second correlations, it becomes possible to calculate the plate thickness of the blank 100 necessary to make the wall thickness of the processed tubular part 110 a target value. As a result, a tubular part of the desired shape can be accurately processed by hole-expanding and drawing. Therefore, the work of further cutting the processed tubular part to achieve the desired shape can be omitted or reduced.

[0057] (Embodiment 2) This embodiment relates to a method for manufacturing a tubular part having a recess by forming a recess in a plate-shaped blank having a through hole and then performing a hole-expanding drawing process. Figure 7 is a perspective view showing an example of a blank. Figure 8 is a cross-sectional view of the blank shown in Figure 7. Figure 9 is a perspective view showing an example of a tubular part obtained by performing a hole-expanding drawing process on the blank shown in Figure 7. Figure 10 is a cross-sectional view of the tubular part shown in Figure 9.

[0058] The blank 100 shown in Figures 7 and 8 is plate-shaped and has an upper surface 2, a lower surface 3, and a hole 1 that penetrates from the upper surface 2 to the lower surface 3. When viewed from above (viewed in the thickness direction), the blank 100 has a hole 1 in the center and a shape that radiates radially from the hole 1. The blank 100 has a donut shape. The outer surface of the blank 100 is the outer diameter surface 4, and the inner surface of the blank 100, i.e., the inner surface of the hole 1, is the inner diameter surface 5.

[0059] A recess 2a is formed on the upper surface 2 of the blank 100. The recess 2a is a groove that surrounds the entire circumference of the hole 1. The recess 2a is a groove with a curved cross-section. The cross-sectional shape of the recess 2a may or may not be an arc. When viewed from above, the recess 2a is formed concentrically with the hole 1. By performing a hole-expanding drawing process on the blank 100, the tubular part 110 shown in Figure 9 is obtained.

[0060] In the examples shown in Figures 7 and 8, the z-axis is in the thickness direction, and the radial direction is the direction radiating from the central axis C1 in the xy-plane perpendicular to the z-axis. Figure 8 shows a cross-section of the blank in a plane parallel to the thickness direction, passing through the center of the through-hole.

[0061] The tubular component 110 shown in Figures 9 and 10 is a hollow member formed by a wall that surrounds the entire circumference of an axis C2 in one direction. Both ends of the tubular component 110 in the axial direction are open. The wall forming the tubular component 110 has an outer circumferential surface 9, an inner circumferential surface 8, and one end face 6 and the other end face 7 in the axial direction. In the example of Figures 9 and 10, the z-axis is the axial direction.

[0062] The outer diameter surface 4 of the blank 100 becomes one end face 6 of the tubular part 110 after hole-expanding and drawing. The inner diameter surface 5 of the blank 100 becomes the other end face 6 of the tubular part 110 after hole-expanding and drawing. The upper surface 2 of the blank 100 becomes the inner circumferential surface 8 of the tubular part 110 after hole-expanding and drawing. The lower surface 3 of the blank 100 becomes the outer circumferential surface 9 of the tubular part 110 after hole-expanding and drawing. The recess 2a on the upper surface 2 of the blank 100 becomes the recess 8a on the inner circumferential surface 8 of the tubular part 110 after processing. Note that the forming process by hole-expanding and drawing can be carried out in the same manner as in Embodiment 1.

[0063] The recess 8a on the inner circumferential surface 8 of the processed tubular part 110 is formed over the entire circumference of the inner circumferential surface 8 in a portion of the axial direction. The cross-section of the recess 8a is curved. The cross-section of the recess 8a may or may not be an arc.

[0064] The distance a0_out from the deepest point C0 of the recess 2a on the upper surface 2 of the blank 100 before processing to the outer diameter surface 4 is smaller than the distance a0_in from the deepest point C0 of the recess 2a to the inner diameter surface 5. The position of the recess 2a is set to have a third correlation with the target position of the recess 8a of the tubular part 110 after processing. Specifically, the ratio a0_out / a0_in, which is the distance a0_in from the deepest point C0 of the recess in the blank 100 before processing to the distance a0_out from the deepest point C0 of the recess 2a to the outer diameter surface 4 of the blank 100, is set to have a third correlation with the target value of the ratio h_up / h_down, which is the distance h_up from the deepest point C of the recess 8a on the inner circumferential surface 8 of the tubular part to one end face 6 and the distance h_down from the deepest point of the recess to the other end face 7. A third correlation can be, for example, one in which the ratio of the recessed area after processing, h_up / h_down, is expressed as a linear function of the ratio of the recessed area before processing, a0_out / a0_in.

[0065] The third correlation can be expressed, for example, by the following formula. The relationship between the ratio of the depression before processing (a0_out / a0_in) and the ratio of the concave area after processing (h_up / h_down) can be expressed, for example, by the following formula. h_up / h_down = 1.17 × a0_out / a0_in + B (where B is a constant) In this case, the slope appears to vary within the range of 1.17 ± 0.12. That is, the range of the correlation can be given as 1.05 × a0_out / a0_in + B ~ 1.29 × a0_out / a0_in + B. The ratio of the recess before processing, a0_out / a0_in, can be determined by substituting the target value of the ratio of the recess after processing, h_up / h_down, into the following formula for h_up / h_down. (h_up / h_down)= K3×(a0_out / a0_in)+ B 1.05 ≤ K3 ≤ 1.29

[0066] Here, B can be a value depending on the conditions. The value of B can be determined, for example, by performing the following preliminary analysis or experiment. Measure or analyze the h_up_0 and h_down_0 values ​​of a tubular part that has undergone the hole-expanding and drawing process of this embodiment on a blank before processing with arbitrary values ​​a0_out_0 and a0_in_0. Substitute these values ​​into B=(h_up_0 / h_down_0)-K3×(a0_out_0 / a0_in_0) to determine B.

[0067] Thus, according to this embodiment, by using the third correlation, it becomes possible to calculate the position of the blank recess necessary to form the recess 8a of the processed tubular part 110 as desired. As a result, a tubular part with a recess formed at the desired position can be manufactured by hole-expanding drawing. Therefore, the work of cutting the tubular part after processing to form the recess can be omitted or reduced.

[0068] This embodiment is not limited to this, but can be suitably applied to tubular components such as bearing raceways. For example, this embodiment can be applied to the manufacture of tubular components such as outer races for rolling bearings and bushings for sliding bearings.

[0069] In the example shown in FIGS. 9 and 10, the wall thickness a_up at one end of the tubular component 110 is thickened, and the wall thickness a_down at the other end is thinned. In the cross-section of the surface passing through the axis C2 of the tubular component 110, the outer peripheral surface 9 and the inner peripheral surface 8 form a trapezoid that is not parallel. This is because, as shown in FIG. 8, the plate thickness t0_out of the outer diameter portion and the plate thickness t0_in of the inner diameter portion of the blank 100 are equal. Therefore, by combining the above Embodiment 1 with Embodiment 2 and adjusting the plate thickness t0_out of the outer diameter portion and the plate thickness t0_in of the inner diameter portion of the blank 100, the wall thickness of the tubular component 110 can be made closer to uniform.

[0070] That is, using the first correlation, the plate thickness t0_out of the outer diameter portion of the blank 100 can be set, using the second correlation, the plate thickness t0_in of the inner diameter portion of the blank 100 can be set, and further, using the third correlation, the ratio a0_out / a0_in indicating the position of the depression of the blank 100 can be set. Thereby, it becomes possible to make the wall thickness a_up at one end, the wall thickness a_down at the other end, and the ratio h_up_0 / h_down_0 indicating the position of the recess 8a of the tubular component 110 approach the target values.

[0071] In this case, for example, as shown in FIG. 11, in the blank 100, the plate thickness t0_out of the outer diameter portion can be set to be smaller than the plate thickness t0_in of the inner diameter portion (t0_out < t0_in), and the a0_out / a0_in of the depression can be set to be smaller than 1 ((a0_out / a0_in) < 1). Thereby, the plate thickness of the tubular component 110 becomes closer to uniform in the axial direction, and the deviation of the deepest point of the recess 8a from the center in the axial direction can be reduced. <000,0305>

[0072] FIG. 12 is a cross-sectional view of the tubular component 110 obtained by performing hole expanding and sizing on the blank 100 shown in FIG. 11. The tubular component 110 shown in FIG. 12 has a substantially uniform wall thickness in the axial direction, and the wall thickness a_up at one end and the wall thickness a_down at the other end are substantially the same.

[0073] As blank materials, for example, steel, aluminum, copper, nickel, titanium, alloys containing at least one of these, and other metals can be used. Alternatively, non-metallic blank materials such as resins like CFRTP (Carbon Fiber Reinforced Thermo Plastics) may be used.

[0074] In embodiments 1 and 2 described above, the blank 100 is donut-shaped and the tubular part 110 is cylindrical. The shapes of the blank 100 and the tubular part are not limited to these. The shape of the outer edge and the edge of the hole of the donut-shaped blank in plan view may be a perfect circle, a flattened circle, or an ellipse. As an example of a donut shape, the shape of the outer edge and the edge of the hole of the blank may be polygonal in plan view. In this case, the tubular part will be a tube with a polygonal cross-section on the plane perpendicular to the axis. The number of corners of the polygonal blank may be increased to make the plan view shape of the outer edge and the edge of the hole of the blank closer to a circle.

[0075] <Analysis results> The correlation between the thickness of the blank before processing and the wall thickness of the tubular part after hole enlargement and drawing was analyzed using FEM (Finite Element Method). Figure 13 is a diagram illustrating the dimensions of the blank model before processing used in the analysis. Figure 13(a) is a perspective view of the blank, and Figure 13(b) shows the cross-section of line AA in Figure 13(a). Figure 14 is a diagram illustrating the dimensions of the tubular part model after processing used in the analysis. Figure 14(a) is a perspective view of the tubular part, and Figure 14(b) shows the cross-section of line BB in Figure 14(a).

[0076] As shown in Figure 13, the dimensions of each part of the blank before processing were defined as follows. D0: Blank outer diameter d0: Blank inner diameter R0: Arc dimension (radius) of the recess C0: Deepest point of the depression a0: Width of the blank from the inner diameter surface to the outer diameter surface in the radial direction. a0_out: Distance from the deepest point of the depression to the outer diameter surface a0_in: Distance from the deepest point of the depression to the inner diameter surface t0_out: Blank outer diameter plate thickness t0_in: Inner diameter plate thickness of the blank t0_min: Blank plate thickness at the deepest point of the depression (the thinnest part of the blank plate)

[0077] As shown in Figure 14, the dimensions of each part of the processed tubular component were defined as follows. D: Outer diameter of the tubular part after processing d: Inner diameter of the tubular part after processing R: Arc dimension (radius) of the recess in the tubular part after processing. C: The deepest point of the recess in the tubular part after processing. h: Axial length (height) of the tubular part after processing. h_up: Distance from the deepest point of the recess to one end face in the axial direction. h_down: Distance from the deepest point of the recess to the other end face in the axial direction. a_up: Wall thickness of one end of the tubular part after processing (corresponding to the outer diameter portion after processing before processing) a_down: Wall thickness of the other end of the tubular part after processing (corresponding to the inner diameter after processing before processing) a_min: Wall thickness at the deepest point of the recess

[0078] The deformation of a blank before processing was calculated when a hole-expanding drawing process was performed. The hole-expanding drawing process consisted of three steps, the first to the third, using different dies. Figure 15 shows the conditions of the dies used in the calculation. In Figure 15, (a) shows the die for the first step, a 45-degree hole-expanding drawing process, (b) shows the die for the second step, a 60-degree hole-expanding drawing process, and (c) shows the die for the third step, the drawing process. The material properties of the blank were those of SUJ2 steel sheet.

[0079] Under the above conditions, we analyzed the correlation between the outer diameter plate thickness t0_out before processing and the wall thickness a_up at one end after processing, the correlation between the inner diameter plate thickness t0_in and the wall thickness a_down at the other end, and the correlation between the recess ratio a0_out / a0_in and the concave ratio h_up / h_down when a blank is subjected to hole enlargement and drawing processing.

[0080] In the analysis, as shown in Table 1, the correlation was analyzed for each condition by varying the following parameters: the inner diameter of the blank before processing (d0), the arc dimension of the recess before processing (R0), the thickness of the blank at the deepest point of the recess (t0_min), the coefficient of friction (μ), and the width from the inner diameter surface to the outer diameter surface of the blank in the radial direction (a0).

[0081] [Table 1]

[0082] <Correlation between plate thickness before processing and wall thickness after processing> Figure 16 is a graph showing the results of the correlation analysis between the blank thickness before processing and the wall thickness after processing. In the graph of Figure 16, the horizontal axis represents the blank thickness before processing (t0_xx), and the vertical axis represents the wall thickness after processing (a_xx). t0_xx is either t0_out or t0_in. a_xx is either a_up or a_down.

[0083] The line L1 in the graph of Figure 16 shows the correlation between the outer diameter plate thickness of the blank before processing (t0_out) and the wall thickness of one end of the tubular part after processing (a_up). The equation for line L1 is as follows. a_up=1.3735 ×t0_out + 0.3763 ​​(R 2 = 0.9728) ···(1) This equation shows that the thickness t0_out of the blank's outer diameter before processing becomes approximately 1.37 times thicker as the wall thickness after processing due to the hole-expanding and drawing process. This is thought to be because the material's fluidity is low in the portion of the blank closest to its outer diameter due to compression during processing.

[0084] The line L2 in the graph of Figure 16 shows the correlation between the inner diameter plate thickness (t0_in) of the blank before processing and the wall thickness (a_down) of the other end of the tubular part after processing. The equation for line L2 is as follows. a_down=0.7291 ×t0_in - 0.0925 (R 2 = 0.9694) ···(2) This equation shows that the thickness t0_in of the inner diameter portion of the blank before processing is reduced to approximately 0.73 times its original thickness as the wall thickness after processing due to the hole-expanding and drawing process. This is thought to be because the material's fluidity increased as the portion of the blank closest to the inner diameter was stretched during processing.

[0085] Furthermore, even when the blank material was changed, the results showed a correlation equivalent to that shown in Figure 16.

[0086] The above approximation formulas (1) and (2) are the correlation coefficient R 2 However, it is not 1. The mean and standard deviation (σ) of the slopes of each equation were calculated. As a result, the mean of the slopes of the analysis points that make up equation (1) was 1.37, and the standard deviation (σ) was 0.089. R 2 Since it is small, approximately 0.97, if we set the variability range to ±2σ, Vertical wall compression surface thickness after processing (a_up)=(1.3735±0.178)×t_out + 0.3763 ​​(3) The possible range is from 1.19 × t_out + 0.3763 ​​to 1.55 × t_out + 0.3763.

[0087] The average slope of the analysis points constituting equation (1) was 0.728, and the standard deviation (σ) was 0.051. Vertical wall extension surface thickness after processing (a_down)=(0.7291±0.102)×t_in - 0.0925 (4) The possible range is from 0.63 × t_in - 0.0925 to 0.83 × t_in - 0.0925.

[0088] <Correlation between the position of the recess before processing and the position of the recess after processing> Figure 17 is a graph showing the results of an analysis of the correlation between the position of indentations in the blank before processing and the position of recesses after processing. In Figure 17, the horizontal axis represents the ratio of indentations before processing (a0_out / a0_in), and the vertical axis represents the ratio of recesses after processing (h_up / h_down).

[0089] As shown in Figure 17, when a0_out / a0_in is 1, the deepest point of the recess is located midway between the inner and outer diameter surfaces in the radial direction. When a0_out / a0_in < 1, the deepest point of the recess is located closer to the outer diameter surface than to the inner diameter surface in the radial direction. When h_up / h_down is 1, the deepest point of the recess is located midway along the axial direction of the tubular part. When h_up / h_down < 1, the deepest point of the recess is located closer to one end face than to the other end face in the axial direction of the tubular part. When h_up / h_down > 1, the deepest point of the recess is located closer to one end face than to the other end face in the axial direction of the tubular part.

[0090] Table 2 shows the equation of the approximation line shown in the graph in Figure 17. [Table 2]

[0091] In the approximation formula showing the correlation between the position of the depression before processing and the position of the depression after processing, as shown in Table 2, the variation in the slope of the line is small. From this, it was found that changes in each parameter (blank inner diameter (d0), depression radius (R0), plate thickness at the deepest point of the depression (t0_min), and width from the inner diameter surface to the outer diameter surface of the blank in the radial direction (a0)) do not have a significant effect on the slope of the linear function showing the correlation. Furthermore, the approximation formula for the case of the friction coefficient μ of the blank is close to the approximation formula for the standard conditions. It was found that the difference in the friction coefficient μ does not affect the correlation.

[0092] The mean and standard deviation (σ) of the slopes of each equation for each parameter shown in Table 2 (blank inner diameter (d0), recess radius (R0), plate thickness at the deepest point of the recess (t0_min), and width from the inner diameter surface to the outer diameter surface in the radial direction of the blank (a0)) were calculated. In all equations, R 2The value is approximately 0.99, which is close to 1. The variability range is estimated to be within ±4σ. The method for calculating the mean and standard deviation (σ) was the same as in the cases of formulas (1) and (2) above. The "slope" was calculated for each condition, and the result obtained from all analysis points yielded a mean of 1.17 and a standard deviation (σ) of 0.03. The following formula shows the correlation between the ratio of the depressions before processing (a0_out / a0_in) and the ratio of the depressions after processing (h_up / h_down). (h_up / h_down)= (1.17)×(a0_out / a0_in)+ B ···(5) The range of variation is (1.17±0.12)×(a0_out / a0_in)+ B ···(6) The possible range is 1.05 × (a0_out / a0_in) + B to 1.29 × (a0_out / a0_in) + B. (5) B is a constant and changes depending on the conditions. For example, B can be determined by performing the preliminary analysis or preliminary experiment described in Embodiment 2.

[0093] Here, the diameter of the deepest point of the recess in the blank before processing can be calculated using the following formula (6). Diameter of the deepest point of the recess in the blank before processing = (D0 + (d0 × a0_out / a0_in)) / ((a0_out / a0_in) + 1) ... (7) The axial position of the deepest point of the recess after machining can be calculated using (8) below. The axial position of the deepest point of the recess after machining = h_down / h = h_down / (h_up+h_down) = 1 / (1+(h_up / h_down)) ... (8) Multiplying the value calculated by equation (7) by the axial length (height) h of the tubular part after processing, the height of the deepest point of the recess from the other end face can be calculated.

[0094] (Example 1) Under the conditions described below, the inner diameter plate thickness was calculated based on the first correlation, and the outer diameter plate thickness was calculated based on the second correlation. A tubular part was fabricated by enlarging and drawing a blank with the conditions and calculated dimensions described below, and its dimensions were measured. (conditions) The blank before processing has an outer diameter D0 of φ83mm and an inner diameter d0 of φ23mm. Target value for the wall thickness a_up at one end of the tubular component = 6 mm Target value for the wall thickness a_down at the other end of the tubular component = 6 mm 1) Outer diameter and thickness t0_out value of the blank before processing From equation (1), a_up = 6mm = 1.3735 × t0_out + 0.3763, t0_out ≈ 4mm From equation (3), it can be inferred that the a_up of the tubular part falls within the range of 5.13 mm to 6.58 mm (with the center being 5.87 mm). 2) Inner diameter plate thickness t0_in value of the blank before processing From equation (2), we get a_down = 6mm = 0.7291 × t0_in - 0.0925, t0_in ≈ 8mm From equation (4), it can be inferred that the a_down of the tubular component falls within the range of 4.95 mm to 6.55 mm (with the center being 5.74 mm).

[0095] The conditions for the hole-expanding and drawing process were the same as those for the three steps shown in Figure 15. The other prototype conditions were as follows. Material: SUJ2 steel plate (outer diameter 4mm, inner diameter 8mm) Lubricating oil: G-3456 (manufactured by Nippon Craft Oil) Press machine: 60-ton power press Pressing speed: 30 SPM

[0096] The measurement items and results for the processed tubular parts are as follows. Axial length (height) h of the tubular component: 37.04 mm Wall thickness at one end a_up: 5.88mm Other end wall thickness a_down: 5.70mm In the measurement results above, both a_up and a_down fell within the range estimated by calculation.

[0097] Figure 18 shows the dimensions of the blank in Example 1 (left) and a photograph of the cross-section of the processed tubular part (right). As shown in Figure 18, the wall thickness of the processed tubular part was substantially uniform in the axial direction.

[0098] (Example 2) Under the conditions described below, the inner diameter plate thickness was calculated based on the first correlation, and the outer diameter plate thickness was calculated based on the second correlation. Furthermore, the position of the recess before processing was calculated based on the third correlation. A tubular part was manufactured by enlarging and drawing a blank with the conditions and calculated dimensions described below, and its dimensions were measured. (conditions) The blank before processing has an outer diameter D0 of φ83mm and an inner diameter d0 of φ23mm. The arc dimension (radius) of the recess is R0 = 15 mm. Plate thickness t0_min = 2mm at the deepest point of the depression Target value for the wall thickness a_up at one end of the tubular component = 6 mm Target value for the wall thickness a_down at the other end of the tubular component = 6 mm The target value for the ratio of the positions of the recesses in the tubular part, h_up / h_down, is 1. In other words, the desired tubular component has a recess in its inner diameter, the deepest point of the recess is at the axial center (half the height), and the wall thickness is the same in the axial direction and 6 mm or less.

[0099] 1) Outer diameter plate thickness t0_out value and inner diameter plate thickness t0_in value of the blank before processing From equation (1), a_up = 6mm = 1.3735 × t0_out + 0.3763, t0_out ≈ 4mm From equation (2), we get a_down = 6mm = 0.7291 × t0_in - 0.0925, t0_in ≈ 8mm

[0100] 2) Position of the deepest point of the recess in the blank before processing For B in equation (5), since this embodiment is equivalent to the standard conditions in the previous section, we apply B = 0.209. From equation (5), h_up / h_down = 1 = 1.17 × (a0_out / a0_in) + 0.209, so a0_out / a0_in ≈ 0.676. Diameter of the latest point of the depression = ((D0 + (d0 × a0_out / a0_in)) / (a0_out / a0_in + 1) =(83+(23×0.676) / (0.676+1) ≒ φ58.8mm h_up / h_down is 0.92 (=(1.05 × 0.676 + 0.209)) from equation (6) ~ 1.08 (=(1.29 × 0.676 + 0.209)), and with the height after processing as h, from equations (7) and (8), h × 0.48 mm ~ h × 0.52 mm It is presumed that the deepest point of the recess is located within the range of h × 0.5 mm (center of the cylinder).

[0101] The conditions for the hole-expanding and drawing process were the same as those for the three steps shown in Figure 15. The other prototype conditions were as follows. Material: SUJ2 steel plate (outer diameter 4mm, inner diameter 8mm) Blank recess remaining: t0_min = 3mm, recess tip position = φ58.8mm Target location of recessed area after processing: Inner center (height x 0.5) Lubricating oil: G-3456 (manufactured by Nippon Craft Oil) Press machine: 60-ton power press Pressing speed: 30 SPM

[0102] The measurement items and results for the processed tubular parts are as follows. Axial length (height) h of the tubular component: 36.18 mm Distance h_up from one end face of the deepest point of the recess: 18.18 mm Distance h_down from the other end face of the deepest point of the recess: 18.00 mm Wall thickness at one end a_up: 5.80mm Wall thickness at the other end a_down: 5.66 mm As described above, the results were obtained as expected.

[0103] Figure 19 shows the dimensions of the blank in Example 2 (left) and a photograph of the cross-section of the processed tubular part (right). As shown in Figure 19, the deepest point of the recess in the wall thickness of the processed tubular part was approximately in the axial direction (height direction). In addition, the wall thickness was approximately uniform in the parts other than the recess.

[0104] (Example 3) Under the conditions described below, the inner diameter plate thickness was calculated based on the first correlation, and the outer diameter plate thickness was calculated based on the second correlation. Furthermore, the position of the recess before processing was calculated based on the third correlation. A tubular part was manufactured by enlarging and drawing a blank with the conditions and calculated dimensions described below, and its dimensions were measured. (conditions) The blank before processing has an outer diameter D0 of φ83mm and an inner diameter d0 of φ23mm. The arc dimension (radius) of the recess is R0 = 15 mm. Plate thickness t0_min = 2mm at the deepest point of the depression Target value for the wall thickness a_up at one end of the tubular component = 6 mm Target value for the wall thickness a_down at the other end of the tubular component = 6 mm The target value for the ratio of the positions of the recesses in the tubular part, h_up / h_down, is 2 / 3. In other words, the desired tubular component has a recess in its inner diameter, the deepest point of the recess is located at 3 / 5 of the axial direction (3 / 5 of the height), and the wall thickness is the same in the axial direction and 6 mm or less.

[0105] 1) Outer diameter plate thickness t0_out value and inner diameter plate thickness t0_in value of the blank before processing From equation (1), a_up = 6mm = 1.3735 × t0_out + 0.3763, t0_out ≈ 4mm From equation (2), we get a_down = 6mm = 0.7291 × t0_in - 0.0925, t0_in ≈ 8mm

[0106] 2) Position of the deepest point of the recess in the blank before processing For B in equation (5), since this embodiment is equivalent to the standard conditions in the previous section, we apply B = 0.209. To make the deepest point of the recess after machining 3 / 5 of the height, h_up / h_down must be 2 / 3. From equation (5), h_up / h_down = 0.666 = 1.17 × (a0_out / a0_in) + 0.209, a0_out / a0_in ≈ 0.391 The diameter of the deepest point of the depression before machining = ((D0 + (d0 × a0_out / a0_in)) / (a0_out / a0_in + 1) =(83+(23×0.391) / (0.391+1) ≒ φ66mm The ratio of the recessed area after processing, h_up / h_down, is 0.62 (=1.05 × 0.391 + 0.209) from equation (6). With a value of 0.71 (=1.29 × 0.391 + 0.209) and a post-processing height of h, it can be inferred from equations (7) and (8) that the deepest point of the recess is located in the range of h × 0.585 mm to h × 0.617 mm (the center being h × 0.6 mm (3 / 5 of the cylinder)).

[0107] The conditions for the hole-expanding and drawing process were the same as those for the three steps shown in Figure 15. The other prototype conditions were as follows. Material: SUJ2 steel plate (outer diameter 4mm, inner diameter 8mm) Blank recess remaining: t0_min = 3mm, recess tip position = φ66mm Position of recessed area after processing: Target: Inner center (height x 3 / 5) Lubricating oil: G-3456 (manufactured by Nippon Craft Oil) Press machine: 60-ton power press Pressing speed: 30 SPM

[0108] The measurement items and results for the processed tubular parts are as follows. Axial length (height) h of the tubular component: 35.77 mm Distance h_up from one end face of the deepest point of the recess: 13.81 mm Distance h_down from the other end face of the deepest point of the recess: 21.96 mm Wall thickness at one end a_up: 5.81mm Wall thickness at the other end a_down: 5.05 mm As described above, the results were obtained as expected.

[0109] Figure 20 shows the dimensions of the blank in Example 3 (left) and a photograph of the cross-section of the processed tubular part (right). As shown in Figure 20, the deepest point of the recess in the wall thickness of the processed tubular part was at 3 / 5 of the axial direction (3 / 5 of the height). In addition, the wall thickness was approximately uniform in the parts other than the recess. [Explanation of Symbols]

[0110] 100 Blank 110 Tubular parts 1 hole 2 Top surface 3 Bottom surface 4 Outer diameter surface 5. Inner diameter surface 6 One end face 7 Other end surface 8 Inner surface 9 Outer surface

Claims

1. A method for manufacturing tubular parts, A preparation step of preparing a plate-shaped blank having an upper surface, a lower surface, and a hole penetrating from the upper surface to the lower surface, The process includes a molding step of forming the blank into a tubular part by hole-expanding and drawing, In the molding process, The outer diameter portion, including the outer diameter surface of the blank before processing, becomes one end of the tubular part, including one end face in the axial direction, through the hole-expanding and drawing process. The inner diameter portion of the blank before processing, including the inner diameter surface of the hole, becomes the other end portion of the tubular part, including the other end face in the axial direction, through the hole-expanding and drawing process. In the aforementioned preparation step, The outer diameter thickness (t0_out), which is the thickness of the outer diameter portion of the blank before processing, is set to have a first correlation with the target value of the wall thickness (a_up) at one end of the tubular component. The inner diameter thickness (t0_in), which is the thickness of the inner diameter portion of the blank before processing, is set to have a second correlation with the target value of the wall thickness (a_down) at the other end of the tubular component. Both the first and second correlations are relationships in which the wall thickness after processing is expressed as a linear function of the plate thickness before processing, and the slope of the linear function showing the first correlation is greater than the slope of the linear function showing the second correlation. In the preparation step, a plate-shaped blank having a recess formed on one of the upper and lower surfaces is prepared. The molding process is a process of forming the blank into a tubular part having a recess on its inner surface by hole-expanding and drawing. In the molding process, One of the upper and lower surfaces of the blank before processing becomes the inner circumferential surface of the tubular part through the hole-expanding and drawing process. The other of the upper and lower surfaces of the blank before processing becomes the outer surface of the tubular part through the hole-expanding and drawing process. A method for manufacturing a tubular part, wherein the recess in the blank before processing becomes a recess on the inner surface of the tubular part by the hole-expanding and drawing process.

2. In the aforementioned preparation step, The method for manufacturing a tubular part according to claim 1, wherein the ratio (a0_out / a0_in) of the distance (a0_in) from the deepest point of the recess on one surface of the blank before processing to the inner diameter surface and the distance (a0_out) from the deepest point of the recess to the outer diameter surface of the blank is set to have a third correlation with respect to a target value of the ratio (h_up / h_down) of the distance (h_up) from the deepest point of the recess on the inner circumferential surface of the tubular part to one end surface and the distance (h_down) from the deepest point of the recess to the other end surface, and the third correlation is such that the ratio (h_up / h_down) of the recess of the tubular part is expressed as a linear function of the ratio (a0_out / a0_in) of the recess of the blank before processing.

3. A method for manufacturing a tubular part according to claim 1 or 2, wherein the distance from the deepest point of the recess on one surface of the blank before processing to the inner diameter surface (a0_in) and the distance from the deepest point to the outer diameter surface (a0_out) are different.

4. A method for manufacturing a tubular part according to any one of claims 1 to 3, wherein the distance (a0_out) from the deepest point of the recess on one face of the blank before processing to the outer diameter surface is smaller than the distance (a0_in) from the deepest point of the recess to the inner diameter surface.

5. A method for manufacturing a tubular part according to any one of claims 1 to 4, wherein the ratio (a0_out / a0_in) of the distance (a0_in) from the deepest point of the recess on one surface of the blank before processing to the inner diameter surface and the distance (a0_out) from the deepest point of the recess to the outer diameter surface of the blank is different from the ratio (h_up / h_down) of the distance (h_up) from the deepest point of the recess on the inner circumferential surface of the tubular part to one end surface and the distance (h_down) from the deepest point of the recess to the other end surface.

6. The method for manufacturing a tubular part according to claim 2, wherein the ratio of the recess in the blank before processing (a0_out / a0_in) is set to have the third correlation with respect to the target value of the ratio of the recess in the tubular part (h_up / h_down) expressed by the formula: (h_up / h_down) = K3 × (a0_out / a0_in) + B (1.05 ≤ K3 ≤ 1.29, B is a constant).

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