Processed product and processed product producing method

Abstract

There is provided a processed product (1) formed from a plated steel sheet including a plating layer (13f) on a surface of the plated steel sheet which includes a cut end (13) on a side wall of the processed product (1), the side wall being in a hollow-shell cylindrical shape, including the cut end (13) is flush with an exterior of the side wall of the processed product (1), and includes a shear surface (13c), or the shear surface (13c) and a rupture surface (13d) in this order in a sheet thickness direction of the cut end (13), and a ratio L / t1 between a plating component remaining length L by which the shear surface (13c) is covered with the plating layer (13f) on the surface and a sheet thickness t1 of the cut end (13) of the processed product (1) is 0.70 or more.

Description

Processed products and manufacturing methods for processed products

[0001] The present invention relates to a processed product having a cut edge, made from a plated steel sheet having a plated layer on the surface, and a method for manufacturing the processed product.

[0002] In recent years, processed products made of plated steel sheets having a plating layer on the surface have increasingly been used as parts for devices such as automobiles and home appliances. By using plated steel sheets as the material, it is possible to omit surface treatment after forming the processed product, thereby reducing manufacturing costs. Furthermore, by omitting surface treatment after forming, it is possible to avoid deterioration of the dimensional accuracy of the part due to the surface treatment after forming. Omitting surface treatment after forming is particularly considered for parts that require high dimensional accuracy, such as motor cases.

[0003] If surface treatment after forming is omitted, areas of exposed steel sheet base material will appear at the cut edges of the processed product. Depending on the environment in which the processed product is placed, red rust may form in the areas where the steel sheet base material is exposed. Red rust deteriorates the appearance of the processed product. In addition, as the area where red rust occurs spreads over time, there is concern that the red rust may reduce the strength of the processed product. In particular, in the case of home appliances, there is concern that missing rust may cause electrical short circuits.

[0004] Additionally, some motor cases do not have flanges. These motor cases are used by inserting the motor through an opening in the motor case, which is then sealed with a separate part called a bottom plate. Since moisture entering the motor case can cause motor failure or performance degradation, a high level of airtightness is required between the opening and the bottom plate. To ensure high airtightness, the opening needs to have a specific flat surface.

[0005] As a method for improving the rust prevention ability of the cut end portion of a processed product, for example, Patent Document 1 proposes a method in which a Zn-based plated steel sheet having a thickness of 2 mm or less is punched using a die having a shoulder portion of a punch or die with a radius of curvature that is 0.1 to 0.5 times the thickness of the Zn-based plated steel sheet, thereby increasing the shear surface ratio of the punched end face after punching to 90% or more and the zinc coverage rate of the shear surface to 50% or more.

[0006] Furthermore, Patent Document 2 proposes a method in which a punching clearance is set to 1 to 20% of the sheet thickness regardless of the thickness of the zinc-based plated steel sheet, and the zinc-based plated steel sheet is cut using a die having a shoulder portion of a punch or die with a radius of curvature that is 0.12 times or more the thickness of the zinc-based plated steel sheet, thereby obtaining a processed product in which sag Z at the cut end surface is 0.10 × the sheet thickness or more and sag X is 0.45 × the sheet thickness or more.

[0007] Furthermore, Patent Document 3 proposes a method for obtaining a product with corrosion resistance at the end face by half-punching a plated steel sheet to 60 to 95% of the sheet thickness with a negative clearance and then shearing the sheet from the opposite side of the half-punching by flat pressing.

[0008] Furthermore, Patent Document 4 discloses a method for press working metal sheet material, which includes a first step of using a first punch and a first die to half-punch the metal sheet material and leaving a shaving allowance on the final processed surface of the punched portion of the metal sheet material, and a second step of using a second punch and a second die to further shaving the half-punched portion, mainly by shearing, thereby ensuring a sheared surface of 70% or more on the final processed surface of the punched portion.

[0009] Japanese Patent No. 5272518 Japanese Patent No. 6073025 Japanese Patent Application Laid-Open No. 2002-321021 Japanese Patent Application Laid-Open No. 2004-174542

[0010] However, the method described in Patent Document 1 is intended for steel plates with a thickness of 2 mm or less, and when steel plates with a thickness of more than 2 mm are used as the raw material, the zinc coverage rate on the sheared surface may be insufficient, making it difficult to prevent the occurrence of red rust. It is also difficult to apply this method to drawn products, such as motor cases, in which increased thickness occurs at the flange ends.

[0011] In the method described in Patent Document 2, the punching clearance is set to a positive clearance, which makes it easy for fracture surfaces exceeding 0.5 mm to occur in the later stages of cutting. Furthermore, setting the positive clearance prevents high surface pressure between the die and the plating layer surface, which means that when the material stretches, the plating layer does not follow and breaks, exposing the steel base.

[0012] In the method described in Patent Document 3, the plated steel sheet is half-punched with a negative clearance and then sheared by flat pressing from the opposite side of the half-punched. This can result in fracture surfaces at the midpoint of the cut end of the plated steel sheet in the thickness direction, and can also result in whisker-like burrs being generated during flat pressing, deteriorating the shape quality.

[0013] The method described in Patent Document 4 is a technology related to shaving, and improves the final processed surface of the metal sheet by forming a large sheared surface. Even if a metal sheet having a plating layer on its surface is shaved by the method described in Patent Document 4, almost no plating layer remains on the surface of the final processed surface, resulting in low corrosion resistance of the final processed surface.

[0014] Therefore, the present invention has been made in consideration of the above problems, and an object of the present invention is to provide a processed product that has good corrosion resistance and shape quality even when a plated steel sheet having a thickness of more than 2.0 mm is used as a raw material, and a method for manufacturing the processed product.

[0015] In order to solve the above-mentioned problems, according to one aspect of the present invention, there is provided a processed product made from a plated steel sheet having a plating layer on its surface, the processed product having a cut end on a hollow cylindrical side wall, the cut end being flush with the outer surface of the side wall of the processed product, the cut end having a shear surface and a fracture surface in that order in the thickness direction of the cut end, or the shear surface, and the ratio L / t1 of the remaining length L of the plating component where the shear surface is covered by the plating layer on the surface to the thickness t1 of the cut end of the processed product is 0.70 or more.

[0016] The length W1 of the fracture surface of the cut end in the thickness direction may be greater than 0 mm and less than or equal to 1.0 mm.

[0017] The length W1 of the fracture surface of the cut end in the thickness direction may be 0.5 mm or less.

[0018] The ratio Lt / t of the length Lt of the flat surface of the end face of the processed product perpendicular to the side wall to the thickness t of the side wall of the processed product may be 0.35 or more.

[0019] The length of the burr on the cut edge may be less than 0.2 mm.

[0020] The cut end has a shear surface, a fracture surface, and a coining surface in that order, or a shear surface and a coining surface in that order, in the thickness direction of the cut end, and the length W2 of the fracture surface between the shear surface and the coining surface in the thickness direction of the cut end may be greater than 0 mm and less than or equal to 0.5 mm.

[0021] In order to solve the above-mentioned problems, according to another aspect of the present invention, there is provided a method for manufacturing a processed product using a plated steel sheet having a plating layer on its surface as a raw material, and for manufacturing a processed product having a cut end on a hollow cylindrical side wall, the method comprising: a half-cutting step of half-cutting a cut portion of a first element formed from the raw material in a thickness direction using a first die and a first punch, the clearance between the first die and the first punch being set to a negative clearance; and a finish-cutting step of finish-cutting the half-cut first element from the same direction as the half-cutting, using a second die and a second punch, to obtain a processed product having a cut end that is flush with an outer surface of the side wall of the processed product; ３２ is the inner diameter D of the first die ３１ Assuming that the thickness of the cut portion of the first body is t1 and the remaining thickness of the cut portion after the half-cutting step is t2, the clearance C between the first die and the first punch in the half-cutting step is ３１－４１ satisfies the following formula (a1), the radius of curvature R1 of the cutting edge of the first die satisfies the following formula (a2), the amount of thrust D of the first die or the first punch against the cutting portion of the first blank satisfies the following formula (a3), and the distance C between the first die and the first punch at the bottom dead center Ｐ－Ｄ satisfies the following formula (a4), and in the finish cutting process, the clearance C between the second die and the second punch ３２－４２ satisfies the following formula (a5), and the radius of curvature R2 of the cutting edge of the second die satisfies the following formula (a6): −0.35×t1≦C ３１－４１ ≦-0.01 ... (a1) 0.10 x t1 ≦ R1 ≦ 0.50 x t1 ... (a2) D≧0.70 x t1 ... (a3) ​​C Ｐ－Ｄ ≧0.20 ... (a4) 0.01≦C ３２－４２≦0.2×t2 (a5) 0.25≦R2≦1.50×t2 (a6) where, C ３１－４１ , C Ｐ－Ｄ , C ３２－４２ and R2 is in mm.

[0022] Furthermore, in order to solve the above-mentioned problems, according to another aspect of the present invention, there is provided a method for manufacturing a processed product using a plated steel sheet having a plating layer on its surface as a raw material, and for manufacturing a processed product having a cut end on a hollow cylindrical side wall, the method comprising: a half-cutting step of half-cutting a cut portion of a first element formed from the raw material in a thickness direction using a first die and a first punch, the clearance between the first die and the first punch being set to a negative clearance; and a finish-cutting step of finish-cutting the half-cut first element from the same direction as the half-cutting, using a second die and a second punch, to obtain a processed product having a cut end that is flush with an outer surface of the side wall of the processed product; ３２ is the inner diameter D of the first die ３１ Assuming that the thickness of the cut portion of the first body is t1 and the remaining thickness of the cut portion after the half-cutting step is t2, the clearance C between the first die and the first punch in the half-cutting step is ３１－４１ satisfies the following formula (b1), the radius of curvature R11 of the cutting edge of the first die satisfies the following formula (b2-1), the radius of curvature R12 of the cutting edge of the first punch satisfies the following formula (b2-2), the amount of pressing D of the first die or the first punch into the cutting portion of the first blank satisfies the following formula (b3), and the distance C between the first die and the first punch at the bottom dead center Ｐ－Ｄ satisfies the following formula (b4), and in the finish cutting process, the clearance C between the second die and the second punch ３２－４２ satisfies the following formula (b5), and the radius of curvature R2 of the cutting edge of the second die satisfies the following formula (b6): −0.45×t1≦C ３１－４１ ≦-0.10×t1 ... (b1) 0.10×t1≦R11≦0.65×t1 ... (b2-1) 0.10×t1≦R12≦0.65×t1 ... (b2-2) D≧0.70×t1 ... (b3) C Ｐ－Ｄ≧0.20 ... (b4) 0.01≦C ３２－４２ ≦0.2×t2 (b5) 0.25≦R2≦1.50×t2 (b6) where, C ３１－４１ , C Ｐ－Ｄ , C ３２－４２ and R2 is in mm.

[0023] The above-described method for manufacturing a processed product may further include a coining step in which the processed product obtained in the finish cutting step is used as a second element, and corners of the cut end portion of the second element are pressed against a pad to obtain a processed product having coining surfaces formed on the corners.

[0024] Inner diameter D of the first die ３１ and the inner diameter D of the second die ３２ Difference D ３２ -D ３１ may be 1.00 mm or less.

[0025] The above-described method for manufacturing a processed product may further include, before the semi-cutting step, a preparation step of forming a first body having a hollow side wall and a flange portion from a flat plated steel sheet.

[0026] As described above, according to the present invention, even when a plated steel sheet having a thickness of more than 2.0 mm is used as a raw material, the corrosion resistance and shape quality of the obtained processed product can be improved.

[0027] 11 is a perspective view showing an example of a processed product manufactured by a processed product manufacturing method according to a first embodiment of the present invention. It shows a cut end portion in region A of the processed product in FIG. 1 , with the left side being a cross-sectional view in the ZX plane including the central axis of the processed product, and the right side being a side view from the X direction. It is a detailed view of the cross-sectional view on the left side of FIG. 2. It is a schematic view explaining airtightness depending on the size of the flat surface of the processed product end portion. It is an explanatory view showing a processed product manufacturing method according to the same embodiment. It is an explanatory view showing a half-cutting step in which the cutting edge of the die used in the half-cutting step is rounded. It is an explanatory view showing a finish-cutting step performed subsequent to the half-cutting step shown in FIG. 6. It is an explanatory view showing a half-cutting step in which the cutting edges of the die and punch used in the half-cutting step are rounded. It is an explanatory view showing a finish-cutting step performed subsequent to the half-cutting step shown in FIG. 8. It is an explanatory view showing a processed product manufacturing method according to a second embodiment of the present invention. It is a schematic view showing an example of a die used in coining. It is a partial enlarged view of region B of FIG. 11. It shows the cut end portion of the processed product after the coining step, with the left side being a cross-sectional view in the ZX plane including the central axis of the processed product, and the right side being a side view from the X direction. Fig. 1 is a photograph showing an example of a cut end portion of a processed product after a coining process. Fig. 2 is an explanatory diagram showing the volume of a corner portion crushed by a pad in the coining process. Fig. 3 is a photograph showing a profile-drawn product as an example of a processed product of the present invention. Fig. 4 is a photograph showing a square-tube-drawn product as an example of a processed product of the present invention.

[0028] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this specification and drawings, components having substantially the same functional configurations are designated by the same reference numerals, and redundant explanations will be omitted.

[0029] [1. First Embodiment] [1-1. Worked Product] First, a worked product 1 manufactured by a worked product manufacturing method according to a first embodiment of the present invention will be described with reference to FIG. 1. FIG. 1 is a perspective view showing an example of the worked product 1 manufactured by the worked product manufacturing method according to the first embodiment of the present invention. The worked product 1 shown in FIG. 1 is a motor case made of a plated steel sheet having a plated layer on its surface. The motor case shown in FIG. 1 can be formed by subjecting a flat plated steel sheet to a forming process such as drawing.

[0030] As shown in FIG. 1 , the processed product 1 according to this embodiment has a body portion 10 and a protrusion portion 11 .

[0031] The body 10 has a hollow cylindrical side wall 101 and a top wall 103 formed to cover one end of the side wall 101. The top wall 103 may be called a bottom wall or other name depending on the orientation of the processed product 1. The body 10 of the processed product 1 shown in FIG. 1 has a perfect circular cross-sectional shape in the XY plane, but the present invention is not limited to this example. The cross-sectional shape of the body 10 in the XY plane may be other shapes, such as an ellipse or a polygon. The body 10 has an opening on the side opposite the top wall 103. A motor is inserted through the opening.

[0032] The protrusion 11 is a protruding body that protrudes outward from the top wall 103 in the central axis direction (Z direction) of the body 10. Note that the protrusion 11 does not necessarily have to be formed, and the top wall 103 may be flat.

[0033] The body 10 according to this embodiment has a cut edge 13 on the outer surface of the end on the opening side. The cut edge 13 is formed by cutting an element to be processed into the processed product 1. The cut edge 13 is formed so as to be flush with the outer surface of the body 10.

[0034] Cutting processes include cutting, punching, and drilling. Cutting is a process of cutting an object along a predetermined straight line or curve. Punching is a process of punching a product out of an object. Punching is a process of punching out a non-product part from an object to obtain a product with an opening. The body 10 having the cut end 13 shown in FIG. 1 can be obtained by punching out from a blank.

[0035] As the plated steel sheet, it is preferable to use a plated steel sheet having various plating layers. As the plated steel sheet, various steel sheets can be used, but it is preferable to use a Zn-based plated steel sheet. Zn-based plating includes Zn plating, Zn-Al-based alloy plating, Zn-Al-Mg-based alloy plating, and Zn-Al-Mg-Si-based alloy plating. As the plated steel sheet, it is particularly preferable to use a steel sheet that has been subjected to Zn-Al-Mg-based alloy plating. Here, the alloy plating preferably contains 80 mass% or more of Zn, and more preferably contains 90 mass% or more of Zn, based on the total number of moles of the plating.

[0036] The base steel sheet of the plated steel sheet may be any steel sheet, but may be, for example, ultra-low carbon steel.

[0037] The coating weight of the plated steel sheet is preferably 30 g / m ２ is the lower limit, and more preferably 45 g / m ２ The lower limit of the coating weight of the plated steel sheet is preferably 450 g / m ２ The upper limit is more preferably 190 g / m ２ The upper limit may be set to 45 g / m. ２ By doing so, the plating metal can easily get around the sheared surface of the cut end portion 13 (sheared surface 13c in FIG. 2), thereby improving the corrosion resistance after cutting.

[0038] The thickness of the plated steel sheet (the thickness of the base steel sheet plus the thickness of the plating layer) is arbitrary, but may be 2.0 mm or less or may exceed 2.0 mm. The thickness of the plated steel sheet may be, for example, 0.8 mm or more and 6.0 mm or less, more preferably 2.0 mm or more and 4.5 mm or less.

[0039] [1-2. Cut End of Workpiece] Next, the cut end 13 of the workpiece 1 according to this embodiment will be described with reference to Figures 2 and 3. Figure 2 shows the cut end 13 in region A of the workpiece 1 in Figure 1, with the left side being a cross-sectional view in the ZX plane including the central axis of the workpiece 1, and the right side being a side view from the X direction. Figure 3 is a detailed view of the cross-sectional view on the left side of Figure 2. Note that the plating layers 13f1 and 13f2 are omitted from Figure 2.

[0040] 2 and 3, the cut end 13 of the processed product 1 is formed so as to be flush with the outer surface of the processed product 1, for example, the outer surface 101a of the side wall 101, in the Z direction. The cut end 13 is formed in a direction parallel to the central axis of the processed product 1 and along a direction (hereinafter also referred to as a "second direction") T2 that is perpendicular to the thickness direction (hereinafter also referred to as a "first direction") T1 of the side wall 101. As shown in FIGS. 2 and 3, the cut end 13 has a shear surface 13c and a fracture surface 13d, respectively, in the second direction T2.

[0041] In FIG. 2 , the boundary between the outer surface 101 a and the cut end 13 of the processed product is exaggerated to show a slight curved surface Rd. However, the curved surface Rd does not create a large step at the boundary between the outer surface 101 a and the cut end 13, and the outer surface 101 a and the cut end 13 can be considered to be flush. Here, if the step between the surface of the cut end 13 and the outer surface 101 a of the side wall 101 is 0.5 mm or less, it is determined that there is no large step, and the outer surface 101 a and the cut end 13 are considered to be flush. If necessary, the upper limit of this step may be 0.4 mm, 0.3 mm, 0.2 mm, or 0.1 mm. The thickness t of the processed product 1 is the thickness of the bottom of the side wall 101 of the processed product 1. That is, the thickness of the side wall 101 directly above the curved surface Rd at the boundary between the outer surface 101 a of the side wall 101 and the cut end portion 13 is defined as the thickness t of the processed product 1 .

[0042] The shear surface 13c is a surface where the base material of the processed product 1 is sheared by the cutting edge of the cutting die. The fracture surface 13d is a surface where cracks that have occurred in the base material from the cutting edge of the cutting die meet and fracture. The fracture surface 13d is adjacent to the shear surface 13c in the second direction T2. ​​Burrs may occur on the lower side of the fracture surface 13d (i.e., the side opposite the shear surface 13c). The burrs are portions where the base material is stretched or torn when the fracture surface 13d is formed.

[0043] As shown in FIG. 3 , the processed product 1 manufactured by the processed product manufacturing method according to this embodiment has a portion of the sheared surface 13c of the cut end 13 covered with a plating layer 13f1. When the cutting edge of the cutting die penetrates the base body, the plating layer 13f1 is stretched by the cutting die and wraps around the sheared surface 13c. This wrapping of the plating layer 13f1 results in at least a portion of the sheared surface 13c being covered with the plating layer 13f1. The generation of red rust can be suppressed in the portion of the sheared surface 13c covered with the plating layer 13f1. Furthermore, when the plating layer 13f1 is a Zn-based plating layer, the sacrificial corrosion protection effect of the Zn-based plating layer can also suppress the generation of red rust near the portion covered with the plating layer 13f1. Note that the processed product 1 shown in FIG. 3 has almost no step at the boundary between the outer surface 101a and the cut end 13, so the curved surface Rd is not shown in FIG. 3 .

[0044] In this case, the length L of the plating layer 13f1 covering at least a portion of the sheared surface 13c of the cut end 13 of the processed product 1 is 0.70 times or more the thickness t1 of the cut end 13 of the processed product 1 (hereinafter also referred to as the "length t1 of the cut end 13"). That is, the ratio L / t1 of the remaining length L of the plating component where the sheared surface 13c is covered by the plating layer 13f1 to the thickness t1 of the cut end 13 of the processed product 1 is 0.70 or more. The larger the ratio L / t1, the more preferable it is. The lower limit of the ratio L / t1 may be 0.75, 0.78, 0.81, 0.83, 0.85, or 0.88. The upper limit of the ratio L / t1 is 1.00. The thickness t1 of the cut end 13 is the length in the second direction T2 from the lower end of the curved surface Rd to the end face of the trunk portion 10 (end face 14a in FIG. 3), as shown in FIG. 2.

[0045] The fracture surface 13d is a newly formed rough surface that is formed when cracks that have occurred in the element body coalesce. Metallic components of the steel substrate are exposed at the fracture surface 13d. The plating layer 13f1 covering the sheared surface 13c does not easily extend to the fracture surface 13d. Therefore, red rust is more likely to develop on the fracture surface 13d than on other surfaces of the cut end 13.

[0046] The inventors conducted experiments in which the thickness t1 of the cut end 13 of the workpiece 1, the cutting conditions, the surface treatment conditions, etc. were varied over various ranges to investigate the occurrence of red rust. The thickness t1 of the cut end 13 of the workpiece 1 was varied by changing the thickness of the flange portion 20 (i.e., the thickness of the plated steel sheet) shown on the left side of FIG. 5 (described later). As a result, they came up with the idea of ​​making the plating layer 13f1 wrap around the shear surface 13c when cutting the plated steel sheet, thereby obtaining a workpiece 1 having a ratio L / t1 of 0.70 or more. It was found that this method can suppress the occurrence of red rust at the cut end 13 over time after cutting.

[0047] Furthermore, the length W1 of the fracture surface 13d in the thickness direction (i.e., the second direction T2) of the cut end 13 of the workpiece 1 (hereinafter also referred to as the "fracture surface length") is preferably greater than 0 mm and less than 1.0 mm. If the fracture surface length W1 of the workpiece 1 is 1.0 mm or less, even if red rust occurs on the fracture surface 13d, it will not be noticeable, and it can be determined that this will not pose a practical problem. The fracture surface length W1 of the workpiece 1 is preferably small, and may be 0.8 mm or less or 0.6 mm or less. It is more preferable that the fracture surface length W1 of the workpiece 1 be 0.5 mm or less, 0.3 mm or less, or 0.2 mm or less. Furthermore, the ratio W1 / t1 of the fracture surface length W1 to the thickness t1 of the cut end 13 of the workpiece 1 may be less than 0.15, less than 0.10, less than 0.08, less than 0.06, or less than 0.04. Note that the fracture surface length W1 of the workpiece 1 may be 0 mm. That is, the cut end 13 of the workpiece 1 does not have to have a fracture surface 13d. In this case, the cut end 13 has only a shear surface 13c in the second direction T2.

[0048] Furthermore, the end surface 14a of the opening (opening 14 in FIG. 4 ) of the processed product 1 according to this embodiment has a flat surface 13k. In a product without a flange, such as that shown in FIG. 1 , the end surface 14a of the body portion 10 is typically used as a mounting surface for other components. For example, in the motor case example shown in FIG. 1 , a bottom plate 15 is fixed to the end surface 14a of the body portion 10 to seal the opening, as shown in FIG. 4 . In this case, the longer the length Lt of the flat surface 13k of the end surface 14a of the body portion 10, the larger the contact area with the mounting surface 15a of the bottom plate 15, thereby improving airtightness. To achieve this effect, the ratio Lt / t of the length Lt of the flat surface 13k to the thickness t of the side wall 101 of the processed product 1 is preferably 0.35 or greater, 0.40 or greater, or 0.50 or greater, and more preferably 0.60 or greater, 0.70 or greater, 0.80 or greater, or 0.85 or greater.

[0049] Furthermore, the length of burrs generated on the lower side of the fracture surface 13d of the cut end portion 13 of the processed product 1 may be less than 0.2 mm. Burrs can cause dents, electrical short circuits, etc. By keeping the burr length less than 0.2 mm and minimizing the amount of burrs remaining on the processed product 1, the occurrence of dents, electrical short circuits, etc. can be suppressed. It is more preferable that the length of the burr is less than 0.1 mm.

[0050] The processed product according to this embodiment is manufactured by cutting the plated steel sheet in two steps, a semi-cutting step and a finish-cutting step, rather than cutting it in a single step. This allows the processed product 1 to have a larger amount of the plating layer 13f1 extending around the shear surface 13c. The processed product manufacturing method according to this embodiment will be described below.

[0051] [1-3. Processed Product Manufacturing Method] First, the processed product manufacturing method according to this embodiment will be described with reference to Fig. 5. Fig. 5 is an explanatory diagram showing the processed product manufacturing method according to this embodiment. As shown in Fig. 5, the processed product manufacturing method according to this embodiment includes a preparation step, a semi-cutting step, and a finish cutting step.

[0052] The preparation step is a step of preparing a first element body 2. The first element body 2 can be obtained by performing a forming process such as drawing on a flat plated steel sheet. That is, the first element body 2 is made of plated steel sheet, just like the processed product 1. The first element body 2 has a flange portion 20 at a position that will become the cut end 13 shown in FIG. 1. The flange portion 20 may have a circular or non-circular outer shape in a plan view. The first element body 2 may have a shape similar to that of the processed product 1 except for the flange portion 20. Note that the preparation step is not essential to the implementation of the present invention. If an element body that has been processed by a third party using some method is available, the preparation step can be omitted.

[0053] The half-cutting process is a process for half-cutting the first element body 2. In the half-cutting process, the flange portion 20 is half-cut. Half-cutting is a process for cutting the flange portion 20 to a midpoint in the cutting direction of the flange portion 20. In this embodiment, the flange portion 20 is a removed portion 20a that will ultimately be outside the product, and is cut at the boundary position with the portion that will become the side wall 101 of the body portion 10 of the processed product 1. The cutting direction of the flange portion 20 is the plate thickness direction of the flange portion 20.

[0054] The finish cutting process is a process for finish-cutting the first element body 2. In the finish cutting process, the half-cut flange portion 20 is cut and separated from the portion that will become the side wall 101 of the trunk portion 10 of the processed product 1. By cutting the flange portion 20, the processed product 1 is obtained, with the cut end portion 13 formed flush with the side wall 101. As shown in FIG. 3 , the end surface 14a of the opening 14 of the processed product 1 is covered with the plating layer 13f2 on the inner surface 101b side of the trunk portion 10. In addition, the end surface 14a of the opening 14 of the processed product 1 is formed so as to have a flat surface 13k.

[0055] In the semi-cutting step and the finish-cutting step of the processed product manufacturing method according to this embodiment, the first body 2 is machined using a die and a punch. Hereinafter, the semi-cutting step and the finish-cutting step will be described in detail, with two forms corresponding to the shapes of the cutting edges of the die and punch used in the semi-cutting step. The cutting edges of the die and punch may also be referred to as "shoulders." In the following description, for convenience, the upper die (upper die) and the lower die (lower die) used to obtain the processed product 1 will be referred to as the die and the punch, respectively. Therefore, the present technology is naturally applicable to cases where the upper die (upper die) is referred to as the punch and the lower die (lower die) is referred to as the die. Furthermore, the movement direction of the die and punch is determined depending on the installation state, and they may move vertically or horizontally.

[0056] (a. When only the cutting edge of the die used in the half-cutting step is rounded) First, the half-cutting step and the finish-cutting step when only the cutting edge of the die used in the half-cutting step is rounded will be described with reference to Fig. 6 and Fig. 7. Fig. 6 is an explanatory diagram showing the half-cutting step when the cutting edge of the die used in the half-cutting step is rounded. Fig. 7 is an explanatory diagram showing the finish-cutting step that is performed subsequent to the half-cutting step in Fig. 6.

[0057] (Half-Cutting Process) In the half-cutting process, as shown in Fig. 6 , the flange portion 20 of the first element body 2 is half-cut using a first die 31 and a first punch 41. Fig. 6 shows, as one mode of half-cutting, a mode in which the flange portion 20 is half-punched from the first element body 2 in which the portion that will become the side wall 101 of the trunk portion 10 is clamped between the first punch 41 and the first guide 51. The first die 31 constitutes a cutting mold that is pressed into the flange portion 20 during half-cutting. In this embodiment, the first punch 41 is the mold that presses the portion that will become the end face of the side wall 101 of the trunk portion 10 (end face 14a in Fig. 3 ), and the first die 31 is the mold that presses the flange portion 20 (i.e., the removed portion 20a).

[0058] Here, the clearance C between the first die 31 and the first punch 41 ３１－４１ is considered to be a negative clearance. ３１－４１represents the gap between the first die 31 and the first punch 41, and specifically, as shown in FIG. 6, is represented by the distance between the side surface 31a of the first die 31 and the side surface 41a of the first punch 41. In the state where there is no clearance (i.e., C ３１－４１ When viewed from the pushing direction of the first die 31 (i.e., the plate thickness direction of the flange portion 20, the Z direction), the clearance when the first die 31 and the first punch 41 are separated from each other is referred to as a positive clearance, and the clearance when the first die 31 and the first punch 41 partially overlap each other is referred to as a negative clearance. In this specification, regarding the clearance between the die and the punch, a positive clearance is represented by a positive value, and a negative clearance is represented by a negative value.

[0059] As shown in Figure 6, the first die 31 and the first punch 41 that cut the first element body 2 in half are arranged so that the first die 31 and the first punch 41 partially overlap when viewed from the pushing direction of the first die 31. ３１－４１ If the clearance C is a positive clearance, cracks generated from the cutting edges of the first die 31 and the first punch 41 may meet, as in a single punching process, and the removed portion 20a may be completely cut off from the flange portion 20. In addition, the cutting position of the flange portion 20 may be separated from the side wall 101 of the body portion 10, and the cut end portion 13 may not be flush with the side wall 101, resulting in a step on the outer surface of the processed product 1. ３１－４１ By making this a negative clearance, it is possible to avoid the flange portion 20 (i.e., the removed portion 20a) being completely cut off from the first body 2 in the half-cutting process, and to make the cut end portion 13 flush with the side wall 101.

[0060] Also, clearance C ３１－４１By providing a negative clearance, large hydrostatic stress is generated in the region sandwiched between the first die 31 and the first punch 41. Therefore, the proportion of tensile stress generated between the material that will become scrap (i.e., the removed portion 20a) after cutting and the sidewall material that will become the sidewall 101 of the body portion 10 is reduced in the stress generated when the first die 31 is pressed into the flange portion 20. As a result, the material that will become scrap after cutting and that contacts the cutting edge of the first die 31 is more likely to flow from the cutting edge of the first die 31 toward the side surface 31a of the first die 31, thereby increasing the wraparound of the plating layer 13f1 onto the sheared surface 13c. Furthermore, the reduction in the proportion of tensile stress increases compressive stress, and the material that would normally flow toward the scrap side is pushed back toward the sidewall 101. As a result, the portion that will become the end surface 14a of the opening 14 after cutting is compressed and flattened.

[0061] Clearance C between the first die 31 and the first punch 41 ３１－４１ As shown in the following formula (a1), [mm] is set to be equal to or less than −0.01 mm and equal to or greater than −0.35 times the thickness t1 [mm] of the cut portion (i.e., flange portion 20) of the first element body 2. The thickness t1 of the cut portion (i.e., flange portion 20) of the first element body 2 is equal to the thickness (t1) of the cut end portion 13 of the workpiece 1.

[0062] −0.35×t1≦C ３１－４１ ≦-0.01...(a1)

[0063] Clearance C ３１－４１ If the clearance C is -0.01 mm or less, a partial positive clearance will not occur due to the sliding accuracy of the press machine or misalignment of the die, and a negative clearance can be maintained. As a result, a crack will not occur during partial cutting, causing a complete cut and resulting in a large fracture surface. On the other hand, if the clearance C is ３１－４１ is at least −0.35 times the plate thickness t1 of the flange portion 20, the forming load required for half-cutting does not increase and does not exceed the press capacity. Therefore, the burden on the mold is small, and a decrease in the mold life can be suppressed.

[0064] More preferably, the clearance C３１－４１ is set to be −0.30 times or more, −0.25 times or more, or −0.20 times or more the plate thickness t1 of the flange portion 20. ３１－４１ is set to be −0.30 times or more, −0.25 times or more, or −0.20 times or more the thickness t1 of the flange portion 20, the width Lt of the flat surface 13k of the end face 14a of the opening 14 after cutting can be set to be 0.35 times or more the thickness t of the side wall 101 of the processed product 1. ３１－４１ The upper limit of the thickness t1 of the flange portion 20 may be set to −0.05 times, −0.10 times, or −0.15 times.

[0065] The cutting edge of the first die 31 is rounded with a radius of curvature R1 as shown in Fig. 6. As shown in Fig. 6, the first die 31 is pressed into the flange portion 20, so the cutting edge of the first die 31 is rounded with a radius of curvature R1.

[0066] The radius of curvature R1 is 0.10 to 0.50 times the thickness t1 [mm] of the flange portion 20 of the first element body 2, as shown in the following formula (a2).

[0067] 0.1×t1≦R1≦0.5×t1 (a2)

[0068] If the radius of curvature R1 is 0.10 times the sheet thickness t1 or more, a large hydrostatic force is generated under a negative clearance without scraping away the plating layer 13f1, causing the material to become scrap directly below the first die 31 to flow from the cutting edge of the first die 31 toward the side surface 31a of the first die 31. This flow reduces the proportion of tensile stress generated between the material to become scrap (i.e., the removed portion 20a) after cutting and the sidewall material to become the sidewall 101 of the body portion 10, among the stresses generated when the first die 31 is pressed into the flange portion 20. As a result, the sheared surface 13c can be caused to flow around the plating layer 13f1. On the other hand, if the radius of curvature R1 is 0.50 times the sheet thickness t1 or less, less material is present at the cutting edge of the first die 31 during half-cutting, thereby reducing the generation of fractured surfaces 13d during the subsequent finish cut.

[0069] The cutting edge of the first punch 41 is rectangular and not rounded, as shown in Fig. 6. In this case, the cutting edge of the first punch 41 may have a radius of curvature that is less than 0.1 times the thickness t1 of the flange portion 20 of the first element body 2. The radius of curvature of the cutting edge of the first punch 41 may also be less than 0.06 times, less than 0.04 times, or less than 0.02 times the thickness t1 of the flange portion 20 of the first element body 2, as necessary.

[0070] The pushing amount D [mm] of the first die 31 into the flange portion 20 of the first element body 2 is set to be 0.70 times or more the thickness t1 [mm] of the cut portion of the first element body 2 (i.e., the flange portion 20), as shown in the following formula (a3). The pushing amount D is the amount of movement of the first die 31 from the position where the first die 31 contacts the upper surface of the flange portion 20 of the first element body 2 to the position where the pushing of the first die 31 stops (hereinafter, this position will also be referred to as the "bottom dead center"). In addition, the distance C between the first die 31 and the first punch 41 at the bottom dead center is Ｐ－Ｄ [mm] is set to 0.20 mm or more as shown in the following formula (a4).

[0071] D≧0.70×t1...(a3) C Ｐ－Ｄ ≧0.20...(a4)

[0072] The remaining thickness t2 of the flange portion 20 (i.e., the removed portion 20a) remaining on the first body 2 after half-cutting may be 0.30 times or less the thickness t1 [mm] of the flange portion 20. Here, the remaining thickness t2 is the remaining thickness on the outer surface 101a of the side wall 101 of the workpiece 1. If the push-in amount D is 0.70 times or more the thickness t1, it becomes difficult to generate a fracture surface 13d in the subsequent finish cutting. On the other hand, the distance C between the first die 31 and the first punch 41 at the bottom dead center Ｐ－Ｄ By ensuring that the gap C is 0.20 mm or more, it is possible to prevent cracks from occurring during partial cutting, which can result in partial complete cutting. In addition, the burden on the mold is small, and the reduction in the mold life can be suppressed. Ｐ－Ｄ is the minimum value of the distance between the first die 31 and the first punch 41 at the bottom dead center.

[0073] The pushing amount D of the first die 31 into the flange portion 20 of the first body 2 should be at least 0.70 times the plate thickness t1 [mm] of the flange portion 20 of the first body 2, as shown in the above formula (a3), but may also be set to no more than 0.95 times (0.70 × t1 ≦ D ≦ 0.95 × t1).

[0074] 6, the remaining thickness t2 is a value obtained by subtracting the amount of pressing D of the first die 31 into the flange portion 20 from the thickness t1 of the flange portion 20 and adding the radius of curvature R1 (t2=t1-D+R1). Therefore, the remaining thickness t2 is calculated by subtracting the distance C between the first die 31 and the first punch 41 at the bottom dead center from the thickness t1 of the flange portion 20. Ｐ－Ｄ If the push-in amount D is 0.70 times the plate thickness t1 or more, it is difficult for the fracture surface 13d to be generated in the subsequent finish cutting. On the other hand, if the push-in amount D is 0.95 times the plate thickness t1 or less, cracks will occur during partial cutting due to the slide accuracy of the press machine or misalignment of the die, which will result in complete cutting and will not result in large fracture surfaces. In addition, the burden on the die is small, and a decrease in the die life can be suppressed.

[0075] (Finish Cutting Process) In the finish cutting process, as shown in FIG. 7 , the half-cut flange portion 20 is finish-cut using a second die 32 and a second punch 42. FIG. 7 shows one mode of finish cutting in which the portion that will become the side wall 101 of the trunk portion 10 is sandwiched between a second punch 42 and a second guide 52, and the flange portion 20 (i.e., the removed portion 20 a) is finish-punched out of the first body 2. The second die 32 constitutes a cutting die that is pressed into the flange portion 20 in the finish cutting. In this embodiment, the die that presses the portion that will become the end face (end face 14 a in FIG. 3 ) of the side wall 101 of the trunk portion 10 is the second punch 42, and the die that presses the flange portion 20 (i.e., the removed portion 20 a) is the second die 32. The second die 32 may be the same as the first die 31. In other words, the first die 31 used in the half-cutting process may be used as the second die 32 in the finish cutting process.

[0076] The positional relationship between the second die 32 and the first element body 2 is preferably the same as the positional relationship between the first die 31 and the first element body 2. If these positional relationships are not the same, for example, if the diameter of the second die 32 is larger than the diameter of the first die 31, a step will occur at the cut edge 13. Conversely, for example, if the diameter of the second die 32 is smaller than the diameter of the first die 31, the second die 32 will come into contact with the half-cut cut edge produced in the half-cutting step, and the second die 32 may scrape off the plating layer 13f that has wrapped around the sheared surface 13c.

[0077] The finish cutting according to this embodiment is performed in the same direction as the half cutting. That is, when the first die 31 is pressed into the flange portion 20 from above in the half cutting as shown in Fig. 6, the second die 32 is also pressed into the flange portion 20 from above in the finish cutting as shown in Fig. 7. This separates the removed portion 20a from the first body 2.

[0078] Clearance C between the second die 32 and the second punch 42 ３２－４２ is a positive clearance. Clearance C ３２－４２ is expressed as the distance between the side surface 32 a of the second die 32 and the side surface 42 a of the second punch 42. Here, as in the half-cutting process, the clearance when the second die 32 and the second punch 42 are separated from each other is called a positive clearance, and the clearance when the second die 32 and the second punch 42 are partially overlapping each other is called a negative clearance.

[0079] Clearance C between the second die 32 and the second punch 42 ３２－４２ [mm] is set to be 0.01 mm or more and 0.2 times or less the remaining thickness t2 of the removed portion 20a remaining in the flange portion 20 of the first base body 2 after half-cutting, as shown in the following formula (5).

[0080] 0.01≦C ３２－４２ ≦0.2×t2 (5)

[0081] Clearance C ３２－４２ If the clearance C is 0.01 mm or more, the blade of the second die 32 and the blade of the second punch 42 will not come into contact with each other even if the slide accuracy of the press machine or the center misalignment of the die occurs during the finish cutting.３２－４２ If the clearance C is 0.2 times or less the remaining plate thickness t2, burrs are less likely to be generated at the tip of the fracture surface 13d. ３２－４２ The lower limit may be 0.05 times or 0.10 times the remaining plate thickness t2.

[0082] The cutting edge of the second die 32 is rounded with a radius of curvature R2. As shown in FIG. 7 , the second die 32 is pressed into the portion of the flange portion 20 where finish cutting is performed, so the cutting edge of the second die 32 is rounded with a radius of curvature R2. The cutting edge of the second punch 42 is rectangular with no rounding, as shown in FIG. 7 . In this case, the cutting edge of the second punch 42 may have a radius of curvature of less than 0.25 mm, less than 0.15 mm, less than 0.10 mm, or less than 0.05 mm. Alternatively, the radius of curvature of the cutting edge of the second punch 42 may be less than 0.1 times the thickness t1 of the flange portion 20 of the first element 2, and may be less than 0.06 times, less than 0.04 times, or less than 0.02 times, as necessary.

[0083] The radius of curvature R2 [mm] is set to 0.25 mm or more and 1.50 times or less the remaining plate thickness t2 of the half-cut portion, as shown in the following formula (6).

[0084] 0.25≦R2≦1.50×t2 (6)

[0085] If the radius of curvature R2 is 0.25 mm or more, the plating layer 13f1 that has wrapped around the sheared surface 13c will not be scraped off by the second die 32. On the other hand, if the radius of curvature R2 is 1.50 times the remaining sheet thickness t2 or less, burrs are less likely to be formed at the tip of the fractured surface 13d.

[0086] The inner diameter D of the second die 32 ３２ is the inner diameter D of the first die 31 ３１ Specifically, the inner diameter D of the first die 31 is set to be equal to or slightly larger than ３１ and the inner diameter D of the second die 32 ３２ Difference D ３２ -D ３１ In this way, the difference D between the inner diameters of the dies 31 and 32 is preferably 1.00 mm or less in order to perform two steps, namely, the half-cutting step and the finish-cutting step. ３２ -D ３１This makes it possible to reduce the step that occurs at the cut end 13 of the processed product 1, and to obtain a good cut cross section. ３２ -D ３１ The difference in inner diameter D may be greater than 1.00 mm. ３２ -D ３１ The upper limit of the inner diameter difference D is preferably small, and may be set to 0.75 mm, 0.50 mm, 0.35 mm, or 0.20 mm. ３２ -D ３１ The lower limit is 0 mm.

[0087] (b. When the cutting edges of the die and punch used in the semi-cutting process are rounded) Next, the semi-cutting process and the finish-cutting process when the cutting edges of the die and punch used in the semi-cutting process are rounded will be described with reference to Fig. 8 and Fig. 9. Fig. 8 is an explanatory diagram showing the semi-cutting process when the cutting edges of the die and punch used in the semi-cutting process are rounded. Fig. 9 is an explanatory diagram showing the finish-cutting process that is performed following the semi-cutting process in Fig. 8.

[0088] (Half-Cutting Step) In the half-cutting step, as shown in Fig. 8 , the flange portion 20 of the first element body 2 is half-cut using a first die 31 and a first punch 41. As with Fig. 6 , Fig. 8 shows, as one mode of half-cutting, a mode in which the flange portion 20 is half-punched from the first element body 2 in which the portion that will become the side wall 101 of the trunk portion 10 is clamped between the first punch 41 and the first guide 51. The first die 31 constitutes a cutting mold that is pressed into the flange portion 20 during half-cutting. In this embodiment, the first punch 41 is the mold that presses the portion that will become the end face of the side wall 101 of the trunk portion 10 (end face 14a in Fig. 3 ), and the first die 31 is the mold that presses the flange portion 20 (i.e., the removed portion 20a).

[0089] Clearance C between the first die 31 and the first punch 41 ３１－４１ is a negative clearance. Therefore, as shown in Figure 8, the first die 31 and the first punch 41 that cut the first body 2 in half are arranged so that the first die 31 and the first punch 41 partially overlap when viewed from the pushing direction of the first die 31. ３１－４１By making the clearance C a negative, it is possible to prevent the flange portion 20 (i.e., the removed portion 20a) from being completely cut off from the first element body 2 in the half-cutting step, and to make the cut end portion 13 flush with the side wall 101. ３１－４１ The meanings of the negative clearance and positive clearance are the same as those in the above embodiment a.

[0090] Also, clearance C ３１－４１ By providing a negative clearance, large hydrostatic stress is generated in the region sandwiched between the first die 31 and the first punch 41. Therefore, the proportion of tensile stress generated between the material that will become scrap (i.e., the removed portion 20a) after cutting and the sidewall material that will become the sidewall 101 of the body portion 10 is reduced in the stress generated when the first die 31 is pressed into the flange portion 20. As a result, the material that will become scrap after cutting and that contacts the cutting edge of the first die 31 is more likely to flow from the cutting edge of the first die 31 toward the side surface 31a of the first die 31, thereby increasing the wraparound of the plating layer 13f1 onto the sheared surface 13c. Furthermore, the reduction in the proportion of tensile stress increases compressive stress, and the material that would normally flow toward the scrap side is pushed back toward the sidewall 101. As a result, the portion that will become the end surface 14a of the opening 14 after cutting is compressed and flattened.

[0091] Clearance C between the first die 31 and the first punch 41 ３１－４１ [mm] is set to be not more than −0.10 and not less than −0.45 times the thickness t1 [mm] of the cut portion of the first body 2 (i.e., the flange portion 20), as shown in the following formula (b1).

[0092] −0.45×t1≦C ３１－４１ ≦-0.10×t1...(b1)

[0093] Clearance C ３１－４１is less than or equal to -0.10 times the plate thickness t1 of the flange portion 20, large hydrostatic stress occurs in the region sandwiched between the first die 31 and the first punch 41, and the proportion of tensile stress decreases. As a result, cracks do not occur during half-cutting, causing complete cutting and the generation of large fracture surfaces, and it is possible to prevent the flange portion 20 (i.e., the removed portion 20a) from being completely cut off from the first element body 2 in the half-cutting step. On the other hand, when the clearance C ３１－４１ is at least −0.45 times the plate thickness t1 of the flange portion 20, the forming load required for half-cutting does not increase and does not exceed the press capacity. Therefore, the burden on the mold is small, and it is possible to suppress a decrease in the mold life.

[0094] More preferably, the clearance C ３１－４１ is set to be equal to or less than -0.15 times the plate thickness t1 of the flange portion 20. ３１－４１ By setting the clearance C to be −0.15 times or less or −0.20 times or less the thickness t1 of the flange portion 20, the width Lt of the flat surface 13k of the end face 14a of the opening 14 after cutting can be more reliably set to 0.35 times or more the thickness t of the side wall 101 of the processed product 1. ３１－４１ The lower limit of may be −0.40 times, −0.35 times, or −0.30 times the plate thickness t1 of the flange portion 20.

[0095] 8, the cutting edges of the first die 31 and the first punch 41 are rounded. The radius of curvature R11 [mm] of the cutting edge of the first die 31 and the radius of curvature R12 [mm] of the cutting edge of the first punch 41 are set to be 0.10 to 0.65 times the thickness t1 [mm] of the cut portion (i.e., flange portion 20) of the first element 2, as shown in the following formulas (b2-1) and (b2-2). Note that the radius of curvature R11 of the cutting edge of the first die 31 and the radius of curvature R12 of the cutting edge of the first punch 41 may be the same or different.

[0096] 0.10×t1≦R11≦0.65×t1 (b2-1) 0.10×t1≦R12≦0.65×t1 (b2-2)

[0097] If the radii of curvature R11 and R12 are 0.10 times the sheet thickness t1 or more, a large hydrostatic force is generated under a negative clearance without scraping away the plating layer 13f1, causing the material to become scrap directly below the first die 31 to flow from the cutting edge of the first die 31 toward the side surface 31a of the first die 31. This flow reduces the proportion of tensile stress generated between the material to become scrap (i.e., the removed portion 20a) after cutting and the material to become the side wall 101 of the body portion 10, among the stresses generated when the first die 31 is pressed into the flange portion 20. As a result, the sheared surface 13c can be caused to flow around the plating layer 13f1. On the other hand, if the radii of curvature R11 and R12 are 0.65 times the sheet thickness t1 or less, less material is present at the cutting edge of the first die 31 during half-cutting, thereby reducing the generation of fractured surfaces 13d during the subsequent finish cut.

[0098] The pushing amount D [mm] of the first die 31 into the flange portion 20 of the first element body 2 is set to be 0.70 times or more the thickness t1 [mm] of the cut portion of the first element body 2 (i.e., the flange portion 20), as shown in the following formula (b3). The pushing amount D is the amount of movement of the first die 31 from the position where the first die 31 contacts the upper surface of the flange portion 20 of the first element body 2 to the position where the pushing of the first die 31 stops (hereinafter, this position will also be referred to as the "bottom dead center"). The distance C between the first die 31 and the first punch 41 at the bottom dead center Ｐ－Ｄ [mm] is set to 0.20 mm or more as shown in the following formula (b4).

[0099] D≧0.70×t1...(b3) C Ｐ－Ｄ ≧0.20...(b4)

[0100] The remaining thickness t2 of the flange portion 20 (i.e., the removed portion 20a) remaining on the first body 2 after half-cutting may be 0.30 times or less the thickness t1 [mm] of the flange portion 20. Here, the remaining thickness t2 is the remaining thickness of the outer surface 101a of the side wall 101 of the processed product 1, and the distance C Ｐ－ＤIf the pushing amount D is 0.70 times or more the plate thickness t1 of the flange portion 20, the fracture surface 13d is unlikely to be generated in the subsequent finish cutting. On the other hand, the distance C between the first die 31 and the first punch 41 at the bottom dead center Ｐ－Ｄ By ensuring that the gap C is 0.20 mm or more, it is possible to prevent cracks from occurring during partial cutting, which can result in partial complete cutting. In addition, the burden on the mold is small, and the reduction in the mold life can be suppressed. Ｐ－Ｄ is the minimum value of the distance between the first die 31 and the first punch 41 at the bottom dead center.

[0101] By providing the cutting edges of the first die 31 and the first punch 41 with an R-shape, it is possible to increase the amount of flange portion 20 cut away in the half-cutting step, compared to when the cutting edges of only one of the first die 31 or the first punch 41 are R-shaped, as shown in Fig. 6. In other words, by providing the cutting edges of the first die 31 and the first punch 41 with an R-shape, it is possible to reduce the remaining plate thickness t2 in which the flange portion 20 (i.e., the removed portion 20a) remains in the first body 2 after half-cutting, compared to when the cutting edges of only one of the first die 31 or the first punch 41 are R-shaped, as shown in Fig. 6.

[0102] In the case where only the cutting edge of the first die 31 is rounded as in the above-described embodiment a, if the indentation amount D of the first die 31 is set to be equal to or greater than the thickness t1 of the cut portion (i.e., the flange portion 20), the cutting edge of the first die 31 will contact the cutting edge of the first punch 41. Therefore, in the above-described embodiment a, the indentation amount D of the first die 31 cannot be set to be equal to or greater than the thickness t1 of the flange portion 20. However, if the cutting edges of the first die 31 and the first punch 41 are rounded, the indentation amount of the first die 31 before contacting the cutting edge of the first punch 41 increases, as shown in FIG. 8 . Therefore, compared to embodiment a, it is possible to cut a larger amount of the flange portion 20, thereby increasing the proportion of the sheared surface 13c in the cut end portion 13. This allows the plating layer 13f1 to wrap around the sheared surface 13c more, thereby increasing the proportion of the cut end portion 13 covered by the plating layer 13f1. Furthermore, by reducing the remaining plate thickness t2, the amount of cutting in the finish cutting step is reduced, and it is possible to avoid a situation in which no plating layer remains in part of the finish-cut portion.

[0103] (Finish Cutting Process) In the finish cutting process, as shown in Fig. 9 , the half-cut flange portion 20 is finish-cut using the second die 32 and the second punch 42. The finish cutting process may be performed in the same manner as the finish cutting process shown in Fig. 7 , which is performed after half-cutting is performed by forming the cutting edge of only one of the first die 31 and the first punch 41 into an R shape.

[0104] 9 shows, as one mode of finish cutting, a mode in which the portion that will become the side wall 101 of the body portion 10 is sandwiched between the second punch 42 and the second guide 52, and the flange portion 20 (i.e., the removed portion 20a) is finish-punched out of the first body 2. The second die 32 constitutes a cutting mold that is pressed into the flange portion 20 during finish cutting. In this embodiment, the second punch 42 is the mold that presses the portion that will become the end face (end face 14a in FIG. 3 ) of the side wall 101 of the body portion 10, and the second die 32 is the mold that presses the flange portion 20 (i.e., the removed portion 20a). The second die 32 may be the same as the first die 31. In other words, the first die 31 used in the half-cutting step may be used as the second die 32 in the finish-cutting step.

[0105] The positional relationship between the second die 32 and the first element body 2 is preferably the same as the positional relationship between the first die 31 and the first element body 2. If these positional relationships are not the same, for example, if the diameter of the second die 32 is larger than the diameter of the first die 31, a step will occur at the cut edge 13. Conversely, for example, if the diameter of the second die 32 is smaller than the diameter of the first die 31, the second die 32 will come into contact with the half-cut cut edge produced in the half-cutting step, and the second die 32 may scrape off the plating layer 13f that has wrapped around the sheared surface 13c.

[0106] The finish cutting according to this embodiment is performed in the same direction as the half cutting. That is, when the first die 31 is pressed into the flange portion 20 from above in the half cutting as shown in Fig. 8, the second die 32 is also pressed into the flange portion 20 from above in the finish cutting as shown in Fig. 9. This separates the removed portion 20a from the first body 2.

[0107] Clearance C between the second die 32 and the second punch 42 ３２－４２ [mm] is a positive clearance. ３２－４２ As shown in the above formula (5), the clearance C is set to be 0.01 mm or more and 0.2 times or less the remaining plate thickness t2 of the removed portion 20a remaining in the first element body 2 after half-cutting. ３２－４２ If the clearance C is 0.01 mm or more, the blade of the second die 32 and the blade of the second punch 42 will not come into contact with each other even if the slide accuracy of the press machine or the center misalignment of the die occurs during the finish cutting. ３２－４２ If is 0.2 times or less the remaining plate thickness t2, burrs are less likely to be generated at the tip of the fracture surface 13d.

[0108] The cutting edge of the second die 32 is rounded with a radius of curvature R2. As shown in FIG. 9 , the second die 32 is pressed into the portion of the flange portion 20 where the finish cutting is performed, so the cutting edge of the second die 32 is rounded with a radius of curvature R2. The cutting edge of the second punch 42 may be rectangular with no rounding as shown in FIG. 7 , or may have a radius of curvature. If the cutting edge of the second punch 42 is rectangular with no rounding, burrs generated at the tip of the fracture surface 13d can be reduced. The curvature radius of the cutting edge of the second punch 42 may be less than 1.00 mm, less than 0.50 mm, less than 0.20 mm, less than 0.10 mm, or less than 0.05 mm. Alternatively, the curvature radius of the cutting edge of the second punch 42 may be less than 0.3 times the thickness t1 of the flange portion 20 of the first element 2, and may be less than 0.1 times, less than 0.06 times, less than 0.04 times, or less than 0.02 times, as necessary.

[0109] As shown in the above formula (6), the radius of curvature R2 [mm] is set to be 0.25 mm or more and 1.50 times or less the remaining sheet thickness t2 of the half-cut portion. If the radius of curvature R2 is 0.25 mm or more, the second die 32 will not scrape off the plating layer 13f1 that has wrapped around the sheared surface 13c. On the other hand, if the radius of curvature R2 is 1.50 times or less the remaining sheet thickness t2, burrs are less likely to form at the tip of the fracture surface 13d.

[0110] The above has described the method for manufacturing a processed product according to the first embodiment of the present invention. According to this embodiment, the method includes a half-cutting step in which a first element body 2 formed from a plated steel sheet and having a flange portion 20 is cut in half using a first die 31 and a first punch 41, the clearance between which is set to a negative clearance, to cut off the flange portion 20 of the first element body 2 in half, and a finish-cutting step in which a second die 32 and a second punch 42 are used to finish-cut the half-cut flange portion 20 in the same direction as the half-cutting, to obtain a processed product 1 having a cut edge 13 that is flush with the side wall 101 of the trunk portion 10.

[0111] The cut end 13 of the workpiece 1 cut through these two processes has a shear surface 13c and a fracture surface 13d, in that order, in the thickness direction of the cut portion. The shear surface 13c is at least partially covered with a plating layer 13f1. The ratio L / t1 of the remaining length L of the plating component where the shear surface 13c is covered with the plating layer 13f1 to the thickness t1 of the cut end 13 of the workpiece 1 is 0.70 or greater. Thus, in the workpiece 1, a larger portion of the plating layer 13f1 wraps around the shear surface 13c. Even when a plated steel sheet having a thickness of more than 2.0 mm is used as the raw material, the corrosion resistance and shape quality can be improved.

[0112] Furthermore, in the processed product manufacturing method according to this embodiment, at least the cutting edge of the die used in the semi-cutting process and the finish cutting process is rounded. This eliminates the need for a gap between the body portion 10 of the processed product 1 and the die pressed into the cutting section. As a result, a processed product 1 having a cut edge 13 flush with the body portion 10 and no steps on the outer surface of the processed product 1 can be obtained. If the cutting edge of the die is also sharp, the die, which is a blade, is installed away from the body portion 10 to avoid contact with the body portion 10. This is because if the die pressed into the cutting section comes into contact with the body portion 10, it will scrape off the plating layer 13f1 on the surface of the body portion 10. If the die is installed away from the body portion 10 in this manner, steps will be created on the outer surface of the processed product 1 after cutting the flange portion 20. According to the processed product manufacturing method according to this embodiment, it is unnecessary to provide a gap between the body portion 10 of the processed product 1 and the die pressed into the cutting section, and a processed product 1 having a cut edge 13 flush with the body portion 10 can be obtained.

[0113] Furthermore, according to the method for manufacturing a processed product of this embodiment, it is possible to flatten the end surface 14a of the opening 14 of the processed product 1. In the method for manufacturing a processed product of this embodiment, the clearance C between the die and the punch in the half-cutting step is ３１－４１By providing a negative clearance, a large hydrostatic stress is generated in the region sandwiched between the first die 31 and the first punch 41. This compresses the portion that will become the end face 14a of the opening 14 after cutting, forming a large flat surface 13k. In a product without a flange as shown in FIG. 1, the end face 14a of the body 10 typically serves as the attachment surface for another component. By forming a large flat surface 13k, the contact area between the attachment surface of another component and the end face of the body 10 can be increased when the body is attached to the other component, thereby improving airtightness.

[0114] Furthermore, the processed product manufacturing method according to this embodiment allows more plating layer 13f to be formed around shear surface 13c, thereby suppressing red rust that occurs on cut end 13 over time after cutting.

[0115] In addition, the clearance C between the second die 32 and the second punch 42 ３２－４２ is set to be 0.01 mm or more and 0.2 times or less the remaining plate thickness t2 of the half-cut portion of the first element body 2. This makes it possible to prevent damage due to contact between the blade of the second die 32 and the blade of the second punch 42 during finish cutting, while suppressing the generation of burrs.

[0116] The tip of the cutting edge of the second die 32, which is pressed into the portion of the first body 2 that is to be finish-cut, is curved with a radius of curvature R2 that is 0.25 mm or more and 1.50 times or less the remaining thickness t2 of the half-cut portion. This prevents the cutting die from scraping off the plating layer 13f1 that has reached the sheared surface 13c, and suppresses the generation of burrs.

[0117] 2. Second Embodiment Next, a processed product manufacturing method according to a second embodiment of the present invention will be described with reference to Fig. 10. Fig. 10 is an explanatory view showing a processed product manufacturing method according to the second embodiment of the present invention. As shown in Fig. 10, the processed product manufacturing method according to this embodiment includes a preparation step, a semi-cutting step, a finish cutting step, and a coining step.

[0118] The processed product manufacturing method according to this embodiment is a method in which a coining step is added to the processed product manufacturing method according to the first embodiment shown in Fig. 6. As shown in Fig. 10, in this embodiment, as in the first embodiment, the first element body 2 prepared in the preparation step is subjected to the semi-cutting step and finish-cutting step. Therefore, detailed description of the preparation step, semi-cutting step, and finish-cutting step will be omitted.

[0119] In the coining step, the workpiece obtained in the finish cutting step is used as the second element 6, and the second element 6 is subjected to a coining process. In the coining step, after the finish cutting step, the corner 13g of the cut end 13 on the fracture surface 13d side is pressed against a coining lower die (coining lower die 7 in FIG. 11 ) to obtain a workpiece 1 having a coining surface 13h formed on the corner. The coining process can narrow the area of ​​the fracture surface 13d, which is a newly formed rough surface, and can suppress the area where red rust occurs. Furthermore, the coining process can crush burrs, more reliably suppressing burrs from remaining in the workpiece 1.

[0120] The coining process will be described in more detail with reference to Figures 11 to 14. Figure 11 is a schematic diagram showing an example of a die used in the coining process. Figure 12 is a partial enlarged view of region B in Figure 11. Figure 13 shows the cut end of the processed product 1 after the coining process, with the left side being a cross-sectional view in the ZX plane including the central axis of the processed product 1 and the right side being a side view from the X direction. Figure 14 is a photograph showing an example of the cut end of the processed product 1 after the coining process.

[0121] 13 , as in FIG. 2 , the plating layers 13f1 and 13f2 are omitted. Also, in FIG. 13 , the curved surface Rd at the boundary between the outer surface 101a and the cut end 13 of the processed product is exaggerated to appear slightly present. However, the curved surface Rd does not create a step at the boundary between the outer surface 101a and the cut end 13, and the outer surface 101a and the cut end 13 can be considered to be flush with each other. Furthermore, the cut end 13 of the processed product 1 shown in FIG. 14 is not flush with the outer surface of the trunk portion 10, but is the cut end of a processed product having a flange portion on the outer periphery of the trunk portion 10, and is located at the tip of the flange portion. While the processed product shown in FIG. 14 differs from the processed product 1 of this embodiment, the appearances of the shear surface 13c, fracture surface 13d, and coining surface 13h of the processed product 1 of this embodiment are the same as those in FIG. 14 .

[0122] In the coining process according to this embodiment, as shown in FIG. 11 , for example, the second element body 6 is processed using a coining lower die 7 and a coining upper die 8. The coining lower die 7 and the coining upper die 8 have recesses formed therein that correspond to the outer shape of the second element body 6. The coining lower die 7 accommodates the opening 14 side of the second element body 6, and the coining upper die 8 accommodates the protrusion 11 side of the second element body 6. In the coining process, the second element body 6 is sandwiched between the coining lower die 7 and the coining upper die 8, and a coining surface is formed on the cut end 13 of the second element 6 by pressing a corner 13g of the cut end 13 against the pressing surface of the coining lower die 7 (pressing surface 72 in FIG. 12 ). After the coining process, the cut end 13 of the processed product 1 is in a state, for example, as shown in the photograph in FIG. 14 .

[0123] More specifically, as shown in FIG. 12, the coining lower die 7 has a vertical wall surface 70, a bottom wall surface 71, and a pressing surface 72.

[0124] The vertical wall surface 70 is disposed so as to face and be substantially parallel to the sheared surface 13c of the second element 6 when the cut end portion 13 of the second element 6 is sandwiched between the coining lower die 7 and the coining upper die 8. The vertical wall surface 70 is disposed so as to be parallel to the direction in which the coining upper die 8 advances and retreats (the Z direction in FIG. 12 ).

[0125] The bottom wall surface 71 is disposed so as to face the end surface 14a across the second element body 6. The bottom wall surface 71 extends in a direction perpendicular to the vertical wall surface 70.

[0126] The pressing surface 72 is a surface that connects the bottom wall surfaces 71 to each other. The pressing surface 72 is provided to form a coining surface (coining surface 13h in FIG. 13) on the second element body 6. The pressing surface 72 is formed in a shape corresponding to the shape of the coining surface. For example, as shown in FIG. 13, if the coining surface 13h is a flat chamfered surface (hereinafter referred to as a "C surface"), the pressing surface 72 may be a flat surface that is inclined relative to the vertical wall surface 70 and the bottom wall surface 71. Furthermore, if the coining surface 13h is a curved surface (which may be either a pressing surface or a compression surface; hereinafter referred to as an "R surface"), the pressing surface 72 may be a curved surface.

[0127] 12 , with the cut end 13 of the second element 6 facing the vertical wall surface 70 of the coining lower die 7, the coining upper die 8 is pressed toward the coining lower die 7, and the second element 6 is sandwiched between the coining upper die 8 and the bottom wall surface 71 of the coining lower die 7. The coining upper die 8 is then pressed toward the bottom wall surface 71, and the second element 6 is pressed down to a position where the end face 14 a of the second element 6 contacts the bottom wall surface 71. Here, before the end face 14 a of the second element 6 contacts the bottom wall surface 71, the corner 13 g is pressed against the pressing surface 72. After the corner 13 g is pressed against the pressing surface 72, the coining upper die 8 is pressed further, and the end face 14 a of the second element 6 contacts the bottom wall surface 71. The corner 13g is crushed by the pressing surface 72 to form a coining surface 13h.

[0128] The coining surface 13h is a smooth surface onto which the surface of the pressing surface 72 is transferred, and is therefore less susceptible to red rust than the rough fracture surface 13d. This is thought to be because the smooth surface roughness makes it difficult for moisture to remain on the coining surface 13h. Another factor that is thought to be less susceptible to red rust is that the plating layer 13f2, which extends continuously from the inner surface of the second element 6 and covers the end surface 14a, is thinly extended onto the coining surface 13h. By forming the coining surface 13h on the corner 13g, the fracture surface length W2 (see FIG. 13 ) of the cut end 13 after the coining process is shorter than the fracture surface length W1 (see FIGS. 2 and 3 ) of the cut end 13 before the coining process. In other words, the coining process narrows the area of ​​the fracture surface 13d, which is a newly roughened surface, and thereby reduces the area where red rust occurs. Furthermore, the coining process can eliminate burrs that occur at the corners 13g, so that the length of the burrs remaining on the processed product 1 is less than 0.2 mm, more reliably suppressing the remaining burrs. The length of the burrs is preferably less than 0.1 mm, and more preferably less than 0.05 mm or less than 0.01 mm.

[0129] In the coining process, the pressing surface 72 is pressed against the corner 13g so that the length W2 (fracture surface length) of the fracture surface 13d between the shear surface 13c and the coining surface 13h of the processed product 1 is greater than 0 mm and not greater than 0.5 mm. By setting the fracture surface length W2 to greater than 0 mm and not greater than 0.5 mm, even if red rust occurs on the fracture surface 13d, it is inconspicuous and can be determined that this does not pose a practical problem.

[0130] In the finish cutting process, it is preferable to obtain a second element body 6 having a fracture surface length W1 of less than 1.0 mm. By obtaining a second element body 6 having a fracture surface length W1 of less than 1.0 mm, it is possible to more reliably achieve a fracture surface length W2 of 0.5 mm or less in the coining process. The fracture surface length W2 of the workpiece 1 is preferably small, and may be 0.4 mm or less or 0.3 mm or less. It is more preferable to set the fracture surface length W2 of the workpiece 1 to 0.2 mm or less or 0.1 mm or less. Furthermore, the ratio W2 / t1 of the fracture surface length W2 to the thickness t1 of the cut end portion 13 of the workpiece 1 may be less than 0.15, less than 0.10, less than 0.08, less than 0.06, or less than 0.04. In addition, the fracture surface length W2 of the workpiece 1 may be 0 mm. In other words, the cut end portion 13 of the workpiece 1 may not have a fracture surface 13d. 13 , the cut end 13 may have a shear surface 13c, a fracture surface 13d, and a coining surface 13h, in that order, in the thickness direction of the cut end 13. Alternatively, the cut end 13 may have a shear surface 13c and a coining surface 13h, in that order, in the thickness direction of the cut end 13.

[0131] 15 is an explanatory diagram showing the volume of the corner 13g crushed by the pressing surface 72 of the coining lower die 7 of FIG. 12. As the coining upper die 8 of FIG. 12 is pressed down toward the bottom wall surface 71 of the coining lower die 7, the corner 13g comes into contact with the pressing surface 72 and is crushed. The material (base steel) of the crushed corner 13g moves along the pressing surface 72 toward the shear surface 13c. When the cut end portion 13 is pressed down to a position where the end face 14a contacts the bottom wall surface 71, the volume V1 of the corner 13g of the second element 6 crushed by the pressing surface 72 changes depending on the position and angle of the pressing surface 72, etc.

[0132] 15 , it is preferable that the volume V1 of the corner 13g crushed by the pressing surface 72 be equal to or smaller than the volume V2 of the coining space surrounded by the extension 13j of the shear surface 13c, the fractured surface 13d, and the pressing surface 72. As shown in FIG. 12 , the fractured surface 13d of the cut end portion 13 of the second element 6 is inclined with respect to the vertical wall surface 70, leaving a gap therebetween. The volume V2 of the coining space created by this gap becomes a space into which the material of the corner 13g crushed by the pressing surface 72 flows. If the volume V2 of the coining space is smaller than the volume V1 of the corner 13g crushed by the pressing surface 72, the material of the corner 13g crushed by the pressing surface 72 cannot be contained within the volume V2 and will move toward the upper part of the coining lower die 7.

[0133] Therefore, by setting the volume V1 to be equal to or less than the volume V2, it is possible to prevent the material of the corner 13g crushed by the pressing surface 72 from protruding beyond the extension 13j of the sheared surface 13c. As shown in the lower part of Figure 15, if the volume V1 exceeds the volume V2, the material of the corner 13g crushed by the pressing surface 72 will protrude beyond the extension 13j of the sheared surface 13c and move toward the top of the coining lower die 7. If this occurs, the dimensional accuracy of the cut end 13 will deteriorate. Therefore, it is preferable to process the corner 13g by crushing it with the pressing surface 72 so that the volume V1 is equal to or less than the volume V2.

[0134] The above describes the method for manufacturing a processed product according to the second embodiment. According to this embodiment, as with the first embodiment, a processed product 1 with excellent corrosion resistance and shape quality can be manufactured even when a plated steel sheet having a thickness of more than 2.0 mm is used as the raw material. Furthermore, since there is no need to provide a gap between the body portion 10 of the processed product 1 and the die (or punch) pressed into the cutting portion during the semi-cutting and finish-cutting processes, a processed product 1 having a cut edge 13 flush with the body portion 10 can be obtained, and the end surface 14a of the opening 14 of the processed product 1 can be flattened. Furthermore, the method for manufacturing a processed product according to this embodiment allows a larger portion of the plating layer 13f to extend around the sheared surface 13c, thereby suppressing the formation of red rust on the cut edge 13 over time after cutting.

[0135] Furthermore, by performing the coining process after the finish cutting process, the area of ​​the fracture surface 13d, which is a newly formed rough surface, can be narrowed, and the area where red rust occurs can be suppressed. Furthermore, the coining process can crush burrs, and it is possible to more reliably suppress the burrs remaining on the processed product 1.

[0136] (Example a: Case where only the cutting edge of the die used in the semi-cutting process is rounded) The shoulder of the die (i.e., the cutting edge) in the semi-cutting process is rounded with a predetermined radius of curvature, and processed product samples were produced by the methods shown in Figures 5 and 10. The plated steel sheets had a thickness t1 of 1.3 to 4.4 mm and a coating weight of 90 g / m ２ A Zn-6%Al-3%Mg (by mass) alloy plated steel sheet (one side) was used. ３１ The clearance C between the die and punch is 68.00 mm. ３１－４１ The finish cutting was performed by using a punch whose inner diameter was changed according to the cutting conditions, and holding the plated steel sheet by a guide. The finish cutting was performed by using a die whose shoulder (i.e., cutting edge) had an R-shape with a predetermined radius of curvature, and a clearance C between the die and the punch. ３２－４２ Inner diameter D according to ３２ The test was carried out using a punch with a modified shape and holding the plated steel sheet with a guide.

[0137] For each sample, the flat surface width Lt of the end face, the fracture surface length W1 after finish cutting, and, if coining was performed, the fracture surface length W2 after coining were measured. These were measured using a microscope at 30° intervals around the circumference of the end face of the processed product, and a total of 12 measurement values ​​were averaged. Furthermore, for each sample, the wraparound of the plating layer around the cut end was measured by measuring the length L of the plating layer from the cutting position to the shear surface of the cut end. An electron probe microanalyzer (EPMA-WDS) was used to measure the length L of the plating layer at the cut end. A plating layer was determined to be present in a portion where the detection level of Zn components was three times or more the background level. The measurement targets were the processed product after finish cutting or the second element body and the processed product after coining.

[0138] The shear surface, fracture surface and coining surface at the cut end of each sample are as shown in FIG. 14, and more specifically, they appear as follows.

[0139] The shear surface appears as a smooth surface at the cut edge. The shear surface is created when the die comes into contact with the workpiece and then a compressive (pressure) force is applied, causing the workpiece to bite into the die and rub against the side of the die. Because it is created by rubbing against the die, the shear surface has a metallic luster. Fine, streaky scratches can be seen on the shear surface in the thickness direction of the plate.

[0140] The fracture surface is the surface where cracks that have formed in the workpiece from the sheared surface meet and break, and appears as a dull, rough surface. After the sheared surface has formed in the workpiece, when the die further penetrates into the workpiece, cracks are formed in the workpiece by the cutting edge of the punch, and also by the cutting edge of the die. The cracks that have formed from the punch and die meet and penetrate each other. The surface formed by these cracks is the fracture surface. Because the fracture surface is formed without contact between the punch and die, it is a dull, rough surface. The fracture surface has a slope that corresponds to the gap (clearance) between the punch and die.

[0141] A coining surface appears as a smooth surface where the irregularities on the fracture surface have been flattened. A coining surface is obtained by pressing a sloped or curved coining die against the corner of the fracture surface from the underside of the edge of the fracture surface. The coining surface is a smooth surface where the irregularities on the fracture surface have been flattened by transferring the surface roughness of the coining die.

[0142] A method for identifying the shear surface, fracture surface, and coining surface at the cut end may be, for example, to observe and measure the shape profile of the cut end from the appearance using a microscope or a contrast tracer based on the above characteristics.

[0143] From the viewpoint of ensuring the flatness of the end face of the processed product when it is attached to other parts, the length Lt of the flat surface of the end face was rated as "A (Acceptable)" if it was 0.35 times or more the thickness t of the side wall of the processed product, and "B (Not Acceptable)" if it was less than 0.35 times. Regarding burrs that can cause dents or electrical short circuits, those with a size of less than 0.2 mm were rated as "A (Acceptable)", and those with a size of 0.2 mm or more or those with whisker-like burrs were rated as "B (Not Acceptable)". In addition, the inner diameter D of the die for semi-cutting processing was ３１ and the inner diameter D of the finishing cutting die ３２ Inner diameter difference D ３２ -D ３１ It is desirable to minimize the step on the end face caused by the above in terms of appearance and product dimensional accuracy. Therefore, end face steps of 0.5 mm or less were evaluated as "A (acceptable)," and end face steps of more than 0.5 mm were evaluated as "B (unacceptable)."

[0144] The samples were also subjected to an outdoor atmospheric exposure test, and the number of days until noticeable red rust appeared on the cut edges was observed every 15 days.

[0145] The results are shown in Table 1. Table 1 also shows the plated steel sheets used for each sample, the conditions for the semi-cutting and finish-cutting processes, and whether or not coining was performed on the corners of the cut end. Here, the ratio of the die radius of curvature to the sheet thickness (R1 / t1, R2 / t2) is the ratio of the roundness imparted to the die shoulder by the sheet thickness. Die shoulders (cutting edges) that were not intentionally rounded are marked "<0.01" in this column.

[0146]

[0147] As shown in Table 1, in Examples a1 to a19, the remaining length L of the plating component relative to the sheet thickness t1 of the cut end was 0.70 times or more. In Examples a1 to a19, the fracture surface length W1 of the cut end was 1.0 mm or less, demonstrating good corrosion resistance for 60 days until red rust appeared. In Examples a1 to a16, where the fracture surface length of the cut end was 0.5 mm or less, good corrosion resistance for 90 days or more until red rust appeared was demonstrated. Furthermore, in Example a15, coining was performed after finish punching to form a coining surface with an R-shaped coining surface with a crushed edge length (coining surface width) of 0.6 mm. In Example a16, coining was performed after finish punching to form a coining surface with a C-shaped coining surface with a crushed edge length (coining surface width) of 1.0 mm and a chamfered angle of 45°. The fracture surface length (W2) after coining was smaller than the fracture surface length W1 of the other Examples. The inner diameter D of the semi-cutting die ３１ and the inner diameter D of the finishing cutting die ３２ Inner diameter difference D ３２ -D ３１ In Examples a1 to a17, it was set to 0.05 mm, and in Example a18, it was set to zero (inner diameter D ３１ and inner diameter D ３２ In Example a19, the step height was 1.00 mm, and in both cases the step height on the end face was 0.5 mm or less.

[0148] Based on the above characteristics, it was confirmed from the appearance that the cut end portions of Examples a1 to a14, a18, and a19 have shear surfaces and fracture surfaces in the thickness direction, and that the cut end portions of Examples a15 and a16 have shear surfaces, fracture surfaces, and coining surfaces in the thickness direction, respectively.

[0149] In contrast, in Comparative Examples a1 to a6, a8, and a10 to a13, the remaining length L of the coating layer component relative to the sheet thickness t1 of the cut end of the processed product was less than 0.70, so the number of days until red rust appeared at the cut end was less than 60 days, and the corrosion resistance was inferior to that of the Examples. Comparative Example a9 employed a large negative clearance in the half-cutting process, but the load exceeded the limit during the half-blanking process using a 750 kN mechanical press, causing the press to stop. Comparative Examples a14 and a15 both exhibited good corrosion resistance until red rust appeared at the cut end for more than 90 days, but large burrs of 0.2 mm or more appeared at the cut end. Comparative Example a7 employed a zero clearance between the die and punch during the half-cutting process, and the plated steel sheet completely fractured during the half-cutting process.

[0150] (Example b. When the cutting edges of the die and punch used in the semi-cutting step are rounded) Next, the shoulders (i.e., cutting edges) of the die and punch used in the semi-cutting step were rounded with a predetermined radius of curvature, and processed product samples were prepared by the methods shown in Figures 5 and 10. The plated steel sheets had a thickness of 1.3 to 4.4 mm and a coating weight of 90 g / m. ２ A Zn-6%Al-3%Mg (by mass) alloy-plated steel sheet (one side) was used. Semi-cutting was performed using a die with an inner diameter of 68.00 mm and a punch whose inner diameter was changed depending on the clearance between the die and punch, with the plated steel sheet held by a guide. Finish-cutting was performed using an R-shaped die with a shoulder (i.e., cutting edge) having a predetermined radius of curvature and a punch whose inner diameter was changed depending on the clearance between the die and punch, with the plated steel sheet held by a guide.

[0151] For each sample, flatness evaluation, burr evaluation, and step evaluation were carried out in the same manner as in Example a above, and the number of days until red rust occurred in an atmospheric exposure test was investigated. The results of Example b are shown in Table 2.

[0152]

[0153] As shown in Table 2, in Examples b1 to b19, the remaining length L of the plating component relative to the plate thickness t1 of the cut end of the processed product was 0.70 times or more. In Examples b1 to b19, the fracture surface length W1 of the cut end was 1.0 mm or less, demonstrating good corrosion resistance for 60 days until red rust appeared. In Examples b1 to b16, where the fracture surface length W1 of the cut end was 0.5 mm or less, good corrosion resistance for 90 days or more until red rust appeared. Furthermore, in Example b15, coining was performed after finish punching to form a rounded coining surface with a crushed edge length (coining surface width) of 0.6 mm. In Example b16, coining was performed after finish punching to form a C-shaped coining surface with a crushed edge length (coining surface width) of 1.0 mm and a 45° chamfered angle. The fracture surface length (W2) after coining was smaller than in the other Examples. The inner diameter D of the semi-cutting die ３１ and the inner diameter D of the finishing cutting die ３２ Inner diameter difference D ３２ -D ３１ In Examples b1 to b17, it was set to 0.05 mm, and in Example b18, it was set to zero (inner diameter D ３１ and inner diameter D ３２ In Example b19, the step height was 1.00 mm, and in both cases the step height on the end face was 0.5 mm or less.

[0154] Based on the above-mentioned characteristics, it was confirmed from the appearance that the cut end portions of Examples b1 to b14, b18, and b19 have shear surfaces and fracture surfaces in the thickness direction, and that the cut end portions of Examples b15 and b16 have shear surfaces, fracture surfaces, and coining surfaces in the thickness direction, in that order.

[0155] In contrast, in Comparative Examples b1 to b5, b7, b9 to b11, and b14, the remaining length L of the coating layer component relative to the sheet thickness t1 of the cut end of the processed product was less than 0.70, so the number of days until red rust appeared at the cut end was less than 60 days, and the corrosion resistance was inferior to that of the Examples. Comparative Example b8 employed a large negative clearance in the half-cutting process, but the load exceeded the limit during the half-blanking process using a 750 kN mechanical press, causing the press to stop. Comparative Examples b12 and b13 both showed good corrosion resistance of more than 90 days until red rust appeared at the cut end, but large burrs of 0.2 mm or more appeared at the cut end. In Comparative Examples b6 and b15, the negative clearance between the die and punch during the half-cutting process was insufficient, causing the plated steel sheet to completely break during the half-cutting process.

[0156] From the above, it has been confirmed that in a cutting process in which a semi-cutting step is performed followed by a finish-cutting step, by setting the remaining length L of the plating component to 0.70 times or more the plate thickness t1 of the cut end of the processed product, cut end portions having good corrosion resistance can be obtained.

[0157] Although the preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to these examples. It is clear that a person skilled in the art to which the present invention pertains can conceive of various modifications and alterations within the scope of the technical ideas set forth in the claims, and it is understood that these also naturally fall within the technical scope of the present invention.

[0158] For example, in the above embodiment, a cylindrical processed product as shown in FIG. 1 was shown as an example of the processed product 1, but the present invention is not limited to such an example. The processed product of the present invention may be a drawn product, for example, a profile drawn product as shown in FIG. 16 or a square cylindrical drawn product as shown in FIG. 17. Note that FIG. 17 shows the state of the blank before the half-cutting step, and the half-cutting step and finish-cutting step are performed along the trim line shown by the dashed line. The processed product may have a cut edge that is flush with the outer surface of the side wall only on a portion of the side wall of the processed product, as shown in FIG. 16.

[0159] REFERENCE SIGNS LIST 1 Workpiece 2 First element 6 Second element 7 Coining lower die 8 Coining upper die 10 Body 11 Protrusion 12, 20 Flange 13 Cut end 13c Shear surface 13d Fracture surface 13f, 13f1, 13f2 Plating layer 13g Corner 13h Coining surface 13k Flat surface 14 Opening 14a End surface 20a Removed portion 31 First die 32 Second die 41 First punch 42 Second punch 70 Vertical wall surface 71 Bottom wall surface 72 Pressing surface 101 Side wall 101a Outer surface 101b Inner surface 103 Top wall

Claims

1. A processed product made of a plated steel sheet having a plating layer on its surface, the processed product being a hollow cylindrical side wall having a cut end, wherein the cut end is flush with the outer surface of the side wall of the processed product, and in the plate thickness direction of the cut end, a shear cross-section and a fracture cross-section are arranged in sequence, or the processed product has a shear cross-section, and the ratio L / t1 of the remaining length L of the plating component covered by the plating layer on the surface to the plate thickness t1 of the cut end of the processed product is 0.70 or more.

2. The processed product according to claim 1, wherein the length W1 of the fracture cross-section in the plate thickness direction of the cut end is more than 0 mm and 1.0 mm or less.

3. The processed product according to claim 2, wherein the length W1 of the fracture cross-section in the plate thickness direction of the cut end is 0.5 mm or less.

4. The processed product according to any one of claims 1 to 3, wherein the ratio Lt / t of the length Lt of the flat surface of the end face of the processed product perpendicular to the side wall to the plate thickness t of the side wall of the processed product is 0.35 or more.

5. The processed product according to any one of claims 1 to 4, wherein the length of the burr at the cut end is less than 0.2 mm.

6. The cut end has, in the plate thickness direction of the cut end, the shear cross-section, the fracture cross-section and the coining surface in sequence, or the shear cross-section and the coining surface in sequence, and the length W2 of the fracture cross-section between the shear cross-section and the coining surface in the plate thickness direction of the cut end is more than 0 mm and 0.5 mm or less. The processed product according to any one of claims 1 to 5.

7. A processed product manufacturing method for manufacturing a processed product made of a plated steel sheet having a plating layer on its surface and having a cut end on a hollow cylindrical side wall, including a semi-cutting step of semi-cutting the cut portion of the first element formed from the material in the plate thickness direction using the first die and the first punch with a clearance between the first die and the first punch set to a negative clearance, and a finishing cutting step of finishing cutting the semi-cut first element from the same direction as the semi-cutting using a second die and a second punch to obtain a processed product having a cut end flush with the outer surface of the side wall of the processed product. The inner diameter D of the second die ３２ is the inner diameter D of the first die ３１As described above, with the plate thickness of the cut portion of the first element body being t1 and the remaining plate thickness of the cut portion after the semi-cutting step being t2, in the semi-cutting step, the clearance C between the first die and the first punch ３１－４１ satisfies the following formula (a1), the radius of curvature R1 of the cutting edge of the first die satisfies the following formula (a2), the pushing-in amount D of the first die or the first punch with respect to the cut portion of the first element body satisfies the following formula (a3), and the distance C between the first die and the first punch at the bottom dead center Ｐ－Ｄ satisfies the following formula (a4). In the finish cutting step, the clearance C between the second die and the second punch ３２－４２ satisfies the following formula (a5), and the radius of curvature R2 of the cutting edge of the second die satisfies the following formula (a6). A method for manufacturing a processed product. −0.35 × t1 ≤ C ３１－４１ ≤ −0.01 ... (a1) 0.10 × t1 ≤ R1 ≤ 0.50 × t1 ... (a2) D ≥ 0.70 × t1 ... (a3) C Ｐ－Ｄ ≥ 0.20 ... (a4) 0.01 ≤ C ３２－４２ ≤ 0.2 × t2 ... (a5) 0.25 ≤ R2 ≤ 1.50 × t2 ... (a6) Here, C ３１－４１ 、C Ｐ－Ｄ 、C ３２－４２ and R2 are in units of mm.

8. A method for manufacturing a processed product for manufacturing a processed product having a cut end on the outer surface of a side wall of a hollow cylindrical shape using a plated steel sheet having a plating layer on the surface as a material, the method including: a semi-cutting step of semi-cutting a cut portion of a first element body formed from the material in the plate thickness direction using the first die and the first punch with a clearance set to a negative clearance; and a finish cutting step of finish cutting the semi-cut first element body from the same direction as the semi-cutting using a second die and a second punch to obtain a processed product having a cut end flush with the outer surface of the side wall of the processed product. The inner diameter D ３２ of the second die is the inner diameter D ３１As described above, with the plate thickness of the cut portion of the first element body being t1 and the remaining plate thickness of the cut portion after the semi-cutting step being t2, in the semi-cutting step, the clearance C between the first die and the first punch ３１－４１ satisfies the following formula (b1), the radius of curvature R11 of the cutting edge of the first die satisfies the following formula (b2-1), the radius of curvature R12 of the cutting edge of the first punch satisfies the following formula (b2-2), and the pushing amount D of the first die or the first punch with respect to the cut portion of the first element body satisfies the following formula (b3). The interval C between the first die and the first punch at the bottom dead center Ｐ－Ｄ satisfies the following formula (b4), and in the finish cutting step, the clearance C between the second die and the second punch ３２－４２ satisfies the following formula (b5), and the radius of curvature R2 of the cutting edge of the second die satisfies the following formula (b6). A manufacturing method of a processed product. −0.45 × t1 ≤ C ３１－４１ ≤ −0.10 × t1 ... (b1) 0.10 × t1 ≤ R11 ≤ 0.65 × t1 ... (b2-1) 0.10 × t1 ≤ R12 ≤ 0.65 × t1 ... (b2-2) D ≥ 0.70 × t1 ... (b3) C Ｐ－Ｄ ≥ 0.20 ... (b4) 0.01 ≤ C ３２－４２ ≤ 0.2 × t2 ... (b5) 0.25 ≤ R2 ≤ 1.50 × t2 ... (b6) Here, C ３１－４１ 、C Ｐ－Ｄ 、C ３２－４２ and R2 are in units of mm.

9. Using the processed product obtained in the finish cutting step as the second element body, further including a coining step of pressing the corner of the cut end portion of the second element body against a pad to obtain a processed product in which a coining surface is formed at the corner. The manufacturing method of a processed product according to claim 7 or 8.

10. The difference D ３１ between the inner diameter D ３２ of the first die and the inner diameter D ３２ of the second die ３１The method for manufacturing a processed product according to any one of claims 7 to 9, wherein [the relevant parameter] is 1.00 mm or less.

11. The method for manufacturing a processed product according to any one of claims 7 to 10, further comprising a preparation step of forming a first element having a hollow side wall and a flange portion from a flat plated steel sheet before the semi-cutting step.