JP2022030454A - Manufacturing method of processed material - Google Patents

Abstract

To reduce tensile residual stress of a fracture surface of a processed material when a steel material is sheared to produce the processed material.SOLUTION: In a manufacturing method, a steel material is sheared to produce a processed material. The manufacturing method includes placing the steel material between a first blade and a second blade. The steel material has a first surface and a second surface opposite to the first surface. The first blade has a first bottom surface, a first side surface, and a first tip part, and the second blade has a second bottom surface, a second side surface, and a second tip part. The manufacturing method further includes: moving the first blade and the second blade relative to each other to shear the steel material; and causing pre-deformation in at least one of a part of the first surface and a part of the second surface before the steel material is sheared so that a portion, which contacts with the first tip part, of the first surface of the steel material becomes relatively harder than a portion, which contacts with the second tip part, of the second surface of the steel material.SELECTED DRAWING: Figure 4

Description

The present application discloses a method for producing a processed material.

Patent Document 1 discloses a technique for obtaining a processed material by shearing a steel material using a punch and a die. In Patent Document 1, the tensile residual stress of the fracture surface of the processed material is reduced by pressing the fracture surface of the punched material punched against the fracture surface of the processed material.

Patent Document 2 discloses a technique of providing a groove at a predetermined position on the surface of a work material before shearing. In Patent Document 2, the groove is provided to guide the fracture surface generated in the work material to an appropriate position.

Patent Document 3 discloses a technique of plastically deforming the surface of the work material to form indentations before punching the work material by punching. In Patent Document 3, when the work material is punched out, the outside of the indentation is punched out to leave a compressive residual stress in the cut surface and its periphery.

International Publication No. 2016/136909 Japanese Unexamined Patent Publication No. 2018-158384 Japanese Unexamined Patent Publication No. 2009-012018

As disclosed in Patent Document 1, in a processed material obtained by shearing a steel material, the tensile residual stress of the fracture surface may become large. When a processed material is obtained by shearing a steel material, a new technique capable of reducing the tensile residual stress of the fracture surface of the processed material is required.

The present application is one of the means for solving the above problems.
It is a method of manufacturing processed materials by shearing steel materials.
Arranging the steel material between the first blade and the second blade, where the steel material has a first surface and a second surface opposite to the first surface, and the first blade has a first surface. It has one bottom surface, a first side surface and a first tip portion, and the second blade has a second bottom surface, a second side surface and a second tip portion, and
Shearing the steel material by relatively moving the first blade and the second blade.
Including
The steel material so that the portion of the first surface of the steel material that contacts the first tip portion is relatively harder than the portion of the second surface of the steel material that contacts the second tip portion. Pre-deformation of at least one of a part of the first surface and a part of the second surface before shearing.
including,
Disclose the manufacturing method of the processed material.

In the manufacturing method of the present disclosure, the hardness Ha of the portion of the first surface of the steel material that contacts the first tip portion and the portion of the second surface of the steel material that contacts the second tip portion. Pre-deformation to at least one of the first surface and the second surface before shearing the steel so that the ratio Ha / Hb to the hardness Hb is 1.10 or more. May be applied.

In the manufacturing method of the present disclosure, the hardness Ha of the portion of the first surface of the steel material that contacts the first tip portion and the portion of the second surface of the steel material that contacts the second tip portion. Pre-deformation to at least one of the first surface and the second surface before shearing the steel so that the ratio Ha / Hb to the hardness Hb is 1.20 or more. May be applied.

In the manufacturing method of the present disclosure, the hardness Ha of the portion of the first surface of the steel material that contacts the first tip portion and the portion of the second surface of the steel material that contacts the second tip portion. Pre-deformation to at least one of the first surface and the second surface before shearing the steel so that the ratio Ha / Hb to the hardness Hb is 1.50 or more. May be applied.

In the manufacturing method of the present disclosure, the first surface of the steel material is prior to shearing so as to increase the hardness Ha of the portion of the first surface of the steel material that comes into contact with the first tip portion. Distortion may be introduced in a part of.

In the manufacturing method of the present disclosure, the strain may be continuously or intermittently introduced into a part of the first surface of the steel material so as to be along the cutting line by the first blade.

In the manufacturing method of the present disclosure, by introducing the strain into a part of the first surface of the steel material, the hardness Ha may be increased by 10% or more before and after the strain is introduced. good.

In the manufacturing method of the present disclosure, the steel material may be plate-shaped.

In the manufacturing method of the present disclosure, the tensile strength of the steel material may be 980 MPa or more.

In the manufacturing method of the present disclosure, the tensile strength of the steel material may be 1470 MPa or more.

According to the manufacturing method of the present disclosure, it is possible to manufacture a processed material in which the tensile residual stress of the fracture surface is reduced.

It is a schematic diagram for demonstrating an example of the flow of shearing. (A) shows a state in which a steel material is arranged between the first blade and the second blade, and (B) shows a state in which the first blade and the second blade are relatively moved and brought close to each other, so that the first blade is brought close to each other. Shows a state in which the bottom surface of the steel material is in contact with the first surface of the steel material and the bottom surface of the second blade is in contact with the second surface of the steel material, and (C) shows a state in which a part of the steel material is punched out by the first blade. Shown, (D) shows a state in which the first blade and the second blade are separated and returned to the position of (A). It is a schematic diagram for demonstrating an example of the formation mechanism of a sheared end face at the time of shearing a steel material. It is a cross section along the relative moving direction of the first blade and the second blade, and shows the form of the cross section including the first blade, the second blade and the steel material. (A) indicates a state in which sagging is formed on the steel material by pressing the first blade and the second blade against the steel material, and (B) further presses the first blade and the second blade against the steel material after the sagging is formed. (C) shows a state in which a crack is generated in the steel material, and (C) shows a state in which a part of the steel material is punched out by further pressing the first blade and the second blade against the steel material. It is a schematic diagram for demonstrating the new knowledge by this inventor. When (A) develops a crack from the first blade, (B) develops a crack from both the first blade and the second blade, and (C) develops a crack from the second blade. Is. “◯” means that the tensile residual stress is small, “Δ” means that the tensile residual stress is medium, and “×” means that the tensile residual stress is large. It is sectional drawing for demonstrating an example of the flow of the manufacturing method of a processed material. (A) shows the state of the steel material before pre-deformation, (B) shows the state of the steel material after pre-deformation, and (C) arranges the steel material after pre-deformation between the first blade and the second blade. The state is shown, and (D) shows the state after shearing. It is a schematic diagram for demonstrating the "tip portion" of a blade. (A) shows a cross section when R is given to the tip of the blade or when chamfering is not performed, and (B) shows a cross section when R is given to the tip of the blade. There is. It is a schematic diagram for demonstrating a shear angle. It is a schematic diagram for demonstrating an example of the pre-deformation with respect to a steel material. (A) shows the state of the steel material before the pre-deformation, (B) shows the state of the steel material after the pre-deformation, and (C) arranges the steel material after the pre-deformation between the first blade and the second blade. (D) shows the state in which the first blade and the second blade are relatively moved to shear the steel material, and (E) shows the state of the processed material having the sheared end face. It is a schematic diagram for demonstrating another example of the pre-deformation with respect to a steel material. (A) shows the state of the steel material before the pre-deformation, (B) shows the state of the steel material after the pre-deformation, and (C) arranges the steel material after the pre-deformation between the first blade and the second blade. (D) shows the state in which the first blade and the second blade are relatively moved to shear the steel material, and (E) shows the state of the processed material having the sheared end face. It is sectional drawing for demonstrating an example of the form which introduces strain to the 1st surface of a steel material. It is a schematic diagram for demonstrating an example of the structure of the processed material manufactured by the manufacturing method of this disclosure. The cross-sectional shape of the processed material is shown. It is a schematic diagram for demonstrating an example of the structure of the shear end face of the processed material of this disclosure. The state where the shear end face is seen from the front is shown. It is a schematic diagram for demonstrating the method of discriminating the 1st part and the 2nd part in a fracture surface. (A) schematically shows the direction of hydrogen embrittlement cracks generated in the fracture surface, and (B) indicates an arbitrary position X between the burr side and the sagging side in the fracture surface and the direction of hydrogen embrittlement cracks (B). The relationship with the angle θ) is schematically shown.

1. 1. Issues and new findings A processed material having a sheared end face can be obtained, for example, as follows. First, as shown in FIG. 1A, the steel material 5 is arranged between the first blade 21 and the second blade 22. Here, the steel material 5 has a first surface 10a and a second surface 10b opposite to the first surface 10a, and the first blade 21 has a first bottom surface 21a, a first side surface 21b, and a first tip portion 21x ( The second blade 22 has a second bottom surface 22a, a second side surface 22b, and a second tip portion 22x (see FIGS. 2 and 4). As shown in FIG. 1B, the first bottom surface 21a is in contact with the first surface 10a of the steel material 5, and the second bottom surface 22a is in contact with the second surface 10b of the steel material 5. The first blade 21 may be a punch and the second blade 22 may be a die. Subsequently, as shown in FIGS. 1B and 1C, the steel material 5 is sheared by relatively moving the first blade 21 and the second blade 22. As a result, as shown in FIGS. 1C and 1D, a part of the steel material 5 is punched out as scrap 15 by the first blade 21, and the remaining part of the steel material 5 has a sheared end face 1. Can be. The scrap 15 may be used for some products.

FIGS. 1 (A) to 1 (D) show a form in which a shear angle is not provided between the first blade 21 and the second blade 22, but there is a gap between the first blade 21 and the second blade 22. A shear angle may be provided. Further, in FIGS. 1A to 1D, the line of intersection (the tip of the first blade 21) between the first bottom surface 21a of the first blade 21 and the first side surface 21b is in the longitudinal direction of the first blade 21. Although the form of extending linearly toward the blade is shown, the tip of the first blade 21 may extend linearly in the longitudinal direction. That is, the shape of the sheared end surface 1 in a plan view may be sheared so as to be linear, may be sheared so as to be curved, or may be sheared so as to be a combination of linear and curved. You may. Further, FIGS. 1 (A) to 1 (D) show a form in which the end portion of the steel material 5 is sheared and removed by the first blade 21 and the second blade 22, but the first blade 21 and the second blade By shearing the steel material 5 with 22, a punch hole, a slit, or the like may be formed in a part of the steel material 5. In this case as well, the processed material 10 having the sheared end face 1 can be obtained.

An example of the formation mechanism of the shear end face 1 will be described. As shown in FIGS. 2A to 2C, a case where a processed material 10 having a sheared end face 1 is obtained by shearing a steel material 5 with a first blade 21 and a second blade 22 will be considered. As shown in FIG. 2A, the first bottom surface 21a of the first blade 21 is pressed against the first surface 10a of the steel material 5, so that the sagging 1a is formed on the first surface 10a side of the steel material 5. The sagging 1a is formed in the process until the first tip portion 21x of the first blade 21 bites into the steel material 5. After the sagging 1a is formed, the sheared surface 1e (see FIG. 10) may be formed in the process of the first tip portion 21x biting into the steel material 5. As shown in FIG. 2B, after the sagging 1a and the sheared surface 1e are formed, a first crack 1dx is generated from the first blade 21 side toward the second blade 22 side. On the other hand, also on the second blade 22 side, similarly, after the second tip portion 22x bites into the second surface 10b of the steel material 5, the second crack is made from the second blade 22 side toward the first blade 21 side. 1dy is generated. As shown in FIG. 2C, the fracture surface 1b is formed by each of the first crack 1dx and the second crack 1dy extending and joining each other. Further, by further moving the first blade 21 and the second blade 22, the steel material 5 is separated into the scrap 15 and the processed material 10 which is the target object. At this time, as shown in FIG. 2C, a burr 1c may be formed at a corner portion on the second blade 22 side of the sheared end surface 1 of the processed material 10. FIG. 2 regardless of the presence or absence of a shear angle between the first blade 21 and the second blade 22 and the shape of the shear end surface 1 in a plan view (straight, curved or a combination thereof, punch holes, slits, etc.). The shear end face 1 can be formed by a mechanism such as (A) to (C).

In the shear end face 1 formed as described above, compressive residual stress or tensile residual stress may occur due to damage or strain due to shearing. When a large tensile residual stress is present in the shear end face 1, for example, the hydrogen embrittlement resistance or fatigue strength of the shear end face 1 tends to decrease. In this respect, in order to obtain the processed material 10 having high performance, how to reduce the tensile residual stress in the sheared end face 1 can be one of the problems. In particular, as disclosed in Patent Document 1, it is preferable that the tensile residual stress in the fracture surface 1b of the sheared end face 1 can be reduced.

The present inventor has obtained the following new findings as a result of repeating a number of experiments and analyzes on the relationship between the shearing conditions for the steel material 5 and the properties of the sheared end face 1 generated by the shearing.

As shown in FIGS. 3A to 3C, a case where a part 11 of the steel material 5 is punched out by the first blade 21 and the other part 12 of the steel material 5 is punched out by the second blade 22 will be described. In this case, as shown in FIG. 3A, when the crack grows preferentially from the first blade 21 side, the tensile residual stress at the shear end face of the part 11 increases, while the tensile residual stress at the other part 12 increases. The tensile residual stress on the sheared end face of the is reduced. That is, while a part 11 is used as scrap 15, the other part 12 can be suitably used as a product (processed material 10). Further, as shown in FIG. 3B, when cracks grow equally from both the first blade 21 side and the second blade 22 side, they are equivalent to the shear end faces of both the partial 11 and the other portion 12. Tensile residual stress can occur. That is, the variation in the characteristics between the part 11 and the other part 12 can be suppressed. In this respect, it can be said that it is suitable when both the part 11 and the other part 12 are adopted as products. Further, as shown in FIG. 3C, when the crack grows preferentially from the second blade 22 side, the tensile residual stress at the shear end face of the other portion 12 increases, while the shear of a part 11 The tensile residual stress on the end face becomes smaller. That is, while the other part 12 is used as scrap 15, a part 11 can be suitably adopted as a product.

Based on the above findings, the present inventor has found the following (1) to (4).
(1) The tensile residual stress generated in the fracture surface 1b of the shear end surface 1 changes depending on the growth direction and length of the cracks 1dx and 1dy forming the fracture surface 1b.
(2) In the fracture surface 1b, the longer the crack 1dx extending from the sagging 1a side (first blade side), the smaller the tensile residual stress of the fracture surface 1b of the work material 10, and the tensile residual stress of the fracture surface of the scrap 15. The stress increases.
(3) That is, in the fracture surface 1b of the processed material 10, the area ratio of the portion derived from the first crack 1dx extending from the sagging 1a side is the portion derived from the second crack 1dy extending from the burr 1c side. When it is larger than the area ratio, the area ratio of the part derived from the first crack 1dx extending from the sagging 1a side is smaller than the area ratio of the part derived from the second crack 1dy extending from the burr 1c side. Also, the tensile residual stress of the fracture surface 1b can be relatively reduced.

The present inventor has obtained the following new findings as a result of repeating a number of experiments and analyzes on controlling the growth direction and length of cracks 1dx and 1dy when the steel material 5 is sheared.
(4) In order to preferentially generate and propagate cracks from the first blade 21 side when the steel material 5 is sheared, the first surface 10a of the steel material 5 is made relatively harder than the second surface 10b of the steel material 5. It is effective to do. For example, in order to harden at least the portion of the first surface 10a of the steel material 5 where the first blade 21 bites (the portion in contact with the first tip portion 21x of the first blade 21), before shearing the steel material 5. , It is advisable to pre-deform the steel material 5.

The manufacturing method of the processed material of the present disclosure has been completed based on the above findings.

2. 2. Manufacturing Method of Processed Material As shown in FIGS. 4A to 4D, in the manufacturing method of the processed material 10 of the present disclosure, the steel material 5 is arranged between the first blade 21 and the second blade 22. .. Here, the steel material 5 has a first surface 10a and a second surface 10b opposite to the first surface 10a, and the first blade 21 has a first bottom surface 21a, a first side surface 21b, and a first tip portion 21x. The second blade 22 has a second bottom surface 22a, a second side surface 22b, and a second tip portion 22x. Next, the steel material 5 is sheared by relatively moving the first blade 21 and the second blade 22. In the manufacturing method of the present disclosure, as shown in FIGS. 4A and 4B, the portion 10ax of the first surface 10a of the steel material 5 that comes into contact with the first tip portion 21x is the second surface of the steel material 5. Before shearing of the steel material 5, at least a part of the first surface 10a and a part of the second surface 10b so as to be relatively harder than the portion 10bx of the 10b in contact with the second tip portion 22x. Pre-deform on one side.

2.1 First blade The first blade 21 has a first bottom surface 21a, a first side surface 21b, and a first tip portion 21x. The first bottom surface 21a may have a surface that intersects the relative movement direction of the first blade 21, or may have a surface that is orthogonal to the movement direction. Further, the first side surface 21b may have a surface along the relative moving direction of the first blade 21, or may have a surface inclined with respect to the moving direction. Further, the first tip portion 21x refers to a portion near the line of intersection between the first bottom surface 21a and the first side surface 21b, and specifically, as shown in FIG. 5A, the first bottom surface 21a and the first surface. 1 Refers to a portion within a range of 2 mm from the line of intersection with the side surface 21b toward both the first bottom surface 21a side and the first side surface 21b side. When the tip of the first blade 21 is processed to have R or the tip is chamfered, a surface extended along the first bottom surface 21a and a surface extended along the first side surface 21b. The part included in the range of R + 2 mm from the line of intersection toward both the first bottom surface 21a side and the first side surface 21b side is regarded as the first tip portion 21x (see FIG. 5B). ). The first tip portion 21x can be specified in the same manner when the tip of the first blade 21 is chamfered.

In FIG. 5 (B), R is intentionally shown to be large for convenience of explanation, but the normal R is smaller than that shown in FIG. 5 (B). The R at the tip of the first blade 21 may be, for example, 0.02 mm or more.

The shape of the first bottom surface 21a can be determined according to the shape of the sheared end face 1 of the target processed material 10. The first bottom surface 21a may have a flat surface or a curved surface, and the flat surface or the curved surface may face the first surface 10a when the steel material 5 is sheared.

The shape of the first side surface 21b can be determined according to the shape of the sheared end face 1 of the target processed material 10. The first side surface 21b may be a flat surface, a curved surface, or a combination of a flat surface and a curved surface.

The first tip portion 21x may extend linearly or curvedly in the longitudinal direction of the first blade 21 (direction toward the back of the paper surface in FIG. 4), and may be a target processed material. It can be determined according to the shape of the sheared end face 1 of 10. When the steel material 5 is provided with a punch hole, the shape of the first tip portion 21x may be an annular shape along the edge of the punch hole.

In the standby state before the shearing operation, the first blade 21 may be arranged above the second blade 22. In this case, the first blade 21 may be a punch that punches a part of the steel material 5 placed on the second bottom surface 22a of the second blade 22 from top to bottom.

The first blade 21 is made of a material that is generally used as a blade used for shearing. For example, the first blade 21 may be made of SKD11. Further, the first blade 21 may have a first coating on its surface.

2.2 Second blade The second blade 22 has a second bottom surface 22a, a second side surface 22b, and a second tip portion 22x. The second bottom surface 22a may have a surface that intersects the relative movement direction of the second blade 22, or may have a surface that is orthogonal to the movement direction. Further, the second side surface 22b may have a surface along the relative moving direction of the second blade 22, or may have a surface inclined with respect to the moving direction. Further, the second tip portion 22x refers to a portion near the line of intersection between the second bottom surface 22a and the second side surface 22b, and is specified in the same manner as the first tip portion 21x. That is, it means a portion within a range of 2 mm from the line of intersection between the second bottom surface 22a and the second side surface 22b toward both the second bottom surface 22a side and the second side surface 22b side (FIG. 5A). When the tip of the second blade 22 is machined to have an R or the tip is chamfered, a surface extended along the second bottom surface 22a and a surface extended along the second side surface 22b. The part included in the range of R + 2 mm from the line of intersection toward both the second bottom surface 22a side and the second side surface 22b side is regarded as the second tip portion 22x (FIG. 5 (B)). .. The second tip portion 22x can be specified in the same manner when the tip of the second blade 22 is chamfered. The R at the tip of the second blade 22 may be, for example, 0.05 mm or more. Further, the R of the tip of the second blade 22 may be larger than the R of the tip of the first blade 21.

The shape of the second bottom surface 22a can be determined according to the shape of the sheared end face 1 of the target processed material 10. The second bottom surface 22a may have a flat surface or a curved surface, and the flat surface or the curved surface may face the second surface 10b when the steel material 5 is sheared.

The shape of the second side surface 22b can be determined according to the shape of the sheared end face 1 of the target processed material 10. The second side surface 22b may be a flat surface, a curved surface, or a combination of a flat surface and a curved surface.

The second tip portion 22x may extend linearly or curvedly in the longitudinal direction of the second blade 22 (direction toward the back of the paper surface in FIG. 4), and may be a target processed material. It can be determined according to the shape of the sheared end face 1 of 10. When the steel material 5 is provided with a punch hole, the shape of the second tip portion 22x may be an annular shape along the edge of the punch hole.

In the standby state before the shearing operation, the second blade 22 may be arranged below the first blade 21. In this case, the second blade 22 may be a die on which the steel material 5 is placed.

The second blade 22 is made of a material that is common as a blade used for shearing. For example, the second blade 22 may be made of SKD11. The material of the second blade 22 may be the same as or different from the material of the first blade 21. Further, the second blade 22 may have a second coating on its surface.

2.3 Steel material The shape of the steel material 5 is not particularly limited as long as it can be sheared. The steel material 5 may be, for example, plate-shaped or rod-shaped. When the steel material 5 has a plate shape, the plate thickness may be, for example, 0.8 mm or more, or 3.0 mm or less. Further, when the steel material 5 has a rod shape, its cross-sectional shape is not particularly limited, and may be, for example, a circular shape or a polygonal shape, and the circle-equivalent diameter of the cross-sectional shape may be 5 mm or more, 100 mm. It may be as follows. Further, the steel material 5 may be formed into some shape by bending or the like.

As shown in FIGS. 4A to 4D, the steel material 5 may include a first surface 10a and a second surface 10b opposite to the first surface 10a. The first surface 10a and the second surface 10b may be parallel to each other. The term "parallel" as used in the present application is not limited to perfect parallelism, but may be substantially parallel. That is, even if the first surface 10a and the second surface 10b are not completely parallel, they are regarded as parallel as long as they are within the margin of error allowed in industrial production. Specifically, when the angle formed by the first surface 10a and the second surface 10b is 0 ° ± 1 °, it is considered that the first surface 10a and the second surface 10b are parallel to each other.

The steel material 5 may have a surface treatment layer. Examples of the surface treatment layer include a plating layer and a coating film. Further, the steel material 5 may include a plurality of layers having different steel types. For example, it is also possible to use clad steel as the steel material 5.

The mechanical properties of the steel material 5 are not particularly limited, and may be appropriately determined depending on the use of the processed material 10. However, problems such as a decrease in hydrogen embrittlement resistance due to tensile residual stress are particularly likely to occur in high-strength steel materials. In this respect, the steel material 5 may have, for example, a tensile strength of 980 MPa or more, 1180 MPa or more, or 1470 MPa or more. The upper limit of the tensile strength of the steel material 5 is not particularly limited, but may be, for example, 2500 MPa or less, 2200 MPa or less, or 2000 MPa or less. The "tensile strength" of the steel material referred to in the present application is in accordance with ISO 6892-1: 2009.

The chemical composition and metallographic structure of the steel material 5 are not particularly limited, and may be appropriately determined depending on the use of the processed material 10. According to the technique of the present disclosure, it is possible to reduce the tensile residual stress in the fracture surface 1b regardless of the chemical composition and the metallographic structure of the steel material 5. As an example of the chemical composition, the steel material 5 has a mass% of C: 0.050 to 0.800%, Si: 0.01 to 3.00%, Mn: 0.01 to 10.00%, Al: 0. .001 to 0.500%, P: 0.100% or less, S: 0.050% or less, N: 0.010% or less, Cr: 0 to 3.000%, Mo: 0 to 1.000%, B: 0 to 0.0100%, Ti: 0 to 0.500%, Nb: 0 to 0.500%, V: 0 to 0.500%, Cu: 0 to 0.50%, Ni: 0 to 0 .50%, O: 0 to 0.020%, W: 0 to 0.100%, Ta: 0 to 0.10%, Co: 0 to 0.50%, Sn: 0 to 0.050%, Sb : 0 to 0.050%, As: 0 to 0.050%, Mg: 0 to 0.050%, Ca: 0 to 0.050%, Y: 0 to 0.050%, Zr: 0 to 0. It may have a chemical composition consisting of 050%, La: 0 to 0.050%, Ce: 0 to 0.050%, and the balance: Fe and impurities. Further, in the above chemical composition of the steel material 5, Cr, Mo, B, Ti, Nb, V, Cu, Ni, O, W, Ta, Co, Sn, Sb, As, Mg, which are elements arbitrarily added, The lower limit of the content of Ca, Y, Zr, La, and Ce may be 0.0001% or 0.001%.

2.4 Arrangement of steel material In the manufacturing method of the present disclosure, the steel material 5 is arranged between the first blade 21 and the second blade 22 as described above. There is no particular limitation on the arrangement of the steel material 5 between the first blade 21 and the second blade 22, and the steel material 5 may be arranged so as to be appropriately sheared. For example, as shown in FIG. 4C, even if the steel material 5 is placed on the second bottom surface 22a of the second blade 22 while the first blade 21 is arranged above the steel material 5. good. Further, in the manufacturing method of the present disclosure, in order to facilitate shearing of the steel material 5, when the steel material 5 is arranged between the first blade 21 and the second blade 22, a holding member (holder) (not shown) is used. The steel material 5 may be pressed against the first bottom surface 21a or the second bottom surface 22a. The form of the pressing member is not particularly limited, and a general pressing member may be adopted.

2.5 Operation and relationship between the 1st blade and the 2nd blade during shearing In the manufacturing method of the present disclosure, after the steel material 5 is arranged between the 1st blade 21 and the 2nd blade 22, the 1st blade 21 And the second blade 22 are relatively moved to shear the steel material 5. The relative movement of the first blade 21 and the second blade 22 may be performed by a moving device (not shown). Alternatively, at least one of the first blade 21 and the second blade 22 may be manually moved.

2.5.1 Clearance As shown in FIGS. 4 (C) and 4 (D), a clearance C may be provided between the first blade 21 and the second blade 22 during shearing. The clearance C can be appropriately determined depending on the material, shape, and the like of the steel material 5. For example, when the steel material 5 has a plate shape, the clearance C may be 5% or more of the plate thickness or 25% or less of the plate thickness. The "clearance" referred to in the present application is in accordance with ISO 16630: 2009.

2.5.2 Shear angle As shown in FIG. 6, a shear angle α may be provided between the first blade 21 and the second blade 22 during shearing. The shear angle α can be appropriately determined depending on the material, shape, and the like of the steel material 5. For example, the shear angle α may be 0 ° or more, or 10 ° or less. Further, according to a new finding of the present inventor, when the shear angle is 0 ° or more and 1 ° or less, it is easy to develop the first crack 1dx with respect to the steel material 5 before the second crack 1dy. ..

2.6 Pre-deformation of steel material before shearing In the manufacturing method of the present disclosure, the portion 10ax in contact with the first tip portion 21x of the first surface 10a of the steel material 5 is the second of the second surface 10b of the steel material 5. Prior to shearing of the steel material 5, at least one of a part of the first surface 10a and a part of the second surface 10b is pre-deformed so as to be relatively harder than the portion 10bx in contact with the tip portion 22x. It is important to apply. This makes it easier to generate and propagate the first crack 1dx before the second crack 1dy when the steel material 5 is sheared. In the manufacturing method of the present disclosure, when the first tip portion 21x is in contact with the first surface 10a of the steel material 5, the entire first tip portion 21x is in contact with the first surface 10a of the steel material 5. It is not necessary that the first tip portion 21x is in contact with the first surface 10a. Further, in the manufacturing method of the present disclosure, it is not necessary to pre-deform the entire portion 10ax in contact with the first tip portion 21x, and it is sufficient that at least a part of the portion 10ax is pre-deformed. The same applies to the contact between the second surface 10b and the second tip portion 22x. The timing of pre-deformation may be before shearing and is not particularly limited. According to the findings of the present inventor, the harder the hardness of the portion 10ax in contact with the first tip portion 21x than the hardness of the portion 10bx in contact with the second tip portion 22x, the easier it is for the first crack 1dx to develop. .. For example, in the manufacturing method of the present disclosure, the hardness Ha of the portion 10ax in contact with the first tip portion 21x of the first surface 10a of the steel material 5 and the second tip portion 22x of the second surface 10b of the steel material 5 Before shearing of the steel material 5 so that the ratio Ha / Hb of the contacting portion 10bx with the hardness Hb is 1.05 or more, 1.10 or more, 1.15 or more, 1.20 or more or 1.50 or more. In addition, at least one of a part of the first surface 10a and a part of the second surface 10b may be pre-deformed.

The hardness Ha of the portion 10ax of the first surface 10a of the steel material 5 that contacts the first tip portion 21x and the hardness Hb of the portion 10bx of the second surface 10b that contacts the second tip portion 22x are as follows. Measure as per. That is, the Vickers hardness test is carried out at a position 20 μm from the surface layer of the steel material 5. The load is 30 gf, 10 points are measured within the range included in the portions 10ax and 10bx, and the average value is the hardness Ha and Hb. As will be described later, in the manufacturing method of the present disclosure, in a part of the first surface 10a of the steel material 5, intermittently along the portion 10ax in contact with the first tip portion 21x (along the cutting line). Distortion may be introduced into. As described above, when the pre-deformation applied to the steel material 5 has a partial "interruption", the above-mentioned hardness Ha and Hb are measured at the pre-deformed portion.

As a pre-deformation that makes the portion 10ax in contact with the first tip portion 21x of the first surface 10a of the steel material 5 relatively harder than the portion 10bx in contact with the second tip portion 22x of the second surface 10b of the steel material 5. Can be various.

In the manufacturing method of the present disclosure, the first surface of the steel material 5 is first placed before the shearing of the steel material 5 so as to increase the hardness Ha of the portion 10ax of the first surface 10a of the steel material 5 that comes into contact with the first tip portion 21x. Distortion may be introduced in a part of the surface 10a. Specifically, as shown in FIGS. 7A and 7B, a part of the first surface 10a of the steel material 5 is formed along the portion 10ax in contact with the first tip portion 21x (along the cutting line). You may introduce continuous strain. For example, if the cutting line is linear, strain can be introduced linearly along the cutting line. The strain may be introduced along at least the portion 10ax, and the strain may be introduced to a portion other than the portion 10ax. If the strain is introduced on the entire surface of the first surface 10a of the steel material 5, the desired effect can be obtained by shearing any part of the steel material 5, but the surface texture of the steel material 5 may deteriorate. From the viewpoint of ensuring the effect of the present disclosure, it is sufficient to introduce strain into a part of the first surface 10a of the steel material 5. After the strain is introduced in this way, as shown in FIGS. 7 (C) to 7 (E), the first blade 21 and the second blade 22 are arranged along the portion 10ax in which the strain is introduced. Then, the steel material 5 may be sheared by relatively moving the first blade 21 and the second blade 22.

In the manufacturing method of the present disclosure, strain is continuously applied to a part of the first surface 10a of the steel material 5 along the cutting line by the first blade 21 as shown in FIGS. 7A to 7E. It may be introduced, or it may be introduced intermittently (so as to have a partial break) as shown in FIGS. 8A to 8E. When the strain is intermittently introduced into a part of the first surface 10a of the steel material 5, the length L1 of the portion where the strain is not introduced and the length L2 of the portion where the strain is introduced are the lengths along the cutting line. The ratio L1 / L2 of may be 0.5 or less.

The rate of increase in hardness due to the introduction of strain into a part of the first surface 10a of the steel material 5 is not particularly limited. For example, by introducing strain into a part of the first surface 10a of the steel material 5, the hardness Ha may be increased by 10% or more or 15% or more before and after the strain is introduced. It may be increased by 20% or more. This makes it easier to generate and propagate the first crack 1dx before the second crack 1dy when the steel material 5 is sheared.

The method of introducing strain into the first surface 10a of the steel material 5 is not particularly limited. For example, as shown in FIG. 9, compression strain may be applied to a part of the first surface 10a by pressing the tool 30 against a part of the first surface 10a. The form of pressing with a tool is not particularly limited, and for example, a form in which the tip thereof is pressed against the first surface 10a by using a rod-shaped hard member, or an end portion extending along a cutting line of the steel material 5 is formed. Examples thereof include a form in which the end portion is pressed against the first surface 10a by using a wide hard member. Alternatively, shot peening may be applied to a part of the first surface 10a.

In addition to the above, for example, a part of the first surface 10a of the steel material 5 may be relatively hardened by subjecting the steel material 5 to pre-deformation by bending.

3. 3. Processed Material According to the manufacturing method of the present disclosure, among the sheared end faces 1, a processed material 10 in which the tensile residual stress is reduced particularly in the fracture surface 1b can be obtained. Hereinafter, an example of the processed material 10 having the sheared end face 1 will be described, but the form of the processed material 10 is not limited to the following. As shown in FIGS. 10 and 11, the sheared end surface 1 of the processed material 10 includes a sagging 1a, a fracture surface 1b, and a burr 1c. The fracture surface 1b includes a first portion 1bx and a second portion 1by. The first portion 1bx is formed by the first crack 1dx extending from the sagging 1a side to the burr 1c side, and the second portion 1by is formed by the second crack 1dy extending from the burr 1c side to the sagging 1a side. Will be done. The area ratio of the first portion 1bx in the fracture surface 1b is larger than the area ratio of the second portion 1by in the fracture surface 1b.

3.1 Shear end face As shown in FIGS. 10 and 11, the shear end face 1 includes a sagging 1a, a fracture surface 1b, and a burr 1c. Further, the sheared end surface 1 may include a sheared surface 1e. Of the sheared end faces 1, the sagging 1a, the burrs 1c, and the sheared surface 1e can take any form depending on the form of the processed material 10. The sagging 1a, the burr 1c, and the sheared surface 1e may have the same form as the conventional one.

The processed material 10 has one feature in the structure of the fracture surface 1b of the sheared end face 1. As shown in FIGS. 10 and 11, the fracture surface 1b includes a first portion 1bx and a second portion 1by. The first portion 1bx is formed by the first crack 1dx extending from the sagging 1a side to the burr 1c side, and the second portion 1by is formed by the second crack 1dy extending from the burr 1c side to the sagging 1a side. Will be done.

The growth direction of the first crack 1dx may be any direction from the sagging 1a side to the burr 1c side. When the processed material 10 has a plate shape, the growth direction of the first crack 1dx is a direction along the plate thickness direction of the processed material 10 (a direction orthogonal to the first surface 10a and the second surface 10b). It may be the direction inclined with respect to the plate thickness direction. Further, the growth direction of the second crack 1dy may be any direction from the burr 1c side to the sagging 1a side. When the processed material 10 has a plate shape, the growth direction of the second crack 1dy is a direction along the plate thickness direction of the processed material 10 (a direction orthogonal to the first surface 10a and the second surface 10b). It may be the direction inclined with respect to the plate thickness direction. For example, when a clearance C (see FIG. 4) is provided between the first blade 21 and the second blade 22 when the steel material 5 is sheared, the growth directions of the first crack 1dx and the second crack 1dy are It can be tilted with respect to the plate thickness direction, and the larger the clearance, the larger the tilt.

The first crack 1dx may be one that extends from the sagging 1a side to the burr 1c side and is combined with the second crack 1dy on the burr 1c side, and is not necessarily the first from the sagging 1a side to the burr 1c side. It is not necessary to travel in the shortest path toward 2 cracks 1 dy. For example, the first crack 1dx is in the direction toward the back of the paper surface in FIG. 2B (for example, in the plate width direction when the processed material 10 is plate-shaped) while extending from the sagging 1a side to the burr 1c side. You may progress towards. The same applies to the second crack 1dy.

In the sheared end face 1, the area ratio of the first portion 1bx in the fracture surface 1b is larger than the area ratio of the second portion 1by in the fracture surface 1b. In other words, on the sheared end face 1, the average length of the first crack 1dx extending from the sagging 1a side toward the burr 1c side is the average of the second crack 1dy extending from the burr 1c side toward the sagging 1a side. Longer than the length. As described above, when the area ratio of the portion of the fracture surface 1b derived from the crack 1dx extending from the sagging 1a side is larger than the area ratio of the portion derived from the crack 1dx extending from the burr 1c side, the fracture occurs. The tensile residual stress of the cross section 1b can be relatively reduced.

In order to specify the area ratio of each of the first portion 1bx and the second portion 1by and the length of each of the first crack 1dx and the second crack 1dy in the fracture surface 1b, the unevenness of the surface of the fracture surface 1b is determined. It shall not be considered. For example, as shown in FIG. 11, when the sheared end surface 1 is viewed from the front, the position that is the starting point of the first crack 1dx is P1, the position that is the starting point of the second crack 1dy is P2, and the first one. When the position where the crack 1dx and the second crack 1dy meet is P3, the area ratio of the first portion 1bx in the fracture surface 1b when the distance between P1 and P3 is larger than the distance between P2 and P3. However, it can be determined that the area ratio of the second portion 1by in the fracture surface 1b is larger than the area ratio.

According to the findings of the present inventor, the larger the area ratio of the first portion 1bx in the fracture surface 1b, the smaller the tensile residual stress of the fracture surface 1b. For example, in the processed material 10, the area ratio of the first portion 1bx in the fracture surface 1b may be 1.2 times or more, or 1.5 times or more, the area ratio of the second portion 1by in the fracture surface 1b. It may be 1.7 times or more, 2.0 times or more, 2.2 times or more, or 2.5 times or more.

The burr 1c may have a size that cannot be visually confirmed. Regarding which of the first surface 10a and the second surface 10b of the processed material 10 is the surface on the sagging 1a side and which is the surface on the burr 1c side, the shape of the processed material 10 even if the burr 1c cannot be confirmed. Can be easily identified by observing.

In the sheared end surface 1, the properties of the sheared surface 1e and the fracture surface 1b are different. For example, the shear surface 1e and the fracture surface 1b have different roughness (glossiness). In this respect, the sheared surface 1e and the fracture surface 1b can be easily distinguished only by observing the appearance.

In the fracture surface 1b, the boundary between the first portion 1bx and the second portion 1by (the position where the first crack 1dx and the second crack 1dy meet) is formed by, for example, introducing a large amount of hydrogen into the shear end surface 1. It can be discriminated. As mentioned above, the stress generated during crack growth depends on the crack growth direction. That is, as shown in FIGS. 12A and 12B, it can be said that the residual stress suddenly changes at the position where the first crack 1dx and the second crack 1dy meet. Therefore, the direction of hydrogen embrittlement cracks caused by the intrusion of hydrogen also suddenly changes at the position where the first crack 1dx and the second crack 1dy meet. Considering this, the position where the direction of the hydrogen embrittlement crack suddenly changes can be regarded as the position where the first crack 1dx and the second crack 1dy meet.

3.2 Structures other than the sheared end face The processed material 10 may have a sheared end face 1, and the structure other than the sheared end face is not particularly limited. The shape of the processed material 10 corresponds to the shape of the steel material 5 described above. That is, the processed material 10 may be in the shape of a plate as described above or in the shape of a rod. Further, the processed material 10 may include a first surface 10a and a second surface 10b on the opposite side of the first surface 10a as surfaces other than the sheared end surface 1, and the first surface 10a and the second surface 10a may be provided. The surface 10b may be connected via the sheared end surface 1. The first surface 10a and the second surface 10b may be parallel to each other. Further, the processed material 10 may have a surface treatment layer as described above. Further, the processed material 10 may include a plurality of layers having different steel types. The mechanical properties, chemical composition, and the like of the processed material 10 are also as described above.

4. Action / Effect As described above, according to the manufacturing method of the present disclosure, it is possible to manufacture the processed material 10 in which the tensile residual stress is reduced particularly in the fracture surface 1b among the sheared end faces 1. By reducing the tensile residual stress of the fracture surface 1b, for example, hydrogen embrittlement resistance or fatigue strength of the sheared end face 1 can be improved.

1. 1. Steel Material As the steel material to be processed, a steel plate A having a tensile strength of 980 MPa (plate thickness 1.6 mm) and a steel plate B having a tensile strength of 1470 MPa class (plate thickness 1.6 mm) were prepared.

2. 2. Shearing conditions for steel sheet A Strain was introduced at a predetermined position on the surface of steel sheet A using a tool (material: SKD11, radius of tip: 10 mm) as shown in FIG. The strain was set to a width of about 2 to 4 mm and was continuously introduced along the cutting line during shearing. By arranging the steel plate A in which the strain is introduced between the punch and the die and moving the punch and the die relatively, the portion of the steel plate A in which the strain is introduced includes a cutting line. It was punched to obtain a processed material having a sheared end face on the die.

2.1 Example 1
By introducing strain on the punch side surface of the steel plate A, the hardness Ha of the portion of the punch side surface of the steel plate A that contacts the punch tip portion and the portion of the die side surface of the steel material A that contacts the die tip portion. The ratio Ha / Hb to the hardness Hb was set to 1.11.

2.2 Example 2
By introducing strain on the punch side surface of the steel plate A, the hardness Ha of the portion of the punch side surface of the steel plate A that contacts the punch tip portion and the portion of the die side surface of the steel material A that contacts the die tip portion. The ratio Ha / Hb to the hardness Hb was 1.20.

2.3 Example 3
By introducing strain on the punch side surface of the steel plate A, the hardness Ha of the portion of the punch side surface of the steel plate A that contacts the punch tip portion and the portion of the die side surface of the steel material A that contacts the die tip portion. The ratio Ha / Hb to the hardness Hb was set to 1.51.

2.4 Comparative Example 1
No strain was introduced into either the punch-side surface or the die-side surface of the steel plate A, and shearing was performed with the hardness of the front and back surfaces of the steel plate A being equal.

2.5 Comparative Example 2
By introducing strain on the die-side surface of the steel plate A, the hardness Ha of the portion of the punch-side surface of the steel plate A that contacts the punch tip and the portion of the die-side surface of the steel material A that contacts the die tip. The ratio Ha / Hb to the hardness Hb was set to 0.85.

3. 3. Shearing conditions for steel sheet B Strain was introduced by shot peening at a predetermined position on the surface of steel sheet B. A direct pressure type air shot peening machine was used for shot peening. The projection material was φ0.25 mm, the projection pressure was 0.4 MPa, and the projection amount was 8.0 kg / min. The projection time was changed in the range of 100 to 5000 seconds, and the hardness of the surface was changed. The strain was set to a width of about 5 mm and was continuously introduced along the cutting line during shearing. The strain-introduced steel plate B is placed between the punch and the die, and the punch and the die are relatively moved so that the portion of the steel plate B in which the strain is introduced includes a cutting line. It was punched to obtain a processed material having a sheared end face on the die.

3.1 Example 4
By introducing strain on the punch side surface of the steel plate B, the hardness Ha of the portion of the punch side surface of the steel plate B that contacts the punch tip portion and the portion of the die side surface of the steel material B that contacts the die tip portion. The ratio Ha / Hb to the hardness Hb was set to 1.09.

3.2 Example 5
By introducing strain on the punch side surface of the steel plate B, the hardness Ha of the portion of the punch side surface of the steel plate B that contacts the punch tip portion and the portion of the die side surface of the steel material B that contacts the die tip portion. The ratio Ha / Hb to the hardness Hb was 1.19.

3.3 Example 6
By introducing strain on the punch side surface of the steel plate B, the hardness Ha of the portion of the punch side surface of the steel plate B that contacts the punch tip portion and the portion of the die side surface of the steel material B that contacts the die tip portion. The ratio Ha / Hb to the hardness Hb was set to 1.51.

3.4 Comparative Example 3
No strain was introduced into either the punch-side surface or the die-side surface of the steel plate B, and shearing was performed with the hardness of the front and back surfaces of the steel plate B being equal.

3.5 Comparative Example 4
By introducing strain on the die-side surface of the steel plate B, the hardness Ha of the portion of the punch-side surface of the steel plate B that contacts the punch tip and the portion of the die-side surface of the steel material B that contacts the die tip. The ratio Ha / Hb to the hardness Hb was set to 0.86.

4. Evaluation conditions For each of the processed materials according to Examples 1 to 4 and Comparative Examples 1 to 4, the residual stress on the sheared end face was measured as follows. That is, at the center position in the plate thickness direction, the residual stress was measured by X-ray with a spot diameter of φ500 μm (three points different in the plate width direction). The residual stress was measured in three directions: the plate thickness direction, the plate width direction, and the 45 degree direction from the plate thickness direction, and the sin ² ψ method was used to calculate the residual stress. Assuming that the residual stress in the normal direction of the end face is zero, the maximum principal stress was calculated from the calculated residual stress in the three directions. The values of the maximum principal stress calculated at three points were averaged.

5. Evaluation Results The evaluation results are shown in Tables 1 and 2 below.

As shown in Tables 1 and 2, the punch-side surface of the steel plate was pre-deformed, and the steel plate was sheared in a state where the hardness Ha of the punch-side surface of the steel plate was harder than the hardness Hb of the die-side surface. In this case, it can be seen that the tensile residual stress of the fracture surface can be remarkably reduced at the sheared end face of the processed material obtained after shearing. It is probable that the area ratio of the first portion derived from the first crack extending from the punch side could be increased in the fracture surface of the processed material. It can be seen that such an effect is similarly observed regardless of the strength of the steel sheet.

In the above embodiment, the embodiment in which the steel plate is used as the steel material is exemplified, but the technique of the present disclosure is not limited to this embodiment. As described above, the technique of the present disclosure is characterized in that the friction coefficient of the front and back surfaces of the steel material is adjusted, and the same effect can be exhibited regardless of the shape of the steel material.

The processed material produced by the shearing processing apparatus of the present disclosure can be used as a constituent material of, for example, automobiles, home appliances, building structures, ships, bridges, construction machinery, various plants, pen stocks and the like.

1 Shear end face 1a Dripping 1b Fracture cross section 1b x 1st part 1by 2nd part 1c Bali 1dx 1st crack 1dy 2nd crack 1e Shear surface 5 Steel material 10 Machining material 10a 1st surface 10ax 1st tip of 1st blade Contacting part 10b Second surface 10bx Contacting part with the second tip of the second blade 11 Part of the steel 12 Other part of the steel 15 Scrap 21 First blade 21a First bottom surface 21b First side surface 21x First tip 22 2nd blade 22a 2nd bottom surface 22b 2nd side surface 22x 2nd tip

Claims (10)

It is a method of manufacturing processed materials by shearing steel materials.
Arranging the steel material between the first blade and the second blade, where the steel material has a first surface and a second surface opposite to the first surface, and the first blade has a first surface. It has one bottom surface, a first side surface and a first tip portion, and the second blade has a second bottom surface, a second side surface and a second tip portion, and
Shearing the steel material by relatively moving the first blade and the second blade.
Including
The steel material so that the portion of the first surface of the steel material that contacts the first tip portion is relatively harder than the portion of the second surface of the steel material that contacts the second tip portion. Pre-deformation of at least one of a part of the first surface and a part of the second surface before shearing.
including,
Manufacturing method of processed materials. The ratio Ha of the hardness Ha of the portion of the first surface of the steel material that contacts the first tip portion and the hardness Hb of the portion of the second surface of the steel material that contacts the second tip portion. Prior to shearing of the steel material, at least one of a part of the first surface and a part of the second surface is pre-deformed so that / Hb is 1.10 or more.
The manufacturing method according to claim 1. The ratio Ha of the hardness Ha of the portion of the first surface of the steel material that contacts the first tip portion and the hardness Hb of the portion of the second surface of the steel material that contacts the second tip portion. Prior to shearing of the steel material, at least one of a part of the first surface and a part of the second surface is pre-deformed so that / Hb is 1.20 or more.
The manufacturing method according to claim 1. The ratio Ha of the hardness Ha of the portion of the first surface of the steel material that contacts the first tip portion and the hardness Hb of the portion of the second surface of the steel material that contacts the second tip portion. Prior to shearing of the steel material, at least one of a part of the first surface and a part of the second surface is pre-deformed so that / Hb becomes 1.50 or more.
The manufacturing method according to claim 1. Before shearing the steel material, strain is introduced into a part of the first surface of the steel material so as to increase the hardness Ha of the portion of the first surface of the steel material that comes into contact with the first tip portion. do,
The manufacturing method according to any one of claims 1 to 4. The strain is continuously or intermittently introduced into a part of the first surface of the steel material along the cutting line by the first blade.
The manufacturing method according to claim 5. By introducing the strain into a part of the first surface of the steel material, the hardness Ha is increased by 10% or more before and after the strain is introduced.
The manufacturing method according to claim 5 or 6. The steel material is plate-shaped,
The manufacturing method according to any one of claims 1 to 7. The tensile strength of the steel material is 980 MPa or more.
The manufacturing method according to any one of claims 1 to 8. The tensile strength of the steel material is 1470 MPa or more.
The manufacturing method according to claim 9.

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