US-12617011-B2 - Method for manufacturing pressed component, method for manufacturing blank material, and steel sheet

Abstract

A technology capable of suppressing end cracking due to a delayed fracture without restrictions on the target pressed component shape. When it is estimated that the end cracking due to the delayed fracture in an end of a material to be pressed is concerned, double cutting processing including performing cutting processing of the end containing at least a place where the end cracking is concerned twice is provided as preprocessing for the press forming causing the concern about the end cracking. The double cutting processing includes performing, in first cutting, cutting to form a partial beam-shaped projection portion at a position containing the place where the end cracking is concerned, and cutting the projection portion in second cutting.

Inventors

• Eiji Iizuka
• Toyohisa Shinmiya
• Takeshi Ogawa

Assignees

• JFE STEEL CORPORATION

Dates

Publication Date

20260505

Application Date

20210318

Priority Date

20200331

Claims (18)

1. 1 . A method for manufacturing a blank material that is to be manufactured into a pressed component through one or two or more times of press forming, the method comprising: performing a simulation to determine whether or not at least one press forming of the one or two or more times of press forming causes a concern about end cracking due to a delayed fracture at a place at an end of the blank material to be pressed; determining whether or not there is the concern about end cracking because the place at the end of the blank material is where the delayed fracture has occurred when the simulation is not performed; and performing double cutting processing at the place at the end of the blank material to be pressed after determining from the simulation that there is the concern about end cracking due to the delayed fracture at the place at the end of the blank material to be pressed or after determining that there is the concern about end cracking because the place at the end of the blank material is where the delayed fracture has occurred when the simulation is not performed, wherein the double cutting processing includes performing a first cutting to form a projection portion at a position containing the place at the end of the blank material where the delayed fracture is concerned, and performing a second cutting to cut the projection portion.
2. 2 . The method according to claim 1 , wherein a width of the projection portion is set to a length of ⅓ or less of a length of an edge of a flange portion that is to be formed from the end of the blank material.
3. 3 . The method according to claim 2 , wherein a projection amount of the projection portion is set to 10 times or less a sheet thickness of the blank material to be pressed.
4. 4 . The method according to claim 3 , wherein the one or two or more times of press forming includes stamping or drawing.
5. 5 . The method according to claim 2 , wherein a projection amount of the projection portion is set to 5.0 mm or less.
6. 6 . The method according to claim 5 , wherein the one or two or more times of press forming includes stamping or drawing.
7. 7 . The method according to claim 2 , wherein the one or two or more times of press forming includes stamping or drawing.
8. 8 . The method according to claim 1 , wherein a width of the projection portion is set to 150 times or less a sheet thickness of the blank material to be pressed.
9. 9 . The method according to claim 8 , wherein a projection amount of the projection portion is set to 10 times or less the sheet thickness of the blank material to be pressed.
10. 10 . The method according to claim 9 , wherein the one or two or more times of press forming includes stamping or drawing.
11. 11 . The method according to claim 8 , wherein a projection amount of the projection portion is set to 5.0 mm or less.
12. 12 . The method according to claim 11 , wherein the one or two or more times of press forming includes stamping or drawing.
13. 13 . The method according to claim 8 , wherein the one or two or more times of press forming includes stamping or drawing.
14. 14 . The method according to claim 1 , wherein a projection amount of the projection portion is set to 10 times or less a sheet thickness of the blank material to be pressed.
15. 15 . The method according to claim 14 , wherein the one or two or more times of press forming includes stamping or drawing.
16. 16 . The method according to claim 1 , wherein a projection amount of the projection portion is set to 5.0 mm or less.
17. 17 . The method according to claim 16 , wherein the one or two or more times of press forming includes stamping or drawing.
18. 18 . The method according to claim 1 , wherein the one or two or more times of press forming includes stamping or drawing.

Description

TECHNICAL FIELD The present invention is a technology related to the manufacture of a pressed component having a component shape with concern about the occurrence of a delayed fracture in press forming. The present invention is a technology particularly suitable for the manufacture of a pressed component using metal sheets containing high-strength steel sheets having a tensile strength of 980 MPa or more. BACKGROUND ART At present, automobiles have been required to improve fuel consumption by a reduction in weight and collision safety. For the purpose of achieving both the reduction in weight of a vehicle body and the protection of passengers in the event of a collision, high-strength steel sheets tend to be used for structural components for automobiles. Particularly in recent years, as the high-strength steel sheets, ultrahigh-strength steel sheets having higher strength, i.e., having a tensile strength of 980 MPa or more, have been applied to the vehicle body. A delayed fracture is one of the problems when the high-strength steel sheets are applied to the vehicle body. In particular, a delayed fracture occurring from the end surface after shearing work (hereinafter also referred to as sheared end surface) is a serious problem in high-strength steel sheets having a tensile strength of 1180 MPa or more among the high-strength steel sheets. Herein, it is known that a large tensile stress remains in the sheared end surface. The remaining of the tensile stress causes concern about the occurrence of the delayed fracture in the sheared end surface with time in a product after pressing (pressed component). To suppress the delayed fracture in the sheared end surface, it is required to reduce the tensile residual stress in the sheared end surface. As a method for reducing the tensile residual stress of the sheared end surface, a method for raising the steel sheet temperature in shearing work (NPLS 1, 2), a method using a stepped punch in punching work (NPL 3), and a method using shaving (NPL 4, PTL 1) are mentioned, for example. However, the method for raising the steel sheet temperature in the shearing work requires time to heat the steel sheet. Therefore, this method is not suitable for a mass production step of automobiles and the like. The method using a stepped punch has a problem that an effect of improving a delayed fracture resistance property is low. The method using shaving has a problem of difficulty to manage the clearance in a shaving step. NPL 5 describes a cut-off punching method by double punching. However, the method of NPL 5 is a punching work technology, and thus cannot be applied to an outer peripheral portion of a product. CITATION LIST Non Patent Literatures NPL 1: Kenichiro Mori et al.: Sosei to Kako, 52-609 (2011), 1114-1118NPL 2: Kenichiro Mori et al.: Sosei to Kako, 51-588 (2010), 55-59NPL 3: 326th Symposium on Technology of Plasticity “Sendankako no saizensen”, 21-28NPL 4: M. Murakawa, M. Suzuki, T. Shinome, F. Komuro, A. Harai, A. Matsumoto, N. Koga: Precision piercing and blanking of ultrahigh-strength steel sheets, Procedia Engineering, 81 (2014), pp. 1114-1120NPL 5: Sosei to Kako, Vol. 10, no. 104 (1969-9) Patent Literature PTL 1: JP 2004-174542 A SUMMARY OF INVENTION Technical Problem The present invention has been made focusing on the above-described points. It is an object of the present invention to provide a technology capable of suppressing a delayed fracture occurring with time while suppressing the occurrence of restrictions on the target pressed component shape. Solution to Problem To solve the problems, one aspect of the present invention is a method for manufacturing a pressed component including manufacturing a pressed component through one or two or more times of press forming, and the method includes: when it is estimated that at least one press forming of the one or two or more times of press forming causes concern about a delayed fracture in an end of a material to be pressed, double cutting processing including performing cutting processing of the end containing at least a place where the delayed fracture is concerned twice as preprocessing for the press forming causing concern about end cracking due to the delayed fracture, in which the double cutting processing includes performing, in first cutting, cutting to form a partial beam-shaped projection portion at a position containing the place where the delayed fracture is concerned, and cutting the projection portion in second cutting. Another aspect of the present invention is a method for manufacturing a blank material to be formed into a pressed component through one or two or more times of press forming, and the method includes: when it is estimated that at least one press forming of the one or two or more times of press forming causes concern about end cracking due to a delayed fracture in an end of a material to be pressed, double cutting processing including performing cutting processing of the end containing a