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Hot-pressed member and method for manufacturing same, and cold-rolled steel sheet for hot pressing and method for manufacturing same

A technology of cold-rolled steel plate and manufacturing method, which is applied in the fields of hot-pressed components and its manufacture, as well as cold-rolled steel plate for hot-pressing and its manufacture, capable of solving problems such as delayed fracture of nuts and steel plates, and achieving excellent delayed fracture resistance and stable characteristics , Excellent delayed fracture resistance effect

Active Publication Date: 2020-02-14
JFE STEEL CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0008] As mentioned above, although the residual stress of the hot-pressed member is reduced, in order to ensure the rigidity of the entire automobile body, stress is also applied after hot pressing, so there is a concern that delayed fracture may occur at the welded part of the nut and the steel plate

Method used

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  • Hot-pressed member and method for manufacturing same, and cold-rolled steel sheet for hot pressing and method for manufacturing same
  • Hot-pressed member and method for manufacturing same, and cold-rolled steel sheet for hot pressing and method for manufacturing same
  • Hot-pressed member and method for manufacturing same, and cold-rolled steel sheet for hot pressing and method for manufacturing same

Examples

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Embodiment

[0182] Hereinafter, examples of the present invention will be described.

[0183] It should be noted that, of course, the present invention is not limited to the examples described below, and can also be implemented with appropriate changes within the scope consistent with the gist of the present invention, and these contents are included in the technical scope of the present invention.

[0184] Steel with the composition shown in Table 1 was smelted and cast to form a slab, heated to 1250° C., and then hot-rolled at the finishing temperature (FDT) shown in Table 2. Next, after cooling the hot-rolled steel sheet to the cooling stop temperature (first cooling temperature) at the first average cooling rate (cooling rate 1) shown in Table 2, it is cooled to the coiling temperature at the second average cooling temperature (cooling rate 2). temperature (CT), coiled into coils. It should be noted that some samples were not subjected to two-stage cooling treatment after hot rolling...

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Abstract

In the hot-pressed member according to the present invention, after the component composition thereof is properly adjusted, the microstructure thereof is configured so that there are an average of 5 or more Ti-based deposits having a grain size of 0.10 [mu]m or less per 100 [mu]m2 of a cross section parallel to the thickness direction of the member in a range from the member surface to a depth of100 [mu]m in a sheet thickness direction, the microstructure has a volume fraction of martensite of 95-100% in a depth range of 20-100 [mu]m in the sheet thickness direction from the member surface, and there are an average of 10 or more cementites having a grain size of less than 0.20 [mu]m among prior austenite grains, whereby the hot-pressed member not only has an extremely high tensile strength TS of 1780 MPa or greater after hot pressing, but excellent delayed fracture resistance after projection welding can also be obtained.

Description

technical field [0001] The present invention relates to a hot-pressed member and its manufacturing method, as well as a cold-rolled steel sheet for hot-pressing and its manufacturing method, and particularly to a hot-pressed member whose delayed fracture resistance after projection welding is to be improved. [0002] In the present invention, a hot-pressed member refers to a member obtained by hot-press forming a hardenable cold-rolled steel sheet to increase its strength. [0003] In addition, the cold-rolled steel sheets of the present invention include not only general cold-rolled steel sheets, but also hot-dip galvanized cold-rolled steel sheets (including alloyed hot-dip galvanized cold-rolled steel sheets), electro-galvanized cold-rolled steel sheets (including electro-galvanized ), aluminized cold-rolled steel sheets, etc. Background technique [0004] In recent years, due to the increase of environmental problems, CO 2 Emission regulations have become stricter, and...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C22C38/00C21D1/18C21D9/00C21D9/46C22C38/14C22C38/60
CPCC21D1/18C22C38/14C22C38/60C21D7/13C21D9/48C21D6/02C21D6/005C21D6/008C21D8/0426C21D8/0436C21D8/0463C22C38/04C22C38/02C22C38/06C22C38/32C22C38/002C22C38/008C22C38/10C22C38/12C22C38/005C23C2/12C23C2/06C23C2/28C23C2/40C25D5/50C25D7/0614C21D1/84C21D1/25C23C2/29C21D9/46B21D22/20B21D22/022B32B15/012B32B15/013C21D6/001C21D6/002C21D8/0205C21D8/0226C21D8/0236C21D8/0263C21D2211/004C21D2211/008C22C38/001C22C38/08C22C38/16C22C38/26C22C38/28Y10T428/12958Y10T428/12799
Inventor 高岛克利小林崇船川义正中岛清次
Owner JFE STEEL CORP
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