Cold-rolled steel sheet and manufacturing method therefor

A technology of cold-rolled steel sheet and manufacturing method, which is applied in the field of cold-rolled steel sheet, can solve the problems of increased residual stress, deterioration of resistance to delayed failure of steel plate, delayed failure, etc., and achieves the effect of improving the strength of parts and excellent resistance to delayed failure.

Active Publication Date: 2017-12-01
JFE STEEL CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0004] However, when a high-strength steel plate with a TS of 1320 MPa or higher is formed into a part by cold pressing, there is a possibility that delayed fracture may occur due to an increase in residual stress in the part and a deterioration in the resistance to delayed fracture caused by the steel plate itself.

Method used

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  • Cold-rolled steel sheet and manufacturing method therefor
  • Cold-rolled steel sheet and manufacturing method therefor
  • Cold-rolled steel sheet and manufacturing method therefor

Examples

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Embodiment

[0197] Steels with steel codes A to AF shown in Table 1 were melted and then cast into slabs with a thickness of 130 to 230 mm. According to the conditions shown in Table 2, the steel slab heating temperature (SRT) is set to 1100-1260°C, the soaking time is set to 60 minutes, and the finishing temperature (FT) is set to 850-910°C, and the cast steel slab is heated. After rolling, the average cooling rate (cooling rate) up to 700°C is set at 30-200°C / sec for cooling, and the holding temperature is set at 620-730°C for 2-10 seconds for holding , cooled again, and coiled at a coiling temperature (CT) of 490 to 620°C. The obtained hot-rolled sheet was pickled, and cold-rolled at a rolling ratio of 44 to 72% to obtain a cold-rolled steel sheet with a thickness of 0.5 to 2.0 mm.

[0198] In the continuous annealing line, according to the conditions shown in Table 2, the annealing temperature (AT) is set to 850-910°C, and the soaking time is set to 120-960 seconds, and the obtained ...

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Abstract

The invention relates to a cold-rolled steel and a manufacturing method thereofr. The cold-rolled steel sheet has a structure: which has a prescribed component composition; in which the total area ratio of tempered martensite and bainite with respect to the structure as a whole is 95% to 100%; in which there are not more than 0.8 / mm2 of prescribed inclusion groups that extend and / or are distributed in a series of points in the rolling direction and are configured from at least one inclusion particle with a long axis of at least 0.3 [mu]m; in which there are not more than 3500 / mm2 of carbides of a prescribed size that have Fe as the main component; in which there are at least 0.7 x 107 / mm2 of carbides of 10-50 nm diameter that distribute in the interior of the tempered martensite and / or bainite; and in which the mean particle size of prior [gamma] grains is not more than 18 [mu]m.

Description

technical field [0001] The present invention relates to a cold-rolled steel sheet, and particularly relates to a high-strength cold-rolled steel sheet suitable for manufacturing parts such as automobiles and home appliances formed by cold pressing. Moreover, this invention also relates to the manufacturing method of the said cold-rolled steel plate. Background technique [0002] In recent years, due to the further increase in the demand for lightweight automobile bodies, high-strength steel plates with a TS of 1320-1470 MPa have been promoted in body frame parts such as center pillar R / F (reinforcement parts), bumpers, and anti-collision beam parts. etc. (hereinafter also referred to as components). In addition, from the viewpoint of further reducing the weight of automobile bodies, studies have also begun on the application of steel sheets having a TS of 1800 MPa class (1.8 GPa class) or higher strength. [0003] In the past, the application of high-strength steel sheets ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C22C38/00C21D9/46C22C38/06C22C38/60
CPCC22C38/00C22C38/06C22C38/60C21D9/46C21D8/0236C21D2211/002C21D2211/008C22C38/001C22C38/02C22C38/04C21D8/0247C22C38/12C22C38/14
Inventor 小野义彦船川义正山口竜介中村展之
Owner JFE STEEL CORP
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