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Cold-rolled steel sheet and manufacturing method thereof

A technology of cold-rolled steel sheets and manufacturing methods, applied in the field of cold-rolled steel sheets, capable of solving problems such as increased residual stress, deterioration of the steel plate's resistance to hysteresis failure, and hysteresis failure, and achieving the effects of improving component strength and excellent resistance to hysteresis failure

Active Publication Date: 2019-04-23
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 thereof
  • Cold-rolled steel sheet and manufacturing method thereof
  • Cold-rolled steel sheet and manufacturing method thereof

Examples

Experimental program
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Effect test

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 present invention provides a cold-rolled steel sheet having a predetermined composition and the following structure: the total area ratio of tempered martensite and bainite to the total structure is 95% or more and 100% or less; 0.8 inclusions / mm 2 Below, carbides of a given size with Fe as the main component are 3500 pieces / mm 2 Hereinafter, carbides with a diameter of 10 to 50 nm distributed in the tempered martensite and / or the bainite are 0.7×10 7 piece / mm 2 In the above, the average particle size of the original γ grains is 18 μm or less.

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 Patents(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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