Heat-treated steel sheet member, and production method therefor

一种制造方法、钢板的技术，应用在热处理炉、热处理设备、制造工具等方向，能够解决高加工部位断裂、压制成形性降低、不容易高强度压制成形等问题，达到拉伸强度高的效果

Active Publication Date: 2018-01-02
NIPPON STEEL CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, the press-formability of the steel sheet decreases with the increase in strength, so it is difficult to manufacture products with complex shapes
Specifically, due to the reduction in ductility of the steel plate accompanying the increase in strength, there is a problem of fracture at the highly processed part
In addition, there are problems of springback due to residual stress after processing, wall warpage, and deterioration of dimensional accuracy.
Therefore, it is not easy to press-form high-strength steel sheets, especially those having a tensile strength of 780 MPa or more, into products with complex shapes.
It should be noted that if roll forming is used instead of press forming, although it is easy to process high-strength steel plates, its application is limited to parts with the same cross-section in the longitudinal direction

Method used

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  • Heat-treated steel sheet member, and production method therefor
  • Heat-treated steel sheet member, and production method therefor
  • Heat-treated steel sheet member, and production method therefor

Examples

Experimental program
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Effect test

Embodiment

[0215] Steels having the chemical compositions shown in Table 1 were smelted in a test converter, and continuously cast by a continuous casting test machine to produce slabs with a width of 1000 mm and a thickness of 250 mm. At this time, the heating temperature of molten steel and the pouring amount of molten steel per unit time were adjusted according to the conditions shown in Table 2.

[0216] [Table 1]

[0217]

[0218] The cooling rate of the slab is controlled by changing the amount of water in the secondary cooling spray zone. In addition, the central segregation reduction treatment was carried out by performing light reduction at a gradient of 1 mm / m using rolls at the end of solidification, and discharging the enriched molten steel in the final solidification part. A part of the slabs were then soaked at 1250° C. for 24 hours.

[0219] The obtained slab was hot-rolled using a hot-rolling testing machine to form a hot-rolled steel sheet having a thickness of 3.0 ...

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Abstract

This heat-treated steel sheet member has a chemical composition which includes, expressed in mass%, 0.05-0.50% of C, 0.50-5.0% of Si, 1.5-4.0% of Mn, not more than 0.05% of P, not more than 0.05% of S, not more than 0.01% of N, 0.01-0.10% of Ti, 0.0005-0.010% of B, 0-1.0% of Cr, 0-2.0% of Ni, 0-1.0% of Cu, 0-1.0% of Mo, 0-1.0% of V, 0-0.01% of Ca, 0-1.0% of Al, 0-1.0% of Nb, and 0-0.1% of REM, theremainder being Fe and impurities. The heat-treated steel sheet member has a metallographic structure which mainly consists of martensite, and which has a retained austenite volume fraction of 0.2-1.0%. The number density of carbides present in the steel sheet member which have a circle equivalent diameter of at least 0.1 Mum is not more than 4.0*103 per mm2. The heat-treated steel sheet member has a tensile strength of at least 1.4 GPa, and a yield ratio of at least 0.65.

Description

technical field [0001] The present invention relates to a heat-treated steel plate member and its manufacturing method. Background technique [0002] In the field of steel sheets for automobiles, the application of high-strength steel sheets with high tensile strength is expanding in order to achieve both fuel efficiency and collision safety against the backdrop of recent environmental regulations and stricter crash safety standards. However, since the press formability of the steel sheet decreases with the increase in strength, it is difficult to manufacture products with complex shapes. Specifically, due to the reduction in ductility of the steel sheet accompanying the increase in strength, there has been a problem of breakage at heavily processed portions. In addition, problems of springback, wall warpage, and deterioration of dimensional accuracy due to residual stress after processing also arise. Therefore, it is not easy to press-form a high-strength steel sheet, esp...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C22C38/00C21D1/18C21D9/00C21D9/46C22C38/60
CPCC21D1/19C21D1/22C22C38/02C22C38/04C22C38/14C22C38/20C22C38/22C22C38/26C22C38/28C22C38/32C21D9/46C21D6/004C21D6/005C21D6/008C21D8/0205C21D8/0263C21D2211/001C21D2211/008C22C38/001C22C38/002C22C38/005C22C38/06C22C38/24C22C38/34C22C38/42C22C38/44C22C38/48C22C38/50C22C38/54C22C38/58C22C38/60C22C38/38C21D1/18
Inventor 诹访嘉宏田畑进一郎东昌史匹田和夫
Owner NIPPON STEEL CORP
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