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High-tensile strength hot-rolled steel sheet excellent in elongation properties and stretch flangeability and producing method thereof

A technology of hot-rolled steel sheet and manufacturing method, applied in the direction of manufacturing tools, metal rolling, heat treatment furnaces, etc.

Inactive Publication Date: 2007-01-24
JFE STEEL CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, as mentioned above, no technology exists in the past that can achieve this

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment

[0066] Steel slabs having the composition shown in Table 1 were produced, samples were taken from each slab and Ar was measured 3 Phase transition point (°C). That is, after the sample was heated at 1250°C for 30 minutes, it was cooled at a cooling rate of 1°C / sec, and Ar was measured with a differential thermal dilatometer 3 phase transition point. Table 1 also shows that Ar 3 The measured value of the phase transition point.

[0067] Billets A-D are examples satisfying the composition range of the present invention. On the other hand, billet E is an example in which the S content is outside the range of the present invention, and billet F is an example in which the contents of silicon and titanium which do not satisfy the formula (1) are outside the range of the present invention. Billet G is an example in which the carbon and manganese contents are outside the range of the present invention. Steel billet H is an example in which the contents of silicon and aluminum are...

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PUM

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Abstract

A high-tensile strength hot-rolled steel sheet that satisfies, in addition to TS of 780 MPa or more or furthermore 980 MPa or more, TS x EL >= 20000 MPa% and TS x lambda >= 82000 MPa%, and a method of producing the same are provided. Specific resolution means are as follows. That is, a high-tensile strength hot-rolled steel sheet including a composition that includes C of 0.04% by mass or more and 0.25% by mass or less; Si of 0.4% by mass or more and 2.0% by mass or less; Mn of 3.0% by mass or less; Al of 0.2% by mass or less; S of 0.007% by mass or less; Ti of 0.08% by mass or more and 0.3% by mass or less; and the balance of Fe and inevitable impurities, in the above, the contents of the C, the Si and the Ti satisfing (%C / 12 - %Ti / 48) / (%Si / 28) <= 0.4; and a microstructure that includes ferrite; bainite; and retained austenite; in the above a fraction of the ferrite in an entire microstructure is 40% or more and an average grain size of the ferrite is 5 mu m or less; a fraction of the bainite is in the range of 20% to 48% with respect to an entire microstructure; and a fraction of the retained austenite is in the range of 2% to 7% with respect to an entire microstructure is produced.

Description

technical field [0001] The present invention relates to a high-strength hot-rolled steel sheet having both excellent ductility and excellent stretch-turning property and a manufacturing method thereof. Background technique [0002] Among hot-rolled steel sheets for automobiles, high-strength hot-rolled steel sheets with a tensile strength of 780 MPa to 980 MPa are used for body members, wheel parts (such as wheels, rims, chassis, etc.) and strength parts (such as insurance Bars, door guide rods, etc.), among them, in order to achieve lower fuel consumption and improve crash safety, hot-rolled steel sheets used for car bodies are required to meet high strength and high processability. [0003] Among the hot-rolled steel sheets developed from this point of view, there are known, for example, steels with a composite structure mainly composed of ferrite and martensite (so-called dual-phase steels) and steels with a structure composed of ferrite, bainite and residual steel. Resi...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C22C38/14B21B1/22B21B3/00C21D8/02C21D9/46C22C38/00C22C38/02C22C38/04
CPCC22C38/14C22C38/02C21D8/0226C22C38/04C21D8/0263C21D2211/005C21D2211/001C21D2211/002C22C38/00
Inventor 妻鹿哲也坂田敬濑户一洋
Owner JFE STEEL CORP