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Thin steel sheet and process for producing same

A manufacturing method and technology for thin steel sheets, which are applied in the directions of manufacturing tools, metal rolling, furnaces, etc., can solve problems such as difficulty in changing the shape of parts, and increased welding conditions and costs.

Inactive Publication Date: 2015-07-22
JFE STEEL CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0004] However, when used as an automotive part, it is not easy to change the shape of the part in the limited space in the car, and there are problems such as an increase in cost when changing welding conditions.

Method used

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  • Thin steel sheet and process for producing same
  • Thin steel sheet and process for producing same
  • Thin steel sheet and process for producing same

Examples

Experimental program
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Effect test

Embodiment 1

[0125] First, steel A having the composition shown in Table 1 was melted in a vacuum melting furnace, pickled after hot rolling, annealed after cold rolling, and cold-rolled steel sheets were produced. At this time, the following conditions are used as the basic conditions: heating conditions before rolling: heating at 1250°C for 1 hour, finishing temperature of hot rolling: 880°C, plate thickness after hot rolling: 4.4mm, coiling conditions: the same as at 600°C After holding at ℃ for 1 hour, furnace-cooled coiling equivalent treatment was carried out, the reduction rate of cold rolling: 68%, the plate thickness after cold rolling: 1.4mm, (Ac 1 -100℃)~Ac 1 Average heating rate: 20°C / s, soaking temperature: holding time at 830°C: 60s, average cooling rate up to 300°C: 15°C / s, subsequent cooling up to room temperature: air cooling. These basic conditions are shown in Table 2.

[0126] And, as shown in Table 3, the cold rolling reduction in the above-mentioned basic conditions...

Embodiment 2

[0140] In addition, steels B to N having the compositions shown in Table 4 were melted in a vacuum melting furnace, and hot rolling, pickling, cold rolling, and annealing were performed sequentially under the conditions shown in Table 5.

[0141] The same investigations as in Example 1 were carried out on the cold-rolled steel sheets thus obtained.

[0142] The obtained results are shown in Table 5 together.

[0143]

[0144]

[0145] As shown in Table 5, the steel sheets obtained according to the present invention (steel sheets: B to G, L to N) all had excellent properties such as TS of 780 MPa or more, TS×El of 16500 MPa·% or more, and Ec of 240 GPa or more.

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Abstract

A thin steel sheet having sheet thickness ‰¤ 1.6 mm, but tensile strength ‰¥ 780 MPa and Young's modulus ‰¥ 240 GPa in transverse direction is provided, where the steel sheet has composition including, in mass%, C: 0.06-0.12 %, Si: 0.5-1.5 %, Mn: 1.0-3.0 %, P: 0.05 % or less, S: 0.01 % or less, Al: 0.5 % or less, N: 0.01 % or less, Ti: 0.02-0.20 %, and the balance being Fe and incidental impurities, where the composition satisfies relations of Formula (1) and (2), and microstructure such that ferrite phase has area ratio ‰¥ 60 % and martensite phase has area ratio of 15-35 %, ferrite and martensite phases are 95 % or more in total, average grain size of ferrite is ‰¤ 4.0 µm and that of martensite is ‰¤ 1.5 µm, 0.11 ‰¤ % C - 12 / 47.9 × % Ti * ‰¤ 0.15 , where Ti * = % Ti - 47.9 / 14 × % N - 47.9 / 32.1 × % S

Description

technical field [0001] The present invention mainly relates to a high-strength high-strength steel sheet suitable for use as an automobile body and a method for producing the same. The high-strength thin steel plate of the present invention is suitable for structural members such as central pillars, side beams, side frames, and cross beams of automobiles, whose rigid plate thickness sensitivity index is close to 1, with columnar or columnar cross-sectional shapes, and therefore has a tensile strength of more than 780MPa. Tensile strength and ductility are also excellent. Background technique [0002] In recent years, as concerns about global environmental issues have increased, and restrictions on exhaust emissions have been imposed on automobiles, reducing the weight of automobile bodies is an extremely important issue. Therefore, in order to reduce the thickness of the steel plate by increasing the strength of the steel plate, it is intended to reduce the weight of the ve...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C22C38/00B21B3/00C21D9/46C22C38/06C22C38/58
CPCC21D8/0473C22C38/02C22C38/58C22C38/04C21D8/0263C22C38/14C21D8/0436C22C38/08C22C38/16C22C38/06C21D8/0463C21D2211/008C21D9/46C22C38/12C22C38/001C21D2211/004C22C38/00B21B3/00C22C38/38C22C38/002C21D2211/005C22C38/28
Inventor 河村健二横田毅
Owner JFE STEEL CORP