High-strength steel sheet and production method for same, and production method for high-strength galvanized steel sheet

A high-strength steel plate and a technology for manufacturing methods, which are applied in manufacturing tools, chemical instruments and methods, hot-dip plating processes, etc., can solve problems such as poor shape, reduced mass production efficiency, and increased deviation, and achieve excellent plate passability, Improved fuel efficiency and excellent fatigue properties

Active Publication Date: 2017-04-19
JFE STEEL CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0006] However, the amount of shape change is estimated based on TS. Therefore, when the TS of the steel sheet fluctuates, the deviation between the predicted value of shape change and the actual amount of shape change increases, causing shape defects.
In addition, steel sheets with such poor shapes need to be corrected one by one by sheet metal processing after stamping, which significantly reduces mass production efficiency.

Method used

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  • High-strength steel sheet and production method for same, and production method for high-strength galvanized steel sheet
  • High-strength steel sheet and production method for same, and production method for high-strength galvanized steel sheet
  • High-strength steel sheet and production method for same, and production method for high-strength galvanized steel sheet

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Embodiment

[0188]Steel having the composition shown in Table 1, with the balance consisting of Fe and unavoidable impurities was melted in a converter and cast into billets by continuous casting. The obtained slabs were heated under the conditions shown in Table 2, and hot-rolled to obtain steel sheets. Then, pickling treatment was performed on the steel sheet. Then, for No.1-19, 21, 22, 25, 27, 29, 31, 32, 34-39, 41, 43-55 shown in Table 2, implement hot-rolled sheet heat treatment, and further, for No. For 31, 32, 34-39, 41, and 43, pickling treatment is carried out after the heat treatment of the hot-rolled sheet.

[0189] Next, after cold rolling under the conditions shown in Table 2, annealing treatment was performed twice under the conditions shown in Table 2 to obtain high-strength cold-rolled steel sheets (CR).

[0190] Furthermore, a part of the high-strength cold-rolled steel sheet (CR) is galvanized to obtain a galvanized steel sheet (GI), an alloyed galvanized steel sheet (...

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Abstract

The present invention provides a high-strength steel sheet having a tensile strength (TS) of at least 780 MPa, excellent ductility and fatigue characteristics, and excellent stretch flangeability, surface quality and sheet-conveying properties, achieved by: having a specific component composition; the steel structure having, in terms of area ratio, 20-50% ferrite, 5-25% bainitic ferrite, 1-10% martensite, 5-15% tempered martensite, and having, in terms of volume fraction, at least 10% retained austenite; the average crystalline particle diameter of the retained austenite being not more than 2[mu]m; the average Mn volume (mass%) in the retained austenite being at least 1.2 times the Mn volume (mass%) in the steel; the mean free path of the retained austenite being not more than 1.2[mu]m; and the mean free path of the tempered martensite being not more than 1.2[mu]m.

Description

technical field [0001] The present invention relates to a high-strength steel sheet with excellent formability mainly suitable for structural members of automobiles and a method for producing the same. In particular, to obtain a high-strength steel sheet having a tensile strength (TS) of 780 MPa or more, not only excellent in ductility, but also excellent in fatigue properties, and stretchable High-strength steel sheet with excellent flangeability, surface quality, and passability. Background technique [0002] In recent years, the application of high-strength steel plates with a tensile strength (TS) of 780 MPa or more and a thinner plate thickness has been actively promoted in order to ensure the safety of crew members during collisions and improve fuel efficiency due to lightweight vehicles. in the dynamics of automotive structural components. [0003] Furthermore, recently, the application of high-strength steel sheets having extremely high strengths of 980 MPa class an...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C22C38/00C21D9/46C22C38/04C22C38/60
CPCC22C38/00C22C38/04C22C38/60C21D9/46B32B15/013C21D1/60C21D8/0226C21D8/0236C21D8/0263C21D8/0278C21D2211/001C21D2211/002C21D2211/005C21D2211/008C22C38/001C22C38/002C22C38/005C22C38/008C22C38/02C22C38/06C22C38/12C22C38/14C22C38/16C22C38/38C23C2/28C23C2/06C23C2/40C23G1/00
Inventor 川崎由康松田广志田原和宪横田毅奥田金晴濑户一洋
Owner JFE STEEL CORP
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