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Hot rolled steel sheet

A technology of hot-rolled steel sheet and sheet width, which is applied in the field of hot-rolled steel sheet with high strength and excellent ductility and stretch flangeability, can solve the problems of damaged hole expandability, etc., and achieve the effect of excellent strength

Active Publication Date: 2021-05-25
NIPPON STEEL CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

In the steel sheet containing retained austenite in the metal structure, although the austenite undergoes martensitic transformation during processing and thus exhibits a large elongation due to transformation-induced plasticity, the hole expandability will be affected by Damaged by the formation of hard martensite

Method used

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  • Hot rolled steel sheet
  • Hot rolled steel sheet
  • Hot rolled steel sheet

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Embodiment Construction

[0078] Hereinafter, the chemical composition and metal structure of the hot-rolled steel sheet (hereinafter, sometimes abbreviated as steel sheet) according to the present embodiment will be specifically described. However, the present invention is not limited to the configuration disclosed in this embodiment, and various changes can be made without departing from the gist of the present invention.

[0079] In the numerical ranges described below, the lower limit and the upper limit are included in the range. For numerical values ​​expressed as "less than" or "exceeded", the value is not included in the numerical range. In the following description, % related to the chemical composition of the steel sheet is mass % unless otherwise specified.

[0080] 1. Chemical composition

[0081] The hot-rolled steel sheet of the present embodiment contains C: 0.100-0.250%, Si: 0.05-3.00%, Mn: 1.00-4.00%, Nb: 0.005-0.050%, sol.Al: 0.001-2.000%, P: 0.100% or less, S: 0.0300% or less, N: ...

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Abstract

This hot rolled steel sheet has a predetermined chemical composition, wherein the metallic structure in a sheet-width cross section in parallel with the rolling direction, at a 1 / 4 depth of the sheet thickness from the surface, and at the center position in the sheet-width direction includes, by area%, a total of 77.0-97.0% of bainite and tempered martensite, 0-5.0% of ferrite, 0-5.0% of pearlite, not less than 3.0% of retained austenite, and 0-10.0% of martensite. The average crystal particle size in the metallic structure excluding the retained austenite is not more than 7.0 micron. The C concentration in the retained austenite is not less than 0.5 mass%. The number density of iron-based carbides with a diameter of not less than 20 nm is not less than 1.0*106 pieces / mm2.

Description

technical field [0001] The present invention relates to hot-rolled steel sheets. Specifically, it relates to a hot-rolled steel sheet that is formed into various shapes by press working or the like and is used, and particularly relates to a hot-rolled steel sheet that is high in strength and excellent in ductility and stretch flangeability. [0002] This application claims priority based on Japanese Patent Application No. 2018-197937 filed in Japan on October 19, 2018, and the content thereof is incorporated herein. Background technique [0003] In recent years, efforts have been made to reduce the emission of carbon dioxide gas in many fields from the viewpoint of global environmental protection. Among automobile manufacturers, the development of technology to reduce the weight of the vehicle body for the purpose of reducing fuel consumption is also prevailing. However, in order to ensure the safety of the occupants, the focus is also on improving the crash resistance cha...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C22C38/00C22C38/58C21D8/02C21D9/46
CPCC22C38/02C22C38/04C22C38/06C22C38/12C22C38/14C22C38/16C22C38/08C22C38/26C22C38/34C22C38/38C22C38/002C22C38/005C22C38/008C22C38/10C21D1/02C21D6/008C21D6/005C21D9/48C21D8/0463C21D8/0426C21D8/0447C21D2211/002C21D2211/008C21D2211/001C21D1/84C21D1/19C21D6/001C21D6/002C21D8/0205C21D8/0226C21D8/0236C21D8/0263C21D9/46C21D2211/005C21D2211/009C22C38/001
Inventor 首藤洋志榊原章文甲斐真辅林宏太郎海藤宏志
Owner NIPPON STEEL CORP