High-strength steel sheet and method for producing same

A technology of high-strength steel plates and manufacturing methods, applied in the direction of manufacturing tools, furnaces, heat treatment equipment, etc., can solve problems such as meeting difficulties

Active Publication Date: 2020-01-10
KOBE STEEL LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0011] However, in the high-strength steel sheet disclosed in Patent Document 1, it is difficult to satisfy all of these requirements, and a high-strength steel sheet that can satisfy all of these requirements is required.

Method used

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  • High-strength steel sheet and method for producing same
  • High-strength steel sheet and method for producing same
  • High-strength steel sheet and method for producing same

Examples

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Embodiment Construction

[0049] As a result of intensive research by the present inventors, in a steel having a predetermined composition, by making the steel structure (metal structure) as follows: ferrite fraction: 5% or less, tempered martensite and tempered bainite Total fraction of body: 60% or more, retained austenite content: 10% or more, average size of retained austenite: 1.0 μm or less, retained austenite with a size of 1.5 μm or more: 2 of the total amount of retained austenite % or more and the amount of dissolved nitrogen in the steel sheet: 0.002 mass % or less, the tensile strength (TS), the cross tensile strength of the welded part (SW cross tensile), the yield ratio (YR), the tensile strength can be obtained The product of (TS) and total elongation (EL) (TS×EL), LDR, and hole expansion ratio (λ) are all high-strength steel sheets at high levels.

[0050] 1. Steel structure and solution nitrogen content

[0051] Hereinafter, details of the steel structure and the amount of dissolved n...

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Abstract

This high-strength steel sheet contains 0.15% to 0.35% by mass of C, 0.5% to 3.0% by mass of the total of Si and Al, at least 0.01% by mass of Al, no more than 0.01% by mass of N, 1.0% to 4.0% of Mn,no more than 0.05% by mass of P, and no more than 0.01% by mass of S, with the remainder being made up of Fe and unavoidable impurities. The steel structure is such that the ferrite fraction is no more than 5%, the total fraction of tempered martensite and tempered bainite is at least 60%, the quantity of retained austenite is at least 10%, the average size of MA is does not exceed 1.0 [mu]m, theaverage size of retained austenite does not exceed 1.0 [mu]m, retained austenite having a size of at least 1.5 [mu]m accounts for at least 2% of total retained austenite content, and the solute nitrogen content of the steel plate does not exceed 0.002% by mass.

Description

technical field [0001] The present invention relates to a high-strength steel sheet that can be used in various applications including automobile parts. Background technique [0002] Steel sheets (for example, cold-rolled steel sheets, hot-dip galvanized steel sheets, etc.) used for automotive parts (for example, frame parts) are required to be thinned in order to improve fuel efficiency by reducing the weight of the vehicle body. And to ensure the strength of the parts, the high strength of the steel plate is required. On the other hand, such steel sheets are also required to have excellent workability in order to be formed into complex-shaped parts. Patent Document 1 discloses a high-strength steel sheet having a tensile strength of 980 to 1180 MPa and showing good deep drawability. [0003] 【Prior technical literature】 [0004] 【Patent Literature】 [0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-203548 [0006] However, in various applicati...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C22C38/00C21D9/48C22C38/06C22C38/58C21D9/46
CPCC21D9/46C21D9/48C22C38/00C22C38/06C22C38/02C22C38/04C22C38/001C22C38/12C22C38/14C22C38/16C22C38/38C22C38/08C22C38/002C22C38/005C21D8/02C21D8/0205C21D8/0226C21D8/0236C21D6/00C21D6/008C22C38/18C22C38/58C21D6/005C21D8/0263C21D2211/001C21D2211/002C21D2211/005C21D2211/008
Inventor 枣田浩和村上俊夫齐藤贤司村田忠夫
Owner KOBE STEEL LTD
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