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Steel sheet

A steel plate, high-quality technology, applied to the field of steel plates containing a high concentration of Mn, can solve problems such as difficulty in ensuring sufficient weldability, restrictions on the use of structural members, etc.

Active Publication Date: 2020-10-30
NIPPON STEEL CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, when the steel plate is used as a structural member, the steel plate is often welded, but if the C content in the steel plate is large, it becomes difficult to ensure sufficient weldability, and the use as a structural member is limited.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment

[0191] The steel plate of this application is demonstrated more concretely with reference to an example. However, the following examples are examples of the steel sheets of the present application, and the steel sheets of the present application are not limited to the aspects of the following examples.

[0192] 1. Manufacture of steel plates for evaluation

[0193] Steels having the chemical compositions shown in Table 1 were melted in a converter and continuously cast to obtain 245 mm thick slabs.

[0194] Table 1

[0195]

[0196] The down arrow in Table 1 means the same as the previous column.

[0197] The obtained slabs were hot-rolled under the conditions shown in Table 2 to produce hot-rolled steel sheets with a thickness of 2.6 mm. Next, the obtained hot-rolled steel sheets were pickled and cold-rolled at the cold-rolling ratios shown in Table 2 to produce cold-rolled steel sheets with various thicknesses shown in Table 2.

[0198] Table 2

[0199]

[0200]Th...

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Abstract

Provided is a steel sheet that has a high Mn concentration, and has excellent local ductility and high strength. This steel sheet is characterized by containing predetermined amounts of C, Si, and acid-soluble Al and in mass%, more than 4% but less than 9% of Mn, limited amounts of P, S, N, and O, and an arbitrarily selected element, the balance being iron and impurities, wherein the metal structure at a 1 / 4t portion in an L cross-section thereof contains, in an area proportion, 25-90% of tempered martensite, 3% or less of ferrite, 10-50% of residual austenite, and 25% or less of fresh martensite, and has an interface density of 2.7 mum-1 or more determined by dividing, by the total area of the first and second regions, the total sum of the lengths of boundaries between first regions thatcontain either residual austenite or fresh martensite, and second regions which are regions obtained by removing the first regions from the metal structure at the 1 / 4 position.

Description

technical field [0001] The present application relates to a steel sheet having excellent formability and ultrahigh-strength properties, and specifically, to a steel sheet containing a high concentration of Mn having excellent local ductility and high tensile strength. Background technique [0002] In order to achieve both weight reduction and safety of automobile bodies, components, etc., high strength of steel sheets which are their raw materials is progressing. In general, when the strength of a steel sheet is increased, the elongation decreases and the formability of the steel sheet is impaired. Since automobile body parts using steel sheets as raw materials are often formed by press working, high-strength steel sheets used as vehicle body parts are required to have excellent press formability. In particular, a member for a vehicle body that is mainly formed by stretch flange forming or hole expansion is required to have high strength and high local ductility as mechanic...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C22C38/00C21D9/46C22C38/60
CPCC22C38/00C21D9/46C22C38/60Y02P10/20
Inventor 海藤宏志林宏太郎
Owner NIPPON STEEL CORP
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