HIGH STRENGTH STEEL SHEET AND HIGH STRENGTH GALVANIZED STEEL SHEET

Title:

HIGH STRENGTH STEEL SHEET AND HIGH STRENGTH GALVANIZED STEEL SHEET

Document Type and Number:

WIPO Patent Application WO/2017/164346

Kind Code:

A1

Abstract:

This high strength steel sheet has a specific chemical composition, has microstructures containing, in terms of volume percentages, 85% or less of ferrite, 3-95% of bainite, 1-80% of tempered martensite, 1-25% of retained austenite, a total of 5% or less of pearlite and coarse cementite and 5% or less of fresh martensite in a region corresponding to 1/8 to 3/8 of the thickness of the sheet from a surface of the sheet, with the center of the region being 1/4 of the thickness, and is such that the quantity of solid solution carbon in retained austenite is 0.70-1.30 mass%, the aspect ratio is 2.50 or less, and among all grain boundaries of retained austenite grains having circle-equivalent diameters of 0.80 μm or more, the proportion of boundaries with tempered martensite or fresh martensite is 75% or less.

Inventors:

KAWATA HIROYUKI (JP)
YAMAGUCHI YUJI (JP)
KITAZAWA TAKAYUKI (JP)
UCHIDA SATOSHI (JP)
UEDA KOHEI (JP)
MARUYAMA NAOKI (JP)

Application Number:

PCT/JP2017/011883

Publication Date:

September 28, 2017

Filing Date:

March 23, 2017

Export Citation:

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Assignee:

NIPPON STEEL & SUMITOMO METAL CORP (JP)

International Classes:

C22C38/00; C22C18/00; C22C38/06; C22C38/58; C23C2/06; C23C2/40; C21D9/46

Domestic Patent References:

WO2013018741A1	2013-02-07
WO2013047821A1	2013-04-04
WO2012036269A1	2012-03-22
WO2013047739A1	2013-04-04

Foreign References:

JP2009209451A

2009-09-17

Other References: