HOT-ROLLED STEEL SHEET, FORGED STEEL PART AND PRODUCTION METHODS THEREFOR

Title:

HOT-ROLLED STEEL SHEET, FORGED STEEL PART AND PRODUCTION METHODS THEREFOR

Document Type and Number:

WIPO Patent Application WO/2018/179391

Kind Code:

A1

Abstract:

A hot-rolled steel sheet, wherein: the steel sheet chemical composition, in mass%, is C: 0.020-0.070%, Si: 0.05-1.70%, Mn: 0.60-2.50%, Al: 0.005-0.020%, N>0.0030-0.0060%, P≤0.050%, S≤0.005%, Ti: 0.015-0.170%, Nb: 0-0.100%, V: 0-0.300%, Cu: 0-2.00%, Ni: 0-2.00%, Cr: 0-2.00%, Mo: 0-1.00%, B: 0-0.0100%, Ca: 0-0.0100%, Mg: 0-0.0100%, REM: 0-0.1000%, Zr: 0-1.000%, Co: 0-1.000%, Zn: 0-1.000%, W: 0-1.000%, Sn: 0-0.050%, balance: Fe and impurities, Ca+Mg+REM ≥0.0005; the steel sheet metal structure is, in area%, ferrite: 5-70%, bainite: 30-95%, retained γ ≤2%, martensite ≤2%, pearlite ≤1%; ferrite + bainite ≥95%; the number density of micro Ti deposits in the ferrite grains is 1.0×1016-50.0×1016 /cm3; the mean equivalent circular diameter of the TiN deposits in the steel sheet is 1.0-10.0 µm; the mean value for the shortest distance between adjacent TiN deposits is at least 10.0 µm; and the standard deviation of the nano-hardness is 1.00 GPa or less.

Inventors:

YOKOI TATSUO (JP)
YOSHIKAWA NOBUO (JP)
YONEMURA SHIGERU (JP)
OOTSUKA KAZUYA (JP)

Application Number:

PCT/JP2017/013749

Publication Date:

October 04, 2018

Filing Date:

March 31, 2017

Export Citation:

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Assignee:

NIPPON STEEL & SUMITOMO METAL CORP (JP)

International Classes:

C22C38/00; C21D9/46; C22C38/58

Domestic Patent References:

WO2014171427A1

2014-10-23

Foreign References:

JP2007253199A	2007-10-04
JP2015054974A	2015-03-23
JP2014514443A	2014-06-19
JP2017504722A	2017-02-09
JP2002105595A	2002-04-10
JP2002322540A	2002-11-08
JP2002322541A	2002-11-08

Other References: