HIGH-STRENGTH HOT-DIP GALVANIZED STEEL SHEET HAVING EXCELLENT FATIGUE CHARACTERISTICS AND MANUFACTURING METHOD THEREFOR

WIPO Patent Application WO/2012/043863

A1

Provided are: a high-strength hot-dip galvanized steel sheet that has a tensile strength of at least 590 MPa and excellent fatigue characteristics with respect to hole punching; and a manufacturing method therefor. The structure of said steel sheet comprises a ferrite phase, with a mean grain diameter of 15 µm or less and an area ratio of at least 60%, and a martensite phase, with an area ratio of 5-40%. For each surface of the steel sheet, the total mass of one or more oxides selected from among iron, silicon, manganese, aluminum, phosphorus, niobium, and titanium oxides generated in a surface layer from the surface of the base steel directly beneath a galvanization layer to a depth of 100 µm into the steel sheet is less than 0.060 g/m². When manufacturing said steel sheet, during a continuous hot-dip galvanization process, soaking is performed at a temperature of 700-900°C, with the dew point of the surrounding atmosphere brought to −40°C or less for the temperature range of 700°C and up.

KARIYA NOBUSUKE (JP)
SAITO HAYATO (JP)
YOKOTA TAKESHI (JP)
FUSHIWAKI YUSUKE (JP)

PCT/JP2011/072902

April 05, 2012

September 28, 2011

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JFE STEEL CORP (JP)
KARIYA NOBUSUKE (JP)
SAITO HAYATO (JP)
YOKOTA TAKESHI (JP)
FUSHIWAKI YUSUKE (JP)

C23C2/06; C21D9/46; C22C38/00; C22C38/60; C23C2/02; C23C2/28

WO2009084795A1

2009-07-09

JP2007092126A	2007-04-12
JP2004211138A	2004-07-29
JPH0978214A	1997-03-25
JPH11199973A	1999-07-27
JPH11279690A	1999-10-12
JP2004315902A	2004-11-11

See also references of EP 2623629A4

OCHIAI, Kenichiro (JP)
Ken-ichiro Ochiai (JP)

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