THICK STEEL SHEET HAVING EXCELLENT CTOD PROPERTIES IN MULTILAYER WELDED JOINTS, AND MANUFACTURING METHOD FOR THICK STEEL SHEET

WIPO Patent Application WO/2014/141633

A1

　Provided are a thick steel sheet having excellent CTOD properties in low-medium heat input multilayer welded joints, and a manufacturing method for the thick steel sheet.　The component composition of the steel sheet includes, in mass%, 0.03-0.12% of C, at most 0.5% of Si, 1.0-2.0% of Mn, at most 0.015% of P, 0.0005-0.0050% of S, 0.005-0.060% of Al, 0.5-2.0% of Ni, 0.005-0.030% of Ti, 0.0015-0.0065% of N, 0.0010-0.0050% of O, 0.0005-0.0060% of Ca and contains at least one type of Cu when necessary. The Ti/N, Ceq, Pcm, and ACR values are within a defined range, the effective crystal grain size of the base material in the center of the sheet in the sheet thickness direction is at most 20μm, and a defined amount of composite inclusions having a circle equivalent diameter of at least 0.1 μm are present at 1/4 and 1/2 the sheet thickness, the composite inclusions comprising a sulfide containing Ca and Mn, and an oxide containing Al. After heating steel having the above composition to a defined temperature, the steel is hot rolled and cooled.

TERAZAWA YUSUKE (JP)
ICHIMIYA KATSUYUKI (JP)
HASE KAZUKUNI (JP)
ENDO SHIGERU (JP)

PCT/JP2014/001220

September 18, 2014

March 05, 2014

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JFE STEEL CORP (JP)

C22C38/00; C21D8/02; C22C38/14; C22C38/58

WO2009072753A1

2009-06-11

JPH0277521A	1990-03-16
JPH05271766A	1993-10-19
JPH1017982A	1998-01-20
JPH11140582A	1999-05-25
JP2010202949A	2010-09-16
JP2012162797A	2012-08-30
JP2013023713A	2013-02-04
JP2013095927A	2013-05-20
JP2013095928A	2013-05-20

KUMASAKA, Akira et al. (JP)
Akira Kumasaka (JP)

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