STEEL MATERIAL

WIPO Patent Application WO/2023/167319

A1

Provided is a steel material that can reduce the hydrogen embrittlement susceptibility of bolts. This steel material contains, in mass%, 0.30-0.50% of C, 0.01-0.30% of Si, 0.10-1.50% of Mn, 0.030% or less of P, 0.030% or less of S, more than 0.80% and no more than 1.50% of Cr, 0.35-1.50% of Mo, 0.01-0.50% of V, 0.005-0.100% of Al, and 0.0010-0.0300% of N, with the remainder comprising Fe and inevitable impurities, wherein the area percentage of hard phases is at least 90%, the Vickers hardness is 220-400 HV, the number density of cementite in the hard phases is at least 4.0/μm2, the number percentage of cementite having an area of 0.0005-0.0100 μm2 among a plurality of cementite phases in the hard phases is at least 50.0%, and the sample standard deviation of the areas of the plurality of cementite phases in the hard phases is 0.070 μm2 or less.

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SHIGA AKIRA (JP)
UMEHARA MIYURI (JP)

PCT/JP2023/008074

September 07, 2023

March 03, 2023

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NIPPON STEEL CORP (JP)

C21D8/06; C21D9/00; C22C38/00; C22C38/24; C22C38/60; C21D1/32

WO2020162616A1

2020-08-13

JP2020128592A	2020-08-27
JP2012233244A	2012-11-29
JPH05255738A	1993-10-05

ASCEND IP LAW FIRM (JP)

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