To provide a steel material excellent in fatigue-crack propagation resistance and low-temperature toughness of HAZ.
The steel material excellent in fatigue-crack propagation resistance and low-temperature toughness at a weld heat-affected zone contains, by mass, 0.01-0.10% C, 0.04-0.60% Si, 0.5-2.0% Mn, ≤0.015% P, ≤0.004% S, 0.005-0.07% Al, 0.004-0.025% Ti, 0.0005-0.0040% B, 0.0040-0.0090% N, and the balance Fe with impurities. The steel material has, by area ratio, ≥50% of bainitic structure, ≤5% of pearlitic structure and the balance of ferritic structure, has the difference of Vickers hardness of a surface layer part and a thickness center part, of ≤50 and satisfies formula (1): Ti/N≤3.4 and formula (2): 0.0003≤B-10.8/14.1×(N-Ti/3.4)≤0.003 (wherein atomic symbols each means the content (mass%) of the element).
YODA NOBORU
SHINTAKU YOSHIAKI
FUJIWARA TOMOYA
| JP2008169468A | 2008-07-24 | |||
| JP2011094214A | 2011-05-12 | |||
| JP2008255458A | 2008-10-23 |
Chihara