| 摘要 |
PROBLEM TO BE SOLVED: To provide weather-resistant, fireproof steel for welding, which has high weather resistance in an environment where salt of >=0.05∼<10 mdd flies, and also has excellent fire resistance. SOLUTION: The steel has a composition containing, by mass, <=0.15% C, <=0.7% Si, 0.2 to 1.6% Mn, 0.01 to 0.1% Al, 0.4 to 4.0 Ni and 0.2 to 1.5% Mo, and in which the content of Cr is limited to <=0.1%, and further, the weld cracking sensitivity parameter (PCM) shown in the following satisfies PCM=C+Si/30+ Mn/20+Cu/20+Ni/60+Cr/20+Mo/15+V/10+5B<=0.25 mass%.
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