PURPOSE: To manufacture the rolled steel for welding structures having excellent high temp. proof stress and weldability by preparing a rolled steel having a specified compsn. in which the content of Mo, Nb and V and weld crack sensitivity compsn. are specified.
CONSTITUTION: A rolled steel contg., by weight, 0.05 to 0.15% C, 0.05 to 0.60% Si, 0.50 to 2.00% Mn and >0.20 to 0.70% Mo, furthermore contg. one or 2 kinds of 0.010 to 0.10% Nb and 0.010 to 0.10% V, contg., at need, one or ≥2 kinds among 0.05 to 0.50% Cu, 0.05 to 0.50% Ni, 0.05 to 0.70% Cr, 0.005 to 0.070% Ti and 0.0005 to 0.010% Ca and the balance Fe with inevitable impurities as well as in which the weld crack sensitivity compsn. (PcM) shown by formula is prescribed to ≤0.24% is prepd. In this way, the rolled steel for welding structures combining high proof stress at about 600°C and good weldability can be obtd.
IWAI KIYOSHI
NISHIJIMA AKIHITO
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