To provide a method for producing a stock plate for round column for building, having yield ratio as low as ≤80% and also having high toughness even if SR treatment is omitted.
A steel slab, having a composition containing, by weight, 0.06-0.17% C, 0.06-0.50% Si, 0.5-1.6% Mn, ≤0.015% P, ≤0.005% S, ≤0.07% Al, ≤0.006 N, and further one or ≥2 kinds selected from the group consisting of 0.005-0.5% Cu, 0.05-0.8% Ni, 0.05-0.5% Cr, and 0.005-0.05% Nb, is used. This steel slab is heated to ≥1000°C and hot-rolled. The resulting plate is cooled rapidly without delay from a temp. not lower than the Ar3 point down to ordinary temp. This plate is cooled rapidly again from 740-780°C and then tempered at 400-550°C. By this method, the stock plate for round column for building, having ≤80% yield ratio at the tensile test in a tube-axis direction, can be obtained.
WADA NORIKI
OSANAWA YUTAKA
TANI SABURO
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