PURPOSE: To produce hot rolled steel plate and cold rolled steel sheet excellent in high temp. strength characteristics by subjecting a slab of a steel having a specific composition where respective contents of B, Nb, Ti, and V are controlled to heating up to a specific temp. and to hot rolling or further to cold rolling and also specifying subsequent conditions.

CONSTITUTION: A slab of a steel having a composition consisting of, by weight, >0.008-0.15% C, ≤1.00% Mn, 0.01-0.10% Al, 0.0002-0.005% B, 0.004-0.12% Nb, 0.01-0.10% Ti and/or 0.02-0.30% V, and the balance iron with inevitable impurities is prepared. This steel slab is heated up to ≥1050°C and hot-rolled at a finishing temp., preferably, of ≥Ar3, or, cold rolling is done after hot rolling and the resulting steel sheet is heated at a rate of ≥1°C/S and annealed at a temp. between the recrystallization temp. and 1000°C. By this method, the hot rolled steel plate and the cold rolled steel sheet remarkably excellent in high temp. strength characteristics and having extremely superior workability and weldability can be obtained.