High-tensile-strength steel plate and process for producing same

A high-tensile-strength steel plate produced on the basis of a novel composition design whereby the yield stress is rendered unaffected by plate thickness and even the steel plate with a thickness of 100 mm or greater is guaranteed to have performance equal to that of the steel plate with a thickness of 50 mm. The high-tensile-strength steel plate has a composition which contains, in terms of mass%, 0.02-0.08% C, 0.01-0.35% Si, 1.4-2.0% Mn, up to 0.007% P, up to 0.0035% S, 0.010-0.060% Al, 0.5-2.0% Ni, 0.10-0.50% Mo, 0.005-0.040% Nb, 0.005-0.025% Ti, less than 0.0003% B, 0.002-0.005% N, 0.0005-0.0050% Ca, and up to 0.003% O and in which the components satisfy given relationships.