High-strength steel plate reduced in softening in weld heat-affected zone

摘要

A high-strength steel sheet having excellent fatigue property, excellent formability and resistance to softening of the heat affected zone after welding, comprising: 0.01 to 0.15 mass % of C, 0.005 to 1.0 mass % of Si, 0.1 to 2.2 mass % of Mn, 0.001 to 0.06 mass % of P, 0.001 to 0.01 mass % of S, 0.0005 to 0.01 mass % of N, 0.001 to 0.1 mass % of Al, 0.005 to 0.05 mass % of Nb, 0.05 to 0.5 mass % of Mo, when necessary, 0.001 to 0.02 mass % of Ti, 0.2 to 2.0 mass % of Cu and 0.05 to 2.0 mass% of Ni, and the remainder of Fe, wherein the components satisfy the following expression (A). $\mathop{\mathrm{image}}$