Workability-weld heat-affected zone toughness high corrosion resistance hot-rolled steel sheet and its manufacturing method with excellent resistance

摘要

PROBLEM TO BE SOLVED: To provide a highly corrosion resistant hot rolled steel sheet having excellent workability/weld zone toughness, and to provide a method for producing the same.;SOLUTION: The highly corrosion resistant hot rolled steel sheet having excellent workability/weld zone toughness has a composition comprising, by mass, 0.02 to 0.1% C, 0.01 to 2.0% Si, 1.5 to 4% Mn, ≤0.03% P, ≤0.01% S, 5 to 9% Cr, 0.1 to 2.0% Al and ≤0.02% N, and in which the fraction of martensite in a microstructure after continuous hot rolling is ≤70%. The highly corrosion resistant hot rolled steel sheet can be produced by a method where a steel ingot is hot-rolled after heating, is coiled at ≥800°C after the rolling, and is thereafter air-cooled to room temperature, or a method where a steel ingot is hot-rolled after heating, is coiled, is subsequently cooled to room temperature, is thereafter heated to an Ac₁ point or lower, and is cooled to room temperature.;COPYRIGHT: (C)2006,JPO&NCIPI