The cold rolling steel sheet null mass which prevents the material degradation of the weld and the welding thermal effect

摘要

PROBLEM TO BE SOLVED: To provide a steel sheet preventing deterioration in the material of a welded joint without damaging its formability for the purpose of being applied, e.g. to automotive parts requiring the good mechanical properties of a welded joint. ;SOLUTION: This steel sheet prevented from deterioration of the material in the weld zone and heat-affeced zone has a composition containing, by mass, 0.0001 to 0.20% C, 0.01 to 2.5% Si, 0.01 to 3.0% Mn, 0.001 to 0.2% P, 0.0001 to 0.02% S, 0.001 to 0.05% Al, 0.0001 to 0.6% Mg and 0.001 to 0.10% O and also containing Mg-containing oxides and/or sulfides, and the balance Fe with inevitable impurities, and the ratio of the maximum grain size in the weld zone and the heat-affected zone to the average grain size in the base metal is ≤3.0.;COPYRIGHT: (C)2001,JPO