SURFACE TREATED STEEL SHEET FOR WELDED CAN, EXCELLENT IN HIGH SPEED WELDABILITY AND LAMINATE ADHESION

摘要

PURPOSE: To produce a surface treated steel sheet for welded cans, excellent in laminate adhesion and high speed weldability and capable of being produced at a relatively low cost. CONSTITUTION: This surface treated steel sheet for welded cans can be produced by dispersively forming granular tin of 0.3-<2.0μm 50% separation average grain size on the surface of a steel sheet by a coating weight of (300 to <800)mg/m<2> per side so that coating rate on the steel sheet surface becomes 5-50% and further forming a chromate layer on the granular tin and on the steel sheet surface uncoated with the granular tin. At this time, the coating weight of the chromate layer on the granular tin is regulated to (4 to 30)mg/m<2> expressed in terms of metallic chromium. Because the steel sheet surface is provided with a conjugated coating structure inwhich a part having the granular tin and a part consisting of the chromate film alone are disposed microscopically alternately, excellent high speed weldability can be obtained by the presence of the granular tin and also superior laminate adhesion can be obtained owing to the chromate film existing in netlike state on the steel sheet surface.