PRECOATED STEEL PLATE EXCELLENT IN HARDNESS AND WORKABILITY AND ITS MANUFACTURE

摘要

PROBLEM TO BE SOLVED: To provide a precoated steel plate with high coat hardness which does not allow the easy generation of a molding flaw and outstanding workability which makes cracks in a coat hardly develop even during harsh forming. SOLUTION: This precoated steel plate has a primer coat and a top coat formed on the surface of a galvanized steel plate which is chemically treated. The top coat is formed by applying a coat composition composed mainly of (A) to (C). (A) is 1-18 wt.% of polyester compound of formula I as a main repeating unit. (B) is 40-90 wt.% of polyol excepting (A).(C) is 9-50 wt.% of curing agent. The primer coat is characterized by that the rupture strength measured in terms of film with a width of 5 mm and a thickness of 8±1μm is 50 kg/cm<2> or more and the rupture elongation is 50% or more.