PURPOSE: To improve the corrosion resistance of the titled steel sheet by plating a steel sheet subjected to annealing and temper rolling with nickel to a specified thickness, diffusing the nickel by heat treatment, carrying out tinning to a specified thickness, and melting the resulting tin layers by heating.
CONSTITUTION: The surfaces of a steel sheet subjected to annealing and temper rolling are plated with nickel to 0.001W0.05μm thickness, and the steel sheet is heat treated in a nonoxidizing atmosphere to form diffusion layers of nickel on the surfaces of the steel sheet. Tinning is then carried out to 0.01W0.2μm thickness, and the resulting tin layers are melted by heating to manufacture a surface treated steel sheet for a welded can having improved corrosion resistance and suitability to coating. Chromium oxide films or chemically treated films each consisting of a metallic chromium layer and a chromium oxide layer may be formed on the tin layers by 5W20mg/m2 (expressed in terms of metallic chromium) per one side so as to improve remarkably the corrosion resistance after coating.
KOKADO FUMIO
KAWAMURA KATSUTO
