After administering spelter or spelter alloy plating

摘要

PROBLEM TO BE SOLVED: To provide a method for preventing the occurrence of cracking and powdering of a film formed by a non-chromium treating liquid in subjecting a zinc system plated steel sheet to post treatment by using the non-chromium treating liquid.;SOLUTION: A non-chromium treated film including at least either of an oxide or hydroxide of a valve metal and a fluoride is formed on a front surface of a zinc system plated steel strip 11 subjected to zinc or zinc alloy plating and is subjected to drying and baking treatment by heating the steel strip in such a manner that the ultimate warm-up temperature of the zinc system plated steel strip 11 formed with the non-chromium treated film attains 100 to 140°C or the warm-up rate attains 2 to 9°C/sec. Thereby the thermal stress generated between the film and the plating layer at the time of the drying and baking treatment is suppressed and the reaction time of the film and the plating layer is sufficiently assured and therefore the defectless non-chromium treated film which does not give rise to the cracking and powdering can be obtained.;COPYRIGHT: (C)2005,JPO&NCIPI