PRODUCTION OF HOT-DIP PLATED STEEL STRIP EXCELLENT IN WORKABILITY AND PLATING ADHESION AND DEVICE THEREFOR

摘要

PROBLEM TO BE SOLVED: To produce a hot-dip plated steel strip in which the growth of Fe-Zn alloy phases is suppressed in hot-dip plating equipment using an air pot and good in plating adhesion and workability. SOLUTION: In applying hot-dip plating by using an overhead pot in which an opening part for carrying-in steel strips is formed at the bottom wall of the pot and having a nozzle spraying hot-dip plating metal on both faces of the surface and back of a steel strip 1 fed from the opening part for carrying-in steel strips, a plating layer formed on a hot-dip galvanized steel strip 2 pulled out from a plating bath 15 held in the air pot 20 is subjected to X-ray diffraction 42 to detect the growing degree of Fe-Zn alloy phases, the detected alue is compared with the set value, and in the case that the detected value is higher than the set value, the amt. of the hot-dip plating metal to be sprayed on both faces of the surface and back of the steel strip and/or the amt. of Al contained in the hot-dip plating metal to be added is increased.