AFTER-TREATMENT OF STEEL SHEET COATED WITH ALUMINUM BY HOT DIPPING

摘要

PURPOSE:To enhance the corrosion and weather resistances of a steel sheet coated with Si-contg. Al by hot dipping by heat treating the sheet to spheroidize Si particles in the hot dipped Al layer. CONSTITUTION:A steel sheet coated with Al by hot dipping with a bath usually contg. 4-11% Si is heat treated at 500-570 deg.C. As a result, the form of eutectic part Si particles is converted from the needlelike form into coarse spheroidal form to reduce the surface area of the Si particles and increase the distance between the particles, whereby the corrosion of the hot dipped layer is made hard to occur and proceed. By the heat treatment the weather and corrosion resistances of the sheet are enhanced considerably.