STEEL SHEET COATED WITH AL-SI BY HOT DIPPING AND HAVING HIGH CORROSION RESISTANCE

摘要

PURPOSE:To reduce pinholes and to improve the corrosion and heat resistances and workability by successively forming an Al-Fe-Si-Ni-Cr alloy layer having a specified composition and a coating layer of an Al-Si alloy on the surface of steel. CONSTITUTION:An Al-Fe-Si-Ni-Cr alloy layer contg. 0.2-30% Ni and 0.2-10% Cr is formed on the surface of steel to 1-7mum thickness. A coating layer of an Al-Si alloy is formed on the surface of the alloy layer to 3-40mum thickness. Thus, the corrosion and heat resistances, workability and other characteristics of a steel sheet coated with Al-Si by hot dipping are improved. More significant effects are produced by interposing an Ni-Fe diffusion layer having 50% average conc. of Ni between the surface of the steel and the Al-Fe-Se-Ni-Cr alloy layer. The thickness of the diffusion layer is =2mum.