2-5 Study of Aluminum-Zinc-Silicon Hot-Dip Liquid Causticity and The Alloy Coating Microstructure

摘要

The relationship of thickness loss of normal low- carbon cold-rolled steel sheet in aluminum-zinc- silicon hot dip galvanizing liquid (55% aluminum, 43.4% zinc and 1.6% silicon) at 600°C and dipping time has been studied in this paper. And SEM, microprobe, and X-ray diffractometer were applied to analyze the microstructure, micro-chemical composition and phases of this alloy coating, as well as to the phases of bottom dross which formed in this process. The results showed that the weight losing of steel sheet in the hot liquid and dip time has a close linear relation and the alloy coating was mainly composed of four parts which were rich- aluminum dendrite, aluminum-zinc eutectic between dendrite, needle-like rich-silicon phase and alloy layer between the coating and the steel subsurface. Due to this peculiar microstructure of aluminum-zinc- silicon alloy coating, the coated steel sheet had excellent corrosion and heat resistance.