THE COATING STRUCTURE AND APPLIICATION RESEARCH OF HOT STAMPING GALVANIZED SHEET
Hot-formed galvanized steel is a new kind of hot-formed coated steel after aluminium-silicon coating.It has good corrosion resistance and cathodic protection performance,prevents the surface from scaling and decarburization at high temperature when heating the steel plate,has excellent appearance and stamping performance,and good welding and coating performance.The chemical composition of the zinc-based coating is 99％of Zn,＜1％Al and other impurities.When the coating temperature is less than 600 ℃,the Al and Fe in the substrate forms a Fe2Al5 inhibition layer of about 1 um thickness at the interface between the coating and the iron substrate,preventing the diffusion of Fe atoms in the substrate into the coating;When the coating temperature is 800 ℃,the Al elements in the coating basically migrate to the coating surface,forming a continuous Al2O3 film to prevent the evaporation of Zn.When the coating temperature increases more than 700 ℃,the inhibition layer is destroyed,a large number of Fe elements diffuse into the coating to form Al and Fe compound phases,and the coating thickness increases with the change of coating bulk density.The austenitizing heating temperature,holding time and injection molding temperature of galvanized hot-formed steel have a direct impact on the corrosion resistance of parts and LME prevention and control of liquid phase brittleness of coating.The best process parameters are which with heating temperature 880 ℃,heating time 360 s,injection molding temperature less than 700 ℃.The galvanized hot-formed steel sheet has good welding and coating properties,and has great application prospects in the safety structural parts of automobile body.
hot stampinggalvanized layerinhibition layerdiffusioninjection temperatureliquid phase metal brittleness
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