Effect Of Rare Earth Element On Molten Aluminum Wetting To Steel Sheet

Hot-dip aluminizing rolled steel products is provided with series prominent advantages in technical performance and economic effect comparing with other rolled steel protective technologies and measures. However, hot-dip aluminizing also has some intrinsic limitations and disadvantages, for instance, there are often pinhole and leakage of hot-dip aluminizing decreasing erosion resisting performance of plating layer in aluminum plating process. The objective of this experiment is to find some alloy elements capable of enhancing aluminum liquid wetting property to steel sheet through adding different alloy elements to aluminum liquid and research on its effect on wetting property. By adding some alloy elements able to enhancing aluminum liquid wetting property to steel sheet to aluminum liquid, not only pinhole and leakage of hot-dip aluminizing are reduced, but also plating layer performance is more superior.This thesis selects alloy to be added through measuring spreading area size of molten aluminum on steel sheet. At first, four aluminum alloys, namely Al-Zn,Al-Mn,Al-Re and Al-Mg, are smelted. Five ingredients are smelted in each alloy, with a smelting temperature of 760℃. Then the alloy is poured into cylinder sample and processed to (?)10×2 mm sample by machine. Do spreading experiment under adopting analog hot-dip condition (put steel sheet in fused-salt solution) in stainless steel pot, with a spreading temperature of 740℃and a spreading temperature of 10 minutes. The four alloys can enhance molten aluminum wetting property by measuring and comparing spreading area and the spreading area of aluminum alloy adding 0.2% rare earth is the largest.This thesis studies rare earth's effect on hot-dip aluminizing workpiece through hot-dip aluminizing rare earth aluminum alloy of different content. Main experiments are as follow: Observe microstructure with 4XC series metallographic microscope, do composition analysis with stereoscan, observe rare earth's effect on molten aluminum non-oxidizability and surface quality of aluminum plated sample, examine plating layer continuity through dilute nitric acid immersion test, and examine plating layer erosion resistance through salt water (3%NaCl solution) immersion test. The result is that the accession of rare earth can reduce plating layer surface layer thickness and make male and female face appear on alloy layer and body, but it has little effect on alloy layer thickness. This thesis learns the rare earth really diffuses to the inside of plating layer. This thesis also discovers rare earth enrichment phenomenon appears when the amount of rare earth is 0.3%, and the phenomenon is clearer when increasing rare earth accession. Oxidation degree of aluminum alloy liquid is alleviated when adding right amount of rare earth to aluminum liquid; when the amount of rare earth is 0.2～0.3%, pin hole and leakage of hot-dip aluminizing are effectively reduced; when the amount of Re is 0.1～0.3%, erosion resisting effect of sample is very evident. This thesis also analyzed and discussed rare earth's effect on molten Aluminum wetting to Steel Sheet plating and rare earth enhancing plating layer erosion resisting mechanics.