钢板连续热浸镀铝硅镀层的微观结构和冷成形性能

Microstructure and Cold Formability of Continuous Hot-dip Aluminum-silicon Coating on Steel Sheet

采用连续热浸镀工艺和成分为Al-10%Si(质量分数)的镀液在0.8 mm厚的冷轧低碳钢板上制备铝-硅涂层。检测了连续热浸镀铝硅镀层的形貌、元素分布、微观结构和相成分。研究了钢板浸入渡槽的温度(640~710℃)对镀层组织和冷成形时开裂倾向的影响,并分析了涂层开裂的原因。结果表明:钢板浸入渡槽的温度对热浸镀铝硅镀层的组织和冷成形过程中镀层开裂的倾向有显著影响;钢板冷成形时,铝-硅涂层的裂纹产生在粗大的富硅相处;浸入640℃渡槽的钢板涂层中粗大富硅相贯穿了铝-硅涂层,且随着钢板浸入渡槽的温度的提高,富硅相更为弥散和细小,这有利于提高镀层性能,减小镀层的开裂倾向。

Aluminum-silicon coating was fabricated on cold-rolled low-carbon steel sheet 0.8 mm thick by a continuous hot-dip technology in molten aluminum with 10%Si by mass.The morphology,element distribution,microstructure and phase composition of the continuous hot-dip aluminum-silicon coating were detected.The effect of temperatures ranging from 640 to 710℃at which the sheet was dipped into coating bath on microstructure of the coating and its tendency to crack during cold forming was investigated,and the cause for the coating cracking during cold forming was studied.The results showed that(a)the temperature at which the sheet was dipped into coating bath had significant influence on microstructure of the coating and its tendency to crack during cold forming;(b)crack emanated from coarse silicon-rich phases in cold forming;and(c)the coarse silicon-rich phases ran through the aluminum-silicon coating on the sheet dipped into the coating bath at 640℃,and as the temperature of coating bath at the time of the sheet being dipped into it increased,the silicon-rich phases became more disperse and finer,which is advantageous to the improvement in performance of the coating and to the decrease in tendency of the coating to crack.