熔体过热对AISI 304不锈钢亚快速凝固薄带组织的影响

EFFECT OF MELT SUPERHEATING ON THE SUBRAPIDLY SOLIDIFIED MICROSTRUCTURE OF AISI 304 AUSTENITIC STAINLESS STEEL STRIP

采用水冷铜模薄带铸造方法研究了熔体过热对AISI 304不锈钢亚快速凝固薄带组织的影响.结果表明:AISI 304不锈钢亚快速凝固薄带由外层的胞状奥氏体组织、次外层的柱状铁素体枝晶组织和中心的等轴铁素体枝晶组织组成;随着熔体过热度增加,奥氏体胞晶间距和柱状铁素体二次枝晶间距随之增加,残余铁素体含量亦降低.过热度的增加降低了熔体过冷度和冷却速率,造成薄带凝固组织中枝晶间距的增加和残余铁素体含量的降低.

The effect of melt superheating on the sub-rapidly solidified microstructure of AISI 304 austenitic stainless steel strip cast by water-cooled copper mould casting was investigated. The results show that the solidified microstructures from surface to center of the as-cast strip are cellular austenite, columnar ferrite dendrite and equiaxed ferrite dendrite, respectively. With the increase of superheating, both the primary arm spacing of cellular austenite and the secondary arm spacing of ferrite dendrite raise, while the delta ferrite fraction decreases. As the melt superheating raises, the supercooling of meIt falls, then the cooling rate of melt decreases, resulting in the increase of dendritic arm spacings of austenite and delta ferrite. The decrease of cooling rate also accelerates the transformation from delta ferrite to austenite during the subsequent cooling process after solidification, leading to the reduction of residual delta ferrite fraction.