低成本耐腐蚀高强度不锈钢的成分均匀性控制研究

Investigation of Composition Uniformity Control of Low Cost Corrosion Resistant High Strength Stainless Steel

采用Meltflow-VAR模拟仿真手段,研究了真空自耗重熔过程中熔化速率对低成本耐腐蚀高强度不锈钢铸锭熔池形状和宏观偏析的影响规律,熔炼速率从3.2 kg/min增加到6.2 kg/min,金属熔池体积逐渐增加,熔池形貌逐渐由“浅平状”向“U型”再向“深V型”转变;熔炼速率由3.2 kg/min增加到5.2 kg/min,稳态阶段熔池深度由120 mm增加至175 mm,熔速超过5.2 kg/min,熔炼达到稳态所需时间延长,铸锭柱状晶比例增加,合金元素的偏析程度加剧。熔炼速率为4.2 kg/min时,糊状区宽度较窄,稳定熔炼阶段熔池深度为140 mm。对4.2 kg/min熔速下铸锭质量进行评定,该熔速下铸锭不同位置合金成分具有良好的均匀性,低倍组织检测结果显示,铸锭无明显宏观组织缺陷。1220℃均匀化处理4 h后,钢中C、Cr、Ni和Mo的显微偏析得到明显改善。

Melt flow-VAR simulation method was used to study the effect of melting rate on the molten pool shape and macro segregation of low-cost corrosion-resistant high-strength stainless steel ingot during vacuum arc remelting,the morphology of molten pool changed form"shallow flat"to"U-shap",and finally to"deep V-shap",with the increasing of melting rate from 3.2 kg/min to 6.2 kg/min and the metal pool volume was gradually increased.The depth of molten pool increased from 120 mm to 175 mm with increasing the melting rate from 3.2 kg/min to 5.2 kg/min.When the melting rate exceeded 5.2 kg/min,the time to reach steady state was extended,the proportion of ingot cylindrical crystals increased,and the segregation degree of alloying elements was intensified.4.2 kg/min was determined as the actual melting rate,the mushy zone width was narrow,and the molten pool depth was 140 mm in the stable melting stage.The metallurgical quality of the ingot remelted at 4.2 kg/min was evaluated,the alloy compositions at different positions of the ingot at the said melting speed had good uniformity,the result of macrostructure inspection showed that there was no obvious macrostructure defects in the ingot.After homogenization at 1220℃for 4 h,the micro segregation of C,Cr,Ni and Mo elements in the steel was significantly improved.