49MnVS3非调质钢内部缺陷原因分析及控制

ANALYSIS AND CONTROL OF INTERNAL DEFECTS OF 49MnVS3 NON-QUENCHED AND TEMPERED STEEL

利用金相显微镜和电子探针等技术手段,分析了49MnVS3非调质钢内部缺陷的产生原因,并提出了控制措施。结果表明:圆钢内部缺陷为夹渣和异金属夹杂,均含有典型的Na、F等成分,且组织为珠光体+网状渗碳体,与基体的典型珠光体+铁素体存在明显的不同,认为该内部缺陷为冷料和保护渣带入所致。在对接快换生产工艺过程中,由于对接笼设计不当,导致冷料从对接笼掉入钢液中,未完全熔化的冷料形成了异金属组织;同时在对接过程中,由于将保护渣带入,出现了异金属组织与夹保护渣并存的现象。通过优化对接生产工艺,在对接笼底部增加一钢板,使对接过程中冷料不容易掉落进入钢中;同时适当提高首炉过热度至30~45℃,避免对接处冷料未熔化的现象;另外引进自动加渣设备,连续地向结晶器内吹入保护渣,在保护渣上面形成氩气保护层,49MnVS3非调质钢质量得到有效改善。

The causes of internal defects of 49MnVS3 non-quenched and quenched steel were analyzed by metallographic microscopy and electron probe,and control measures were proposed.The results show that the internal defects of round steel are slag inclusions and heterometallic inclusions,both containing typical Na,F and other components,and the structure is pearlite+reticulated cementite,which is obviously different from the typical pearlite+ferrite of the matrix,and it is believed that the internal defect is caused by the introduction of cold material and protective slag.In the process of butt quick change production process,due to improper design of the butt cage,the cold material falls from the butt cage into the molten steel,and the cold material that is not completely melted forms a heterometallic structure;at the same time,in the docking process,due to the introduction of protective slag,the phenomenon of coexistence of heterometallic structure and clamp protective slag occurs.By optimizing the butt production process,a steel plate is added at the bottom of the butt cage to make it difficult for the cold material to fall into the steel during the docking process;at the same time,appropriately increase the superheat of the first furnace to 30~45°C to avoid the phenomenon that the cold material at the butt joint is not melted;in addition,the automatic slagging equipment is introduced to continuously blow the protective slag into the crystallizer,forming an argon protective layer on the protective slag,and the quality of 49MnVS3 non-quenched and quenched steel is effectively improved.