Research On Evolution Law And Control Of Inclusions In High Carbon Hard Wire Steel LF-CC Process

At present,the large Ca O-Si O₂-Al₂O₃-Mg O composite inclusion in domestic hard wire steel is the main cause of wire fracture.Through the study of the stability and deoxidizing capacity of the refining slag composition of high carbon hard wire steel,as well as different deoxidizing methods,this paper studies the variation rules of the types,quantity and sizes of inclusions in the refining and continuous casting process of high carbon hard wire steel,and the results show that:（1）The slag basicity and C/A（Ca O/Al₂O₃）ratios of 70#steel which is from LF station to soft blowing are increased from 0.7～1.22 and 1.84～6.41 to 2.1～2.93 and4.3～22.5.At the end of soft blowing,the C/A ratio of slag fluctuates greatly.It is mainly because of Al₂O₃ content in slag when it is in LF station is not stable.Al₂O₃content may come from the converter process when ferrosilicon is added.So you need to track the main source of Al₂O₃ in LF station in order to fulfill its slag C/A ratio and the stability control of Al₂O₃ in steel.T[O]content in molten steel increases significantly from pouring 0t to 75t.The increase of oxygen content in molten steel indicates that secondary oxidation of 70#steel exists in the casting process of tundish and the casting protection of tundish needs to be strengthened.（2）In the study of the influence of the refining slag system on inclusions in no.70 steel,it is found that the refining slag system with basicity of 1.5 and Al₂O₃ content of 8%in the slag is most conducive to adsorbing the original Ca O-Si O₂-Al₂O₃-Mg O composite inclusions in no.70 steel,which will not cause new foreign inclusions in the steel;At the same time,it can promote the adsorption capacity of slag to Mg O and other inclusions in 70#steel and improve the deformation capacity of Ca O-Si O₂-Al₂O₃-Mg O composite inclusions.（3）In LF refining process,adding deoxidizer in different batches has a more effective deoxidizing effect.Studies have found that adding deoxidizer during the first power transmission can further reduce the oxygen in the steel during the second power transmission,and reduce the total oxygen content in the refined billet to within the range of 0.0013%～0.0015%.Therefore,the deoxidization method designed as the deoxidizing agent is divided into two stages and added with 1.2kg/t in three batches in each stage,which is the best deoxidizing method.The types and quantities of inclusions found in 70#steel changed,but different deoxidizing methods had little effect on the size of inclusions.