Research And Application On Inclusion Control Technologies For 45# Automobile Steel

With the rapid development of social economics,automobiles are used widely in many families and become a necessary part of people's daily life.But inclusions in steel will weaken the mechanical properties of automobile parts,even induce traffic accidents in the process of driving,which seriously threaten personal safety.Thuse,the formation process of inclusions in 45#automobile steel was studied in order to reduce the inclusions in automobile steel and improve the quality of automobile steel.In this paper,the effects of deoxidation process and slag composition on inclusion formation are analyzed,and the rule about inclusion removal in the refining process is studied by tracer experiment,premelted slag experiment and ladle water model experiment.The following conclusions are obtained:(1)Compared with the deoxidation technology "adding silicon manganese after adding aluminum",the deoxidation technology "adding silicon manganese before adding aluminum"has the better deoxidation effect and forms smaller inclusions.(2)The reasonable chemical components of the quaternary slag system are w(CaO)=38%-48%,w(Al2O3)=14%-24%,w(SiO2)<15%,w(MgO)=5%-8%.(3)To control the peroxidation degree of liquid steel and ensure the tapping temperature,can shorten the time to form white slag in refining process.To extend the time of keeping white slag and soft blowing properly,and control the thickness of the covering agent reasonably can control the inclusion number.(4)After the premelted slag is applied in the LF refining process,A type,B type,C type and D type inclusions decreases with the smelting process.(5)Under different process parameters,the critical penetration height of the vortex is less than 41mm in the ladle water model,and the related critical penetration height of the vortex is less than 123mm in the industrial ladle.Before the ladle vortex penetrates the melting bath,the half opening for nozzle can weaken the vortex and keep the smaller vortex for a long time.After a new masonry technology is applied in the 40 ton ladle,the residue steel is less than 900 kg in the ladle.(4)In LF refining with premelting slag,high level inclusions of A,B,C and D in steel show decreasing trend with smelting process.The level of Ds inclusion is the highest in the refining process and decreases gradually with the refining process.The inclusion content reaches a lower level before the vacuum treatment.And the inclusion content begins to increase after the vacuum treatment.However,the Ds inclusions keep decreasing after the soft blowing process,the Ds inclusions reached the lowest value again in the runner,the average value level less than 1.(5)Under different technological conditions,the penetration height of ladle vortex is less than 41mm,and the corresponding height of field ladle vortex is less than 123mm.When the ladle vortex is about to be connected,the half-open nozzle can make the vortex smaller for a long time.And when the liquid level is close to the nozzle,it still maintains the same shape and is not connected.The surplus steel in the ladle can be controlled at 900 kg,when masonry technology is applied in the 40 ton steel ladle bottom.(6)These measures(A12O3 mass fraction is 36%-38%in refining slag,the calcium treatment is cancelled,CaO mass fraction decreased in the slag,aluminum mass fraction takes the lower or middle limit in the molten steel before VD vacuum treatment)can avoid the occurrence of slag entrapment during VD vacuum treatment and reduce Al2O3 inclusion mass fraction in the steel.