Research On Special Slag And Deoxidation Process For Electroslag Remelting Of 316H Large Slab Ingot

The electroslag remelting(ESR)process and experimental equipments are relatively simple.The steel ingots produced by ESR are relatively pure and contain fewer inclusions.They have dense internal structure and good surface quality.However,when the ingots with lowhydrogen and low-oxygen are remelted,the hydrogen content and oxygen content in steel tend to increase,and there exist the phenomenon of uneven distribution of easily oxidezable elements along the axial direction of the ingots.At present,one steel plant uses ANF-6 to produce 316H stainless steel,the mass fractions of hydrogen and oxygen exceed the standard,and the oxidizable elements burn out.Therefore,this subject has carried out the research on slag system for electroslag remelting 316H large slab ingot.Firstly,this paper compared melting point,viscosity,density and conductivity of different slags.Then the hydrogen permeability test was performed.Under the conditions of no deoxidation,deoxidation with pure silicon-calcium powder,deoxidation with pure aluminum particles,and composite deoxidants,slag-metal balance experiments were made.The mass fractions of oxygen and burnable elements were analyzed,and the mass fractions of oxides in the slag were also tested.Finally,the best slag system and deoxidizer were applied to the industrial test.The following conclusions were achieved through the above experiments.(1)The higher melting point of S5 slag is not conducive to production of 316H stainless steel.(2)The hydrogen permeability of S5 slag is lowest,reaching 1.89 mol·cm-1·min-1,and the hydrogen permeability of S4 slag also reaches 2.18 mol·cm-1·min-1,both of which are less than the original S1 slag,so they are suitable for electroslag remelting 316H.(3)Under conditions of no deoxidation,deoxidation with pure silicon-calcium powder,deoxidation with pure aluminum particles,and composite deoxidants,the slag-metal balance experiments were performed on S1,S2 and S4 slag systems.The results show that S4 slag shows a better effect on preventing burnout of easily oxidizable elements in steel,and the easily oxidizable elements in steel are more stable.Compared with the two deoxidation methods of pure silicon-calcium powder deoxidation and pure aluminum particle deoxidation,the deoxidation effect of composite deoxidation is more obvious,which can effectively reduce the burning loss of aluminum and silicon elements in steel.(4)The application of S4 slag and composite deoxidizer in industrial test shows that the hydrogen content of the steel ingot is less than 2×10-6.The mass fractions of O,Al and Si in the steel ingots meet the production requirements.There is no obvious burnout phenomenon of Al and Si in the steel.The distribution is more uniform along the axial direction.