Evolution Of Interfacial Tension Of Molten Steel And Slag During Temperature Variation

The interfacial tension of slag-steel in the mould has great influence on the slag entrapment,the meniscus shape and associated behavior of oscillation marks formation and inflow behavior of mould flux,further effect the cleanness and the surface quality of the billet or slab.It exists a continuous temperature variation process on slag-metal interface in the mould.The investigation of the transition of the slag-steel interfacial tension with the variation of temperature is very significant for the analysis of the complex slag-steel interfacial behavior in the mould and the improvement of the billet/slab quality.To obtain the surface tension of mould flux and molten steel,a calculation program was developed based on the sessile drop method combined with digital image processing and curve fitting technology.Verification experimental result showed that,the degree of accuracy and stability are enough for the surface tension calculation.Using the developed program,the surface tension of some typical steels and corresponding mould fluxes were measured.Results showed that,Above the liquidus temperature,the surface tension of Q235B steel and SPHC steel increases with the increase of temperature,while the surface tension of X70 steel,Q195L steel and DQ2J steel decreases with the increase of temperature.The variation amplitude of the surface tension of Q235B steel,SPHC steel,X70 steel and Q195L steel are smaller as 100mN·m-1?33mN·m-1?81mN·M-1 and 39mN·m-1 respectively,while the amplitude of the surface tension of DQ2J steel is bigger as 1350mN·m-1.Especially,the surface tension of the steels decrease in different degree with the temperature decreasing between the liquidus and solidus temperature.The surface tension of the mould fluxes decrease gradually with the temperature increasing.Between the temperature of 1100? and 1400?,the variation amplitude of the surface tension is 100-200 mN·m-1.The interfacial tension coefficient of slag-steel was estimated according with the chemical composition of the mould flux.Based on the results of surface tension measurement,the interfacial tension of molten slag-steel was calculated.The interfacial tension of slag-steel depends mainly on the surface tension of the steel,and the variation trend is consistent with the steel surface tension,but the variation amplitude is some degree decreased.