The Rate and Mechanism of the Silicon Transfer between Molten Slag and Metal

Abstract

Some experiments on the rate oj silica reduction by iron saturated with carbon have been carried out in the range oj 1 550 0 to 1 620°C and the mechanism oj silicon transfer has been considered. The /l resent results are compared with the data already /JUblished by many researchers.The results obtained are as Jollows :(1) The reduction oj silica in a graphite crucible is accelerated by the illcrease oj the area oj slag-grallhite illterface, aluminum addition to metal and the application oj extemal electric potential.(2) The present results together with the results already published by mallY researchers on the silica reduction have been IJUt in order by considering the ratio oj areas oj slag-graphite interface and slag-metal intClface r= S s-aiS S-)I' In the range oj small r values, the rate oj reaction is /Jroportional to the activity oj silica in CaO-Si0 2 binalY slag and the apparent activation energy oj silica reduction is about 90 to 100 kcallmol. I n this condition, silica reductioll is intC1preted to be controlled by chemical reaction in general but diffusion call in some extense affect the rate according to the composition alld trans/Jort jHojlerties such as viscosity oj slag. Oil the contrary, ill the range oj r > 30 the dijJusion stell oj silicate ion in slag is considered to be the limiting step. Furthermore, an electrochemical interpretation to the kinetics oj mullicomponent transfers at the molten slagmetal interJace has been proposed and applied to the present results .The polarization curves oj several elements dissolved in iron , which were evaluated Jrom the free energy oj Jorma tion oj oxides and available electrochemical data, are useJul Jor' the explanation oj the reduction kinetics oj silica.