Fundamental Research On Treatment Of Molten Steel And Steelmaking Slag With Super Gravity

The phase separation rate after chemical reaction is the key factor to decide the metallurgical reaction process,which restricts the metallurgical industry production efficiency.In industry,it is the main mothed to improve metallurgical reaction rate by applying external field to promote phase separation.In this paper,super gravity technology which has the charactristics of enhacing mass transfer and phase separation was introduced and applied into different fields of metallurgy,and the effect of super gravity on the removal of non-metalic inclusion from molten steel,refinement of steel solidification structure and separation of phosphorus and iron riched phase in steelmaking slag was studied.The theoretical calculation shows that the removal time of Al2O3 non-metallic inclusion in the super gravity field is greatly reduced compared with that in the normal gravity field,and the calculation result was verified by experiments.After super gravity treatment,a large number of Al2O3 inclusions were concentrated at the upper part of the specimen.Along the direction of the super gravity,the volume fraction,number density and average size of inclusions showed the gradient distribution,and the slope of gradient distribution increased with the increase of gravity coefficient.Under the conditions of G=80 and t=15 min,the oxygen content at the bottom of the sample decreased from 191.7 ppm to 8.37 ppm,and the removal rate was up to 95.6%.At the same time,the sililar results were obtained for the super gravity separation of SiO2 composite inclusion.After super gravity treatment,a large amount of SiO2 composite inclusion gathered at the upper of the sample,however,due to melting in the liquid steel in high temperature,super gravity had no effect on MnS in the composite inclusions.Actually,such small inclusions could not be completely removed under the conditions of G=80 and t=15 min,but in the process of floating,inclusions collided and grew due to the velocity difference,which accelerated separation efficiency.In this study,the effect of super gravity on solidification structure of Cr12 and T10 was very obvious.As the increase of gravity coefficient,the grain size at the center of the Crl2 and T10 sample decreased gradually,while the tensile strength and elongation at corresponding position increased.In the experiment,wide solidification range of Cr12 and T10 provided enough time to refine the solidification structure.At the same time,super gravity can reduce the nucleation energy and enhanced the melt convection and dendrite scouring,which led to the increase of nucleation particle and grain refinement.In this paper,the phosphorus bearing phase in CaO-SiO2-FetO-MgO-P2O5 simulated slag was successfully enriched at the upper of the sample with self-design resistance heating super gravity device,and there was obvious stratification in the middle of sample.Microscopic analysis showed that the size and volume fraction of phosphorus bearing phase appeared gradient distribution along the direction of super gravity,which could be explained by Stokes equation.After the analysis of X-ray diffraction and X-ray fluorescence,the mineral composition and recovery rate of phosphorus and iron in the stratificated sample were obtained.In order to improve the recovery rate,the separated experiment of phosphorus bearing phase was investigated by super gravity.After super gravity treatment,the phosphorus bearing phase particles precipitating at the experimental temperature were all trapped at the upper of the filter,and the remaining melt flew into the lower crucible to form iron bearing slag.Under the conditions of G=600,T=1623 K and t=20 min,the recovery rates of P2O5 and FetO were 85.02%and 76.67%,respectively.The successful enrichment and separation of phosphorus bearing phase from simulated steelmaking slag provides experimental and theoretical basis for the further enrichment and separation of the actual steelmaking slag with super gravity.After the super gravity treatment of actual steelmaking slag,the phosphorus bearing phase was also successfully enriched in the upper part of the sample,and the iron bearing phases,namely calcium aluminoferrite and RO phase,gathered at the lower part of the sample.After filtration separation of actual steelmaking slag with super gravity,the recovery rates of P2O5 and FetO in the separated samples were significantly improved,and unde the conditions of G=600,T1663K and t=15 min,the corresponding values were 82.2%and 68.5%,respectively.