Study Of Al₂O₃ Dissolution Into Mold Flux For High Manganese High Aluminum Steel

The high manganese high aluminum steel has many excellent properties,for example,high strength,high plasticity,etc.Therefore,it is widely applied to the production process of heat-resistant steel,advanced high-strength steel for auto and other varieties of steel with high value-added.However,a large amount of Al₂O₃ has a tendency to produce during the continuous casting process of high manganese high aluminum steel because there are more Al element with strong reductive.Accordingly,the properties of mold flux will be worsened seriously when Al₂O₃ enters the mold flux and the quality of slab is seriously affected because the mold flux loses its function properly.Therefore,it is very important to study the dissolution of Al₂O₃ dissolution into mold flux for high manganese high aluminum steel and improving the ability of mold flux to absorb Al₂O₃for ensure the main function of mold flux running normally and good quality of slab.In order to clarify the dynamics and dissolution mechanism of Al₂O₃ dissolution into mold flux for high manganese high aluminum steel.The kinetic equations of Al₂O₃ dissolution into mold flux were established,on this basis,the kinetic restrictive link of Al₂O₃dissolution into mold flux for high manganese high aluminum steel were analyzed;the influence of relative linear velocity,temperature,compositions and viscosity on the dissolution rate of Al₂O₃ dissolution into mold flux were studied under the dynamic experiment condition;The dissolution mechanism of Al₂O₃ dissolution into mold flux for high manganese high aluminum steel were studied using the scanning electron microscopy-energy dispersive X-ray spectroscopy（SEM-EDS）method.Through the above research,the following conclusions are obtained:（1）The kinetic restrictive link of Al₂O₃ dissolution into mold flux for high manganese high aluminum steel is the reaction products diffuse from the surface of Al₂O₃ to the concentration boundary layer,the process is in-diffusion;the main factors that affecting the dissolution rate of Al₂O₃ dissolution into mold flux are the diffusion driving force that comes from concentration difference of Al₂O₃ and diffusion coefficient of in-diffusion process.（2）The dissolution rate of Al₂O₃ increased with increasing relative linear velocity when Al₂O₃ into low reactivity mold flux,non reactivity mold flux and high SiO₂ content mold flux;the dissolution rate of Al₂O₃ dissolution into non reactivity mold flux is the highest than low reactivity mold flux and high SiO₂ content mold flux under the same experimental conditions;the reason of the dissolution rate increased with increasing relative linear velocity is that the concentration difference of Al₂O₃ was improved.（3）The dissolution rate of Al₂O₃ increased with increasing temperature（1300℃-1430℃）during the process that Al₂O₃ dissolution into low reactivity mold flux,non reactivity mold flux and high SiO₂ content mold flux;the influence of temperature on the dissolution rate of Al₂O₃ dissolution into mold flux has two aspects:the diffusion coefficient of in-diffusion process increases with increasing the temperature;the concentration difference of Al₂O₃ indirectly increases with increasing the temperature.The activation energy of restrictive link are 150.8kJ·mol^-1 for low reactivity mold flux A-1,156.1kJ·mol^-1 for low reactivity mold flux A-2,131.4kJ·mol^-1 for non reactivity mold flux,162.49kJ·mol^-1 for high SiO₂ content mold flux.（4）The dissolution rate of Al₂O₃ decreases with increasing Al₂O₃ content and viscosity of mold flux;the dissolution rate of Al₂O₃ rises with increasing the（CaO+BaO）/（Al₂O₃+SiO₂）ratio,Li₂O,F^-,B₂O₃ and Na₂O contents,and the order of influence on the dissolution rate was Li₂O>F^->B₂O₃>Na₂O;the influence of compositions and viscosity of mold flux on the dissolution rate of Al₂O₃ is due to they have indirectly changed the concentration difference of Al₂O₃ of the in-diffusion process.After absorbing a certain amount of Al₂O₃,the increase of viscosity of non reactivity mold flux less than low reactivity mold flux and high SiO₂ content mold flux.（5）It is found that there are boundary layer at Al₂O₃–slag interface,and the thickness of transition layer are about 15μm for low reactivity mold flux A-1,9μm for low reactivity mold flux A-2,6μm for non reactivity mold flux and 4μm for high SiO₂ content mold flux;The reaction products at Al₂O₃–slag interface are BaO·6Al₂O₃ and BaO·2CaO·4Al₂O₃ when Al₂O₃ dissolution into low reactivity mold flux,the reaction product is BaO·2CaO·4Al₂O₃ when Al₂O₃ dissolution into non reactive mold flux,and the reaction products are CaO·6Al₂O₃ and 2CaO·Al₂O₃·SiO₂ when Al₂O₃ dissolution into high SiO₂ content mold flux.