Experimental Study On Slag Steel Reaction Of Rare Earth Steel In Tundish

In the continuous casting process of 253MA rare-earth heat-resistant steel with high rare-earth content and rare-earth iron-chromium-aluminum alloy with high aluminum and high rare-earth content,more severe slag metal reactions generally occur in tundish.The composition of tundish flux deviates,the performance gradually deteriorates,and crust phenomenon occurs frequently,which seriously deteriorates its service performance and affects the production process.In addition,the content of reducing elements such as rare earth and aluminum in the rare earth heat resistant steel and rare earth iron chromium aluminum alloy is much higher than that of ordinary steel.The mechanism of slag steel reaction in tundish during the continuous casting process of above-mentioned steels have not been analyzed.The behavior and effects of different elements in the steel and different components in the slag remain to be determined during the slag steel reaction process.In this paper,with reference to the composition of rare earth heat-resistant steel and iron-chromium-aluminum alloy contain rare-earth element,the slag steel reaction process in tundish during continuous casting was studied using high temperature simulation experiments.The types of slag steel reaction,the competition of rare earth,aluminum and other components in steel during the reaction process were discussed.At the same time,the changes of the crystalline phase of the tundish flux and the inclusions in the steel during the slag steel reaction were analyzed.Under the experimental conditions employed in this work,the conclusions were as follows:(1)In the low-aluminum(0.03%)system,the slag steel reactions that are Ce and Si in the steel reacted with Al2O3 in the slag,and increasing the amount of Ce can promote the slag steel reaction.In high-aluminum(5%)systems,the slag metal reaction is the reduction of SiO2 in the slag by Al and Ce in the steel.(2)In the high aluminum system,when the Ce content is 0.03%,the reaction between Al in the steel and SiO2 in the slag is dominat,increasing the Al content and suppressing the reactivity of Ce;when Ce content is increased at 0.12%,the reaction process is mainly based on the reduction reaction of Ce in the steel to SiO2 in the slag.(3)The phase of slow-cooling crystals for industrial tundish flux is 4CaO·Al2O3·2SiO2.After the reaction of slag steel reaction,the main crystalline phase in the final slag is changed to rare earth calcium aluminate.(4)In the low aluminum and low rare earth system,as the slag steel reaction proceeds,the inclusions in the steel gradually change from CeAlO3 inclusions to Al2O3 inclusions.In the low aluminum and high rare earth system,as the slag steel reaction proceeds,the inclusions in the steel gradually change from Ce2O3 and Ce2O2S inclusions to CeAlO3 inclusions.In the high-alumina system,the rare earth inclusions in the steel at the end of the slag steel reaction gradually turned into alumina inclusions,and aluminum nitride precipitated in the liquid of the high-alumina system during the solidification process of the molten steel.