Al_(2)O_(3)对超高碱度连铸保护渣理化性能的影响

Effect of Al_(2)O_(3)on the physical and chemical properties of ultrahigh-basicity continuous casting mold flux

Al_(2)O_(3)是一种两性氧化物,在高碱度条件下呈现酸性氧化物特征,而在低碱度条件下表现出碱性氧化物的行为,是冶金熔渣中常见的一种组元.以超高碱度保护渣(综合碱度R=1.75)为研究对象,分析了Al_(2)O_(3)对保护渣流动特性、熔化特性和凝固特性的影响规律.研究结果显示:渣中Al_(2)O_(3)质量分数每增加1%,熔化温度上升5℃左右,转折温度下降12℃左右,开始结晶温度平均下降11℃左右.平均结晶速率随渣中Al_(2)O_(3)质量分数的增加而减小.且随着Al_(2)O_(3)质量分数的增加,保护渣结晶矿相中晶体比例逐渐降低,但晶体保持枪晶石的种类不变.

Aluminum oxide is a common component in mold powder and is a kind of amphoteric oxide.It shows the characteristics of acid oxide under high-alkalinity conditions and of alkaline oxide under low-alkalinity conditions.In general,adding Al_(2)O_(3)to the traditional CaO-SiO_(2)-based mold flux will increase the viscosity and melting point of the mold flux,which will consequently reduce the mold flux’s ability to adsorb inclusions.In addition,as the content of Al_(2)O_(3)in the slag increases,the solidification temperature of the slag can be reduced,thereby improving the lubricating ability of the mold flux.At present,the research on the crystallization performance of Al_(2)O_(3)on mold fluxes mainly focuses on low-reactivity or non-reactive mold fluxes for high-aluminum steel and high-titanium steel.Relevant studies have shown that Al_(2)O_(3)in low-reactivity or non-reactive mold fluxes can increase the crystallization incubation time of the mold flux,reduce the critical cooling rate of the flux,and inhibit the crystallization process of the flux.In mold powder with low to medium alkalinity content(R=1.2-1.5)or new CaO-Al_(2)O_(3)-based low-reactivity mold powder,the addition of Al_(2)O_(3)will increase the viscosity of the slag and melting point and decrease(or increase)the solidification temperature and crystallization performance.In recent years,ultrahigh-alkalinity mold powder(R=1.65-1.85)has been successfully applied in peritectic steel continuous casting mold powder,effectively coordinating the contradiction between the mold powder heat transfer and lubrication function.However,there is no relevant report on the influence of Al_(2)O_(3)on the performance of mold flux under ultrahigh-alkalinity conditions.In this study,an ultra-high-alkalinity mold flux(comprehensive alkalinity R=1.75)is taken as the research object,and the influence of Al_(2)O_(3)on the flow,melting,and solidification characteristics of the mold flux is analyzed.The research results show that as Al_(2)O_(3)increases,the viscosity and melting temperature increase,and the transition temperature decreases.Particularly,with an average increase of 1%Al_(2)O_(3),the melting temperature of the mold flux will increase by approximately 5℃,and the turning temperature will decrease by approximately 12℃.In addition,as the Al_(2)O_(3)content in the slag increases by 1%,the starting crystallization temperature drops by approximately 11℃on average.The average crystallization rate decreases with the increase in Al_(2)O_(3)in the slag,and Al_(2)O_(3)has a significant effect on the crystallization rate.Moreover,with the increase in the content of Al_(2)O_(3)in the slag,the proportion of crystals in the crystalline phase of the mold slag gradually decreases,but the type of crystals remains unchanged.