Research progress of mold fluxes for high-Al steel
Continuous casting shows an advantage in energy saving,cost and scale in comparison with mold casting,and the continuous casting production of various kinds of low-density high-Al steels with aluminum content from 0.5%-3%or even up to 5%-12%have been implemented or planned in recent years.However,the reaction of high-Al steel with mold flux(i.e.[Al]+(SiO2)→[Si]+(Al2O3))can change the composition and properties of mold flux,which prevents the normal functions of lubrication of casting strand and control of heat transfer.As a result,the casting strand surface quality such as depression and crack and the production accidents such as sticking breakout occur frequently,and this is the main bottleneck and limiting step of continuous casting of high-Al steel.In order to improve the surface quality of casting strand and assure the smoothness of continuous casting process,it is the inexorable requirement for the continuous casting of high-Al steel to weaken the change range of flux properties caused by slag-steel reaction.Therefore,lots of attempt and exploration have been taken by the researchers at home and abroad,and different technological ideas and realizing approaches have been put forward.The low basicity and low viscosity mold flux is first proposed to realize the rapid renewal of flux composition.However,the viscosity of flux will increase gradually and the consumption of flux will decrease in the process of reaction.Consequently,it is hard to maintain the relative stability of flux properties,and the industrialization of the continuous casting can be hin-dered by frequent casting strand surface quality and sticking breakout.Thus,low reactivity and non-reactive flux emerges as the times require,and it becomes a research hotspot in the field of mold flux for high-Al steel.This paper reviews the characteristics and research progress of high basicity and high glassy mold flux,CaO-SiO2-based high reactivity mold flux,CaO-SiO2-Al2O3-based low reactivity mold flux and CaO-Al2O3-based non-reactive mold flux,and the research emphasis and development direction of mold flux for high-Al steel in the future is also put forward.
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