高铝钢连铸保护渣研究进展

Research progress of mold fluxes for high-Al steel

由于连铸相对于模铸在能耗、效率和成本等方面具有优势,近年来,各种铝质量分数为0.5%~3%甚至高达5%~12%的低密度高铝钢相继采用或计划采用连铸生产,然而高铝钢连铸结晶器内存在的渣-金反应[Al]+(SiO_(2))→[Si]+(Al_(2)O_(3))引起保护渣成分和性能变化,妨碍了保护渣正常发挥润滑和控制传热的冶金功能,导致凹陷、裂纹等铸坯表面质量问题以及漏钢等生产事故频发,成为影响高铝钢连浇的主要限制性环节。为保证铸坯表面质量和连铸过程的顺行,除提高钢水洁净度外,减弱因渣-金反应所引起的保护渣性能的大幅变化是高铝钢连铸的必然要求。为此,国内外研究人员以减弱渣-金反应性或稳定渣-金反应后性能为目标,进行了各种尝试和探索。首先提出了可促进熔渣快速更新的低碱度低黏度保护渣技术思路,但当钢中铝质量分数较高时,随着反应进行,保护渣黏度逐渐增大,消耗量降低,难以维持保护渣性能的相对稳定,实际生产过程中铸坯表面质量问题突出,黏结频发,无法稳定实现多炉连浇。为此,低反应性和非反应性连铸保护渣应运而生,成为高铝钢连铸保护渣研究热点。在渣-金反应性综述的基础上,重点介绍了高碱性高玻璃化、CaO-SiO_(2)基高反应性、CaO-SiO_(2)-Al_(2)O_(3)基低反应性和CaO-Al_(2)O_(3)基非反应性等保护渣的特点及其研究进展和存在的问题,并提出了高铝钢连铸保护渣今后研究重点和发展方向。

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]+(SiO_(2))→[Si]+(Al2O3))can change the composition and properties of mold flux,which prevents the normal functions of lubrication of billet and control of heat transfer.As a result,the billet surface quality such as depression and crack and the production accidents such as bonding and 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 billet 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 hindered by frequent billet 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 filed of mold flux for high-Al steel.This paper reviews the characteristics and research progress of high basicity and high glassy mold flux,CaO-SiO_(2)-based high reactivity mold flux,CaO-SiO_(2)-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.