碱度对高TiO_(2)保护渣流动、结晶和结构的影响

Effect of basicity on flow,crystallization and structure of high TiO_(2)-containing mold slags

针对传统保护渣浇注高钛钢时钢渣反应引起TiO_(2)增加和渣变性的问题,采用旋转黏度测量仪、半球点测试仪、FactSage热力学计算、原位观察和拉曼光谱等方法,研究了碱度对高钛钢保护渣流动、结晶行为以及结构的影响,便于通过成分变化对含TiO_(2)保护渣的性能进行调控。研究表明,当保护渣(TiO_(2)质量分数为8%)的碱度由0.6增加到1.2,其1300℃的黏度由0.33 Pa·s降低至0.21 Pa·s,保护渣的熔化温度由1111℃增加至1161℃,这是由于受熔渣结构和结晶相析出双重作用的影响;保护渣的转折温度则由1128℃升高为1264℃。随着碱度的增加,热力学计算析出的CaTiO_(3)晶体比例逐渐增大,同时XRD衍射峰强度有明显的增强。在熔渣微观结构方面,随着碱度的增加,熔渣中简单结构单元Al-O^(-)和Q^(0)、Q^(1)增加,复杂结构单元Q^(2)和Q^(3)等减少,熔渣整体的聚合度及复杂程度呈下降趋势,这与黏度的变化一致。综合来看,碱度增加会引起保护渣的黏度降低、熔点升高、结晶性能增强,合理控制保护渣的碱度可以优化其基础性能,有利于高钛钢连铸过程的稳定。

In order to solve the problem for the increase of TiO_(2)content and the variation of slag property caused by steel-slag reaction when traditional mold slag was used to cast high-titanium steel,the effect of basicity on the flow,crystallization and structure characteristics of mold slag for high-titanium steel was studied by means of rotational viscometer,hemispherical point method,thermodynamic calculation by FactSage software,Raman spectroscopy and in-situ observation,so as to regulate the performance of TiO_(2)-containing mold slag through the adjustment of slag composition.Results show that when the basicity of mold slag(with TiO_(2)mass fraction of 8%)increases from 0.6 to 1.2,the viscosity at 1300℃has the tendency to decrease from 0.33 Pa·s to 0.21 Pa·s,the melting temperature of mold slag increases from 1111℃to 1161℃,which is related to the slag structure and the precipitation of crystallization phases.With the increase of basicity from 0.6 to 1.2,the break temperature of mold slag gradually increases from 1128℃to 1264℃,the proportion of precipitated CaTiO_(3)crystals gradually increases with the increase of basicity,and the intensity of XRD diffraction peak is significantly enhanced.In terms of the slag microstructure,with the increase of basicity,the number of simple structural units Al-O^(-)and Q^(0),Q^(1)in the slag increases,the number of complex structural units Q^(2)and Q^(3)decreases,and the overall polymerization degree and complexity of the slag show a downward trend,which has the same variation of the viscosity.On the whole,increase of basicity will lead the slag viscosity to decrease,melting point to increase and crystallization property to increase,therefore,reasonable control of mold slag basicity can optimize its basic properties,which is conducive to continuous casting process stability of high-titanium steel.