CaO-SiO_2-Al_2O_3渣系连铸保护渣结构的拉曼光谱研究

在高铝钢连铸过程中,钢水中的Al与CaO-SiO2基连铸保护渣中的SiO2反应导致保护渣中SiO2含量降低而Al2O3含量大幅增加,CaO-SiO2基转变为CaO-SiO2-Al2O3基连铸保护渣而影响高铝钢连铸,所以研究CaO-SiO2基向CaO-SiO2-Al2O3基保护渣转变过程中结构上发生的变化有助于开发出满足高铝钢连铸需求的保护渣。本文利用拉曼光谱研究了CaO-SiO2基和CaO-SiO2-Al2O3基连铸保护渣的结构特点。研究结果表明,CaO-SiO2基保护渣主要由Q0,Q1,Q2和Q3等微结构单元构成的硅酸盐网络结构;当转变为CaO-SiO2-Al2O3基保护渣后,渣样中的网络破坏体优先用于破坏硅酸盐网络结构,当渣中SiO2含量较低时,部分网络破坏体会促进Al 3+形成AlO4]四面体结构。渣中生成的AlO4]四面体会进入硅酸盐网络结构形成铝硅酸盐网络结构,以Al-O-Al或Al-O-Si等方式连接,导致渣样结构变得复杂多变。使用Li2O对Na2O和CaO对MgO等摩尔替代研究表明相同价态离子之间的替换能够改变AlO4]四面体在硅酸盐网络结构上的连接方式,导致CaO-SiO2-Al2O3基保护渣渣样结构易受成分变化而改变;CaF2对CaO等摩尔替代研究发现,当渣中CaF2小于13mol%,CaF2促进渣样网络结构解体,当高于13mol%时,CaF2又会导致渣样聚合度增加。由此可见,在设计CaO-SiO2-Al2O3基保护渣时,既要考虑不同种类离子对渣样结构产生的影响,又要考虑离子含量的影响。

Raman Spectroscopic Study of the Structure of CaO-SiO2-Al2 O3-Based Flux

Due to the Al]reaction with the CaO-SiO2-based mold flux used in the high-Al steels continuous casting processes, decreasing the SiO2 content is decreased and the Al2 O3 content in mold flux is increased,thus converting the original CaO-SiO2-based mold flux into a CaO-SiO2-Al2 O3-based mold flux.This conversion of the mold fluxes can cause the problem of high-Al steels continuous casting.Hence,study on the structural characteristics of the CaO-SiO2-Al2 O3-based mold flux can provide fundamental data to design optimum fluxes for high Al-containing steels.In this paper,the structural characteristics of the CaO-SiO2-based and CaO-SiO2-Al2 O3-based flux were studied by Raman spectroscopy.The results have shown that,the CaO-SiO2-based flux was the silicate structure whose main micro-structure units were Q0 ,Q1 ,Q2 and Q3 .The network breakers prefer to depolymerize the silicate network in CaO-SiO2-Al2 O3-based flux.While the CaO-SiO2-Al2 O3-based flux with low SiO2 content, the AlO4 ]tetrahedron was entered the silicate network and the melt converted into the aluminosilicates structure,the formation of Al-O-Al linkages and Si-O-Al linkages increased the degree of disorder of network.The results of Li2 O replace Na2 O and CaO replace MgO have shown that the ions will influence the formation of AlO4 ]tetrahedron linkages.CaF2 replace CaO shown that the polymerization degree of mold slag decreased first,and then increased with the content of CaF2 more than 1 3 mol%.So,the influences of the ions type and the ions content on the structure were both need considered while designing the CaO-SiO2-Al2 O3-based flux.