二氧化硅微粉结合MgO-SiC复合材料的渣蚀机理

Study on slag resistance of MgO-SiC composites bonded by microsilica

采用静态坩埚法研究了多次加渣对SiO2微粉结合MgO -SiC复合材料的渣蚀机理 ,并借助X射线衍射仪和扫描电镜对材料在渣蚀过程中的物相变化和显微结构进行了观察和分析。结果发现 ,在第一、二次渣侵蚀试验中 ,渣对MgO -SiC复合材料的渗透与侵蚀较严重 ,但随后迅速减轻。分析认为 :MgO -SiC复合材料中SiC的氧化 ,促进了M2 S的生成 ,产生了体积膨胀 ,阻塞了材料中的气孔 ,抑制了渣的渗透 ;SiC氧化生成的SiO2 与MgO溶入渣中 ,使渣中的SiO2 与MgO含量增加 ,提高了渣的粘度 ,起到抑制渣渗透的作用 ,同时也减弱了M2 S与MgO向渣中的进一步溶解 。

The crucibles with internal hole of 25mm in diameter and height of 40 mm were made of batch mixture consisting of SiC 25%,MgO 70% and microsilia 5%.About 30 g slag with CaO/SiO 2 mass ratio of 0.94 were put into the crucibles and heated at 1500 ℃ for 3 h.The crucibles were divided into three groups.The first group was added slag and heated once, the second group was added slag and heated twice,and the third group was added slag and heated five times.The specimens corroded were examined by X-Ray and SEM.It was found that in first group the penetration of slag was serious,but the corrosion of slag was less.During secondary heating,the penetration of slag in second group was weakened,but the corrosion became serious.In the specimens of third group,the increasing of penetration index and corrosion index were small from two heats to five heats.And these two indeces were almost the same after five heats.The reasons are that the expansion resulting from forsterite formation by reaction between MgO and SiO 2 produced by oxidation of SiC closes the pores in the specimen and inhibit slag penetration.As well dissolution of MgO and SiO 2 into slag,increases viscosity of slag and inhibits slag penetration.