裂纹敏感性钢不同板坯工艺的渣膜矿相特征

Characteristics of Flux Film Mineralogical Structure in Different Slab Processes for Crack Sensitive Steel

针对包晶钢、中碳钢2种裂纹敏感性钢的特点,采集薄、厚板坯连铸工艺的渣膜及对应保护渣,利用偏光显微镜、X射线衍射仪等手段,系统对比分析不同板坯类型的渣膜矿相结构。研究结果表明:薄、厚板坯连铸保护渣渣膜均呈"玻璃层—结晶层"交替结构,结晶矿物主要是黄长石、枪晶石及少量硅灰石。包晶钢厚板坯渣膜的晶体发育程度高,多呈二层结构,结晶率高达90%,黄长石含量占80%左右;中碳钢厚板坯渣膜结晶率仅有50%左右,枪晶石含量为25%。而对薄板坯研究发现,包晶钢渣膜的晶体粒度却较小,结构多呈3层,结晶率约为85%;中碳钢渣膜的突出特点是结晶率低至60%,枪晶石含量却达到35%。对于裂纹敏感性钢,厚板坯渣膜的高析晶率特点益于控制传热;薄板坯渣膜结晶率低、枪晶石矿物多,适宜润滑同时减缓散热,减少裂纹发生。

On the issue of the cracked sensitive steel cracking,flux film and corresponding slag which were produced in thin and thick slab processes for crack sensitive steel were collected,the flux film structure of different slab processes was analyzed by means of polarizing microscope and X-ray diffractometer.The results showed that,the microstructures of flux film in thin slab and thick slab continuous casting for crack sensitive steel were layereduniformly.The flux was layered glass layer to crystallizing layer from slab to mold.The main phases of flux films are melilite,cuspidine and little wollastonite.The crystalline development degree of flux film for thick slab is high,mostly the flux film structure is two layers.The crystallization rate of peritectic steel slag film for thick slabis up to 90%,the melilite is 80%.And the crystallization rate of medium carbon steel slag film is about 50%,the cuspidine is about 25%.Variously,crystal size of thin slab is small,mostly the flux film structure is three layers.Its crystallization rate of peritectic steel slag film is about 85%,the melilite is 50%,and which of medium carbon steel is up to 60%,the cuspidine is 35%.For crack-susceptible steels,the high crystallization rate of thick slab slag film is beneficial to controlling heat transfer.The film of thin slab has low crystallization rate and much cuspidine,which is suitable for lubrication,thermal transmission and the prevention of slab crack.