MgO对连铸保护渣的结构和结晶矿相微观形貌的影响

Effect of MgO on Microstructure and Crystalline Morphology of Mold Fluxes in Continuous Casting

研究了MgO的含量对保护渣的结构和析晶行为的影响,并分析了晶相的种类、含量和形貌对热导率的影响。利用DSC测量了保护渣的析晶温度,表明析晶温度随MgO含量的增加而降低,在841℃位置的析晶峰强度随MgO的含量增加而降低。通过FT-IR和Raman光谱分析发现保护渣网络聚合程度随MgO的增加而降低。XRD结果表明保护渣在不同温度下析出的主晶相为镁黄长石,其含量随MgO含量的增加而降低,次晶相主要为镁橄榄石且其含量随MgO的增加而增加。同时也发现随热处理温度的提高镁橄榄石的含量也在不断增加,但是镁黄长石的含量随热处理温度提高而降低。此外,还有氟晶云母相和钾霞石相也存在于保护渣中。FE-SEM图说明黄长石主要为层状的晶体结构,晶体的排列致密程度、晶体的尺寸、界面以及其分布情况都会对热导率产生很大影响。当MgO含量小于12%时,保护渣在热处理以后的热导率随MgO含量的增加而增加,当MgO含量超过12%时,其热导率随MgO含量增加而迅速降低,但是在1100℃热处理的保护渣的热导率随MgO的含量增加而不断增加。

The effect of MgO content on the structure and crystallization behavior of mold fluxes was studied.The effects of crystalline phase,content and morphology on thermal conductivity were also analyzed.The crystallization temperature of the mold flux was measured by DSC.It was shown that the crystallization temperature decreased with the increase of MgO content and the crystallization peak at 841 decreased with the increase of the content of MgO.Through FT-IR and Raman spectroscopic analysis,it indicated that the degree of polymerization of mold flux network decreased with increasing MgO content.XRD results shown that the main crystalline phase precipitated at different temperatures was akermanite,and its content decreased with the increase of MgO content,and the second phase was forsterite,and its content increased with the increase of MgO.It was also found that the content of forsterite increased with the increase of heat-treated temperature,but the content of akermanite decreased with the increase of heat-treated temperature.In addition,fluorophlogopite and kaliophylite were also found in the mold fluxes.The FE-SEM images shown that akermanite was mainly a layered crystal structure.The size of the crystal,the boundary and the distribution of the crystals all had a great influence on the thermal conductivity.When the content of MgO is less than 12%,the thermal conductivity of the mold flux after heat-treated increased with the increase of MgO content.When the content of MgO is more than 12%,the thermal conductivity decreased rapidly with the increase of the content of MgO,but the thermal conductivity of the mold flux heat-treated at 1100 increased with the increase of the content of MgO.