IF钢铸坯中高SiO_2类夹杂来源探讨

Source analysis on high SiO_2 inclusions in interstitial free(IF) steel slab

采用X射线衍射、扫描电镜及能谱、夹杂物无损伤提取等手段研究和跟踪了IF钢铸坯中大颗粒高SiO2类夹杂物的特征及来源.结果表明:IF铸坯中存在大量大颗粒固相夹杂物,其中高SiO2类夹杂约占总数的60%,尺寸较大,一般>50μm,形状不规则;铸坯中高SiO2夹杂的主要来源是未预熔充分的结晶器保护渣,粉渣颗粒内部存在多个物相,其中部分高熔点固相氧化物(SiO2,Al2O3)在浇注过程中未完全溶解就伴随卷渣进入钢中被坯壳捕获,最终形成铸坯中夹杂物.改善保护渣的预熔性能,很大程度可以降低高SiO2类固相大颗粒夹杂物对铸坯造成的质量缺陷.

The characteristics and source of high SiO2 inclusions in IF steel slab were studied through a variety of methods,such as X-ray diffraction( XRD),scanning electron microscopy /energy dispersive spectroscopy( SEM /EDS),and non-destructive inclusion extraction. Results showed that many solid macro-inclusions existed in the IF steel slab,and the high SiO2 inclusions in irregular shape and large size( > 50 μm) occupied 60% of the total number. This kind of inclusions was mainly from the bad pre-melt mould power.High-melting-point solid oxides,such as SiO2 and Al2O3existed inside the power particles,and these solid oxides were captured by the shell before dissolved completely during the casting,and finally formed inclusions in the slab. quality defects of the slab caused by high SiO2 inclusions can be reduced by improving the pre-melting performance of the mould powder.