转炉→吹氩站→连铸工艺生产SPHC钢洁净度研究

Research on cleanliness of SPHC steel produced by BOF→Ar→CC process

通过对"转炉→吹氩站→连铸"工艺流程生产SPHC钢各工艺环节系统取样,采用氧氮化学分析、光学显微镜分析、扫描电镜-能谱分析和大样电解等多种方法,研究了炼钢全流程中夹杂物的形貌、尺寸、数量及组成。结果表明:全流程总氧含量呈现下降趋势;整个炼钢流程钢中夹杂物成分基本分布在高Al2O3附近,铸坯中夹杂物成分分布比较分散,主要为Al2O3夹杂、单独的MnS夹杂以及Al2O3-MnS、Al2O3-CaS、MnS-CaS复合夹杂物;各工序夹杂物的尺寸以小于5μm为主,铸坯中夹杂物数量为6.2个/mm2;钢中大型夹杂物主要为Al、Si、Ca、Ti、Mn、Mg的部分或全部元素的复合夹杂物,主要为外来夹杂物及二次氧化的产物,部分夹杂物中含有K、Na元素,这说明在浇铸过程中存在结晶器保护渣的卷入。

The shapes, sizes, quality and components of inclusions in cold-rolled plate SPHC produced by＂BOF→Ar-blowing station→CC＂process were studied by systematic sampling in each step in steel production. Analysis methods mainly include total oxygen and nitrogen content analysis, optical microscopy, scanning electronic microscope （SEM） ,energy dispersive X-ray spectroscopy （EDS）, and slime（Electrolysis）. The re- sults indicate that： the total oxygen content is trending downward in the processes and the average mass fraction of total oxygen is 16. 3 ~ 10-6 in slab; Inclusion compositions are basically distributed near the high A12 03 in the whole process, more dispersive in slab which mainly contain A1203 inclusions, separate MnS inclusions and A1203-MnS, A1203-CaS, MnS-CaS composite inclusions. The size of inclusions is mostly less than 5 t^m and the inclusion quantity density is 6. 2/mm2 in the slab. Macro-inclusions in steels mostly are composite inclusions of some or all of the elements of A1, Si, Ca, Ti, Mn, Mg. They mainly originate from external inclusions and secondary oxidation products, and parts of the inclusions contain K, Na elements, which shows that mold powder en- trapment occurs .