超低碳钢AISI 1006铸坯夹杂物的分布及工艺改进

为研究90 t BOF-RH-LF-CC流程生产的超低碳钢AISI1006夹杂物控制情况，通过对200 mm×200 mm铸坯横断面不同位置夹杂物进行统计分析，结果表明：钢中小颗粒夹杂占比较大，尺寸5～10μm的夹杂物占比达到91.0%,10～13μm的占比3.6%,13μm以上占比5.4%。尺寸较大夹杂主要分布于铸坯中心。在铸坯1/4边长处夹杂物分布最多，其次是近中心处，铸坯近表面处夹杂物最少。铸坯内夹杂物主要为Al₂O₃、Al₂O₃·CaO·(CaS·MnS)、Al₂O₃·CaO·MgO·(CaS·MnS)、MgO·Al₂O₃·(CaS·MnS)复合夹杂物，为内生夹杂物。开展工艺优化改进，RH高真空保持时间控制在15 min以上，LF精炼做好脱氧造渣及脱硫，精炼时间控制在90 min以内，精炼终渣碱度在6～7,出站前喂入硅钙线进行变性处理，软吹时间控制在25 min以上，连铸做好保护浇注，中间包开大氩气流量吹扫10 min以上，避免二次氧化，将夹杂物往钙铝酸盐方向控制，工艺优化后，钢水T.O含量≤20×10^-6,B、D、Ds夹杂级别≤1.0。 

Distribution and Improvement Process of AISI 1006 Casting Bloom Inclusion of Ultra-Low Carbon Steel

In order to study the control of 90 t BOF-RH-LF-CC flowsheet produced ultra-low carbon steel AISI 1006 inclusions, the sample was taken at different sampling point at cross section of 200 mm×200 mm cast bloom to analyze inclusions, the analysis results show that the ratio of inclusions of small particles in the steel are relatively large, and the inclusions with size of5- 10 μm accounted for90. 1%,3.6% of the 10- 13 μm,and5.4% above 13 μm,and the larger size inclusions are mainly distributed in the center of the casting bloom. The largest distribution of inclusions is at the length of side 1/4 of the cast billet, followed by the near center, and the least inclusions near the surface of the cast bloom. The inclusions in the casting bloom are mainly Al₂O₃,Al₂O₃ ·CaO · (CaS ·MnS),Al₂O₃ ·CaO ·MgO · (CaS ·MnS),MgO · Al₂O₃ · (CaS ·MnS)composite inclusions, which are endogenous inclusions. The process optimization is carried out, RH high vacuum holding time is controlled for more than 15 minutes, Deoxygenation slagging and desulfurization be controlled well during LF refining, the refining time is controlled for within 90 minutes, the alkalinity of the refining final slag is 6 to 7, the silicon calcium line is fed before leaving the station for modification treatment, the soft blowing time is controlled for more than 25 minutes, the continuous casting is well protected, the tundish large argon flow is purged for more than 10 minutes to avoid the secondary oxidation, the inclusions are controlled in the direction of calcium aluminate, and the T.O content of molten steel is reduced, after process optimization, T.O content of mloren steel ≤20×10^-6,rate of B 、D 、Ds inclusion≤1.0.