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针对贵钢在使用55SiMnMo中空钢实心坯制造的钎杆出现因硬性夹杂导致断裂的问题,对55SiMnMo中空钢生产工艺Consteel-LF-VD-CC进行全流程取样,对钢中气体含量和夹杂物进行分析,找到钢水洁净度的限制性环节,并由此得出改进措施.钎杆断裂面的夹杂物分析显示,主要为较大粒径的带棱角的纯Al2O3硬性夹杂以及不规则形状的MgO-CaO-SiO2复合夹杂.分析钢样可发现以下工艺问题:LF精炼后期渣面裸露吸气,钙处理后夹杂物变性不完全,钢包开浇过程中存在明显吸气和卷渣现象.铸坯中T[O]含量为9×106,显微夹杂物以MnS,Al-Mn的复合氧化物夹杂为主,大型夹杂物以SiO2-Al2O3-MnO-CaO复合夹杂为主.
In view of the problem of fracture caused by the hard inclusions in the drill rod made of 55SiMnMo hollow steel solid billets, the whole process of the Consteel-LF-VD-CC for the 55SiMnMo hollow steel production process was sampled. The gas content and inclusions in the steel Analysis and find the limiting part of the cleanliness of molten steel and the resulting improvement measures.The analysis of inclusions on the fracture surface of the drill rod shows that the inclusions mainly consist of pure Al2O3 with large grain size and irregular MgO- CaO-SiO2 composite inclusions.Analysis of the steel samples revealed the following technological problems: the slag surface was barely aspirated during the LF refining stage, the inclusions were not completely denatured after calcium treatment, and there was obvious inspiratory and entangled phenomenon in the ladle pouring process. The content of T [O] is 9 × 106. The microscopic inclusions are mainly composed of mixed oxides of MnS and Al-Mn, and the large inclusions are mainly composed of SiO2-Al2O3-MnO-CaO composite inclusions.