Consteel-LF-VD-CC生产55SiMnMo钢种的洁净度研究

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TO]含量为9×10-6，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.

Study on the Cleanliness of 55SiMnMo Steel Produced by Consteel-LF-VD-CC Process

In order to study the fracture problem of drill rod caused by its hard inclusions which were found in the 55SiMnMo hollow steel billet produced by Consteel-LF-VD-CC process, the cleanliness of 55SiMnMo steel during the whole production process was analyzed by the methods of systematic sampling and comprehensive analysis of gas content and inclusions in it. The influential factors on the steel cleanliness were discussed and some measures to improve steel cleanliness were proposed. It was found that the reason for the fracture of drill rod was pure big Al2O3 inclusion with sharp corners and irregularly shaped MgO-CaO-SiO2 inclusion. Three process problems were found: air absorption happened during later refining; calcium treatment was not perfect to change inclusions; obvious air absorption and slag entrapment happened at the beginning of molten steel pouring. The TO] content of billet was 9×10-6, and the main micro-inclusions were MnS and Al-Mn composite inclusions and SiO2-Al2O3-MnO-CaO for the macro-inclusions.