Abstract: The flowsheet for steelmaking of 280 mm x 325 mm casting bloom of steel 55SiCr (/% : 0.55C, 1. 42Si, 0. 67Mn, 0. 008S, 0. 67Cr) is 80 t BOF-LF-RH-CC process. With during BOF tapping adding Al, ferrosilicon and refining slag, controlling slag basicity R (CaO/SiO₂) about 2. 0, RH refining for ≥ 20 min, soft blowing stirring for ≥15 min to control the transformation of inclusions in steel, the clean spring steel 55SiCr is gotten. Analysis results show that during LF refining process the inclusions in liquid transformfrom earlier period Al₃O₃ -SiO₂-MnO and Al₂O₃ inclusions to inclusion Al₂O₃-CaO-SiO₂ , after RH vacuum treatment the inclusions in liquid all transform to inclusion Al₂O₃-CaO-SiO₂, the T[0] and [N] at beginning LF refining are respectively 36 x 10^-6 and 26 x 10^-6 , and the T[0] and [N] in casting bloom are respectively 7 x 10^-6 and 43 x 10^-6 , and the inclusions in casting bloom are mainly Al₂O₃-CaO-SiO₃ and Al₂O₃ with size≤10μm

Key words: 80 t BOF-LF-RH-CC Flowsheet, Spring Steel 55SiCr, T[O], [N], Inclusions, Cleanliness

摘要： 55SiCr钢280 mm×325 mm铸坯（/%:0.55C,1.42Si,0.67Mn,0.008S,0.67Cr）的冶炼流程为80 t BOF-LF-RH-CC工艺。通过BOF出钢加Al和硅铁合金,同时加入精炼渣,控制精炼过程渣碱度R（CaO/SiO₂）为2.0左右,RH≥20 min,软吹搅拌≥15 min,控制钢中夹杂物转变,得到洁净弹簧钢55SiCr。分析结果表明,LF精炼过程中夹杂物由早期的Al₂O₃-SiO₂-MnO和Al₂O₃夹杂将逐渐转变为Al₂O₃-CaO-SiO₂夹杂,RH真空处理后夹杂物全部转变为Al₂O₃-CaO-SiO₂夹杂,LF开始精炼T[O]和[N]分别为36×10^-6和26×10^-6,铸坯T[O]、[N]分别为7×10^-6和43×10^-6,铸坯中夹杂物主要为Al₂O₃-CaO-SiO₂和Al₂O₃,尺寸≤10μm。