90t BOF-LF-VD工艺冶炼GCr15轴承钢的氧化物夹杂变化行为

Behavior of Variation of Oxide Inclusions in Bearing Steel GCr15 Steelmaking by 90 t BOF-LF-VD Process

GCr15钢的生产流程为90 t转炉-LF-VD-250 mm×280 mm方坯连铸-轧制。转炉出钢加铝脱氧,LF由高碱度渣[/%:55~58CaO,3~10MgO,12~16SiO_2,16~24Al_2O_3,≤1(MnO+FeO)]精炼,LF喂Al后T[O]为14×10^(-6),LF终点T[O]10×10^(-6)。采用SEM(扫描电镜)+EDS(能谱仪)的方法,研究了线材中超标DS类夹杂物的成分分布,发现夹杂物中心以复合氧化物CaO-MgO-Al_2O_3为主,外围包裹少量CaS;这些氧化物中,Al_2O_3含量约占65%,分布最为均匀;CaO含量约占20%,MgO含量约占15%。统计分析结果表明,VD真空处理后每平方毫米13μm以上大颗粒夹杂物数量增至7,软吹后降至2.1,线材中1/3大颗粒夹杂物来源于钢包渣带入。

The production flowsheet for steel GCrl5 is 90 t converter-LF-VD-250 mm x 280 mm bloom casting-rolling process.With adding aluminium to deoxidize during converter tapping and refining by high basicity slag[/%：55~58CaO,3~10MgO,12~16SiO_2,16~24Al_2O_3,≤1（MnO ＋ FeO）],theT[O]after feeding Al in LF process is 14×10^-6,and the T[O]at end of LF refining is 10×10^-6.With using SEM（scanning electron microscope） and EDS（energy dispersive spectroscope） to study the composition distribution of unqualified large DS series inclusions in rod products,it is found that at the center of inclusion the main composition is compound oxide CaO-MgO-Al_2O_3,outside is wrapped by a small amount of CaS,in this oxides the Al_2O_3 content is up to about 65%with even distribution,the CaO content is about20%and the MgO content is about 15%.Statistics analysis results show that after VD vacuum treatment the number of diameter more than 13 μm large inclusions per mm increases to 7,after soft stirring that decreases to 2.1,and in rod products the one of three large inclusions come from ladle slag.