120 t BOF-LF-RH-CC流程生产高速轨U71MnG的工艺实践

The Process for Production of High Speed Rail U71MnG by 120 t BOF-LF-RH-CC

高速轨钢U71MnG(成分:w(C)0.65~0.75,w(Si)0.15~0.38,w(Mn)0.70~1.20,w(P)≤0.025,w(S)≤0.025,w(V)≤0.030,w(Al)≤0.004)经120 t BOF-LF-RH-CC流程生产,通过控制BOF终点w(C)≥0.06,终点w(P)≤0.015,出钢过程采用硅钙钡预脱氧;LF精炼过程造白渣,顶渣碱度控制在1.8~2.2;RH真空精炼采用本处理模式,67 Pa真空度下保持15 min,连铸保护浇注等工艺措施保证钢中T.[O]含量降到20×10^-6以内,w(N)≤40×10^-6,w(H)≤1.5×10^-6。成品非金属夹杂物检测中,A类夹杂物评级≤1.5级,B类夹杂物评级≤1.0,C类夹杂物评级≤1.0,D类夹杂物评级≤1.0,完全满足TB/T3276-2011高速轨标准要求。

The high speed rail steel U71MnG,(with element contents of w(C)0.65~0.75,w(Si)0.15~0.38,w(Mn)0.70~1.20,w(P)≤0.025,w(S)≤0.025,w(V)≤0.030,w(Al)≤0.004),has been produced by 120t BOF-LF-RH-CC process,with final control of[C]≥0.06 and[P]≤0.015 in BOF,and deoxidation during the tapping by adding Si-Ca-Ba.White slag forming is made in the LF,and the basicity of top slag is controlled to 1.8~2.2.This treatment mode is adopted for RH vacuum refining,in which the vacuum is maintained at a 67Pa for 15 minutes,and continuous casting protection pouring and other technological measures ensure that the content of T.[O]in steel is reduced to less than 20×10^-6,w(N)≤40×10^-6,and w(H)≤1.5×10^-6.In the test of nonmetal inclusions for rail,the appraisal of type A inclusion is equal or lesser than 1.5 degree,the appraisal of type B inclusion is equal or lesser than Level 1.0,the appraisal of type C inclusion is equal or lesser than Level 1.0,the appraisal of type D inclusion is equal or lesser than Level 1.0,which fully meet the requirement of TB/T3276-2011.