Abstract: The steel 25 CrMpVNi is produced by 120 t EAF-LF-RH degassing-φ600 mm round bloom casting process with adding Al to pre-deoxidize during EAF tapping, and get [ Al ] s 0. 030% and adding lime slagging for pre-refining, adding aluminium shot at surface of refining slag (/% : 53 - 57CaO, 10 -13SiO₂,27 -28Al₂O₃, 6 - 9MgO, 0. 09 - 0. 10MnO) for diffusion deoxidation during LF refining. The RH degassing refining results show that at end RH process the T[O] decreases from begining RH 0. 0013% - 0. 001 5% to 0.0005% ; TCa in steel decreases From 0.001 9% to 0.000 9% - 0. 001 7% ； the inclusions transform from MgO· Al₂O₃ to ( MgO) z ( CaO) x ( Al₂O₃ ) y and into ( CaO)x (Al₂O₃ )y, finally the amount of spinel type solid, phase inclusions decreases rapidly, the amount of calcium aluminate type liquid phase inclusions increases first and then decreases, and the number density of inclusions in steel decreases from 6. 7/mm² to 2. 7/mm².

Key words: 120 t EAF-LF-RH-CC Flowsheet, RH Degassing, Ultra-Low Oxygen Steel for High Speed Rail Axles, Inclusions, Spinel

摘要： 25CrMoVNi钢由120 t EAF-LF-RH脱气-φ600 mm圆坯连铸工艺生产,EAF出钢时加Al预脱气使[Al]s≥0.030%,并加入石灰造渣预精炼,LF精炼时炉渣表面加Al粒扩散脱氧,LF精炼渣的组成为（/%）:53~57CaO,10~13SiO₂,27~28Al₂O₃,6~9MgO,0.09~0.10MnO。RH脱气精炼结果表明,RH后T[O]由脱气前0.001 3%~0.001 5%降至0.000 5%;钢中TCa由0.001 9%降至0.000 9%~0.001 7%;夹杂物发生MgO·Al₂O₃→（MgO）z（CaO）x（Al₂O₃）y→（CaO）x（Al₂O₃）y的转变;最后以尖晶石类固相夹杂物数量迅速减少,以钙铝酸盐类的液相夹杂物数量呈现出先增加后减少,钢中夹杂物由6.7个/mm²下降至2.7个/mm²

关键词: 120 t EAF-LF-RH-CC流程, RH脱气, 超低氧高铁车轴钢, 夹杂物, 尖晶石