The 230mm×230 mm×1350 mm LZ50 steel billet for vehicle axle is produced by quality hot metal pretreatmnent - 120 t converter melting and SiAlBaSrCa combined deoxidiing- ladle refiring with Si-Ca powder injection + RH- TB vacuum degassing- 5 t ingot casting - rolling process. The production results showed that due to controlling C content be- tween0.47%～0.50%

Si0.20%～0.35%

Mn0.71%～0.85%

both P

S in steel ≤0.02%

average[H]=1.77 ×10-⁶

average  [O]=12.22×10-⁶

the  LZ50  steel  billet  had  excellent  macro  structure  and  constant  mechanical  properties

and the quality of products was up to the requirement of TB/T2945 standard.