Abstract: Aiming at the problem of non-metallic inclusions in smelting process, the transformation of inclusions in refining process of alloy spring steel 51CrV4 was studied by sample analysis, SEM and EDS. The origination and formation of MgO·Al2O3 spinel inclusions was analyzed, and the feasibility of inclusion modification by calcium treatment was discussed. The results showed that MgO·Al2O3 spinel inclusions could generate when [Mg] mass fraction between (0.55－30.6)×10-6, and start converted into liquid when [Ca] mass fraction reached 6×10-6. The liquid inclusions content increased rapidly with the improvement of [Ca] content in the steel, and the conversion could be completed when [Ca] mass fraction in the steel reached around 35×10-6.

Key words: alloy spring steel, MgO·Al2O3 spinel inclusions, inclusion behavior