Formation and Evolution of Non-Metallic Inclusions in Calcium Treatment H13 Steel during Electroslag Remelting Process

In the current study, the evolution of inclusions in H13 steel electrode with different Ca content refined through ESR process were analyzed, the formation and evolution of sulfide and oxide inclusions during ESR process was determined based on experiments and thermodynamic calculation. The results showed: The inclusions of remelted ingot were Al2O3, CaO–Al2O3–CaS and CaO–Al2O3–MgO–CaS, more than half of the total inclusions were smaller than 3 µm. The cleanliness and inclusions of remelted ingot had no difference with different Ca content in electrode. MnS inclusions in electrode precipitated while the solid fraction reached 0.98. MnS inclusions cannot precipitate due to the low level of S content in remelted ingot and the decrease of Mn and S segregation on the front edge of solidified shell. The low-melting-temperature inclusions were dissolved and disappeared completely before liquid metal droplets collected in the liquid metal pool. The different of local cooling intensity during ESR process and high Al2O3 content of liquid inclusion in molten pool promoted the formation of large amount of tiny Al2O3 inclusions in remelted ingot.