2018 Volume 58 Issue 7 Pages 1275-1284
The current study focuses on the effect of directional solidification in electroslag remelting (ESR) on the removal efficiency of inclusion and the shape of molten metal pool during this refining process as well as on solidification structure of remelted ingot. Two ingots were remelted through traditional ESR process and continuous directional solidification in electroslag remelting (ESR-CDS) process for comparison, respectively. Moreover, a two-dimensional (2D) coupled mathematical model was employed to simulate the temperature field, solidification and velocity fields as well as inclusion motion to reveal the refinement mechanism of inclusion removal, microstructure and carbides during remelting process. The results showed that the macro-segregation of carbon was reduced and the microstructure of columnar grains paralleled to axis of ingot was obtained through ESR-CDS process, together with the refinement of carbides distribution. Moreover, the number and size of inclusions in ingot were much more reduced remelting through ESR-CDS process compared to ESR process. The total number and average diameter of MnS particles are obviously reduced from 689 and 2.28 µm in S1 ingot to 78 and 1.78 µm in S2 ingot respectively, remelting through ESR-CDS process. Meanwhile, the number of MnS particles with size >3 µm is reduced from 15.67% in S1 ingot to 1.28% in S2 ingot, and that with size 1–2 µm is increased from 49.93% in S1 ingot to 67.95% in S2 ingot. It was found that ESR-CDS technology was beneficial for refinement of microstructure and carbides as well as removal of inclusions, thus achieving considerable improvement in mechanical properties of austenitic hot-work die steel.