Role of slag on inclusions control and its effect on primary carbides in H13 steel

Abstract

The relationship of inclusions and primary carbides in H13 ingot processed by ESR with ANF-6 slag was investigated. It is found that inclusions in H13 ESR ingot are Al2O3, MnS and calcium-aluminate inclusions. The Al2O3 and MnS inclusions are found to be the nucleation cores of the primary carbides, whereas the calcium-aluminate inclusions are not. In order to study the effect of slag on inclusions and primary carbides of H13 steel further, the characteristics of inclusions and primary carbides in steel remelted by ANF-6 and ANF-8 slags were analyzed, and compared to the steel remelted without slag. After being remelted with the ANF-6 (70 mass% CaF2 + 30 mass% Al2O3) and ANF-8 (60 mass% CaF2 + 20 mass% CaO + 20 mass% Al2O3) slags, Al2O3 and CaO contents in calcium-aluminate inclusions increase, respectively. The ANF-8 slag shows stronger desulfurization ability than ANF-6 slag, which contributes to the delay of MnS inclusions precipitation and the decrease of inclusion number, and finally helps to inhibit the precipitation of primary carbides. It implies that the ANF-8 is the promising slag for the ESR process of H13 steel.