Effect of mold rotation on inclusion distribution in bearing steel during electroslag remelting process

To remove the inclusions in the ingots by conventional electroslag remelting(ESR), the bearing steel was prepared using ESR process but with mold rotation in this study. Experimental results show a reduction in amount of large inclusions when the mold rotation rate is 6 r·min-1, and the inclusions are uniformly distributed in the ESR ingot. As comparison with the electroslag ingots of conventional ESR(stationary mold), the portion of the Al2O3 inclusions smaller than 1 μm in size increase from 38% to 41.4%, whereas that of the SiO2 inclusions increases from 48% to 74% in the ingots when mold rotation is applied. This phenomenon is caused by the decrease in metal droplet size, resulting in large contact area between the slag pool and metal droplets in ESR process with mold rotation. Moreover, the metal droplets have relatively long movement routes, leading to long metal contact time between the slag pool and metal droplets when a relative motion between the consumable electrodes and mold is present. However, when the mold rotation rate is increased to 45 r·min-1, inclusion removing effect decreases. An excessive rotation rate causes wild motion in the slag pool, which drives the molten metal droplets to move violently, and as a result, the slag is entrapped into the metal pool, decreasing the ability of slag absorbing inclusions.

To remove the inclusions in the ingots by conventional electroslag remelting （ESR）, the bearing steel was prepared using ESR process but with mold rotation in this study. Experimental results show a reduction in amount of large inclusions when the mold rotation rate is 6 r＆#183;min-1, and the inclusions are uniformly distributed in the ESR ingot. As comparison with the electroslag ingots of conventional ESR （stationary mold）, the portion of the Al2O3 inclusions smal er than 1 μm in size increase from 38% to 41.4%, whereas that of the SiO2 inclusions increases from 48% to 74% in the ingots when mold rotation is applied. This phenomenon is caused by the decrease in metal droplet size, resulting in large contact area between the slag pool and metal droplets in ESR process with mold rotation. Moreover, the metal droplets have relatively long movement routes, leading to long metal contact time between the slag pool and metal droplets when a relative motion between the consumable electrodes and mold is present. However, when the mold rotation rate is increased to 45 r＆#183;min-1, inclusion removing effect decreases. An excessive rotation rate causes wild motion in the slag pool, which drives the molten metal droplets to move violently, and as a result, the slag is entrapped into the metal pool, decreasing the ability of slag absorbing inclusions.