Reoxidation of liquid steel and evolution of inclusions during protective atmosphere electroslag remelting of Ce-containing heat-resistant stainless steel

The evolution of Ce-containing inclusions and its correlation with the reoxidation of liquid steel during protective atmosphere electroslag remelting (ESR) of heat-resistant steel were studied. The reoxidation of liquid steel took place during the ESR, resulting in the oxygen pickup from 0.0014 to 0.0053 wt.%. The inclusions in the consumable electrode, liquid metal pool and remelted ingot are Ce2O2S and Ce2O3inclusions invariably. The inclusions in the remelted ingot are originated from three ways: (I) the original inclusions from the electrode; (II) the newly formed Ce2O2S and Ce2O3inclusions in the liquid metal pool by reoxidation remaining still in remelted ingot; (III) the newly generated Ce2O2S and Ce2O3inclusions during cooling and solidification of liquid steel. The relative proportions of Ce2O3inclusions in liquid metal pool and remelted ingot are 41% and 76.5%, respectively. The inclusions ranging from 2 to 5 μm in the remelted ingot take up 55%, followed by the inclusions smaller than 2 μm (43% of total inclusions). The number proportion of the Ce2O3inclusions in the liquid metal pool which were removed by floating up into slag is 1.96 × 10−5%.