Characterization of Inclusions during the Production of Stainless Steel with Focus on Submerged Nozzle Clogging

Submerged Entry Nozzle (SEN) clogging is a problem encountered by a local steel industry during continuous casting of High Silicon Non Calcium treated (HSiNC) stainless steel. As part of solving this problem, inclusions were characterised during the production of the stainless steel. Samples were taken from two stainless steel heats (clogging Fe-23CR-19Ni-Si and non clogging Fe-19CR-12Ni-2Si) during ladle treatment and continuous casting. After sample preparation, inclusions characteristics (size, morphology, composition and number) were investigated using the 2D cross-sectional analytical method. The acquired inclusion information was then used to explain the reason for SEN clogging. Spinels (MgO-Al2O3) were the dominant inclusions found in the clogging heat and they formed clusters in the tundish during continuous casting. The solid spinel clusters blocked the submerged nozzle during continuous casting leading to SEN clogging. Calcium-Silicate-Magnesia-Aluminates (Ca-Si-Mg-Al) -O spherical inclusions were the dominant inclusions found in the non clogging heat. These inclusions were found to be liquid inclusions and therefore did not cause clogging.