The Effect of Submerged Entry Nozzle Materials on Alumina-Buildup and Steel Composition

摘要

A low-expansion type MgO-C material has recently been developed for nozzles in the steel continuous-casting process. The alumina-buildup characteristics and composition changes of the molten steel have been investigated by an erosion/corrosion test that compared the newly developed MgO-C with Al_2O_3-C and Al_2O_3-SiO_2-C materials, all of which had the same C vol%. The average alumina buildup-rate decreased in the order MgO-C, Al_2O_3-C and Al_2O_3-SiO_2-C. Therefore, the testing confirmed that the rate of alumina-buildup was lowest for MgO-C. The carbon concentration change in the molten steel was checked before and after the test, and the C content of the molten steel with the MgO-C material was approximately 40% lower than that of the Al_2O_3-SiO_2-C material. So the alumina buildup-rate for the MgO-C material was the lowest of the materials tested, and also less inclusions were dissolved/ eroded into the molten steel. These results for MgO-C were attributed to a smooth and high density MgO-rich continuous layer formed on the contact surface of the refractory with the molten steel, which had low permeability for the gases that were generated in the hot face reactions.