Stainless steel continuous casting and ordinary steel continuous casting have many similarities, but also differences, mainly manifested in:
(1) The low-magnification structure of stainless steel ingot is a coarse columnar crystal area, which is particularly developed and even forms a transgranular structure. Columnar crystals may cause defects such as center segregation, center porosity and center cracks;
(2) Stainless steel contains a variety of alloying elements, especially Ti, Al, Cr and other elements, which are easily oxidized to form TiO2, Ti(CN), Al, Al2O3, Cr2O3 and other elements during the casting process. These oxides are concentrated on the surface of the ingot, which will deteriorate the product quality and easily accumulate on the inner wall of the nozzle, causing nozzle blockage;
(3) The contact time between the molten steel and the ladle and the tundish lining bricks and the oxygen in the air is longer than that of die casting, so it is easy to produce oxide inclusions;
(4) The solidification morphology of stainless steel is relatively complex, and there is a brittle temperature during the solidification and cooling process, so the ingot is prone to cracks, especially single-phase austenitic stainless steel, such as SUS316, SUS316L, SUS321 and other steel grades;
(5) Due to the poor thermal conductivity of stainless steel molten steel, there are strict requirements on cooling and billet drawing speed.
These characteristics of stainless steel determine that stainless steel continuous casting has higher requirements on technology and equipment than ordinary steel continuous casting, and also determine that the requirements on refractory materials used for stainless steel continuous casting are more stringent, especially the submerged nozzle and tundish coating.
