Some specifics of the billet open and submerged stream casting

Abstract

Experimental series of steel casting were carried out to determine the effect of the continuous casting method on the fre-quency of defects formation in billets. At the same time, the 125x125 mm square billets production was carried out on a six-strand caster with casting speeds of 2.8-4.3 m/min. In the process of research, a series of 5 melts of steel 60 (St60) was initially casted with an open stream. After that, using the same molds, 5 melts of steel 40X were sequentially casted with a submerged stream. As a result of an industrial experiment, it was found that because of the open stream continuous casting the number of rhomboidal billets was 4.5 %. In the case of using the submerged stream technology defects in the billet shape were not observed. The use of the "stopper rod” — "tundish nozzle" — "submerged entry nozzle" system allows to control metal consumption during casting more accurate and timelier in automatic mode without changing the billet casting speed. At the same time, the position of the metal level in the mold is constantly ensured, which most accurately considers the features of the billet solid shell formation over the entire mold length at the current casting speed. The absence of the need to control the casting speed by the level of metal in the tundish makes it possible to maintain the optimal amount of melt in it, which sta-bilizes the casting temperature. The submerged casting prevents bubbling at the phase boundary in the mold and provides the possibility of a significant increase in the nozzle inner diameter (compared to the open stream) that reduces the rate of its clogging with corundum deposits several times. In addition, submerged casting allows the use of special mold powders, which improve the surface quality of the billets. It is possible to additionally improve billets quality using electromagnetic stirring of liquid steel during continuous casting.