Estudo de caso: caracterização da Romboidade nos tarugos Sinobrás e a avaliação dos principais intrínsecos ao defeito geométrico

Abstract

The continuous casting was introduced on the world stage with great success, generating increased revenue, reduced energy costs and improved product quality. Since then, continuous casting has increased its stake in the world and has become one of the most important processes of solidification. This process is responsible for turning the liquid steel from the steel mill, plates or billets that are subsequently rolled to ensure marketing quality. In the process of production of long steel through continuous casting, one of the most common defects that compromise the quality index of the steelworks is romboidity. The romboidity is determined by the difference between the diagonals of the cross section of the billet. It is considered severe if it exceeds 6 mm to 8 mm. The romboidity can generate broken corner obtuse angle or diagonal cracks and compromise the steps of the process for producing steel. A number of factors can lead to romboidity, including non-uniform cooling of the mold (mold geometry) and chamber sprays; flow of water used, the purity of the water used, ratio Mn / S steel, among others. In this paper we present a case study for evaluation of the parameters that cause the appearance of this defect through stages of observation of the dynamic behavior of the system, evaluation procedures operacionaise and process variables defining the elements causing the defects being possible preparation new production patterns. The factors considered in this study were the characteristics of the mold and its cooling and secondary cooling, and operating mode of the machine casting. The results show that the design of the mold and its wear during the process variables that are more accentuated the formation of geometric defects during solidification of the billet.