Analysis and verification of process variables as causes for macroinclusions and scrapping in a special steel melt shop

Abstract

The technology used in manufacturing steel for mechanical constructions has made great progress in recent years, resulting in a remarkable reduction of the impurities in special steel. One of these impurities is known as macroinclusion, the presence of which can cause serious defects in the steel structure. In a melt shop, where the semi-finished product is formed, there are several variables that can cause the formation of impurities in the steel and must be controlled. Therefore, by analyzing the influence of the primary melt shop variables, including: the iron and manganese oxides of the ladle slag (FeO+MnO), the stopper rod level variation and the argon pressure in the shroud between ladle and tundish in continuous casting; it was possible to establish a relationship between scrap generation and these process variables, through the creation of an investigation method. As result it was possible to identify the scrapping relationship with the presence of high FeO and MnO contents in the slag, during ladle furnace starting operations, along with stopper rod level variation in the tundish.