Split Ends During Long Products Rolling: Billet Quality or Rolling Process?

摘要

During rolling of long products in continuous or semi-continuous mills, end splitting (alligatoring, split ends) and central bursting may occur, with an impact on productivity and quality. In figure 1, the typical aspect of this defect is presented. This phenomenon may occur in the roughing passes of the roughing mil, particularly in open mills. Steel grades affected include free cutting steel, rebar, wire rod and shapes. Although out of the scope of this paper, this problem is also known in flat rolling of steel and aluminum. As an example, in figure 1 the aspects of bars opened in stand 10 of a rebar rolling mill of Tata Steel Jamshedpur (departing from 130 mm square billets), and the state of the bars after rolling, is presented [1]. It can be seen that a cobble may take place, with safety risk, or a defect in the product may be generated.