Influence of Hot Rolling and Cooling Conditions on the Grain Refinement of Hot Rolled Extralow-carbon Steel Bands

Abstract

In this paper, the effect of various operational parameters in a hot strip rolling process on the grain refinement of hot rolled plain extralow-carbon steel bands has been investigated. The finishing temperature and the onset time of cooling after hot rolling influence the grain refinement significantly. The finishing temperature just above Ar3 is optimum for the grain refinement. The reducing of the onset time of cooling not only refines the grain size, but also decreases the finishing temperature-dependence of grain size. The increase in the reduction of the final hot rolling refines the grain size as well. The cooling rate does not affect the grain size of hot bands in the range between 40 and 120°C/sec significantly. The mechanism of the grain refinement has been discussed with a relation of recrystallization and transformation behavior of austenite and it is concluded that in the case of extralow-carbon steel without Ti and Nb addition, the grain refinement of hot bands is strongly influenced by not only the recrystallization but also grain growth behavior of austenite.