How the skin-pass rolling reduction ratio affects the strain aging behaviour of low-carbon steel sheets

Abstract

When producing cold-rolled steel sheets, the penultimate annealing process is followed by a final skin-pass rolling (or temper rolling) whose purpose is to eliminate any discontinuous yielding which creates stretcher–strain markings when the steel sheets are formed. To find out the critical reduction ratio eliminating the discontinuous yield phenomenon, the samples were annealed at 820°C for 3 min and then subjected to the temper rolling at various thickness reductions at room temperature. Results showed that the discontinuous yield phenomenon could not be eliminated in the case of a thickness reduction less than 0.5%, that a certain reduction ratio should be exceeded to eliminate the discontinuous yielding, and that the aging time varied depending on the reduction ratio. In addition, while the low-carbon steels did not undergo strain aging in three months with a 1% thickness reduction, they underwent strain aging in at least four months with higher thickness reductions.