Mechanism of Formation of Exfoliations on the Surface of Rolls for Cold Rolling

Abstract

We studied the phase composition and the distribution of stresses (residual and contact) over the depth of the surface layer of rolls for cold rolling. The results of this investigation are used to explain the mechanism of formation of exfoliations. Exfoliations appear in the zone of maximum residual tensile stresses on the boundaries of microinclusions of phases. The evolution of exfoliations passes through four stages: initiation of microcracks at a certain depth, formation of the main crack, its stable development, and final fracture. The crack-opening displacement is promoted by stresses and the decomposition of residual austenite under the influence of cyclic loads of rolling. The probability of formation of exfoliations can be lowered by optimizing the conditions of thermal treatment of the rolls.