Prediction of the contact durability of back-up rolls of forge-rolling mills in the process of development of pitting

We construct an algorithm for calculating the residual life of the near-surface layer of back-up rolls of rolling mills according to the development of pitting. Within the framework of the numerical-analytical two-stage model of evaluating the contact durability of rolling solids of revolution under conditions of boundary friction (lubrication) proposed earlier, we construct and analyze the trajectories of propagation of edge cracks at the shear and rupture stages. A criterion of transition between these mechanisms is proposed. Furthermore, we evaluate the durability of rolls with the help of characteristics of the cyclic crack resistance of 9KhF, GH, and SKH roll steels. Using disk specimens made of 9KhS roll steel, we study the dependence of contact durability on the friction coefficient between the rolling solids of revolution, the size of contact area, contact pressure, the slope of the initial shear crack, etc. Finally, we compare the results of theoretical and experimental investigations. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 42, No. 6, pp. 95–105, November–December, 2006.