Predicting the survivability of rolling rolls

Abstract

A new method for predicting the survivability of rolling rolls is proposed. The method distinguishes the evaluation of the parameters of the rolls in the state of delivery and operation. The following parameters of rolls in a state of delivery that, as a rule are regulated in technical documentation are considered: grade and chemical composition of steel; the depth of the hardened layer during heat treatment; hardness of the barrel surface. In addition to these parameters, it is proposed to take into account the following most important in terms of further operation of the rolls: the amount of residual austenite in the hardened layer; density of dendritic structure; the magnitude of residual stresses; uneven hardness on the surface of the barrel of the roll. The greatest impact on the durability of the rolls can have residual stresses arising from heat treatment. Estimation of stresses is expedient to carry out with application of methods of computer modeling that allows tracing all kinetics of formation of structure and residual stresses in rolls at thermal processing. The method takes into account the following parameters of the operation of the rolls: the actual average reduced specific load on the roll, taking into account internal stresses and dynamic loads; the actual average mass operating temperature of the roll; characteristic size and type of defects, intensity of wear of the roll. It is shown that in the conditions of industrial enterprises it is most simple and convenient to estimate durability of a roll by total weight of hire made on this roll before its writing off. Empirical dependences, values of coefficients and basic parameters of working and support rolls of plate mills, hot and cold strip mills for calculation of durability of their operation (survivability) are given. The developed technique allows evaluating the influence of various factors of production and operation of rolls. In particular, calculations show that increasing the depth of the hardened layer of the working roll by 20 % and hardness by 10 % allows increasing the total weight of the rolled product before writing off the rolls by about 50 %.