Evaluation of the Current Condition and the Residual Lifetime of Forming Rolls Using the Magnetic Method of Nondestructive Testing Based on the Coercive Force

The magnetic method on the basis of the coercive force H_c is proposed to use for estimating the current condition and the residual lifetime of forming rolls. Sixty rolls have been tested. It is shown that H_c increases almost twice in exploiting the roll from the beginning of the operation to reaching the limit of its lifetime. Results of observation of the degree of nonuniformity of the H_c distribution over the roll surface in the operation process are given. The results of investigation make it possible to optimize the path of each roll through the mill stands in order to avoid the stress concentration at the same depth of the roll operating (magnetic) coating in the roll change process. Using the magnetic testing method based on H_c makes it possible effectively to estimate the current condition of accumulation of the fatigue in the roll operating (magnetic) coating.