Measurement of Residual Stresses in Work and Backup Rolls for Strip and Plate Mills and its Effect on the Final Load Situation

Abstract

Internal stresses or residual stresses remain in almost every part after manufacturing and/or further processing. Even if the entire stress state inside a system is in an equilibrium, single stresses due to their direction and strength may have positive or negative influences to the properties of a body. Especially in big parts, the residual stress state is relatively unknown, because it can only be determined by destructive methods as sectioning or slitting. The possibility of the use of non destructive measuring methods is only given for surface near regions or thin parts and not useful for the specification of the entire residual stress state inside a large compound work roll. This paper outlines an approach for the determination of residual stresses in centrifugal casted work rolls with an indefinite chill double poured or high speed steel shell. In several steps, different measurement techniques are tested and the results are to be presented. Beside the residual stress state, which is caused by manufacturing or heat treatment, these work rolls with different shell and core material differ in their thermophysical and elastic properties. These parameters in combination with the residual stress state and the thermal and load stresses, which arise during the hot rolling process, are causing a complex stress field that is presented by a combined model for work and backup rolls in operation.