Research On Backup Roll For 3500mm Wide Plate Mill And Calculation Of The Fatigue Life

Since the operation and maintenance for back-up roll is backward in technology, issues of the large heavy plate mill back-up roll occur more frequently. It seriously affects the life of back-up roll and equipment productivity. Contact pressure concentration exists in the edge of back-up roll when the large heavy plate mill works. The fatigue of stress causes hardening on the roll surface. The hardening in the edge is more severe than that in the middle, which causes fatigue cracks appear in the edge of back-up roll. With the crack growing, roll spalling problems will occur.This paper takes the 3500 mm 4-high rolling mills as the object of study. It firstly analyzes the stress state between back-up roll and work roll by using the Hertz contact theory. The Hertz contact theory only considers static load normal pressure, without taking into account the tangential force. So this paper also discusses the roller contact area by using the theory of rolling and analyzes the micro-slip phenomenon between rollers by the knowledge of the micro-tribology.An approach to prevent premature failure of a backup roll is to design a reasonable contour of back-up roll, without changing the structure of the existing mill and affectting the production schedule. A reasonable contour of back-up roll can equalize contact pressure distribution and reduce edge stress concentration. Therefore, this paper propses a new back-up roll contour through considering several existing back-up roll contour, and establish a 3-D finite element rolling model of the 4-high mill by using finite element software ABAQUS to compare the stress field, bending deformation and plate shape between the new contour and the existing contours. The result obtained by ABAQUS can prove that the new contour can effectively reduce localized stress and bending deflection, and can improve the quality of plate shape.Finally, this paper describes the fatigue-related knowledge, and estimates the fatigue life of the new and the existing contour back-up roll by using a local stress-strain method and FE-SAFE fatigue analysis software with the previous results of the finite element stress analysis. The result of fatiue life estimation proves that the new contour of back-up roll can effectively improve the service life of back-up rolls.