FEM Analysis for Asymmetric Bending Roll of Roll Process in Four-High Mill

Accurate prediction for the deformation of the roll system is a key to improve the accuracy of the preset model and on-line control model of strip cold rolling processes. A non-linear finite element contact model to simulate the roll system deformation has been developed for4h cold strip rolling mill. Roll process of 4-high cold strip mill is simulated and analyzed by 3D elastic-plastic FEM on the bases of software ANSYS. In the model, the elastic deformation of work roll and backup roll, the plastic deformation of the strip and the pressure of strip and the work and the backup roll were taken into account. Results show that the work roll HYPERLINK "javascript:showjdsw ('showjd_0','j_0')" asymmetric bending is the most effective mean in these strip shape controlling means. The calculated roll gap profile is close to the measured values. This model can improve the accuracy of final products through a correct preset model and on-line control model of strip.

Effects of chemical composition and heat treatment on wear properties of backup rolls steel

In this study, friction and wear properties of backup roll steels with different chemical compositions subjected to various heat treatment processes were investigated by optical microscopy, scanning electron microscopy and microindentation to figure out changes in microstructure during wear testing. The results showed that wear of backup roll was mainly consisted of sliding wear with some contribution from abrasive wear. The surface of backup roll material depicted obvious ploughing characteristics and plastic deformation zones after wear processing. The wear scar width, wear volume, hardened layer thickness and plastically deformed layer thickness of the backup roll material all decreased as substrate hardness increased. The wear resistance of the material enhanced with the matrix hardness. On the other hand, increasing contents of Mo, V, Nd and other elements influenced dispersion and fine grain strengthening. By comparison, increasing contents of C, Si and Mn affected the solid solution strengthening. Both methods improved wear resistance of the backup roll. The working layer of the backup roll produced by the integral induction hardening process was identified as mainly tempered martensite. In sum, the wear resistance of induction hardened backup roll significantly improved when compared to conventional differential temperature quenching.

A flexible electromagnetic control technique for interference adjustment in large-size sleeved backup rolls

Large-size sleeved backup rolls including the roll core and roll shell play a crucial role of supporting work rolls in the precision-rolling process. However, since the backup roll endures an unavoidable periodic force during the rolling process, the interference between its roll shell and roll core is correspondingly reduced, which leads to rolled strip defects or a decreased service life of the roll. To solve this problem, an interference electromagnetic control technique (IECT) was proposed for large-size sleeved backup rolls to freely regulate contact pressure between the roll core and roll shell using a thermally driven electromagnetic stick mounted inside the roll core, thereby adjusting the interference for large-size sleeved backup rolls. In this study, a finite element method (FEM) simulation of a ϕ1400 × 1420 mm size sleeved backup roll was built to demonstrate the effect of this technique by analysing contact pressure variations and roll profile curves of the backup roll at various heating times. According to the FEM model, the key parameters of the IECT including frequency and current density were optimized based on the simulation results. Compared with the conventional rolling process, the electromagnetic control method on the interference adjustment of the large-size sleeved backup roll is shown to be a possible alternative for a better strip shape with a much longer service life.