Research on formation mechanism and nozzle parameter optimization of residual stress in hot rolling mill rolls based on multi-field coupling

The residual stress distribution in the rolls during the hot rolling process is a crucial factor that affects the roll profile and service performance, and consequently influences the quality of the rolled products. Due to current limitations in measuring residual stress in rolls and the difficulty in accurately characterizing its full-field distribution, this paper establishes a three-dimensional finite element model of the thermal-flow-solid coupling for a hot-rolled four-roll mill to study the temperature field and residual stress field of the rolls during the hot-rolled steady-state rolling process with spray cooling. The accuracy of the model's calculations was verified by comparing with the actual measured temperatures on site. The influence of key parameters, including nozzle flow rate, tilt angle, the overlap rate of the atomization areas, and spray water temperature, on the temperature and stress distributions of the rolls was systematically investigated. The results show that the temperatures of both the work roll and the backup roll reached stability after the work roll had rotated 140 times, and the surface temperatures of the work roll is within 5 % of the measured temperatures. The axial temperature distribution of both the work roll and the backup roll gradually decreases from the middle to the ends due to the actual contact between the rolled plate and the work roll. The increase in nozzle flow rate can significantly enhance the cooling efficiency, but it causes the maximum thermal stress to increase by approximately 2.8 times. When the inclination angle of the spray increases, the cooling effect deteriorates, the stress decreases, and the unevenness of the distribution increases. The temperature difference was minimized to only 4.4 °C when the atomization zones were tangent, while the increase of the overlap rate improved the uniformity of the axial stress distribution. The uniformity of axial stress distribution improves as the overlap ratio increases. The alternating arrangement of dense and sparse nozzles can significantly reduce residual tensile stress and expand the distribution range of compressive stress. The findings of this study can provide guidance for optimizing spray cooling in actual production, controlling the residual stress of the rolls, and thereby evaluating the service safety of the rolls and improving the quality of rolling. • Developed a 3D FEM model integrating roll structure and spray cooling for four-high hot rolling. • Revealed nozzle flow rate increases cooling efficiency but elevates circumferential thermal stress at roll center. • Found larger nozzle tilt angles exacerbate circumferential stress fluctuations. • Demonstrated 25–35 °C cooling water temperature achieves optimal stress stabilization. • Proposed sparse-dense nozzle configuration effectively mitigates tensile stress.