Strip Mill Work Roll Temperature Field And Thermal Deformation In The Hot Strip Rolling

The roll's thermal deformation is an important factor for the strip shape and section quality. With the increase of rolling rhythm, the development of rolling specification and the increase of market demand, the influence of roll's thermal deformation on the strip shape and section quality is becoming a problem in the productive practice. In the hot rolling process, it is an difficulty for strip shape and section quality control technology to accurately predict roll's thermal deformation because the influence factors of roll's thermal deformation are complicated, the boundary condition is intricate and many physical constants are hard to accurately measure. The roll's temperature field, thermal deformation and complicated boundary heat exchange of hot strip rolling mill are selected as researching subject, closely theoretical study and industrial experiments are carried out.First, internal and boundary node difference equations of the cylinder's three-dimensional temperature field are established by control volume balanced method, so that the boundary node difference equations are more accurate and according with the physical practice. The complicated boundary condition of hot rolling work roll's temperature field is analyzed. With a view of the complexity to solve simulation model of temperature field, roll's two-dimensional temperature field finite difference model of plate and strip mill is established. For the first time, combined with off tracking of the strip, modified thermal crown model of the roll is established, and it provides a new way for improving the computing accuracy of in-line thermal crown of plate and strip mills. The heat flow input and output of the roll are analyzed in detail and reasonably simplified. Genetic operation are designed by the improved genetic algorithm——real code, new calibration of sufficiency value and conservation of the best individual, and the optimization model of genetic algorithm about key boundary heat exchange parameters suitable for the roll of different mills is established. Considering the influence of screwdown regulations, rolled piece specification, temperature, rolling rhythm, flux and distribution of cooling water, the simulation and industrial experiments of temperature field and thermal crown of work roll are made in Baogang 1580 hot rolling mill by the above two models. The temperature field and thermal deformation curves of work roll after rolling and cooled in the air are attained and the computation values coincide better with the measured values. It provides a basis for the realization of appropriate roll shape grinding in the productive practice. Then, influence of rolling conditions on thermal crown of work roll was researched quantificationally.Second, the formation mechanics is systematically analyzed that thermal shape of work roll after rolling changes from the convexity to the concave in Baogang1580 hot rolling mill. The variable-width cooling idea is first put forward. The optimization is made for the axial distribution of cooling water of work roll corresponding to each typical rolling specifications in Baogang 1580 hot mill by the temperature field and thermal crown model. The optimization results indicate that the fluctuation of thermal roll shape is greatly improved by the cooling system determined by the product specification. The variable-width work roll's curtain wall cooling analog experiment system is designed and manufactured, and the principle and feasibility experimental researches are made in the laboratory. Experimental results indicate that the designed devices can realize continuous laminar curtain wall, the adjustment in the roll axial direction, and the anticipated effect that middle flux is greater than the marginal flux in the no flux-disturbed area. It provides the important basis for further research on the device for the productive practice.At last, coupled the rolls deformation model, wear, thermal crown and the metal flow models, the strip cross section simulation system of hot tandem mill is established. The simulation and measured values coincide better. The influence of work roll thermal deformation on strip cross section is analyzed, and that faster rolling rhythm can cause marginal spring of strip is first brought forward. The side convex defect of strip coil of cold rolling seriously influences the shape and surface quality of the strip. On the basis of large quantity of field researches in 1220 cold rolling strip factory, experiment scheme is first brought forward for exploring the root of side convex of strip coil of cold rolling. The experiment results are systemically analyzed and can be known that the side convex of strip coil is not the result of the bad strip shape of strip coil of cold rolling, but the side local high spot of the strip, and that the thickness of side local high spot of the cold rolling strip is larger than the middle thickness, and that the wedge shape aggravates the side convex of cold rolling coil. Based on the influence of work roll thermal deformation on strip section, the industrial experiment of reducing the rolling rhythm is made in 1450 hot rolling production line. Experimental results indicate that the above deductions are correct. Then, it brings forward the important basis for the cure of the side convex defect of cold rolling coil.