Papers by Author: Xiao Zhong Du

Abstract: A set of new mathematical models have been developed to calculate the temper rolling force of 2050 strip temper rolling mill. Based on the fact of small plastic deformation and elastic deformation occurring on the entry and exit of the deformation zone, new stress boundary conditions are described. The inhomogeneous distribution of internal stress in thickness direction is taken into account in the models, instead of uniform internal stress and assumption of plane strain traditionally. The new mathematical models have been applied into the temper rolling of 2050 hot rolling mills with good results. Comparison of calculated values and testing values for nine typical products has been given. The result shows that the calculated value of rolling force of temper mill is accurate.

Abstract: In order to analyze the effect of entry strip thickness, entry strip crown and intermediate roll shifting on strip profile and rolling force distribution, a three dimension finite element model of rolls-strip in UCM mill was established and employed. The results showed that the increases of entry strip thickness and entry strip crown would lead to the increase of exit strip crown and edge drop under the same total rolling force; the strip crown and edge drop would be decreased if the intermediate roll shifting δi was decreased. Moreover, the rolling force distribution also was analyzed in details by changing the entry strip thickness, the entry strip crown and the intermediate roll shifting.

Abstract: Bar straightening is an important work before the bar is applied as qualified products. In this paper, the mechanics of the straightening process is analyzed in detail on the base of conjugate quadric theory. A simulation program is developed with the investigation of straightening process as well. The equations, which describe roll contour curve and the longitudinal section, are given and simulated in computer. And a brief method of designing and drawing the straightening roll contour curve is introduced.

Abstract: Asymmetrical rolling is usually used on some special rolling produce. It offers lower rolling pressure, more reduction and better crystallographic textures. In recent years asymmetrical rolling has become more important due to realization of improved properties of the strip. In this paper, a elasto-plastic finite element method code has been developed to simulate the asymmetrical rolling of strip, considering unequal roll radii, unequal speed ratio between the upper roll and lower roll, different exit thickness and different reduction. Meanwhile, The profile, crown and edge drop of strip, as well distribution of front tensile stress were discussed in different rolling process. It makes better preset values for the online control system and good results was obtained.

Abstract: 3D elastic-plastic FEM model was established with ANSYS/LS-DYNA for edger rolling in hot strip mill. The effect of width reduction of edger roll, the slab original width and thickness, and edger diameter on the main parameters of dog-bone shape has been studied. According to many simulated conditions, the formulas of the main parameters of the dog-bone shape have been developed. In order to test the accuracy of the models, multiple correlation coefficient and residual standard deviation were calculated.The results show that multiple correlation coefficients are all above 98% and residual standard deviations are all below 5%, which indicate that these formulas acquire a high precise.

Abstract: Strip shape control during cold rolling of thin strip is a challenge in rolling practice. In the paper, finite element model of strip shape during cold rolling of thin strip in asymmetrical rolling case was successfully developed, and the strip shape such as the thickness distribution along the strip width have been obtained. The developed finite element model has been verified with the experimental value, which shows they are in good agreement. The obtained results are applicable to control the rolled thin strip shape in practice.

Abstract: The slab edge rolling has been widely used in the roughing stand of hot strip mill to control the width of the slab. However, the slab edge rolling and consequent horizontal rolling will cause a significant width change in the head part and tail part of the slab, which have to be trimmed before the finishing stands. The short stroke control (SSC) technology has been developed to overcome this problem. In this paper, the finite element method (FEM) has been used to simulate the unsteady edge rolling process. Three SSC control curves have been compared in order to obtain the best width control result. The optimized SSC control curve has been applied to the industrial rolling mill.

Abstract: During the cold rolling of thin strip on the 1220mm five-stand tandem cold mills, scratch marks occur on the surfaces of strip and work roll. The surface quality of strip is degraded and the roll wear increases, which resulting in significant economic loss. In this paper, the mechanics of strip scratch marks was studied by carrying out both field experiments and theoretical analysis. Slippage Factor (SF) and Scratch Mark Factor (SMF) were presented to indicate the conditions of strip scratch marks. Meanwhile, mathematical models and simulation code were developed to optimise the rolling schedules and to improve the scratch marks. The practical application of the developed models to the 1220 mm five-stand tandem cold mills verifies the effectiveness of the developed models. The mathematical models can be applied to other similar tandem cold mills.