Diping Wu

Non-linear dynamics of inlet film thickness during unsteady rolling process

The inlet film thickness directly affects film and stress distribution of rolling interfaces. Unsteady factors, such as unsteady back tension, may disturb the inlet film thickness. However, the current models of unsteady inlet film thickness lack unsteady disturbance factors and do not take surface topography into consideration. In this paper, based on the hydrodynamic analysis of inlet zone an unsteady rolling film model which concerns the direction of surface topography is built up. Considering the small fluctuation of inlet angle, absolute reduction, reduction ratio, inlet strip thickness and roll radius as the input variables and the fluctuation of inlet film thickness as the output variable, the non-linear relationship between the input and output is discussed. The discussion results show that there is 180° phase difference between the inlet film thickness and the input variables, such as the fluctuant absolute reduction, the fluctuant reduction ratio and non-uniform inlet strip thickness, but there is no phase difference between unsteady roll radius and the output. The inlet angle, the steady roll radius and the direction of surface topography have significant influence on the fluctuant amplitude of unsteady inlet film thickness. This study proposes an analysis method for unsteady inlet film thickness which takes surface topography and new disturbance factors into consideration.

Comparative Analysis of Bulge Deformation between 2D and 3D Finite Element Models

Bulge deformation of the slab is one of the main factors that affect slab quality in continuous casting. This paper describes an investigation into bulge deformation using ABAQUS to model the solidification process. A three-dimensional finite element analysis model of the slab solidification process has been first established because the bulge deformation is closely related to slab temperature distributions. Based on slab temperature distributions, a three-dimensional thermomechanical coupling model including the slab, the rollers, and the dynamic contact between them has also been constructed and applied to a case study. The thermomechanical coupling model produces outputs such as the rules of bulge deformation. Moreover, the three-dimensional model has been compared with a two-dimensional model to discuss the differences between the two models in calculating the bulge deformation. The results show that the platform zone exists in the wide side of the slab and the bulge deformation is affected strongly by the ratio of width-to-thickness. The indications are also that the difference of the bulge deformation for the two modeling ways is little when the ratio of width-to-thickness is larger than six.

Research on creep material models and bulging of cast slab

In this paper, a reasonable creep material model used in FEM analysis for bulging of cast slab was determined based on the comparative results between simulation and experimental data. A thermo-mechanical coupling, creep and dynamic FEM model of continuous casting process has been constructed and applied to case studies. The analysis produces outputs such as the necessity of considering the case slab movement for calculation of bulging, the inconsistency of bulging and the stress and stain rules of cast slab. The indications are that the results provide meaningful experiences for the calculation of slab bulging, and lay the foundation for further three-dimensional FEM analysis.

Structure optimization for link suspension system of a 180t BOF vessel

The link suspension system has been used to install a BOF vessel shell in the trunnion ring and has been adopted widely in many steelmaking workshops all over the world. This system is a key component of the oxygen steelmaking process and combines the advantages of well-proven suspension systems with the design philosophy of static determinacy in any operating condition and status of deformation. Recent researches and publications focus on the application of the system and rarely involve in the design mechanics of the system. This paper describes an investigation into the load of link using ADAMS to model the tilting process of BOF. The factors of influencing the link load are also discussed. The indications are that the distribution and parameters of the vertical and the horizontal links have great impact on the laws of loads. An optimization model including these parameters has been constructed to obtain a reasonable load distribution of these links. The optimization results show that vertical links should be assembled vertically and distributed uniformly along circumference of the trunnion ring to reduce theoretically the link loads.

Optimal design of mechanism parameters of rolling-cut type cut-to-length shears

Rolling-cut shear is the key equipment of medium plate producing 1ine, while pure rolling shear was set as the target, so that the rolling line is smooth, and the quality of products is improved. This paper describes an investigation into the work Mechanism of rolling-cut shear. A parametric model of rolling-cut shear has been constructed by using ADAMS software. This model was used for two working rolling-cut shear to verify factors influencing quality of products. The influences of the amount of scissors overlapping and shear force are also discussed. The indications are that the length of crank and guard bar, preliminary angle of the crank, the articulated point location of guard bar and frame are key factors to the amount of scissors overlapping and equivalent shear angle. These structure parameters are selected as design variables and the optimization model which was used to reduce scissors overlapping and shear force has been suggested. This optimization model has been employed successfully in the developing of rolling-cut shear 3800 to obtain reasonable mechanism dimensions and improve shearing quality and reduce motor power. The study results provide new idea for developing and optimum design of rolling-cut shear.

Research on the mechanism of spray cooling of H-beam after rolling

In order to reduce temperature difference between the web and flange of the H-beam and in the height direction of the web, the spray cooling technology has been proposed to control the temperature difference when the H-beam left the finishing rolling mill. An experiment of spray cooling for a heated plate has been performed, and this cooling process has been simulated using the computational fluid dynamics software Fluent. The re-normalization group k–ε model has been adopted in this study to simulate turbulence model with discrete phase method. And the temperature fields of the simulated are compared with those of the experiment to verify the correctness of the simulation method. Moreover, a three-dimensional of 1/2 H-beam spray cooling model has also been established. In order to obtain a better cooling effect, the angle between the nozzle center outside the R angle and the inner surface of the flange is defined as 45° and the distance between them is defined as 140 mm. The working pressure of the nozzle, the mean droplet size, and the water flow rate are also suggested to be 0.25 MPa, 150 µm, and 16 L/min, respectively. The recommended nozzle interval in the rolling direction is 300 mm to uniform the temperature distribution along the length direction. The temperature difference between the web and flange of the H-beam and the temperature difference in the height direction are decreased 234°C and 71.8°C, respectively.

Structure parameter selection in rolls during hot rolling

Roll that bears large rolling load during the hot rolling process is one of the important components of rolling mill. This paper describes an investigation into the stress level of roll using ANSYS software to model rolling process. Two FEM model involving in three-dimensional and nonlinear contact have been established successfully to evaluate the working stress of the roll barrel and roll end. The influence factors that include roll body diameter, roll neck dimension and root fillet of keyway in the roll end are also discussed to reduce roll stress. Some structural parameters of the roll have been suggested to reduce roll stress and ensure production safety. The study results provide new ideas for designing roll.

Analysis on parameter sensitivity and dynamic response of the mill drive system

In the process of rolling, torsion vibration of mill drive system may decrease the lifetime of components, reduce the production efficiency, and also induce harmful effects on quality of product, even damage the equipment performance. Using the lumped-mass method, the main drive chain is described by a branching asymmetrical model with ten-degree-of freedom. The mechanical subsystem and the electrical control loop are coupled through electromagnetic driving torque, and an electromechanical coupling simulation model is synthesized together. Based on this built model, the sensitivity of natural modes to the moment of inertia and the torsion stiffness is analyzed, and the best ways modifying system parameters to modulate the natural frequencies is studied. Under the different slope-load conditions, the evaluation indexes of dynamic speed droop and torque amplification factors of transition process are calculated and compared. All these research results are significant to structure design, parameter optimization and vibration control for the mill drive system.

Hopf Bifurcation and Feedback Control of Self-Excited Torsion Vibration in the Drive System

According to the general drive system consisting of motor, gear reducer and working-load, a torsion dynamics model with three-degree-of-freedom is established, in which the nonlinear resistance torque is considered. Based on the Hurwitz algorithm criterion, the Hopf bifurcation and critical points are analyzed and the stable parameter domains are obtained. Furthermore introducing the feedback controller into the initial system, the stability of self-excited vibration originating from the way of Hopf bifurcation is investigated. The critical parameters can be shifted by adjusting the linear gain for the purpose of enlarging the stable parameter domains. Applying the central manifold theorem, the amplitude of periodic motion and the unstable divergent vibration can be suppressed through selecting appropriate nonlinear control parameter. In addition, all these theoretical results are verified by numerical simulation.

Study on modal flexibility and sensitivity to parameters in the main drive system of rolling mill

Torsional vibration is universal in the main drive system of rolling mill. In this paper, the spring-mass system dynamic model describing torsional vibration is built, and proved to be feasible through comparing the first-order natural frequency with the experimental result. On the basis of the validated model, the modal energy and flexibility distribution is analyzed and the results indicate that the system energy is mainly centralized at the first-order mode, which is easily excited and most frequently observed in the actual rolling process. Moreover, the system sensitivity to the moment of inertia and the torsional stiffness is analyzed, and the best way modifying system parameters to modulate the natural frequencies is studied. All these conclusions are significant to structure design, parameter optimization and vibration control for the mill drive system.