Mathematical modeling and simulation of the interface region of a tri-layer composite material,brass-steel-brass,produced by cold rolling

The object of this study was to find the optimum conditions for the production of a sandwich composite from the sheets of brass-steel-brass. The experimental data obtained during the production process were used to validate the simulation program, which was written to establish the relation between the interface morphology and the thickness reduction amount of the composite. For this purpose, two surfaces of a steel sheet were first prepared by scratching brushing before inserting it between two brass sheets with smooth surfaces. Three sheets were then subjected to a cold rolling process for producing a tri-layer composite with various thick- nesses. The sheet interface after rolling was studied by different techniques, and the bonding strength for each rolling condition was determined by peeling test. Moreover, a relation between interfacial bonding strength and thickness reduction was found. The simulation results were compared with the experimental data and the available theoretical models to modify the original simulation program with high application efficiency used for predicting the behavior of the interface under different pressures.

Preset model of bending force for 6-high reversing cold rolling mill based on genetic algorithm

The hydraulic roll-bending device was studied, which was widely used in modem cold rolling mills to regulate the strip flatness. The loaded roll gap crown mathematic model and the strip crown mathematic model of the reversing cold rolling process were established, and the deformation model of roll stack system of the 6-high 1 250 mm high crown （HC） reversing cold rolling mill was built by slit beam method. The simulation results show that, the quadratic component of strip crown decreases nearly linearly with the increase of the work roll bending force, when the shifting value of intermediate roll is determined by the rolling process. From the first pass to the fifth pass of reversing rolling process, the crown controllability of bending force is gradually weakened. Base on analyzing the relationship among the main factors associated with roll-bending force in reversing multi-pass rolling, such as strip width and rolling force, a preset mathematic model of bending force is developed by genetic algorithm. The simulation data demonstrate that the relative deviation of flatness criterions in each rolling pass is improved significantly and the mean relative deviation of all five passes is decreased from 25.1% to 1.7%. The model can keep good shape in multi-pass reversing cold rolling process with the high prediction accuracy and can be used to guide the production process.

Mathematic model of rolling pressure during a semisolid shearing-rolling process

A mathematic model of rolling pressure during a novel semisolid shearing-rolling process was established. The rolling pressure in this process is higher than that in the conventional rolling. The increment of rolling pressure in the backward slip zone is higher than that in the forward slip zone, and the neutral plane moves toward to the roll gap entrance. The maximum and the average rolling pressures increase with the decrease of strip thickness, and the effects of strip thickness on the rolling pressure is more obvious in the forward slip zone than in the backward slip zone. Meanwhile, the neutral plane moves toward the roll gap exit with the decrease of strip thickness. The maximum and average rolling pressures increase with the decrease of strip width, and the strip width affects the pressure more obviously in the backward slip zone than in the forward slip zone. At the same time, the neutral plane moves toward the roll gap entrance with the decrease of strip width. The maximum and average rolling pressures increase with increasing roll radius, and the neutral plane moves toward the roll gap exit.

Experimental Study and Finite Element Polycrystal Model Simulation of the Cold Rolling Textures in a Powder Metallurgy Processed Pure Aluminum Plate

Ingot metallurgy (IM) aluminum has long been the subject and attracted the attention of many metallurgists and textural researchers of materials. Due to the introduction of large amounts of ex situ interfaces, however, the textures in powder metallurgy (PM) processed aluminum has been rarely reported. In this article, a pure aluminum plate was prepared via PM route. The starting billet was first produced with uni-axially cold compaction and flat hot-extrusion and then followed by cold rolling processes. The hot-extruded and cold rolling deformation textures of the pure PM aluminum at 50%, 80% and 90% cold rolling reductions were studied by orientation distribution functions (ODFs) analysis. The finite element polycrystal model (FEPM) was finally utilized to simulate the cold rolling textural evolution at various stages of cold rolling. In FEPM simulation, the initial hot-extruded textures were taken into account as inputs. The results showed that typical β-fiber texture formed in pure PM aluminum with the cold rolling reduction increased till 80%, and there was not much change after excessive cold rolling deformation. Homogeneous slip is not the only deformation mode in PM processed pure aluminum plate at over 80% cold rolling reduction. The experimental results were qualitatively in good agreement with the simulated ones.

Force Parameter Model of 3-Roll Mills for Continuous Cold Rolling Wires

Based on experimental data, the mathematical model of rolling force parameters of 3-roll mills was studied. The structure ofthe model was theoretically set up and the coefficients were determined by static analysis of the data. The torque in continuous rollingwas measured, and the characteristics and efficiency of 3-roll mills are investigated.

TOOTH CURVES AND ENTIRE CONTACT AREA IN PROCESS OF SPLINE COLD ROLLING

In spline rolling process, the contact area between roller and workpiece plays an important role in calculating rolling-force and rolling-moment. For the purpose of studying the contact area, contact state between roller and workpiece in process of spline cold rolling based upon cross rolling is analyzed. According to the suitable hypothesis, the mathematic model of roller-tooth-curve in optional position of rolling process is established. Combing the theory of conjugate curves with the theory of envelope curve, the corresponding mathematic model of workpiece-tooth-curve is established. By utilizing establishing mathematic models, the algorithm of entire contact area in rolling process is created. On the basis of the algorithm, calculation-program is compiled under MATLAB program language environment. The calculation-program actualizes quantitative analysis and quantitative calculation of contact areas. Utilizing the calculation-program, the influence of parameters on contact area is analyzed, and the tendency is consistent with the manufacturing experience. In consideration of rolling-force optimization, the primary process parameters may be selected according to results of calculation. The result of the present study may provide basis for research on rolling-force and rolling-moment.

Research and Application of Non-symmetrical Roll Bending Control of Cold Rolling Mill

The existing research of the flatness control for strip cold rolling mainly focuses on the calculation of the optimum adjustment of individual flatness actuator in accordance with the flatness deviation, which can be used for general flatness control. However, it does not work for some special rolling processes, such as the elimination of ultra single side edge-waves and the prevention of strip break due to tilting roll control overshooting. For the purpose of solving these problems, the influences of non-symmetrical work roll bending and intermediate roll bending on flatness control were analyzed by studying efficiencies of them. Moreover, impacts of two kinds of non-symmetrical roll bending control on the pressure distribution between rolls were studied theoretically. A non-symmetrical work roll bending model was developed by theoretical analysis in accordance with practical conditions. The model was applied to the revamp of a 1250 6-H reversible universal crown mill (UCM) cold mill. Theoretical study and practical applications show that the coordination utilization of the non-symmetrical work roll bending control and tilting roll control was effective in flatness control when there appeared bad strip single side edge waves, especially when the incoming strip was with a wedge shape. In addition, the risk of strip break due to tilting control overshooting could be reduced. Furthermore, the non-symmetrical roll bending control can reduce the extent of uneven distribution of pressure between rolls caused by intermediate roll shifting in flatness control and slow down roll wear. The non-symmetrical roll bending control technology has important theoretical and practical significance to better flatness control.

Research and Development Trend of Shape Control for Cold Rolling Strip

Shape is an important quality index of cold rolling strip. Up to now, many problems in the shape control domain have not been solved satisfactorily, and a review on the research progress in the shape control domain can help to seek new breakthrough directions. In the past 10 years, researches and applications of shape control models, shape control means, shape detection technology, and shape con- trol system have achieved significant progress. In the aspect of shape control models, the researches in the past improve the accuracy, speed and robustness of the models. The intelligentization of shape control models should be strengthened in the future. In the aspect of the shape control means, the researches in the past focus on the roll opti- mization, mill type selection, process optimization, local strip shape control, edge drop control, and so on. In the future, more attention should be paid to the coordination control of both strip shape and other quality indexes, and the refinement of control objective should be strengthened. In the aspects of shape detection technology and shape control system, some new types of shape detection meters and shape control systems are developed and have successfully indus- trial applications. In the future, the standardization of shape detection technology and shape control system should be promoted to solve the problem of compatibility. In general,the four expected development trends of shape control for cold roiling strip in the future are intelligentization, coordi- nation, refinement, and standardization. The proposed research provides new breakthrough directions for improv- ing shape quality.

Control of Surface Thermal Scratch of Strip in Tandem Cold Rolling

The thermal scratch seriously affects the surface quality of the cold rolled stainless steel strip. Some researchers have carried out qualitative and theoretical studies in this field. However, there is currently a lack of research on effective forecast and control of thermal scratch defects in practical production, especially in tandem cold rolling. In order to establish precise mathematical model of oil film thickness in deformation zone, the lubrication in cold rolling process of SUS410L stainless steel strip is studied, and major factors affecting oil film thickness are also analyzed. According to the principle of statistics, mathematical model of critical oil film thickness in deformation zone for thermal scratch is built, with fitting and regression analytical method, and then based on temperature comparison method, the criterion for deciding thermal scratch defects is put forward. Storing and calling data through SQL Server 2010, a software on thermal scratch defects control is developed through Microsoft Visual Studio 2008 by MFC technique for stainless steel in tandem cold rolling, and then it is put into practical production. Statistics indicate that the hit rate of thermal scratch is as high as 92.38%, and the occurrence rate of thermal scratch is decreased by 89.13%. Owing to the application of the software, the rolling speed is increased by approximately 9.3%. The software developed provides an effective solution to the problem of thermal scratch defects in tandem cold rolling, and helps to promote products surface quality of stainless steel strips in practical production.

High-speed steel rolls used for cold rolling

During cold rolled production of steel, each change of rolls causes a halt in production and affects the roll＇ s grinding maintenance and consumption. Consequently,rolls are very critical to the costs of steel production. Besides the rolling accidents, surface quality problems, including inhomogeneous wear and a decrease of the surface roughness of the rolls are other main reasons for outage and a change of the rolls. Therefore, safe rolls, with superior wear resistance and roughness retentivity will be a future trend in the cold rolling steel industry. In this study, the property characteristics and in-service performance of high-speed steel （HSS） cold rolling work rolls at Baosteel are discussed. The results of this study indicate that in-service performance of HSS cold work rolls has an improvement over conventional rolls. Implementation of HSS work rolls will prolong the rolling campaign and improve the rolling stability, thus, the cost of cold rolling production can be better controlled.

Numerical simulation of roll temperature field and analysis of influence factor during the single-stand reversing cold rolling process

Accurate calculation results of roll temperature are the key factors in rolling cooling and lubricating technology during the single-stand reversing cold rolling process. By combining the high-strength steel rolling experiments ,the numerical simulation of roll temperature, and the influence factors in reversing cold rolling were studied. The research results correspond with those of rolling experiments and show that the research method could provide effective instruction for roll cooling and emulsion flow rate control during the on-site rolling process.

Slip Line Field Solution for Second Pass in Lubricated 4-High Reversing Cold Rolling Sheet Mill

The development of a possible slip line field (slf) for theoretical calculations of the deforming pressure (load) in a second pass of a lubricated cold rolling sheet mill and validation using values from an aluminium sheet rolling mill was done in this work. This will be relevant in the manufacturing industries providing an easy method for determining necessary applied rolling load. Experimental rolling was carried out to observe the shear lines in the deformation field. Construction of possible slip line field model was developed adhering strictly to assumptions of rigid plastic model. Calculation of the deforming force/load was achieved using Hencky’s equation. Results showed that the load calculations for constructed slip line field using aluminium sheet rolling as an example tallied with values obtained from Tower Aluminium rolling mill. Slip line fields constructed for the second pass described adequately the rolling pressure in the cold rolling process, giving a valid solution of the exact load estimates on comparison with the industrial load values. Roll pressure along the arc of contact rose fairly linearly from the entrance to a maximum at the exit point. This work showed that slf for the first pass in a cold rolling mill cannot be used for subsequent passes;it requires construction of slfs for each pass in the cold rolling process.

Roll gap prediction in acceleration and deceleration process of cold rolling based on a data-driven method

Severe fluctuation of the effective roll gap in the acceleration and deceleration section of the cold rolling process is a significant factor causing thickness deviation.However,the conventional roll gap compensation method and control strategy do not meet the stringent strip quality requirements.The roll gap model in the acceleration and deceleration process is studied to increase the thickness control precision.In order to improve model accuracy,a roll gap prediction method based on data-driven is proposed.Given the complexities of the cold rolling process,the extreme gradient boosting(XGBoost)method is used to predict the roll gap model as the rolling speed changes.Meanwhile,support vector regression and neural network-based methods are taken to evaluate and compare the prediction performances.Based on the field data,the simulation experiments are carried out.It demonstrated that the prediction performance of the proposed method outperformed the other two methods.The values of root mean square error,determination coefficient value,mean absolute percentage error and mean absolute error obtained from the XGBoost model were equal to 0.000346,0.952,7.02,and 0.00028,respectively.In addition,the proposed method analyzed the contribution rates of the rolling affecting parameters on the roll gap.The data showed that in the controllable rolling parameters,the rolling speed is the most impacting factor that disturbs the roll gap model in the acceleration and deceleration process,which can provide a useful direction for actual roll gap adjustment.

Coupling Dynamic Model of Chatter for Cold Rolling

In order to build high accuracy integral dynamic models of cold rolling mill system, by analyzing the vibration process of cold rolling, the dynamic model of 4-h mill, including the rolling process model, the mill roll stand structure model and the hydraulic servo system model is built. These three models are coupled and linearized, then the multiple input and multiple output （MIMO） linear transfer function model of single stand 4-h cold mill system is obtained. The model with the proposed data proves its validity, meanwhile the effects of different working conditions on the stability of cold rolling mill system have been discussed. Simulation resulsts show that the model accords with former models and has its own advancement. It contributes to the further study and supression of coupling vibraiton.

Modeling and Analysis of Interstand Tension Control in 6-high Tandem Cold Rolling Mill

The interstand tension control is one of the most important ways to meet tight tolerances for strip product quality during tandem cold rolling process. Using coordinate analysis and parabolic approximation for the mass flow balance principle, the strip velocities eliminating the use of forward slips and backward slips were calculated. In order to reduce the effect of roll eccentricity on the tension measurement, a filter based on bilinear transformation was de- signed. Applying a first-order Taylor series approximation, the transfer function matrix model of interstand tension stress was derived. The actual measurements on-site and the final calculation results showed that the established model had high calculation accuracy and was beneficial for interstand tension control of random cold rolling process.

Neural Network Friction Model for Cold Strip Rolling

A neural network friction model with very good prediction accuracy was developed on the basis of industrial data. Simulative calculation indicated that the accuracy of rolling force and motor power calculation can be improved using the calculated friction coefficient. It was found that reduction ratio and deformation resistance of strip has more effects than other parameters, and the effects of most parameters are affected by rolling speed.

DECOUPLED MODEL FOR FLATNESS CONTROL IN 4-H CVC COLD ROLLING MILLS

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Mathematical Model and Theoretical Research of Flow Shear Constitutive Relation during Rheo-rolling of Semisolid Alloy

The mathematical model of flow shear constitutive relation during rheo-rolling process has been established. The distribution of velocity and shear stress in rolling cavity was investigated, and the effects of process parameters on shear stress of Sn-15 Pb alloy during rheo-rolling process were studied. In rolling cavity, the nearer the roll is, the bigger the velocity and shear stress are. The shear stress increases with the increment of the roll speed and the roll radius during rheo-rolling process, but deceases with the increment of the thickness of the strip. When the solid fraction of Sn-15 Pb alloy increases from 0.3 to 0.5, the shear stress increases slowly, but when the solid fraction increases from 0.5 to 0.6, the shear stress rapidly.

MODELING OF FERRITE GRAIN GROWTH OF LOW CARBON STEELS DURING HOT ROLLING

For most commercial steels the prediction of the final properties depends on accurately calculating the room temperature ferrite grain size. A grain growth model is proposed for low carbon steels Q235B during hot rolling. By using this model, the initial ferrite grain size after continuous cooling and ferrite grain growing in coiling procedure can be predicted. In-plant trials were performed in the hot strip mill of Ansteel. The calculated final ferrite grain sizes are in good agreement with the experimental ones. It is helpful both for simulation of microstructure evolution and prediction of mechanical properties.

SENSITIVITY ANALYSIS FOR ROLLING PROCESS BASED ON SUPPORT VECTOR MACHINE

A method for the calculation of the sensitivity factors of the rollingprocess has been obtained by differentiating the roll force model based on support vector machine.It can eliminate the algebraic loop of the analytical model of the rolling process. The simulationsin the first stand of five stand cold tandem rolling mill indicate that the calculation forsensitivities by this proposed method can obtain a good accuracy, and an appropriate adjustment onthe control variables determined directly by the sensitivity has an excellent compensation accuracy.Moreover, the roll gap has larger effect on the exit thickness than both front tension and backtension, and it is more efficient to select the roll gap as the control variable of the thicknesscontrol system in the first stand.