Roll Profile Research Articles

열간압연 공정에서 롤 프로파일 예측모델 향상

In hot strip rolling, the work roll profile is one of the main factors in predicting and correcting the strip profile. Various studies concerning the wear profile and the thermal crown of work roll have been performed, and the results of these studies have shown that the work roll profile must be predicted accurately so as to efficiently control the strip qualities such as thickness, crown, flatness, and camber. Therefore, a precise prediction model of roll profile is called for in a perfect shape control system. In this paper, a genetic algorithm was applied to improve on the roll profile prediction model in hot strip rolling. In this approach, the optimal design problem is formulated on the basis of a numerical model so as to cover the diverse design variables and objective functions. A genetic algorithm was adopted for conducting design iteration for optimization to determine the coefficient of the numerical model for minimization of errors in the result of the calculated value and the measured data. A comparative analysis showed a satisfactory conformity between them.

Comprehensive contour prediction model of work roll used in online strip shape control model during hot rolling

Initial, thermal and wear contours of the work roll are three major sources of mill disturbance and play critical roles in crown and shape control of strip. To simplify the complex contour curve of the work roll resulting from superposition of three kinds of contour mentioned above in the online strip shape control model, a comprehensive contour concept of the work roll and its predictive calculation model are put forward in the present work. Predictive calculation of the comprehensive contour of the work roll in the online strip shape control model during hot rolling consists of two important parts, namely wear contour calculation and thermal contour calculation, which have a direct influence on the accuracy of shape control. A statistical wear model and a finite difference thermal contour model of the work roll are described in the present work. The comprehensive contour is the sum of grinding, wear and thermal contours. This comprehensive contour calculation model has been applied successfully in a real online strip shape control model. Its high precision has been proved through the large amounts of actual roll profile measurement and theoretical analysis. The hit rates (per cent of shape index satisfying requirement) of crown and head flatness of the strips rolled by using the shape control model, which includes the comprehensive contour calculation model, have increased about 16 and 10% respectively, compared with that of strips rolled using manual operation.

Real-time kinematic tracking of towed AEM birds

In the absence of attitude and altitude sensors directly attached to the bird, helicopter airborne electromagnetic (AEM) data are typically interpreted assuming that the sensor bird maintains a fixed attitude as well as fixed vertical and horizontal offsets relative to the helicopter during survey. Laser altimeters fitted to the bird can be used for measuring bird-height over land, but these altimeters do not necessarily function over seawater, and in this case a fixed vertical offset is subtracted from the helicopter altimetry to estimate the height of the bird above sea level. With current navigation technology, these assumptions could be overcome by incorporating suitable altimetry and navigation sensors into AEM systems. We constructed an airborne testing rig to represent an AEM bird and fitted GPS, inertial navigation, and altimetry sensors to accurately measure bird attitude and height above seawater (as required for bathymetric mapping) during typical and atypical AEM-survey flight conditions. Bird height above sea level was measured with radar and laser altimeters, and was also estimated from the GPS receiver height. Bird attitude was obtained from the inertial navigation unit (INU) data and was compared with attitude data derived from a triangular configuration of three GPS antennas. Each antenna was linked to a pair of GPS receivers to allow comparison between dual-frequency, high-fidelity and single-frequency, low-fidelity measurements.Bird attitude and altimetry measurements were recorded during surveys flown offshore Tickera Bay (Spencer Gulf, SA) and within Broken Bay (Sydney, NSW). These surveys were flown at a maximum altitude of 180 m, with bird roll angles up to about ± 40°. Using dual-frequency GPS receivers, the agreement between heights derived from GPS and laser (radar) altimeter data is typically ~0.3 m (0.6 m). GPS antenna separations computed during flight from measured GPS positions gave agreement to within 0.4% (typically 0.2%) of measured values. The agreement between pitch and roll angles computed from GPS antenna positions and INU measurements was within ~1° and 2° respectively, neglecting the effects of any offsets in the alignment of coordinate axes between the two systems. A comparison of pitch and roll angles obtained from single and dual-frequency GPS receivers showed that the accuracy of pitch and roll angles obtained from single-frequency GPS receivers is generally about ± 2°. The discrepancy in results from the different GPS receivers increases at various points along the flight path. This increase was attributed to a decrease in accuracy in results from the single frequency GPS receivers. Roll and pitch angle profiles show oscillations consistent with harmonic (pendulum) motion of the bird at the end of the tow cable connecting the bird to the helicopter. We recommend the use of inertial navigation interfaced to a single dual-frequency GPS receiver for accurate attitude and position measurements, combined with laser and radar altimetry sensors. The future implications of this study are that we expect to accurately measure attitude and altitude of a towed bird over seawater and that consequently these altimetry and attitude sensors will be implemented on a new helicopter TEM system (SeaTEM) specifically designed for bathymetric mapping.

Comprehensive contour prediction model of work rolls in hot wide strip mill

The predictive calculation of comprehensive contour of work rolls in the on-line strip shape control model during hot rolling consists of two important parts of wear contour calculation and thermal contour calculation, which have a direct influence on the accuracy of shape control. A statistical wear model and a finite difference thermal contour model of work rolls were described. The comprehensive contour is the equivalence treatment of the sum of grinding, wear, and thermal contours. This comprehensive contour calculation model has been applied successfully in the real on-line strip shape control model. Its high precision has been proved through the large amounts of actual roll profile measurements and theoretical analyses. The hit rates (percent of shape index satisfying requirement) of crown and head flatness of the strips rolled, by using the shape control model, which includes the comprehensive contour calculation model, have about 16% and 10% increase respectively, compared to those of strips rolled by using manual operation.

Use of Taguchi method to study a robust design for the sectioned beams curvature during rolling

Abstract Finite element DEFORM™ 3D software is employed to examine the plastic deformation behavior of V-sectioned and T-sectioned porous beams at the roll gap under various rolling conditions. The finite element code is based on a rigid–plastic model in which it is assumed that the rolls are rigid bodies and that the temperature change induced in the beams during rolling is sufficiently small that it can be ignored. The analytical model is used to systematically examine the effect of the inclination angle of the roll profile, the friction factors between the rolls and the beam, the roll radii and the angular speed of the upper and lower rolls on the curvature of the rolled beam, the rolling torque, the effective strain, the effective stress and the variation of density of the rolled product at the exit. The Taguchi method is employed to design the rolling parameters to optimize the curvature of the beams. The analytic results have shown that: (1) the inclination angle of the inner part (i.e. vacancy) of the upper roll, the friction factor of the lower roll, the angular velocity of the lower roll and the roll radii, respectively, all have a significant influence upon the curvature of the rolled V-sectioned product, κ = 1/ra; (2) the reduction ratio of the porous beam, the friction factor of the lower roll, the angular velocity of the lower roll, and the roll radii, respectively, all have a significant influence upon the curvature of the rolled T-sectioned product, κ = 1/ra.

ワークロールシフトミルにおける板厚・板クラウン予測モデルの開発

In the work roll shift mill, a wide control range of the plate crown can be achieved by using an unsymmetrical work roll profile. The roll deformation of the mill has effected by not only the rolling load and the bending force of the work roll but also the work roll shift position and the work roll profile.The authors have formulated the simplified models of the gauge and the plate crown considering the above effects. These models consist of the mill housing deformation, the roll deformation in the kiss roll state and the roll deformation in the plate rolling, and are derived by dealing strictly with the roll deformation and the mill stretch.The accuracy of the new models has been compared with the point matching method and the actual plate rolling data.It is verified that these models can flexibly follow up the work roll shifting and the unsymmetrical work roll profile.

A Finite Element-based On-line Model for the Prediction of Deformed Roll Profile in Flat Rolling

A sound model for the prediction of the deformed roll profile during rolling is vital for the precision control of the profile and shape of the product. In this paper, the prediction accuracy of the conventional models is examined, using the predictions from the finite element model as benchmarks. Then, it is shown that a new, precision on-line model can be developed on the basis of the finite element model. The prediction accuracy of the new model is demonstrated through comparison with the predictions from the finite element model.

SASS applied to optimum work roll profile selection in the hot rolling of wide steel

The quality of steel strip produced in a wide strip rolling mill depends heavily on the careful selection of initial ground work roll profiles for each of the mill stands in the finishing train. In the past, these profiles were determined by human experts, based on their knowledge and experience. In this research, SASS, a novel heuristic optimisation algorithm that has only one control parameter, has been used to find the optimum profiles for a simulated rolling mill. The best set of profiles found by SASS clearly outperformed the original set and performed equally well as conventional algorithms without the need of finding a suitable set of control parameters.

Cold rolling of galvanized strips: A new approach to the evaluation of zinc fines formation

The study concerns a specific cold rolling process called skin-pass with a very low reduction ratio. The skin-pass allows a roughness transfer from the work roll to the galvanized strip. The goal of this paper is to propose a predictive approach to the formation of zinc fines. First, the skin-pass contact conditions were reproduced on a specific testing device, called the Skin-pass Upsetting Rolling Test (SKURT) developed in the authors’ laboratory. Tests on galvanized strips were performed and the zinc fines produced quantified on the strip and on the tool. Secondly, the numerical model was refined at the vicinity of the contact zone taking into account different surface profiles of the roll. Material data were coupled with Lemaitre's damage criterion in order to predict the wrenching phenomena of the zinc coating. These predictions were compared with experimental measurements. The correlation was found to be good and a less polluting roll profile is numerically validated.

Advanced finite element modelling of plate rolling operations

The aim of this work was to develop an advanced finite element model of a plate mill, including the major mill components, the mill set-up engineering condition, the profile of the mill rolls (incorporating ground-on profile, thermal camber and wear effects), the stock geometry and the stock material properties, allowing detailed study and simulation of plan-view shape evolution. Following calibration, the model results will be used to quantify the influences of mill/rolls/stock condition on PVS/yield loss, and to compare the effectiveness/mutual interactions of potential control actuators/strategies.

Use of Taguchi method to develop a robust design for the shape rolling of porous sectioned sheet

This study applies the Taguchi method to optimize the process parameters for the shape rolling of porous sectioned sheet. A three-dimensional finite element code, DEFORM 3D, is proposed to examine the plastic deformation behavior of the porous sheet at the roll gap during the shape rolling of V-sectioned sheet. The finite element code adopts a rigid-plastic model, in which the rolls are assumed to be rigid bodies and temperature changes during rolling are ignored. The analytical model is used to systematically examine the dependence of the filling ratio at the roll gap, the mean stress and the variation of density at the exit of the rolled product on various rolling conditions, including the inclination of the roll profile, the round arc radius of the inner roll, the rolling radius, and the thickness reduction of the porous sheet, etc. The present simulation results confirm the effectiveness of the proposed robust design methodology for the shape rolling of porous sheets.

Finite-Element Modeling of the Nonlinear Behavior of Bolted T-Stub Connections

This paper describes a finite element model for the characterization of the nonlinear behavior of bolted T-stub connections that idealize the tension zone of bolted joints. Two different types of T-stub elements are considered: rolled profiles that are cut along the web, and two plates, flange and web, that are welded in a T shape by means of a continuous fillet weld. The results of existing experimental work are used to calibrate the models. It is found that the numerical approach allows the quantitative actual response to be accurately reproduced. In the case of welded T-stubs, the differences between the numerical model and the experiments are greater due to the effects of residual stresses and modified mechanical properties close to the weld toe, which are not easy to quantify. A parametric study is also undertaken to provide insight into the overall behavior, failure modes, and deformation capacity of the various specimens. A proposal for prediction of failure criteria of these simple connections is also presented and discussed.

可撓性に優れたバックアップロールとコンケーブ状プロフィールを付与した第1中間ロールによる形状制御

Flexible shaft backing assemblies (FSBAs) have been introduced into an actual 20-high Sendzimir mill and shape control technology using FSBAs has been investigated. In our previous paper, it was found that the shape control range was extended by the introduction of FSBAs, mainly toward the quarter buckles side and edge waves side. Thus, shape control technology with the combination of FSBAs and the first intermediate rolls given a concave profile partially (concave rolls) was investigated to improve quarter buckles. From simulations carried out using the analysis model which was described in the previous paper, it was found that quarter buckles were improved by optimizing the concave roll profile. In experiments using rolls with the concave profile in the 20-high Sendzimir mill, it was confirmed that quarter buckles were improved under extensive rolling conditions. It was also confirmed that better strip shape was obtained by combining FSBAs and concave rolls than using only concave rolls. FSBAs and concave rolls have been applied to commercial production and have contributed to the improvement of strip shape.

Dimensional Analysis in Steel Rod Rolling for Different Types of Grooves

Sequence design for shape-rolling processes consists of roll pass and profile design, i.e., transforming the billet into a final shape. For the prediction of the mean effective strain of the workpiece during rod rolling, an analytical model by Shinokura and Takai was used. They verified the formula by applying it to a variety of rod-rolling geometries (oval-square, oval-round, square diamond, and diamond-diamond). Today, on the other hand, the finite element (FE) techniques allow analysis of rolling processes in such a way as to simplify the work of design engineers. In this study, a round-oval pass and a round-flat oval pass are analyzed for steel rod rolling. In particular, the analysis of the spread, the surface profile, and cross-sectional area of the workpiece were conducted during rolling. Experimental data such as the maximum spread and the radius are compared with the results of the analytical model and FE analysis.

Tribological behaviour of hot rolling rolls

The study of wear mechanisms represents a very important task for the development of roll materials, with improved hot tribological properties. In the present paper the wear behaviour of different materials, i.e., high alloy steels (high speed steels (HSS)) and cast irons (high chromium irons (HiCr) and indefinite chill irons (IC)), produced by centrifugal casting, has been comparatively evaluated by means of a rolling sliding hot wear test. A disc specimen of C40 plain carbon steel, induction heated up to 700 °C, is allowed to rotate against a high alloy steel/iron at 200 rpm, corresponding to a slip rate of 28%, for a total period of time comprised between 1 and 3 h. A maximum contact hertzian stress of 300 MPa was imposed. The wear rates have been evaluated by weight measurements of the specimen, before and after each test period. The surface roughness was also determined as representative for the roll profile retention during service. The friction was continuously monitored. The wear mechanism is given by the combination of abrasion and oxidation. High speed steels show remarkable lower wear rates than high chromium and indefinite chill irons, because of their higher hot hardness. The retention of high hardness at elevated temperature is very important to reduce abrasive wear and also to support the protective oxide layer which develops on the surface of the roll material. As a general rule the roughness at the end of test tends to increase with increasing wear rate, as demonstrated by the relatively soft indefinite chill iron. However, the oxidation resistance also influences the final roughness, higher roughness values being observed for poorly oxidized materials. A simplified model explaining this experimental evidence is proposed.

Mathematical Model for the Thin Strip Cold Rolling and Temper Rolling Process with the Influence Function Method

A mathematical model for the thin strip cold and temper rolling process has been developed using the influence function method. By solving the equations describing the roll gap phenomena in a unique procedure and considering more influence factors, the model offers significant improvements in accuracy, robustness and generality of the solution for the thin strip cold and temper rolling conditions. The relationship between the shape of the roll profile and the roll force was also discussed. Calculation results show that any change increasing the roll force may result in or enlarge the central flat region in the deformation zone. Applied to the temper rolling process, the model can well predict not only the rolling load but also the large forward slip. Therefore, the measured forward slip, together with the measured roll force, was used to calibrate the model. The model was installed in the setup computer of a temper rolling mill to make parallel setup calculations. The calculation results showed good agreement with the measured data and the validity and precision of the model were proven.

An approximate method for the solution of an influence function foil rolling model

Fleck and Johnson (Int. J. Mech. Sci. 29 (1987) 507) and Fleck et al. (Proc. Inst. Mech. Eng. 206 (1992) 119) have developed foil rolling models which allow for large deformations in the roll profile, including the possibility that the rolls flatten completely. However, these models require computationally expensive iterative solution techniques. A new approach to the approximate solution of the Fleck et al. (1992) Influence Function Model has been developed using both analytic and approximation techniques. The numerical difficulties arising from solving an integral equation in the flattened region have been reduced by applying an Inverse Hilbert Transform to get an analytic expression for the pressure. The method described in this paper is applicable to cases where there is or there is not a flat region.

Three-Dimensional UBET Simulation Tool for Seamless Ring Rolling of Complex Profiles

Simulation of complex ring profiles using an improved Upper Bound Elemental Technique (UBET) is presented in this paper. The profile of the ring is approximated with a collection of triangular-prismatic and rectangular-brick elements. A generalized solution procedure is proposed to find the optimized kinematically admissible velocity field for the unique three-dimensional material flow experienced in shape rolling. Close agreement between numerical results obtained from simulations and available data for profile ring rolling has been observed for high-temperature aerospace materials. It has been demonstrated that the complex ring profiles used in aerospace industry can effectively be simulated using the current software tool.

Hard disc drive air bearing design: modified DIRECT algorithm and its application to slider air bearing surface optimization

Hard disk drives continue to increase in areal data density. This requires air bearing sliders with lower and lower flying heights (FH). Also the uniformity of the FH and the flatness of the roll profile with radius become more critical as the FH gets lower. By using modern optimization techniques, it is possible to optimize slider air bearing surface (ABS) designs according to multiple design goals. In this paper, we discuss two modifications to the DIRECT algorithm: one to handle tolerance and one to deal with hidden constraints. Some numerical experiments were carried out using these modifications and the modified DIRECT algorithm was applied to slider ABS optimization. The results show that these two modifications can improve the efficiency of the DIRECT algorithm and they also provide more flexibility in slider ABS optimization.

Finite element simulation of profile rolling of wire

The profile rolling or wire is investigated by means of a finite element model. Three-dimensional simulation of wire rolling process with a round cross-section of wire by two cylindrical rolls is considered. The same example is simulated by a 2D generalised plane strain finite element model. The results for lateral spread from those two models are compared with the experimental one. The results for more complicated shape of rolls for three passes rolling are shown.