Pass Schedule Research Articles

Effect of strain path on recrystallisation kinetics during hot rolling of Al–Mn

Hot rolling of an aluminium–1% manganese alloy has been carried out. Wedge shaped specimens were rolled in two pass schedules, of either two forward passes or a forward and a reverse pass to the same overall net strain. Through thickness marker pins were inserted to allow the investigation of plastic flow during the different rolling schedules. The reversed rolling technique allowed the determination of the effect of a strain path change on the recrystallisation kinetics during hot rolling. Following subsequent annealing, quantitative metallography indicated that the forward–forward specimens showed faster recrystallisation kinetics than the forward–reverse specimens, and produced a finer recrystallised grain size following equivalent thermomechanical treatments differing only in strain path. A through thickness microstructural gradient was found in all materials.

The application of AI techniques in the optimal design of multi-pass cold drawing processes

In the paper the problem of optimal pass schedule design in multi-pass wire drawing process is investigated. An automatic design procedure based on an effective artificial intelligence (AI) technique, namely simulated annealing (SA), is proposed. The developed algorithm is aimed to achieve a satisfactory balance of the drawing stresses on the material along the reduction sequence, maintaining in the meantime the drawing stress at each pass below a safety value. In this way both the optimal number of passes and the optimal drawing sequence are determined. The effectiveness of the design procedure is tested through the comparison of the sequences suggested by the algorithm with a set of industrial sequences for wires of different materials.

Analysis of surface roughness of cold-rolled aluminium foil

This paper describes a detailed analysis of the surface finish of aluminium foil which has been cold-rolled under industrial conditions in the mixed lubrication regime. The foil was rolled with freshly ground rolls at a constant speed for the first pass and at a wide range of speeds for the second pass. Samples were collected after the second pass. For comparison, samples were also collected after rolling with worn rolls. Surface replicas of the rolls were taken with surface replicating tape. The surface roughness of the strip samples and roll surface replicas was measured with a three-dimensional non-contact interferometric profilometer. The spectrum of the surface roughness was analysed by the fast Fourier transform method to identify the way in which different wavelengths of roughness behave. Theory suggests that longer wavelengths of roughness should be crushed more easily. This was confirmed by results. A new image analysis technique has been developed to identify and quantify the area of the micro-pits. To differentiate between these pits and grind marks transferred from the rolls, the height information was first filtered in the rolling direction using a digital filter. The low-frequency component of the surface roughness, which represents the contribution from the roll marks, was subtracted off to leave the pits. Results showed a significant decrease in pit area during the pass schedule, while there was a significant increase in pit area with increasing rolling speed during a single pass.

Bulk Mechanical Alloying for Solid-State Synthesis of Functional Materials

Bulk mechanical alloying is an alternative solid-state process, that can overcome several intrinsic difficulties in conventional mechanical alloying processes. The present process is adaptable to industrial production of functional alloys and compounds because of short processing times and the absence of contamination. With the aid of theoretical simulations in understanding the mechanical behavior, a pass schedule for each material system can be rationalty deduced.

テーパリーフスプリング用テーパ圧延制御法の開発

In order to produce Tapered Leaf Spring (TLS), a new Controlled Taper Rolling (CTR) method is developed. This process is a combination of the edge rolling used grooved rolls and the flat rolling. It is very important in this method to predict the deformation properties such as spread precisely. For the first pass, quadratic equations which relate the reduction in width and the mean thickness increment, is obtained. For the second pass, it was clarified that Ekelund's equation was good agreement with the experimental values even if the rolling diameter changed from 125mm to 720mm and the rolling temperature changed from 1073K to 1223K. The actual pass schedule to produce TLS is designed by using the data obtained from these steady sate rolling.It is afraid that there is large difference in the deformation and loading properties between the steady state rolling and the non-steady state rolling such as tapered rolling. However, it was clarified that the spread is not effected and projected contact length is effected in tapered rolling. The pass schedule based on the steady state rolling can be applicable and the rolling load and the rolling torque might be predicted by concerning the change of the projected contact length.

Satellite-mill rolling of U-shaped and H-shaped wires

The satellite mill with closed pass has been successfully applied to production of U- and H-shaped profiled wires. In this study, the influence of rolling parameters such as the pass schedule, the preform dimensions and the surface roughness of the roll groove has been investigated. It is shown that the satellite-mill rolling can form much higher ribs in products than a conventional method and has an advantage in its ability to fill the metal into roll grooves. This effect is enhanced by rougher grooves and by thicker preforms.

Analysis of asymmetrical hot strip rolling by the slab method

Two analytical models based on the slab method are proposed to examine the behavior of sheet at the roll gap during the asymmetrical hot strip rolling process. In model I, the effect of shear stress in vertical plane at the roll gap is considered, whereas this effect is neglected in model II. Neutral points between rolls and strip, rolling pressure distributions along the contact art length of rolls, rolling forces, and rolling torques can be calculated easily by these proposed analytical models. The results including rolling pressure distributions, rolling forces, and rolling torques by both models are compared. The rolling pressure distribution predicted by model I shows that a “pressure well” develops in the cross shear region. On the other hand, no “pressure well” is predicted in model II. Furthermore, the rolling forces predicted by model I are always lower than those measured in the experiment, whereas those predicted by model II are always higher. However, the averages of the values predicted by model I and II are in fairly good agreement with the experimental data. Thus this analytical approach can offer useful knowledge in designing the pass schedules of the asymmetrical hot strip rolling processes.

A study of the rolling of I-section beams

The shape rolling processes for an I-section beam are simulated by the simplified three-dimensional finite element method and experimented with a model material. Computer simulation results of the four passes in I-section beam rolling include the grid distortions, the cross-sectional area changes, the roll separating forces, and the roll torques. Experiments with plasticine as a model material are performed on the experimental two-high rolling mill. The experimental and the numerical results showed good agreements in the flow pattern and the strain distributions. It is shown that optimally designing the roll pass schedule for I-section beam rolling is possible.

Pass schedule optimal design in multi-pass extrusion and drawing by finite element method

A finite element-based approach is presented for pass schedule optimal design in multi-pass extrusion and drawing. A basic formulation of the design problem is described, with emphasis on employing the criterion of minimum forming energy as a basis for optimization. The procedure for calculating the design sensitivities is given, and a numerical test is conducted to evaluate the accuracy of the predicted design sensitivities. The approach is applied to the problem of optimizing the pass schedule in extrusion and wire-drawing under various design constraints. Comparison is made between the optimal and initial design to examine the effect of optimization on the process and product.

An analytical approach to asymmetrical cold strip rolling using the slab method

An analytical model for general asymmetrical cold rolling is proposed to investigate the behavior of sheet during asymmetrical rolling using the slab analysis. Neutral points between the upper and lower rolls and the strip, rolling pressure distribution along the contact interface of the roll and strip, and rolling forces, as well as rolling torque, can be calculated easily using this model. Rolling pressure distribution, rolling force, and rolling torque, which are affected by various rolling conditions such as roll speed ratio, thick-ness reduction, front and back tension, etc., are analyzed. Additionally, the limiting rolling conditions be-tween reduction and roll speed ratio, or front and back tension, under which the rolling process can be accomplished successfully, are discussed. By comparing analytical results and experimental measure-ments of rolling force, it is apparent that the proposed model can successfully provide useful knowledge for designing the pass schedule of the asymmetrical cold strip rolling process.

ファジィ多目的計画法による熱延仕上げミルのパススケジュール設計

ファジィ多目的計画法による熱延仕上げミルのパススケジュール設計

Improved thickness and shape accuracy with advanced pass scheduling in plate rolling

The so-called CROWN programs have been developed as a result of the co-operation in the Scandinavian Steel Industry. They consist of separate physical models for calculation of plate or strip temperature and roll thermal expansion, wear and elastic deformation. Flatness and residual stresses in the material are deduced from the relative change in profile during rolling with the aid of a shape vector method which considers the transverse metal flow in the roll gap. The CROWNON model is an on-line model which can be used for process control in rolling mills. A new optimized pass schedule generation system has been developed for the plate mill in Rautaruukki. The pass schedule is calculated in the forward direction for the sizing pass, broadside passes and the longitudinal passes. The drafts for the broadside and the first longitudinal passes are limited by maximum force, torque and strain. For the last longitudinal passes, the shape vector method is applied and the draft is restricted by the maximum steepness and flatness criteria. The change in the relative elongation differences between the centre and the edge of the plate together with experimentally determined values for the transverse metal flow (e.g. ξ-values) are used in the schedule calculation. To predict correct rolling loads during the scheduling, an adaptive temperature-dependant force-draft model is used based on statistical analysis of the rolling process. The system has decreased the number of passes, improved the yield and has provided the possibility of rolling thin, wide plates, e.g. 4.7 × 3250 mm with good flatness and minimum crown. The barrel length of Rautaruukki's plate mill is 3,6 m and the maximum rolling speed is 5 m/s. During the last years two dimensional and three dimensional Finite Element simulations of hot rolling of flat products have been made. The calculated rolling forces show very good agreement with experiments made in Rautaruukki's plate mill.

Development of Rib Plate Manufacturing Technique.

The use of concrete-filled, ribbed steel tubular columns has been increasing gradually in construction work. These columns offer high strength and stiffness, in addition to advantages in construction work, such as the elimination of formwork. The demand for integral rib plates in these concrete-filled, tubular columns will increase as more high-rise buildings are built in the future. This report presents a technique for manufacturing rib plate using multi-pass rolling. This technique was established by rolling rib plates on a trial basis using a plate mill at NKK's Fukuyama Works, after experiments on rib formation using lead and hot-rolled carbon steel. To assure the required rib shape and to prevent lap defects and distortion from rolling, the rolling pass schedule was established by combining the optimum rolling reduction in each pass with shape control using work roll shift and work roll bender technology. This technique enabled the efficient production of well formed rib plates by the multi-pass rolling method.

Three-dimensional simulation of gap-controlled plate rolling by the finite element method

It has been suggested that the proper use of a preform plate with a thickness profile could reduce yield loss in plate rolling. A complete three-dimensional rigid-plastic finite element code was developed for simulation of gap-controlled plate rolling in order to investigate the effect of preform shapes on the geometry of the final plates. Simulations are performed for two-pass rolling under several pass schedules of roll gap control. The results are compared to examine the effect of rolling schedule on the shapes of final plates.

Optimization of Pass Schedule from the View Point of Shape and Profile of Cold Rolled Strip

The paper aims at finding analytically an optimum pass schedule for producing strip with uniform thickness across the width and dead flat shape. The profile of strip is calculated by a three-dimensional analysis in which the elastic deformation of rolls and the plastic deformation of strip are considered as one system. The flatness defect is considered as the elastic buckling by the the residual stress which is calculated from the stresses at the exit of roll gap.

アルミニウム熱間粗圧延の計算機制御用数式モデル

Mathematical models to estimate the rolling force P and the rolling torque G of hot roughing mill of aluminum were developed. These models consist of equations to calculate the rolling force function QP, the torque arm coefficient λ and the mean flow stress Kfm. The equation of QP and λ are derived empirically by analysing the rolling data. The equation of Kfm is based on the empirical expression of the experimental data by complastometer. Almost satisfactory accuracy is achieved in estimating P and G. The calculating method to obtain the pass schedule in the restrictions of rolling force, rolling torque, angle of biting etc. was developed. The total number of passes reduces and the productivity of roughing mill for aluminum alloys increases by using this new pass schedule.

大同特殊鋼（株）星崎工場における分塊圧延圧下制御について

We developed an automatic reduction control system using mini-computer for the blooming mill of special steel rolling, for the purpose of improving accuracy of quality control and efficiency management.The functions of the system are (1) automatic selection of the pass schedule according to the rolling size and steel grade, (2) automatic position control and lost control alarm, (3) irregularity control in rolling, (4) systematic control of related equipment, (5) automatic data gathering, and (6) tracking of material from discharge to blooming up.This system has been successfully running at Hoshizaki plant of Daido Steel Co., Ltd. since installed in March, 1987.

Development and Practical Application of a Procedure for Computing Time-Optimized Pass Schedules for Reversing Rolling Mills

The extent of utilization of a rolling mill is essentially determined by the pass schedules used in rolling. Up to now scheduling for rolling in reversing rolling mills has mainly been done on the basis of experience. Owing to the complexity of the rolling process, however, it is often difficult to attain the productivity aimed at when such a procedure is followed. In what follows, a method is described which allows the computation of time-optimized pass schedules in reversing rolling mills, taking into consideration the constraints inherent in the process. The algorithm includes mathematical models describing the deformation process in the roll gap and the temperatures of the strip and the roils for predicting the process. A digital computer program was developed for the practical application of the procedure. It is used successfully in computing pass schedules for a 20-roll Sendzimir mill.

Roll pass design by interactive graphic computing

On the basis of experimentally determined lateral spread data a program for computer aided roll pass design was developed. The experimental data are expressed in terms of area ratios vs width-to-thickness ratio for different material properties. A maximum allowable deformation is put in by the designer and the program iterates until the calculation and experimentally determined value of the lateral spread coincide. Flash and neutral line are interactively selected. Center of gravity, initial cross sectional area (rectangular), and roll pass schedule are calculated. The results for a roll pass schedule are compared successfully with experiments. The program has been applied for different profile types (airfoil shapes, flat, and complex profiles) and compared with manually designed airfoil shapes.

Width necking at the rougher in a hot-strip mill

The accuracy of the width of a hot strip is very important for the improvement of yield, both for the steel maker and the steel user. One of the important technical problems concerning width accuracy is securing a final hot strip with uniform width along the whole length. In the top or tail portion of a hot strip, a local contraction of width unavoidably occurs, called “width necking” or simply “necking”. The amount of necking is determined mainly by the conditions of rougher rolling in the hot-strip mill. In this paper, the mechanism of necking, the influence of rolling conditions on the amount of necking and the optimum edger-rolling pass schedule are described. The main conclusions obtained are as follows: (i) Necking originates from the uneven distribution of dog-bone height along the length of a slab and the local steep width reduction in the top portion of the slab after edger rolling, but is lessened by the formation of flare during subsequent flat rolling; (ii) the amount of necking increases with the increase of slab width and edging draft and with decrease of slab thickness; and (iii) for the minimization of the amount of necking, heavy width-drafts in the early rougher-rolling stage are preferable to heavy width-drafts in the later rougher-rolling stage.