Plate Mill Research Articles

Front End Bending in Plate Rolling Influenced by Asymmetrical Entrance Angle

Material rolled in heavy plate mills and roughing stands often bends upwards or downwards. This phenomenon can lead to poor shape, profile and quality of the product, as well as lower productivity. This paper focuses on the well- known bending due to the related asymmetrical entrance angle between the rolling stock and work roll which can easily cause asymmetrical shape factor in deformation zone. A model for calculating curvature quickly is deduced based on the condition of asymmetrical entrance angle. Results show that the front end bending can occur easily due to the asymmetrical entrance angle. Moreover, the bending inclination of large reduction, large radius of roll and thin rolling stock is greater than that of the reverse; the bending inclination of the entrance thickness of rolling stock is greater than that of the reduction, and the bending inclination of the reduction is greater than that of the radius of roll.

Approach to evaluate the rolling mill capacity in a plate rolling process

This study presents an approach to evaluating the rolling mill capacity from the viewpoints of productivity and revamping cost when a plate mill is upgraded. In this light, a concept is proposed of a ‘characteristic length’, defined as the ratio of the design torque of the drive motor over the design force of the rolling equipment (structure of the rolling mill). A draft schedule algorithm for the plate rolling process is also presented, which consists of a force–thickness relation at each pass, and a roll force and torque prediction model. Using the draft schedule algorithm linked with the characteristic length, a series of plate rolling analyses was performed to examine the productivity of a plate mill while varying: (i) the design force of the rolling equipment; (ii) the design torque of the drive motor; (iii) both its design force and torque; and (iv) the strength of the slab. In addition, as a practical example, the proposed approach has been applied to three actual plate mills in Korea, China, and Russia. The results reveal that upgrading the design torque is the most efficient method from the viewpoint of productivity and revamping cost. It was also found that a critical characteristic length exists in which productivity cannot be increased any further, even though the rolling mill capacity has been upgraded further. Hence, this critical characteristic length can be used as an index to avoid the overcapacity problem of a plate mill when it is revamped.

A Framework for Adaptive Online Thickness Control at Plate Mill of Bhilai Steel Plant

The Plate Mill at Bhilai Steel Plant (BSP) has two reversing stands, one functioning as the roughing mill, and the other as the finishing mill. The nominal thickness of the slab is 245 mm, which is reduced to about 40 mm as thick plates in the roughing mill and the thinner plates are processed further in the finishing mill. The Plate Mill is now undergoing a major revamp with the main component being the hydraulic automation gap control (HAGC) and the supporting automation systems. The HAGC is backed up by proper sensors, instrumentation, microprocessor-based control equipment working in real time. The installation of the HAGC provides for controlling thickness variations due to process variables like plate temperature, mill spring, and so on. Mathematical models for both off-line simulation and adaptive mill setup have been developed indigenously for automatic control of plate thickness in the revamped Plate Mill. The control of thickness of the plate from head to tail is envisaged as a two-step process, viz., (i) a Level II Adaptive Algorithm, where an optimum drafting schedule generated “on the fly” is downloaded as reference points for the Level 1 automation and (ii) a Level 1 Feedback Controller for applying the necessary correction in the roll gap, for process deviations during rolling. The off-line mathematical models have been validated with extensive data collected from the mill. Once they are implemented online, it is anticipated that continuous updating will improve its performance and will reach international levels of performance guarantee.

Artificial Neural Network Modeling for Prediction of Roll Force During Plate Rolling Process

Accurate prediction of roll force during hot rolling process is very important for model based automation (Level-2) of plate mills. Exit thickness of plate for each pass is calculated from roll gap, mill spring, and predicted roll force. The response of gauge control hardware is highly dependant on the accuracy of prediction of roll force. Traditionally, mathematical models based on plane homogeneous plastic deformation theory are used for prediction of roll force. This method is based on many simplified assumptions which are not valid for actual industrial application. An artificial neural network (ANN)–based data driven model has been developed for prediction of roll force during plate rolling process. A very accurate data acquisition system has been installed in Plate Mill of Bhilai Steel Plant through which input and output parameters have been recorded. For a particular grade of steel, inputs to the ANN model are roll gap of previous pass, roll gap of current pass, rolling temperature, rolling speed, plate width, and pass number (6 inputs). The model output is roll force (1 output). In this article, the methodologies of development, training, and validation of ANN model has been discussed. Feed forward network has been chosen as ANN structure. Back propagation algorithm with variable learning rate and conjugate gradient optimization of cost function has been chosen as network training methodology. The model was found to be highly accurate with r-square value about 0.94.

New Method of Characterizing and Quantifying Complex Microstructures in Steels

From the late 1960s through the late 1970s, high strength microalloyed steels hot rolled to strip and plate exhibited ferrite-pearlite microstructures with yield strengths essentially limited to the range of 350–420 MPa. However, the advent of the energy crisis of the late 1970s led to the demand for steels of higher strengths, while maintaining acceptable levels of other properties such as weldability, toughness, and formability. Since the late 1970s, it has been recognized that the strengthening mechanisms present in ferrite-pearlite steels had reached their limit in terms of grain refinement and solute and precipitation hardening; hence the barrier of 350–420 MPa was a real restraint. At about the same time, it was also recognized that higher strengths in as-processed steels could only be achieved through the use of ferrite of lower temperature formation, i.e., non-polygonal, acicular, bainitic, or martensitic ferrite, either as a monolithic matrix microstructure or as a combination. This change in achievable microstructures was abetted by interrupted accelerated cooling, either on the runout table of a strip mill or after the finishing pass in a plate mill. Hence, high strength hot rolled or the later cold work and annealing (CRA) and/or continuous galvanizing line (CGL) processed steels, with strengths in excess of 420 MPa, now exhibit these complex microstructures. It is not uncommon today for a 490 MPa yield strength steel to exhibit a microstructure comprised of several types of microsconstituents: non-polygonal ferrite, bainite, martensite, and perhaps retained austenite. Traditional metallographic techniques are no longer capable of analyzing these complex microstructures, especially in a quantitative fashion. The inability to characterize and quantify these complex microstructures means that the true strengthening mechanisms operative in these steels may be incorrectly understood and evaluated. The recent application of the quantitative analysis of the image quality (IQ) of the Kikuchi pattern resulting from the Electron Bank Scattered Diffraction (EBSD-IQ) has led to an innovative way to quantitatively analyze complex microstructures in the higher strength steels. This article will present the technique and show where it has been used successfully in research studies involving a broad range of steels including high strength low alloy (HSLA), MA, DP, and TRIP steels.

Development of 780MPa Grade Steel Plate by Microstructural Control Containing M-A through the On-Line Heating Process

High strength steel plates with 780MPa in tensile strength, suitable for building construction use, have been developed. The steel plates provide excellent combination of high strength, toughness, deformability and weldability. The key technology to obtain the excellent combination in mechanical properties of the steel is the microstructural control of M-A (martensite-austenite constituent) and the bainitic ferrite dual-phase structure, through the on-line heat treatment immediately after the accelerated cooling in Thermo-mechanical control process (TMCP). The developed steel plates have microstructure of fine M-A dispersed in the bainitic ferrite matrix. Basic metallurgical research revealed that the transformation behavior and microstructural morphologies were varied with the cooling stop temperature before the on-line heating, and the on-line heating temperature itself. Trial production of the developed 780MPa grade steel plates was also carried out with the plate mill. The obtained plates showed the satisfactory combination of high strength, low yield ratio, toughness.

The Analysis of the Process of Asymmetric Rolling of Plates

In this work there has been conducted theoretical analysis of the process of asymmetric rolling of plate in finishers of plate mills. On the basis of the carried out research the influence of asymmetry factor av, deformation ε and strip form h0/D on strip bend during the process of rolling has been determined. For this reason, the following resolutions have been pointed out: velocity of flow, pure shear and intensity of deformation in deformation zone.

Thermal Behaviour of Steel Plate during Accelerated Cooling

Recent trends in the production of high strength steel plate call for increasingly sophisticated thermo-mechanical treatment schedules, including the use of high rate accelerated cooling after finish rolling in order to achieve the desired microstructure and mechanical properties. Achieving the necessary cooling process control accuracy in such cases requires a sound understanding and description of the interactions between external heat transfer processes and changes in internal energy due to phenomena such as solid-state phase transformations. The thermal physical properties of the evolving microstructures of complex phase and martensitic steels vary greatly, and are strongly dependent on temperature and constituent phases. As a result, critical parameters such as thermal diffusivity cannot be accurately estimated without appropriate linkage to both phase transformation kinetics and temperature. In the present study, a numerical simulation has been developed to investigate the unsteady heat transfer and phase transformation behaviour of a moving steel plate during accelerated cooling. The simulation includes semi-empirical microstructure evolution sub-models, fitted to measured CCT data using non-linear regression. These are coupled to thermal-physical properties sub-models and thermal conduction calculations. A comprehensive suite of thermal boundary condition models which account for direct water cooling, forced convection film boiling, air cooling, radiation and heat transfer between plate and transport rollers are also included. The required equations for the plate temperature and microstructure evolution are solved numerically using a cell centred finite volume method, and the model has been validated by comparing simulated cooling stop temperatures with measurements obtained on the plate cooling section of an industrial plate mill. The predicted cooling stop temperatures of steel plates for different thicknesses, velocities and water flow rates are in good agreement with plant operational data.

Suppression of regenerative chatter vibration in simultaneous double-sided milling of flexible plates by speed difference

This paper presents a new method to machine flexible plates with high accuracy and high productivity. Precision steel plates are finished conventionally by face milling with electro-magnetic chucks. It is difficult to correct flatness of the flexible plates, because they deform to fit the chuck surfaces when chucked. To solve this problem, the authors have tried simultaneous double-sided milling, but this causes the regenerative chatter vibration. Thus, the new method is proposed and verified to suppress this chatter vibration, in which the regenerative effects on both sides are cancelled out by rotating the two milling cutters at different speeds.

Cut Scheduling Optimization in Plate Mill Finishing Area Through Mixed-Integer Linear Programming

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> The recent development of steel technologies for plate production introduced new control and optimization issues that modern automation systems need to take into account. In this paper, the integration in an automation system of mixed-integer linear programming, which now relies on extremely efficient algorithms, and the use of new sensors for automatic detection of defects for the optimization of production and quality are presented here. </para>

A Kind of Plate Laminar Cooling Strategy With High Response and Steady Precision

After Smith Predictor being used to laminar cooling system, the control law for integral regulators is introduced. New notion of plate sample length is given for evading the delay time varying with the roll table speed. It is found that the integral algorithm is more controllable for system regulating process and has better steady state precision. Compared with the traditional control strategies, the new control law has faster response speed and higher steady state precision. The controller can be regulated in shorter time and the response is faster than that of routine controller and it can effectively eliminate the oscillatory instability. Owing to its easy realization and high stability, it has been applied to a plate mill. The accuracy of finish cooling temperature can be controlled within ±10 °C.

응집침전에 의한 제철공장 냉각수질향상

This study was initiated to improve the cooling water quality by chemical coagulation and sedimentation in steel mills. Due to the inefficient flocculation in the settling tanks of blast furnace cooling water systems, the solid particles in the cooling water overflow accumulate and clog the cooling system. To protect the cooling water system from such fouling, proper flocculants must be continuously used. Laboratory tests were performed for the indirect cooling water system of a plate mill. The batch test in the gas scrubbing cooling water system of a blast furnace showed that the proposed coagulant was more effective for the improvement of coagulation and sedimentation than the existing one. During the tests, cationic flocculants were more effective than use of only an anionic flocculant. The suggested combination of anionic and cationic flocculants can probably improve the turbidity removal efficiency of the cooling water. Proper control of the overflow rate by the designed residence time would help turbidity removal efficiency in the settling tank. In addition, the settling can be enhanced by adopting rapid and slow mixing alternatively. Scale problems in blast furnace cooling water system were reduced to some extent by efficient settling.

후판 압연시 선단부 두께편차 보상을 위한 롤갭 설정에 관한 연구

The roll gap set-up in the finishing mill is one of the most important technologies in the hot plate rolling process. As the target thickness can be obtained by the correct set-up of the roll gap, improving the roll gap set-up technology is very critical for plate thickness accuracy. The main cause of thickness variation in hot plate mills is the non-uniform temperature distribution along the length of the slab. The objective of this study is to adjust the roll gap set-up for the thickness accuracy of plate in hot rolling process considering top-end temperature drop. Therefore this study has concentrated on determining the correct amounts of thickness variation according to top-end temperature drop and roll gap to compensate thickness variation. The control method of roll gap set-up which can improve the thickness accuracy was proposed. The off-line simulation of compensated roll gap significantly decreases top-end thickness variation.

후판 압연공정에서 퍼지 두께제어 구현

The plate manufacturing processes are composed of the reheating furnace, finishing mill, cooling process and hot leveling. The finishing rolling mill (FM) as a reversing mill has produced the plate steel through multiple pass rolling. The automatic gauge control (AGC) is employed to maintain the thickness tolerance. The high grade products are forming greater parts of the manufacturing and customers are requiring strict thickness margin. For this reason, the advanced AGC method is required instead of the conventional AGC based on the PI control. To overcome the slow response performance of the conventional AGC and the thickness measurement delay, a fuzzy AGC based on the thickness deviation and its trend is proposed in this paper. An embedded controller with the fuzzy AGC has been developed and implemented at the plate mill in POSCO. The fuzzy AGC has dynamically controlled the roll gap in real time with the programmable logic controller (PLC). On line tests have been performed for the general and TMCP products. As the results, the thickness deviation range (maximum - minimum of the inner plate) is averagely from 0.3 to 0.1 mm over the full length. The fuzzy AGC has improved thickness deviation and completely satisfied customer needs.

Methodology for draft schedule design of plate rolling process with peening effect considered

We propose an approach for designing a draft schedule applicable to thick plate rolling. In the proposed approach, the peening effect, i.e. thick material is rolled with a small reduction ratio, is considered fully in computing roll force and torque. To determine an initial draft schedule, we calculate material thickness at each pass and total number of passes by taking the smallest of the critical reduction ratios (reduction ratio by maximum reduction increment, reduction ratio assigned in designing a plate mill, reduction ratios by allowable roll force and roll torque). To make a final draft schedule, we then propose two ways (thickness ratio correction (TRC) method and reduction ratio correction (RRC) method) that redistribute reduction ratios predetermined in the initial draft schedule. The proposed approach has been applied to POSCO No. 2 Plate Mill. Results reveal that the reduction ratios are determined by allowable roll torque if the material being rolled is relatively thick, but reduction ratios are decided by roll force as the material thickness being rolled decreases. It has been found that the thickness ratio correction method is useful when a heavy reduction ratio is necessary in the later part of the rough rolling sequence, and obtaining a uniform microstructure over material thickness during rolling is important. Meanwhile, the reduction ratio correction method is effective if surface defect generation on the material during rolling is a concern.

Evaluation of some chemical and physicochemical properties of meals from pretreated tigernut seeds (Cyperus esculentus)

PurposeThis paper focuses on the effect of different pretreatments on some properties of tigernut, an underutilized crop in Nigeria with the aim of widening its utilization in the country.Design/methodology/approachTigernuts were subjected to various pretreatments such as fermentation, germination, pregelatinization and roasting before drying at 50 ± 2 ○C for 48 h in locally fabricated cabinet drier and milling in commercial plate mill to produce meal which passed through 30 mm pore‐sized sieve. Pretreated and untreated tigernut meals were analyzed using methods reported in the literature for chemical composition, physicochemical and functional properties.FindingsProtein content of the meals ranged from 2.79 ± 0.01 to 3.65 ± 0.02 per cent with sample from fermented tigernut having the highest value and those from roasted ones having the least value. There were slight variations in the crude fat, fiber and ash contents of the resultant meals after pretreatment. There were 10 and 14 per cent enhancement in the ascorbic acid contents of fermented and germinated meals respectively. Titratable acidity, pH and water absorption capacity were affected by pretreatment in this study. Bulk density varied slightly after pretreatment. Germination, roasting and pregelatinization resulted in marked decrease in peak viscosity of the samples. The emulsion capacity ranged from 48.4 to 56 per cent with the untreated sample having the highest value and meals from roasted sample had the least value. Foaming capacity was improved by the pretreatments with the exception of roasting which reduced it from 2.15 to 1.18 per cent.Originality/valueThe paper has demonstrated the effect of pretreatments on tigernut meals and its potential applications in various food formulation and development, e.g. weaning foods, baked goods, beverage products, etc.

부식 및 스케일 억제제에 의한 냉각수 수질향상

This study was investigated to control the corrosion and scale at the cooling water system in steel works. Laboratory and field tests were performed for the indirect cooling water system of plate mill. Throughout the experiment, various factors such as leakage of pipes, heating rate and capacity, and the reaction between existing and substitute inhibitors were carefully monitored. The results showed that the harmful effect of high temperature could be minimized, and satisfactory corrosion/scale controls were effectively achieved using inhibitor, even at the increased temperature of <TEX>$80^{\circ}C$</TEX>. The batch and field tests in the gas scrubbing cooling water system of blast furnace and cooling water system of corex plant indicated that the new inhibitor was more effective for the prevention of corrosion and scale than the existing one.

The Hallen Family, Iron Platers and Frying Pan Makers

AbstractThe Hallen family were iron platers and frying pan makers over six generations and 200 years, providing an unusual example of a specialised trade (manufacture of wrought iron frying pans) dominated by a single immigrant family over a long period in several parts of England. The enterprise began in 1601 at Stanton Drew, Somerset, making armour plate and pans. The chief workman was Cornelius Hallen, possibly from Mechelen, Belgium. A second and larger branch was established at Wandsworth in or about 1634, with about fourteen foreign workmen, some at least from the Liege area. Between 1647 and 1654, the Hallens established three further branches in the West Midlands, at Coalbrookdale, Stourbridge and Newcastle-under-Lyme, with a plate mill and pan shops at each. Around 1700, the two earlier sites were converted to copper working, but the Hallens continued to make iron pans in the Midlands. A Birmingham branch was added in about 1719. There was decline after about 1750, with the end of panmaking in Ne...

Long- and Short-Term Self-Learning Models of Rolling Force in Rolling Process Without Gaugemeter of Plate

Owing to a lack of gaugemeter and the variety of steel grades and standards in some plate mills, the long-and short-term self-learning models of rolling force based on gauge soft-measuring with high precision were brought up. The soft-measuring method and target value locked method were used in these models to confirm the actual exit gauge of passes, and thick layer division and exponential smoothing method were used to dispose the deformation resistance parameter, which could be calculated from the actual data of the rolling process. The correlative mathematical methods can also be adapted to self-learning with gaugemeter. The models were applied to the process control system of AGC (automatic gauge control) reconstruction on 2 800 mm finishing mill of Anyang steel and favorable effect was obtained.

Heavy Wall Thermo ‐ mechanically Rolled Plates for Offshore Construction Use

The growing energy consumption of the world made the exploitation of many offshore oil &amp; gas fields feasible. In order to have the benefit of high strength and toughness together with good weldability, thermo‐mechanical rolling has been developed. In the construction of offshore structures plate thicknesses in excess of 50 mm are common which could up to now only be manufactured with restricted mechanical properties and a loss of productivity. The necessary fine grain structure is obtained by a minimum of four times total deformation in the thermo‐mechanical rolling process with accelerated cooling. For a steel mill this means that a change to a higher slab thickness was obligatory. In the plate mill the main drives were replaced in order to increase the torque and as a consequence get better deformation in the centre of the slabs. The accelerated cooling unit was revamped to a higher water pressure to obtain higher cooling rates and additionally enlarged to reach lower cooling stop temperatures. The results obtained with this new concept are presented in terms of strength, toughness and weldability for a 75 mm plate. This together with fracture mechanical data on the plate and on the weld demonstrates the effectiveness of the new technical concept and set a new benchmark in steel properties.