Rolling Stands Research Articles

High-speed reducing and sizing units in small-section and wire mills. Part 2. (Continuation)

The presentation of materials on the use of high-speed reducing and sizing units in the tail section of small-section and wire mills is continued. Materials are presented on the drive options for the stands included in the units, as well as on the design of these stands, made with a cantilever arrangement of the work rolls. The advantages of the rolling stands are indicated, the features of their operation and settings are described. Information about the design of the stands and the layout of the reducting and sizing units manufactured by Danieli in the line of the wire mill 210 of the Abinsk Electrometallurgical Plant is given.

Phenomenon-Based Model for Virtual Hot Strip Rolling

Every year digitalization is taking a bigger role in the steel industry. Models for predicting metallurgical phenomena, roll forces and microstructure have been commonly used in development of novel steel grades. These individual models may predict certain phenomena thoroughly, but input values are usually based on an assumption or on a “good guess”. To produce reliable boundary conditions for these models of individual phenomena, a virtual rolling model is developed. This model computes the whole process of the hot strip mill from roughing to accelerated water cooling on a run-out table. Strip location and temperature evolution is calculated continuously. Thermal and thermo-mechanical (rolling stands) boundary conditions are according to process layout. Input data for the model is automatically read from raw process data. Rolling parameters are calculated using a coupled ARCPRESS model, which is developed by authors, and calculates normal and frictional shear stress distributions in the roll gap to predict roll forces and displacements of the work roll surface. Recrystallization is considered when calculating the flow stress of the rolled strip. Phase fractions during water cooling are calculated as well. The virtual rolling model minimizes the need for parameter speculation as all parameters are calculated throughout the process. All the input values are read from actual process data and the metallurgical and mechanical state of the strip are computed throughout the whole process. As required by the state-of-art virtual rolling model, this model is based on generally accepted theories and experimentally studied metallurgical and physical phenomena along with the thermo-mechanical response of the actual rolling process.

Perencanaan Jadwal Perawatan Komponen Mesin Roll Forming Baja Ringan Untuk Meminimumkan Biaya Perawatan

PT. Nadha Karya Utama Indonesia, a company engaged in the manufacturing service industry that produces mild steel, located on Jl. Cold Hamlet, RT 04 RW 07, Ngronggot, Kab. Nganjuk, East Java. The purpose of this study is to plan the Roll Forming machine maintenance schedule in order to minimize maintenance costs. The method used in this study is using the Preventive Maintenance method. The calculation results obtain the reliability value of each component on the Roll Forming machine, namely 0.5 for the reliability of the Roll component, 0.5 for the Gear Box component, 0.5 for the Main Engine component, 0.46 for Bearings, and 0.5 for reliability Roll Stand. Determination of maintenance time intervals is based on Peventive Maintenance on Roll components for 37 days, Gear Boxes for 108 days, Main Machinery for 108 days, Bearings for 53 days, and Roll Stands for 146 days. Based on the calculation results, the total cost of maintenance before carrying out preventive with reliability is known to be Rp. 19,340,000, after carrying out preventive calculations with reliability is Rp. 13,120,139.10, it can be seen that before and after carrying out preventive calculations there is a difference in costs of Rp. 6,219. 860.9. From these results it is known that preventive maintenance can reduce the costs incurred by PT. Nadha Karya Utama Indonesia from before the Preventive Maintenance calculations were carried out.

Determination of the wear of the surfaces of barrels of work rolls in a continuous finishing group of stands of a wide-strip hot rolling mill

Compensate for elastic and thermal deformations of the work rolls, as well as to ensure the possibility of rolling a flat strip, the surface of the barrel of the work rolls is profiled. During the production of steel strips on a continuous mill, the initial grinding profiles of the barrel surfaces change due to their wear. According to a number of studies, the shape of the worn surface will be determined by a number of factors: by sliding the rolled metal along the roll in the deformation zone, which depends, among other things, on the length of the produced strip; temperature conditions in the deformation zone; the presence of a movable intermediate layer between the roll and the strip, for example, mill scale during hot rolling or cutting fluid during cold rolling; chemical composition of the rolled steel; quality of rolling rolls; applied steel strip reduction modes in the mill stands; uneven heating of the rolled metal over the section, as well as some other parameters. A study was carried out on the basis of experimental data on evaluating the profile of the barrel of work rolls after they were dumped and cooled from the rolling stands. It was found that the main parameter affecting the wear of the surface is the length of the strip rolled in a given stand. It has been confirmed that wear along the length of the roll barrel is uneven. A method for calculating the wear of the surfaces of the barrels of the work rolls of a wide-strip mill along their length, based on the operating mode, is proposed. The results of the study can be used to improve the shape of the grinding profiling curve of the work roll barrels and it can be used in models for controlling the shape of a strip, and calculate technological rolling conditions

Increase of durability of railway wheels at JSC “Aktyubinsk ferroalloys plant”

Compensate for elastic and thermal deformations of the work rolls, as well as to ensure the possibility of rolling a flat strip, the surface of the barrel of the work rolls is profiled. During the production of steel strips on a continuous mill, the initial grinding profiles of the barrel surfaces change due to their wear. According to a number of studies, the shape of the worn surface will be determined by a number of factors: by sliding the rolled metal along the roll in the deformation zone, which depends, among other things, on the length of the produced strip; temperature conditions in the deformation zone; the presence of a movable intermediate layer between the roll and the strip, for example, mill scale during hot rolling or cutting fluid during cold rolling; chemical composition of the rolled steel; quality of rolling rolls; applied steel strip reduction modes in the mill stands; uneven heating of the rolled metal over the section, as well as some other parameters. A study was carried out on the basis of experimental data on evaluating the profile of the barrel of work rolls after they were dumped and cooled from the rolling stands. It was found that the main parameter affecting the wear of the surface is the length of the strip rolled in a given stand. It has been confirmed that wear along the length of the roll barrel is uneven. A method for calculating the wear of the surfaces of the barrels of the work rolls of a wide-strip mill along their length, based on the operating mode, is proposed. The results of the study can be used to improve the shape of the grinding profiling curve of the work roll barrels and it can be used in models for controlling the shape of a strip, and calculate technological rolling conditions

High-speed reducing and sizing units in small-section and wire mills. Part 2

The presentation of materials on the use of high-speed reducing and sizing units in the tail section of small-section and wire mills is continued. Materials are presented on the drive options for the stands included in the units, as well as on the design of these stands, made with a cantilever arrangement of the work rolls. The advantages of the rolling stands are indicated, the features of their operation and settings are described. Information about the design of the stands and the layout of the reducing and sizing units manufactured by Danieli in the line of the wire mill 210 of the Abinsk Electrometallurgical Plant is given.

Pareto multi-objective optimization of tandem cold rolling settings for reductions and inter stand tensions using NSGA-II

In this paper, multi-objective optimization of tandem cold rolling settings for reductions and inter-stand tensions using NSGA-II and Pareto-optimal front are investigated. In this multi-objective optimization, the total power consumption and uniform power distribution are suggested as objective functions, and reduction thicknesses in each stand and inter stand tensions were selected as problem decision variables. Analytical formulations are introduced to determine the rolling forces and power based on the Stone approach. Then, the main variables of the optimization problem, objective functions, linear and nonlinear constraints, are defined. Moreover, some empirical constraints are introduced regarding the practical limitations of cold rolling equipment and the mechanical properties of the material. At first, considering the conditions of a practical tandem rolling line, single-objective optimization is performed separately, and finally, NSGA-II was used for multi-objective optimization. Compared to the initial setting of the rolling line, the obtained single objective schedules have better performance. Moreover, the multi-objective results based on the Pareto-optimal front are investigated, and an optimized setting for rolling schedule has been suggested. Using this proposed schedule the total power consumption is reduced by more than 11% comparing to the initial setting and more uniform power distribution has been obtained in rolling stands. The normalized reductions calculated from this investigation are compared with numerical and experimental results found in the literature and the similarity was observed in the pattern of thickness reduction distribution.

Регулирование скоростей электроприводов клети толстолистового прокатного стана в режиме формирования «лыжи»

Задача формирования изгиба переднего конца раската в форме «лыжи» является актуальной для электроприводов клетей толстолистовых прокатных станов. Неконтролируемый изгиб раската вверх может привести к повреждению оборудования клети, изгиб вниз - к ударам и застреванию при транспортировке по рольгангу. На основании анализа литературных источников установлено, что причинами неконтролируемого изгиба переднего конца могут быть множество технологических факторов. Основными являются несоответствие скоростей верхнего и нижнего валков, температурный градиент по толщине раската, различие коэффициентов трения и др. Рассогласование скоростей, помимо влияния на форму раската, определяет соотношение моментов электроприводов валков. На примере горизонтальной клети стана 5000 ПАО «Магнитогорский металлургический комбинат» (ПАО «ММК») показано, что при прокатке тяжелых профилей моменты двигателей могут отличаться в три раза. При этом по мере уменьшения толщины раскатов по проходам соотношение нагрузок главных электроприводов верхнего и нижнего валков (ВГП и НГП) меняется на противоположное. Для согласования скоростных и нагрузочных режимов в систему включен регулятор деления нагрузок (РДН). Недостатком является то, что он осуществляет регулирование нагрузок в функции разницы скоростей ВГП и НГП. Представлены осциллограммы, подтвердившие невозможность обеспечения заданного соотношения скоростей в динамическом режиме, возникающем при входе металла в клеть. Для устранения недостатка разработан способ управления электроприводами, согласно которому регулирование скоростей в режиме лыжеобразования осуществляется пропорционально разности сигналов заданий на входах регуляторов скоростей ВГП и НГП. Представлена структурная схема, поясняющая реализацию способа путем включения на вход РДН дополнительного регулятора согласования скоростей. Приведена схема имитационной модели электромеханических систем верхнего и нижнего валков, взаимосвязанных через металл. В результате моделирования установлено, что реализация способа обеспечивает рассогласование скоростей на уровне, близком к заданному, в течение всего времени формирования «лыжи». Алгоритм управления, реализующий разработанный способ, внедрен в АСУ клети стана 5000. Представлены осциллограммы, подтвердившие основные теоретические выводы. Разработанный алгоритм позволяет снизить задание «лыжи» более чем в два раза. За счет этого происходит повышение точности геометрии и сокращение длины изогнутого участка, что обеспечивает меньшее рассогласование моментов двигателей ВГП и НГП и более быстрое их выравнивание. Помимо разгрузки электродвигателей по моменту это обеспечивает повышение их КПД.

Modern materials for cast rolls of hot strip mills

The requirements for the work rolls for the various roll stands of hot strip mills are shown. The modern materials for cast rolls are analyzed and the operational performance of different types of rolls in different stands of the rolling mill is described. The trends in improvement of rolls performance were presented.

THE LATEST IMPROVEMENTS IN I-BEAMS PRODUCTION IN THE WORLD

<p>Some specific aspects in the state of art regarding the improvements related to I-beams and parallel flanged I-beams production are presented in this paper. One practical solution in the variety of the conversions of the classical to the universal rolling stands is described in some more detail, as well as an overview of the latest improvements in I-beams and parallel flanged I-beams production in the world. So-called INP I-beams have tapered flanges v.s. parallel flanges concerned with parallel flanged I-beams, which are very difficult to be produced on classical rolling mills stands, but much easier and better to be produced on so-called universal rolling stands. Since the universal stands are expensive and are very difficult to fix at the existing rolling mills with classical rolling stands, then a conversion of classical to the universal rolling mills stands is the cheapest satisfactory solution. In a short overview are as well presented state of art technological improvements in parallel flanged I-beams production. </p>

Motor Load Balancing with Roll Force Prediction for a Cold-Rolling Setup with Neural Networks

The use of machine learning algorithms to improve productivity and quality and to maximize efficiency in the steel industry has recently become a major trend. In this paper, we propose an algorithm that automates the setup in the cold-rolling process and maximizes productivity by predicting the roll forces and motor loads with multi-layer perceptron networks in addition to balancing the motor loads to increase production speed. The proposed method first constructs multilayer perceptron models with all available information from the components, the hot-rolling process, and the cold-rolling process. Then, the cold-rolling variables related to the normal part set-up are adjusted to balance the motor loads among the rolling stands. To validate the proposed method, we used a data set with 70,533 instances of 128 types of steels with 78 variables, extracted from the actual manufacturing process. The proposed method was found to be superior to the physical prediction model currently used for setups with regard to the prediction accuracy, motor load balancing, and production speed.

Stress due to interfacial slip causing sleeve fracture in shrink-fitted work roll

The rolls are classified into two types; one is a single-solid type, and the other is a shrink-fitted construction type consisting of a sleeve and a shaft. The bimetallic work rolls are widely used in the roughing stands of hot rolling stand mills. Regarding a shrink-fitted construction type, the interfacial slip sometimes appears between the shaft and the shrink-fitted sleeve. This interfacial slip can be regarded as the relative displacement between the sleeve and the shaft. In this paper, the stress due to the interfacial slip is studied because the stress may cause the sleeve fracture. It is found that the stress in the shrink-fitted surface is slightly decreased with increasing number of rotations [Formula: see text]. Therefore, the stress obtained by the simulation at [Formula: see text] can be used to estimate the fatigue strength.

Numerical and experimental simulation of shrinkage porosity closure during hot rolling of bars

Hot rolling of bars issued from continuous-casting aims at refining the material structure and guaranteeing the central soundness of the metallurgical product. The rolling route must be designed to achieve the complete closure of the shrinkage porosity inherent in the continuous casting process. To predict the void evolution, many models exist that can be implemented in the finite element simulation of the process. Nevertheless, these models need parameter adjustments to be adapted to the forming process, the formed material, and the real geometry of the void. Real scale tests being very expensive in the long product rolling mill, an improved representativeness experimental configuration was designed to reproduce at the laboratory scale the key characteristics of the thermomechanical path driving the void closure phenomenon. This testing consists of successive forming stages with shaped anvils applied to samples containing a shrinkage cavity. The shaped anvils and the forming conditions are calibrated to reproduce the levels of strain and the stress triaxiality of rolling stands, and the alternation of the forming direction of the industrial process. The geometry of the voids before and after the forming paths are measured by tomography. The simulation of the test with an explicit modelling of the void is developed parallel to the experiments. The simulation/experiment comparison allows the validation of the numerical model. The obtained model will be used in future works to perform a more extended design of experiments to characterise void closure during hot rolling of bars.

Experimental Parametrization of the Dual-Mass Electromechanical System of a Rolling Mill

Transients in electromechanical systems need to be modeled adequately if the existing electric drive control algorithms are to be improved, or new ones are to be developed. This fully applies to the electric drives of roll-ing mill stands. When studying such drives, one often needs to find a tradeoff between the complexity of Park-Gorev equation-based mathematical description of processes in variable frequency drives, and the capabilities of simpler models that adequately describe the processes relevant for each specific case. The latter include the known dual-mass model of the electromechanical system of a rolling mill stand featuring a flexible shaft and gaps in transmissions. Research presented herein covers the parameters of this model, which need to be ob-tained experimentally. The most accurate way to find the model parameters is to derive them from the oscillo-grams sampled on the object when running in typical transient. This particular paper addresses the electrome-chanical system of the horizontal stand in Plate Mill 5000 deployed at Magnitogorsk Iron and Steel Works (MMK PJSC). The paper substantiates the methodology behind parametrizing the system and shows how to cal-culate the moments of inertia of rotating masses from oscillograms of unloaded drive acceleration. To showcase the method, the paper presents finding the stiffness factor of an elastic coupling from the transients recorded when halting the electric drive. Focus is made on finding the time constants of the internal torque control cir-cuit as approximated by first-order or second-order filters. By comparing the simulation output against the os-cillograms sampled on the mill itself, the model was proven to adequately compute the parameters of the object. The paper concludes with recommendations on how the developed methods could be used to find the parame-ters of a dual-mass system when modeling the electric drives in rolling mills. The conclusions outline possible further research.

Analysis of interconnections between technical systems on hierarchically connected technological levels of steel sheet production by hot rolling

Complexity of modern metallurgical plants, presence of great number of horizontal and vertical interactions between their various structural subdivisions makes it necessary to apply a systems analysis to elaborate effective measures for stable development of a plant operation. Among such measures, digitalization of a plant is widespread at present. To implement the digitalization it is necessary to have clear vision about links at all the levels of the technological system of a plant. A terminology quoted, accepted in the existing regulatory documents for defining of conceptions, comprising the technological system. It was shown, that the following four hierarchical levels of technological systems are distinguished: technological systems of operations, technological systems of processes, technological systems of production subdivisions and technological systems of plants. A hierarchical scheme of technological systems of hot-rolled sheet production at an integrated steel plant presented. Existing horizontal and vertical links between the basic plant’s shops shown. Peculiarities of flows of material, energy and information at the operation “rolling” of the technological system “hot rolling of a steel sheet” considered. As a technical system of the technological process of the hot rolling, the hot rolling mill was chosen. A structural diagram of the hot rolling mill was elaborated, the mill being consisted of reheating furnaces, roughing and finishing stand groups, with an intermediate roll-table between them, and down-coilers section. Since the rolling stands are the basic structural elements of the hot rolling mill, structural diagrams of a roughing and a finishing stands were elaborated. Results of the systems analysis of the technological and technical systems, hierarchically linked in the process of steel sheet hot rolling, can be applied for perfection of organization structure of the whole plant, as well as for elaboration mathematical models of a system separate elements functioning, which is a necessary condition for a plant digitalization.

СИСТЕМНЫЙ ПОДХОД К ОБЕСПЕЧЕНИЮ НАДЕЖНОСТИ РАБОТЫ МНОГОКЛЕТЬЕВЫХ СТАНОВ

Рост объема производства, расширение сортамента продукции и улучшение его качества ведет к увеличению статических и динамических нагрузок, снижению долговечности и поломок прокатного оборудования усталостного характера. Комплексный подход к организации измерений и анализа вибрационных сигналов позволил разработать экспертную систему вибродиагностики «Корунд», которая обеспечивает постоянный контроль технического состояния клетей. В системе применены оригинальные алгоритмы измерений и анализа, учитывающие информацию о текущем техническом состоянии, циклах технологического процесса и особенностях нагружения прокатного оборудования. Диагностический модуль позволяет определить вид дефекта, степень его развития и рассчитать эксплуатационный ресурс узлов механизма. При этом диагностика выполняется как в процессе прокатки металла, так и в режиме холостого хода. Дополнительный функционал позволяет фиксировать время запаздывания сигналов на шестеренном, редукторном, моторном участках и судить о степени износа деталей механизма. Методика защитного мониторинга информирует персонал в режиме реального времени о возникновении внештатных ситуаций на прокатных клетях стана. Программное обеспечение имеет открытую архитектуру, легко конфигурируется под конкретную производственную задачу и работает с базами данных SQL и Oracle.

Experimental and numerical investigation of cold roll forming process

This research work is focused on the cold roll forming process to produce U-channel from the flat sheet. The mechanical properties of aluminum alloy was obtained from the tensile test and subsequently, the properties were incorporated into LS-DYNA to define the material plastic region. The forming process involves the progressive sheet deformation by passing it through a roll pass at constant roll speed. Each sets are designed at different bending angle to increase the deformation until the final geometry is achieved and here, the forming machine with four roll stands were used to manufacture the parts. As a sheet is going into different passes at the same time, the sheet plastic deformation is so complex and highly non-linear because of various stress and strain developments. From experimental results, at low roll speed (RS) the longitudinal bow was observed in the formed parts and to investigate, numerical simulation was modeled at various roll speed and found that as roll speed increasing the longitudinal bow noticed to be decreasing. To confirm the finite element results, one more experiment at high speed was performed and the obtained results showed better agreement with the simulation results. Before confirming the accuracy, many issues were encountered and modified such as mesh size at roller and blank, contact mechanism, choosing element formulation and friction coefficient. Furthermore, the adaptive meshing procedure was adopted to efficiently remesh the sheet at contact locations. The research procedures presented can be utilized to perform the forming process for any existed or new material to form a desired shape for a specific applications in the automobile and aerospace industries.

Способ компенсации динамических нагрузок электропривода прокатной клети за счет опережающего увеличения скорости

Способ компенсации динамических нагрузок электропривода прокатной клети за счет опережающего увеличения скорости

Computer-Integrated Platform for Automatic, Flexible, and Optimal Multivariable Design of a Hot Strip Rolling Technology Using Advanced Multiphase Steels

The paper presents the design and implementation of a computer system dedicated to the optimization of a hot strip rolling process. The software system proposed here involves the flexible integration of virtual models of various devices used in the process: furnace, descalers, rolling stands, accelerated cooling systems, and coiler. The user can configure an arbitrary sequence of operations and perform simulations for this sequence. The main idea of the system and its implementation details are described in the paper. Besides the computer science part, the material models describing the rolling parameters, microstructure evolution, phase transformations, and product properties are also presented. Effect of precipitation was accounted for various stages of the rolling cycle. Experimental tests were performed to generate data for identification of the models. These include plastometric tests, two-step compression tests, and dilatometric tests. Following this, physical simulations of rolling cycles were performed on Gleeble 3800 to supply data for the verification and validation of the models. Finally, case studies of modern industrial processes were performed, and the selected results are presented.

Shape Defects in The Flexible Roll Forming of Automotive Parts

Flexible roll forming allows variable cross sections of profiles to be made by using adaptive roll stands. The most common shape defects that occur during flexible roll forming are edge wave and longitudinal bow. These two defects are necessary to consider together for relatively thin-walled blanks because they usually occur simultaneously during flexible roll forming. To understand the occurrence of these defects, finite element (FE) simulations based on the rigid shell concept were carried out using three blanks with different shapes: trapezoid, concave, and convex. The FE analysis on the flexible roll forming process was performed first, and then the gap of rigid shell has been decreased for reducing the longitudinal bow in roll formed blank. The reduction of longitudinal bow in the web part usually causes edge wave in the flange part. The occurrence of shape defects is investigated based on the relationships among edge curvature, longitudinal stress at the edge, and longitudinal bow height. When longitudinal bow is reduced, the longitudinal stress at the edge of roll formed blank is changed from tensile to compressive in convex blank but in concave blank, tensile residual stress increases. Edge waves occur in the flanges of trapezoid and convex blanks as a result of decreased longitudinal bow. Lab-scale flexible roll forming experiments show multi-stand forming with a leveling roll is desirable to reduce both edge wave and longitudinal bow.