Hot Rolling Operation Research Articles

Applications of genetic algorithm in prediction of the best achievable combination of hardness and tensile strength for graphene reinforced magnesium alloy (AZ61) matrix composite

Due to lack of knowledge about role of process variables in the hot rolling of magnesium alloy composites, the most desirable wrought products of magnesium alloy-based composites could not be successfully produced till date. Moreover, use of wrought graphene reinforced magnesium alloy-based composite has emerged as a lucrative option for developing novel light alloy products in structural applications. The implicative need to obtain the best possible properties of the composite dictates to fix the optimized process variables in rolling operation. The present study envisages the development of data driven model that enables to derive desirable properties of the said composite; so, in order to secure the optimized subset of requirements (process parameters), a metaheuristic optimization tool is employed. We invoke the use of Genetic Algorithm (GA) optimizing tool in association with linear regression, so as to achieve the best combination of hardness and tensile strength of AZ-61-graphene nanoplate (GNP) composite.Modified magnesium AZ-61 alloy composites of varying GNP content (0, 1 and 2 wt.%) are produced by stir casting. The cast composites are homogenized at 450 °C for 12 h, followed by iced water quenching. The quenched materials are subjected to hot rolling and the process variables of hot rolling operation consist of rolling temperature, number of rolling passes as well as the initial stock thickness. The rolled materials are tested for hardness and tensile strength as the response variables. Instead of using artificial neural network to fix the objective function of GA, a mathematical model is developed by regression analysis; the derived equation is used as the objective function for multi-objective optimization task. The present paper explores the usefulness of implementing evolutionary algorithm (as in genetic algorithm) to correctly forecast the effect of rolling process variables onto the hardness and tensile strength of the stir cast AZ alloy-GNP nanocomposite.The experimental results show that the maximum achievable hardness value happens to be 106.6 VHN and is very close to that predicted by GA, ∼107.41VHN. Similarly, the maximum experimental tensile strength is found to be 266.82 MPa whereas, the corresponding GA predicted value is seen to be 253 MPa. A close fit can thus be noticed between the GA predicted and the experimentally obtained values. Barring a couple of exceptions, the difference between the experimental and GA predicted data lies within 1 % to 5 % (based on [Experimental value ∼ predicted value]/ [experimental value]). This entices to believe that the adopted muti-objective optimization strategy is quite useful in determining the optimum combination of rolling parameters that aids in achieving the most desirable property combination.

Development of a solid-state extrusion-roll-bonding based additive manufacturing (ERB-AM) technology for aluminum alloys

To solve the poor printability issue of high-performance aluminum alloys in additive manufacturing processes, a solid-state hybrid additive manufacturing (AM) technology, combining extrusion and roll bonding operations, is proposed, in which the extruded aluminum layers are soundly bonded through the hot-rolling operation. In this feasibility and early-stage research, a lab-scale extrusion-roll-bonding prototype machine is designed and built. Aluminum alloy, AA1060, owing to its relatively low loading requirements for the prototype, is used for the proof of the concept. The extrusion-roll-bonding tests have been undertaken at different temperatures and rolling reductions to identify optimal processing parameters. The corresponding bonding quality was estimated using an optical microscope (OM). Also, miniature AM tensile samples were tested to evaluate the tensile properties of the bonding interfaces. It is of great interest to see that the AM material did not fracture at the bonding interface and its stress-strain response is similar to that of the original material. In-depth analyses on the interfacial grain and oxide distribution and their effects on the interfacial strength were undertaken using a transmission electron microscope (TEM) and scanning electron microscope (SEM)/electron backscatter diffraction (EBSD). This study demonstrates the proposed solid-state AM technique can successfully manufacture aluminum alloys at their solid states, achieving comparable mechanical properties to their wrought states. This new solid state AM technique may enable a wide range of alloys with poor printability to be used in various industries to produce safety-critical and large, structural components with simple geometry.

A Truncated Transient Slab Model for a Reheating Furnace

This paper considers the steel reheating process, in which cold slabs are reheated to a temperature suitable for hot rolling operations. Temperature uniformity within the slab is very important during reheating, as non-uniformities often lead to quality concerns in the later stages of the production process. Attaining slab temperature uniformity is quite challenging, therefore, a thorough understanding of the reheating process becomes very important. Due to the extreme conditions inside the furnace, numerical tools like computational fluid dynamics are necessary for such situations. However, when applied to these complex installations, it often leads to very lengthy computational times. This paper develops a computationally efficient transient model to simulate the environment around a slab. This Truncated Transient Slab Model is a coupled model: it uses the temperature and flow profiles from a full-scale steady-state simulation and imposes those on a smaller domain that represents the immediate environment around the slab. The efficiency of the model is compared to the state of the art. With the simulations available in the literature, it was found that the proposed model can simulate a furnace seven times larger (grid size), with much higher grid and time resolutions, using only a third of the computational resources.

The Hot Ductility, Microstructures, Mechanical Properties and Corrosion Resistance in an Advanced Boron-Containing Complex Phase Steel Heat-Treated Using the Quenching and Partitioning (Q&P) Process

The objective of this research work is to obtain the hot ductility behavior, and the structural, microstructural and mechanical characteristics of one of the latest generation of AHSS steels, a complex phase (CP) steel microalloyed with boron (0.006 wt.%), processed by hot and cold rolling operations and heat-treated using two different quenching and partitioning (Q&P) treatments, a one-step partitioning (quenching to 420 °C) and the other a two-step partitioning (quenching to 420 °C and reheated to 600 °C). The results show that boron has a marked effect on the solidification process of the CP steel, refining the austenitic grain size. Due to its refinement, the boron-containing steel had better ductility throughout the temperature range examined (700–900 °C), i.e., the hot ductility trough. Thus, the minimum percentage of reduction in area (%RA) value occurring at 800 °C was 43% for the boron-free steel, compared with 58% for the boron-containing steel. Hence, cracking would not be a problem when straightening the strand on continuous casting. The benefit of boron addition on the room temperature properties was found to be very marked for the higher temperature two-step partitioning treatment, giving a yield stress of 1200 MPa, a UTS (ultimate tensile strength) of 1590 MPa and a total elongation above 11%. The final Q&P microstructure, in both one- and two-step partitioning conditions, consisted of retained austenite (RA-γ), martensite and ferrite islands in a bainitic matrix. Furthermore, the boron treated steel on quenching produced a greater amount of RA-γ, which accounted for its better room temperature ductility and produced a martensitic matrix rather than a bainitic one, giving it greater strength. The addition of boron improved the corrosion resistance of this type of third generation AHSS steel.

Finite Element Analysis of Large Plastic Deformation Process of Pure Molybdenum Plate during Hot Rolling

The rare molybdenum resources are being increasingly used in heavy industries. In this study, the common unidirectional and cross hot rolling operations, for pure molybdenum plates, were numerically simulated by using MSC. Marc software. An elastic–plastic finite element model was employed, together with the updated Lagrange method, to predict stress and strain fields in the workpiece. The results showed that there was a typical three-dimensional additional compressive stress (σy> σz > σx) in the deformation zone, while strain could be divided into uniaxial compressive strain and biaxial tensile strain (εy > εx > εz). Tensile stress σx increased with the accumulation of reduction and the decrease in friction coefficient at the edge of the width spread. More importantly, the interlaced deformation caused by cross-commutations, which were helpful in repairing the severe anisotropy created by unidirectional hot rolling. The evolution of the temperature field of pure molybdenum plate was investigated. The surface quenching depth of the pure molybdenum plate was about 1/6 H under different initial temperatures and reductions. In addition, the fundamental reason for the nonuniform distribution of stress and strain fields was the joint influence of rolling stress, contact friction, and external resistance. By comparing the theoretical simulation value of the model with the experimental verification data, we found that the model was aligning well with the actual engineering.

Fractional order adaptive MRAC controller design for high-accuracy position control of an industrial robot arm

Most of conventional feedback controllers become inefficient in hard industrial environments like in steel industry, because of uncertainties in the plant model, or process dynamics variation due to nonlinear actuators, and changes in the character of the disturbances. This paper proposes an adaptive control design based on fractional order model reference adaptive control (FOMRAC) strategy in order to deal with an uncertain horizontal positioning control of an unloading machine in a rotary hearth furnace for hot rolling operation. The proposed FOMRAC scheme uses the MIT rule as an adaptive mechanism with two main modifications comparatively to the conventional MRAC: the reference model is an adequate fractional order system and the parameter adjustment rule contains a fractional order integrator. Stability analysis of the proposed control scheme is performed using the Lyapunov stability theorem. Numerical simulations are presented to show the effectiveness of the proposed fractional adaptive schemes applied to an industrial robot arm loading round steel blocks from inside a rotary hearth furnace. After comparison with the conventional MRAC, it is shown that the performances of FOMRAC are superior to classical control schemes.

Thermomechanical Simulation of Ferritic Rolling of Titanium-Niobium Interstitial-Free Steel

Abstract Austenitic or two-phase rolling of ultra-low carbon steels face temperature control issues and generate shape defects. Ferritic rolling has been developed as a solution, and ferritic hot-rolled sheets are used as final products, replacing hot-rolled followed by cold-rolled sheets. However, it is not in regular industrial production because of mill limitations. Hence, ferritic hot rolling must be optimized for developing a ferritic cold-rolled and close-annealed sheet through subsequent processing. In this work, industrial ferritic rolling process was simulated for a titanium-niobium interstitial-free steel using a thermomechanical simulator. Multi-hit plane strain compression tests were carried out at three different regimes below the lower transformation temperature (Ar1). Steels were processed under high strain and strain rates as experienced during industrial hot rolling operation, and the results were compared with the conventional austenitic rolling. The flow stress of the material in the ferritic regime decreased with decreasing deformation temperatures but increased at temperatures below 700°C. Nonuniformity in grains and texture also increased with decreasing temperatures. High-temperature rolling in ferritic condition close to Ar1 temperature does not differ significantly from the austenitic condition, whereas the low-temperature ferritic rolled material had through-thickness microstructural nonuniformity and unwanted goss and brass fibers. The intensity of gamma-fiber {111} || normal direction (ND) required for formability was highest in the intermediate temperature zone. Deformation between temperatures of 850°C and 800°C was found to be ideal. Based on simulation studies, full-scale plant rolling was carried out under the optimized ferritic regime. The microstructure and texture matched closely with the simulation results. This work provides a working window for ferrite rolling in an industrial hot strip mill for developing ferritic cold-rolled close-annealed products.

Modeling and simulation of mass flow during hot rolling low carbon steel I-beam

Abstract Continuously cast near net shape blanks have been widely used in industry owing to the benefit of producing items close to final shape. However, for complicated shaped blanks, such as I and H beams, using near net shape blanks is not enough to prevent unwanted mass flow and deformation during hot rolling. The strength of the rolled material, pre-existing defects, and hot rolling parameters all have a major influence on the final shape of the rolled beam. In this study, the shaping of a low carbon steel during the breakdown mill hot rolling process was investigated using finite element analysis. The geometry of the as cast beam blank, mill roll profiles and hot rolling pass schedule were modeled identically to that used during the production hot rolling operation. The results showed that the I-beam has more deformation in the flange than in the web for breakdown mill rolling. A small depression or waviness was found to develop along the beam flange during the simulation. A parametric study of the effect of the roll gap on mass flow and beam blank surface depressions was performed. It was observed that for a larger roll gap, the surface depression increased in size. In contrast, the depression was found to decrease with a smaller rolling gap due to greater mass flow. These results agreed with the industrial produced I-beam. It was also predicted that the presence of a pre-existing surface defect on the beam blank flange has a significant influence on final size of the depression.

Novel Efficacious Utilization of Fuzzy-Logic Controller-Based Two-Quadrant Operation of PMBLDC Motor Drive Systems for Multipass Hot-Steel Rolling Processes

This study investigates the rough steel-rolling process, which requires repeated and rapid bidirectional hot-rolling operations and proposes a fuzzy-logic-controller-based brushless electric DC (BLDC) motor drive system for the same. We present a modeling of the hot-steel rough-rolling process using a set of metallurgical parameters and mechanical equations based on their operating conditions, specific features and characteristics, all obtained from actual data. The above equations and related parameters were modeled in MATLAB/Simulink schematic under variations in temperature and slab thickness corresponding using three different hot-rolled (HR) steel specimens. This led to the creation of a pair of speed and torque- profiles with alternate polarities for successive passes covering the entire rolling process for each steel specimen. A fuzzy logic controller utilized the above profiles on the motor shaft by incorporating speed and current feedback loops to attain reference speed and calculation of instantaneous stator currents of the BLDC motor with respective phase sequences, so as to satisfy the torque-profile. Simulation results showing the detailed performance of the drive system are presented. Further, experimental work on a BLD-motor-drive system is presented, along with loading arrangements and an arm controller embedded with control algorithm for the multi-loop feedback system used for the closed loop speed control. The efficacy of the new applications proposed in this study for the first time can be seen from the validation of the results from the BLDC motor with its fuzzy-based controller in terms of simulation and hardware, thereby serving to be an attractive alternative to conventional induction motor drive systems for steel rolling.

Application of System Analysis for Technological Processes Investigation

System analysis is used as the effective way for design and modification of different kinds of technical systems. Application of system analysis to any technological process allows to present the links between input and output parameters which makes it possible to analyze its effectiveness and effect on the process for manufacturing of the object with necessary level of quality. The paper presents results of system analysis application for multioperational technological processes. The main aim of hot rolling process is manufacturing the hot rolled metal sheet with definite geometrical parameters which are necessary for further cold rolling process. The scheme of hot rolling operation with its input and output links is presented. The obtained results can be used for mathematical modeling of hot rolling operation. It is shown the application of system analysis for technological process of coating on the example of vacuum ion-plasma coating process. Because of existence of operated, noncontrolled, and indignant parameters of the coating process application of system analysis is the effective way for structural analysis of this technical system. It is proposed to supplement system analysis with function-oriented analysis. This approach can state the links between properties of the object which are sufficient for its application and technological parameters of the manufacturing technological process.

A robust optimization approach for integrated steel production and batch delivery scheduling with uncertain rolling times and deterioration effect

Efficient collaboration between various sub-processes of steel production is of considerable significance, which directly affects a product’s production cycle and energy consumption. However, current collaborative optimisation models and methods in steel production are still limited: (1) Most of the current collaborative manufacturing problems in steel production focus on obtaining joint schedule between steel-making and continuous casting (SCC), and the works considering continuous casting and hot rolling (CCHR) are very few. (2) The processing time is assumed as a constant in most of the existing SCC scheduling models. However, the rolling time of a product in hot rolling operation is actually uncertain and deteriorating. (3) Exact algorithms cannot be applied to solve the complicated collaborative optimisation problems because of their high complexities. To address these problems, we propose an integrated CCHR and batch delivery scheduling model where interval rolling time and linear deterioration effect are considered. With the concept of min–max regret value, we formulate the collaborative optimisation problem as a robust optimisation problem. Instead of using the exact algorithm, we develop an Improved Variable Neighborhood Search (IVNS) algorithm incorporated a novel population update mechanism and neighbourhood structures to solve the robust optimisation problem. Moreover, we develop an exact algorithm that combines CPLEX solver and two dynamic programming algorithms to obtain the maximum regret value of a given rolling sequence. The results of computational experiments show the excellent performance of the proposed algorithms. Abbreviations: IVNS: improved variable neighbourhood search; TOPSIS: technique for order of preference by similarity to ideal solution; PUM-TOPSIS: population update mechanism based on TOPSIS; DP: dynamic programming; NSs-PUC: neighbourhood structures based on the parameterised uniform crossover; SNRT: shortest normal rolling time; SNRT-DP: DP algorithm based on SNRT rule; BRKGA: biased random-key genetic algorithm; SCC: steelmaking and continuous casting; MINP: mixed integer nonlinear programme; CCHR: continuous casting and hot rolling; PSO: particle swarm optimisation; GA: genetic algorithm; VNS-HS: variable neighbourhood search and harmony search; HPSO + GA: hybrid PSO and GA; SA: simulated annealing; B&B: branch-and-bound; TPSO: two-phase soft optimisation; TSAUN: tabued simulated annealing with united-scenario neighbourhood; VNS: variable neighbourhood search; ABC: artificial bee colony; PRVNS: population-based reduced variable neighbourhood search; NS1: neighbourhood structure 1; NS2: neighbourhood structure 2; DE: differential evolution; WSR: Wilcoxon signed-rank test; ENS: exchange neighbourhood structure; IVNS-ENS: IVNS with ENS; RPI: relative percentage increase; ARPI: average RPI; SD: standard deviation.

Analysis of the roll hunting force due to hardness in a hot rolling process

A hot rolling operation is performed to alter the thickness of a metal by passing the material through a pair of rollers, forming a gap that is somewhat narrower than the thickness of the material. Therefore, the quality of the product is a function of the pressure applied by the rollers. However, in this process, a roll hunting force occurs in which the rolling force is irregularly changed during the rotation of the rollers due to various complex mechanisms, which include roll surface hardness, difference in rotational speed between rolls, heat treatment conditions, and roll wear. In this study, roll wear tests were conducted to analyze the roll hunting force caused by variation in the hardness of the work roll. The friction coefficient of the work roll was then examined based on hardness. Then, a two-dimensional finite element model was constructed to investigate the roll hunting force as a function of the change in friction coefficient of the work roll. This finite element model was verified in relation to the theoretical rolling expression. Finite element model analysis was performed for three friction coefficients, and the effect of the roll hunting force was determined based on the reduction ratio and temperature. In addition, the wear depth of the work roll by the hardness was predicted. The influence of the abrasion of the work roll on the hunting force was analyzed.

Finite element modelling of surface defect evolution during hot rolling of Silicon steel

Surface defects on metal strips can be generated during hot rolling from surface cavities and indents. The size and aspect ratio of the initial surface cavities present before rolling are critical parameters that determine the final configuration of the defect. The propagation of these defect through the full rolling process is detrimental to the surface quality of the end product, in particular for electrical steel where these type of defects may directly affect the magnetic properties of the final product. A finite element model was developed in the present research to simulate the evolution of surface defects in a high-silicon electrical steel subjected to a single pass hot-rolling operation. The surface defects were modelled as predefined cavities with various aspect ratios and a multi-scale approach was used to capture the large local deformation gradients at the vicinity of the initial cavities. A user-defined subroutine was developed to describe the material constitutive behaviour at different strain rates and temperatures based on the Sellars-Tegart model in ABAQUS/standard finite element package. The modelling results were validated by laboratory scale hot rolling experiments with respect to the measured rolling forces and the plastic deformation of the initial cavities. This study shows that buckling of the lateral sides and bulging of the floor of the initial cavities are the main mechanisms involved in the formation of sub-surface defects. The developed model can be used to predict the evolution of surface cavities and to optimise the rolling parameters in order to minimise the detrimental effect of these defects in the final stages of the hot rolling process.

Determination of system connections of hot rolled steel sheet manufacturing process

System analysis is used to state links between input and output parameters of any technical system taking into consideration flows of material, energy, and information. This approach makes it possible to find effective ways for improvement of technical system parameters. The paper presents results of system analysis application for multioperational technological process steel sheet of hot rolling. Structural scheme of metal sheet hot rolling process is presented based on principles of system analysis. Hot rolling technological operations such as workpiece heating, hot rolling, cooling, and coiling are presented as subsystems. Due to the obtained schemes metal sheet parameters are stated which have to be controlled during each technological operation of hot rolling technological process. The obtained results can be used as the basics for mathematical modeling of steel sheet hot rolling operation in order to get the final product with the required set of properties.

Effect of the Rolling Temperature on Hot Formability of ZAM100 Magnesium Alloy

Magnesium alloy sheets are usually obtained by complex processing cycles including hot rolling operations. Temperature of the final stage of rolling strongly affects the microstructure and, consequently, the hot formability of the sheets. In this framework, the present work aims at investigating the effect of the rolling temperature on the hot formability of the innovative magnesium alloy ZAM100. To this purpose, two different rolling temperatures were used and hot formability was investigated by tensile tests performed in extended ranges of temperature and strain rate. The flow curves were analyzed in order to obtain constitutive models of hot formability.

Examination of Mechanical and Electrical Properties and Structure of Selected Aluminum Alloy Sheets Produced from TRC Semi-Products

AbstractModern manufacturing methods of non-ferrous metals, especially aluminum and its alloys, are more and more often based on integrated technologies combining multiple operations in a single process. One of the most popular methods for producing flat components by cold working is twin roll casting technology (TRC). It allows to eliminate from manufacturing the extremely expensive hot rolling operation, as the TRC semi-product (strip) can be directly cold rolled. The results of mechanical and electrical properties and structure examination of strips after casting were presented in the paper. The effect of cold rolling parameters on post-process mechanical properties and structure of sheets was investigated too.

Analysis of the Surface Defects in a Hot-Rolled Low-Carbon C–Mn Steel Plate

In the present study, a microstructural investigation was conducted on surface defects occurring in a 28 mm thick low-carbon C–Mn steel plate with ferrite–pearlite microstructure. The plate contained transverse “scraped-out”-like defect at the top surface edge and a continuous longitudinal “V-groove”-like defect throughout the length of the plate in the bottom surface. Detailed microstructural analyses showed formation of several small as well as long shallow unidirectional unbranched cracks with oxide entrapments in the defect region at the top surface associated with partial decarburization and internal oxidation confirming its genesis at the casting stage. On the other hand, extensively branched “stag deer horn” crack heavily filled with compact FeO oxide scale originated from the bottom surface defect with no microstructural abnormality confirmed that the groove existed before the hot rolling operation and the cracks formed during the rolling under differential loading.

An Experimental study: Mechanical properties of Cu-Cr-Zr alloy

This paper presents, the hardness of a material varies depending on the composition of material, and how it is treated when processed. Here observed the changes in hardness of Cu-Cr-Zr (CRZ) alloy resulting from different process types, along with the accompanying changes in microstructure. Tests are carried out to study in detail of the Thermo-Mechanical Processing such as Cold Rolling, Hot Rolling and Tensile test on CRZ. In this paper, the hot rolling operation and cold rolling operation has been performed on small slabs of CRZ alloy. And then for prepared alloy that is hot and cold rolled alloys the microstructure has been evaluated. The hardness of these alloys is also evaluated. So based on the observations are found for each alloy a comparison study has been done. And arrived at the conclusions for each alloy that by cold working the Strength increases and ductility decreases and by hot working the strength decreases and ductility increases. And for the Tensile Test for the Solution treated samples of CRZ alloy found high strength and less ductility in comparison to the room temperature samples. The role of recrystalization on these alloys has also been explained.

An upper-bound finite element solution for rolling of stainless steel 304L under warm and hot deformation conditions

Purpose The purpose of this paper is to investigate the thermomechanical behavior of stainless steel AISI 304L during rolling at elevated temperatures. Design/methodology/approach Two-dimensional finite element analysis together with the upper-bound solution were used for predicting temperature field and required power in warm and hot rolling operations. The required power and heat of deformation were estimated employing an upper-bound solution based on cylindrical velocity field and at the same time, temperature distributions within the rolling steel and the work rolls were determined by means of a thermal finite element analysis. To consider the effect of flow stress and its dependence on temperature, strain and strain rate, a neural network model was used and combined with the thermal and mechanical models. Finally, the microstructure of rolled steel was studied and the effect of rolling conditions was justified employing the predictions. Findings The results have shown that the predicted temperature variations were in good agreement with the experiments. Moreover, the model was shown to be capable of determining the effects of various rolling parameters such as reduction and rolling speed with low-computational cost as well as reasonable accuracy. Originality/value A combined upper-bound finite element analysis was developed to predict the required power and temperature field during plate rolling while the model can be employed under both hot and warm rolling conditions.

Finite element simulation of a cross rolling process

Finite element analyses of unidirectional and cross hot rolling operations, for AISI 304 stainless steel, have been carried out by using DEFORM 3D software. Cross rolling is achieved through changing the rolling direction by 90° i.e. after each pass, the plate is rotated by 90° around the normal direction. In order to get the material constants for the constitutive model, with sine hyperbolic function, compression tests were carried out at different temperatures and strain rates. Rigid-visco-plastic finite element formulation along with incremental Lagrangian method has been used to predict stress and strain fields in the work-piece. The predicted rolling load shows a maximum of 9.91% error with the measured load value. Comparison among the different state variables for unidirectional and cross hot rolling has also been carried out. Effects of roll speed and percentage reduction on temperature, for both cross hot rolling and unidirectional hot rolling, have also been reported.