•A symplectic analytical approach is proposed to study the thermal-metallurgical coupling problems.•The symplectic analytical solution of three-dimensional temperature field is derived directly.•An ...alternating algorithm is designed to realize the nonlinear thermal-metallurgical coupling calculation.•The symplectic approach considers both quantization mechanism and computational efficiency.•The temperature and microstructure evolution during the coil cooling process are precisely calculated.
The cooling process of hot-rolled coil directly affects the mechanical and metallurgical properties of the final product. The non-uniform behavior of temperature and microstructure can easily result in sufficient residual stress to induce subsequent cutting deformation. Therefore, the focus of this study is to analyze the thermal-metallurgical coupling problem during the cooling process of hot-rolled coil. Unlike before, a symplectic analytical approach is proposed to calculate the temperature and microstructure evolution of hot-rolled coil. Firstly, the hot-rolled coil is discretized to convert the three-dimensional heat transfer problem in cylindrical coordinate system to cartesian coordinate system. Then, the traditional heat transfer model is introduced into the symplectic Hamiltonian system and the symplectic superposition method is employed to handle complex cooling boundary conditions. The symplectic analytical solution of the three-dimensional temperature field is obtained through rigorous derivation without any assumptions or predetermined solution forms. Meanwhile, an alternating algorithm is designed between the heat transfer model and the phase transformation dynamics model to realize the coupling process. Moreover, a high-precision finite element model verified by the measured data is established. The symplectic analytical solution of coil temperature and microstructure during the cooling process is in good agreement with the finite element solution. Finally, the symplectic approach has been proven to enable quantitative mathematical analysis of the coupling mechanism of thermal-metallurgical processes.
End-face defect control (EF-DC) of the hot-rolled coil is crucial to the quality management. The core of EF-DC is to identify defects accurately, predict defects in advance, and improve production in ...time to prevent similar defects. The current research works on EF-DC are mainly at the defect recognition stage, which merely rely on the operating data in physical space. However, different types of defects exist in coils with different reasons, therefore it is difficult to accurately control defects in time only through the hot rolling operating data. In order to solve the above problems, first an EF-DC framework based on digital twin with cloud-edge collaboration is designed in this article. The computing tasks are reasonably allocated through cloud-edge collaboration to realize the timeliness of control. Second, the virtual model of hot-rolled coil is constructed from four aspects: geometry, physics, behavior, and rules. Through the analysis of the defect mechanism, the abnormal behavior events are obtained, and the mapping relationship between the defect and the behavior event is established to realize the defect traceability and control. Finally, the feasibility of the proposed method is verified by taking the edge scratch defect as an example.
A large steel company needs to improve its efficiency by integrating the decision making from suppliers to buyers. Therefore, an optimization model is required to determine simultaneously the optimal ...raw material allocation, liquid steel allocation subject to maintenance schedule, and coils allocation from Hot Strip Mill (HSM) to five sub divisions under HSM. The model is aimed at maximizing total profit with several constraints such as production capacity at each sub division, maintenance cost, and inventory balance. We use the operation research methodology to solve the problem, start with problem definition, model development, find optimal solution, and sensitivity analysis. The model was solved using the Oracle Crystal Ball software. Sensitivity analysis results show that the objective function is sensitive to the changes of maintenance cost, raw material price, and product selling price. The allocation of coil, liquid steel, and the amount of raw material orders are sensitive to the maintenance cost and product selling price.
The yield is dependent upon many factors,such as cobbles,total scrap generation,crop loss and scale loss.It appears that the huge quantity of scale is mainly responsible for the yield loss.However,by ...the correlation study,it reveals that the number of cobbles is the major contributor to the yield loss.The innovation lies in changing the focus of attacking the real problem by analysing the operating data which was not surfaced earlier.The focus shifted from the furnace to the mill and the cobbles studied through the years deeply.All the analysis proved to be helpful for the future prevention of the similar kind of failure.The internal target of bringing down the number of cobbles per month in single digit was taken.This also helped in improving the maintenance practice and reducing the amount of delays significantly.The yield was improved by 0.93%.
Steel strip coil is the final product of the hot-rolling process. A model for cooling in hot-rolled coils is presented. Several important factors such as coiling temperature, oxidized layer ...thickness, pressure between different layers of a coil and varying ambient temperature are considered in the model. A computer code based on the model is developed. Satisfactory agreement between experimental and computational results confirms the accuracy of the model. Effects of some factors such as coiling temperature and ambient temperature on required cooling time of both single and multi-stack storing of coils are presented.
Hot-rolled coils take a long time to cool under normal storehouse conditions due to their high mass. Hotter seasons will lead to even longer storage times and, thus, to shortage of space. Forced ...cooling methods such as water-immersion and water-spray can be employed to reduce hot-rolled coil cooling time. In this paper, a mathematical model of the thermal behavior of coils is developed to predict and to evaluate the results expected from employing these methods before any real changes can be made on the ground. The results obtained from the model were compared with those from various experiments to verify the model’s accuracy. The cooling time was then computed based on changes effected in the boundary conditions appropriate to each of the forced cooling methods employed. Moreover, the savings in storage times were compared to identify the best cooling method. Predictions showed that water immersion at the beginning of cooling cycle was more effective and that the cycle should not exceed 1
h for cost efficiency considerations. When using nozzles to spray it was found that spraying water on end surfaces of coils would be the optimum option resulting in savings in time, water and energy, and with restricted temperature gradient.
DANIELI's Coil Quality Estimator (DANIELI-CQE) is an online system meant for estimation of properties of the hot-rolled coil produced in a hot-strip mill. The system predicts the mechanical ...properties, especially the yield strength (YS), tensile strength (TS), elongation (EL), and hardness (HV) at different locations over the length and through the thickness of the strip as soon as the coil is rolled. The estimation is based on the final ferrite grain size and the volume fraction of the microstructural constituents such as ferrite, pearlite, and bainite. The system is available for different grades of steel such as low, medium, and high carbon steels, and high strength low alloy (HSLA) steels microalloyed with niobium, vanadium, and titanium. The prediction of properties is based on a series of physically based interconnected models. Different models-Thermal Model, Deformation Model, Microstructural Model, Precipitation Model, Phase Transformation Model, and Structure-Property Correlation Model together form the CQE's Mathematical Model Suite. The system traces the thermomechanical histories at different sections of the strip, during reheating, rolling, and cooling operations. The process data are captured from the field devices in real time and are fed through the Danieli Mill Level II Automation System. The uncertainties involved in actual processing in plant are addressed by taking advantage of the state-of-the-art soft computing based models such as artificial neural network (ANN). The CQE system is useful for process control and optimization. The accuracy of prediction for the YS is ± 20 MPa, for UTS, ± 20 MPa, and for EL, ± 5%. The system can generate the user report for the purpose of quality control. The archival of the historical data for the coils gives the opportunity for future process analysis, improvement of product quality. It also helps handle specific customer queries. The savings come from reduction in testing samples, shortening the turnaround time between coil production and delivery, lowering inventory, increasing customer satisfaction through in-time delivery of better quality of product to the customers.
The performed research is devoted to the development and testing of synchronization process for the electric motors of rough group stands of the hot strip mill (HSM) 1700 PJSC "ILYICH IRON AND STEEL ...WORKS OF MARIUPOL". The load on the electric motors directly depends on the distribution of pre-rolled strip reductions, which was developed in the research as favourable schedule and is in accordance with analytical calculations and experimental studies in the HSM 1700 shop environment. Reducing peak loads on electric motors due to the redistribution of reductions and synchronization of their work allowed increasing the mass of hot rolled coils at the intermediate stage of reconstruction of HSM 1700 from 9 tons to 15.83 tons. It was determined by calculation that the maximum length of a slab with a basic thickness of 150 mm, which allows implementing the synchronization processes on the HSM 1700, is 9320 mm. It is shown that a further increasing in the slab length requires of additional synchronization of electric motors of HSM 1700 rough stands No. 2-4. The required power of the electric motors of the stands was determined after synchronization, taking into account the load while the pre-rolled strip was in two adjacent stands at the same time. It was found that the required electric motor power does not exceed the design value of 8000 kW.
A significant quantity of cold-reducible hot-rolled (HR) coils is produced every year. These are basically low-carbon steels; however, the quality of HR coils with respect to cold reducibility had ...not been entirely satisfactory. The hardness of HR coil was generally higher (≥65 HR^sub B^) than desirable for attaining satisfactory cold reducibility. A systematic study was, therefore, undertaken with the objective to control the hardness to ≤55 HR^sub B^ by modifying the existing chemistry, finish rolling temperature (FRT), and the coiling temperature (CT). To find the optimum conditions for lower hardness, trial rolling of slabs of cold reducers' grade of selected chemistry was conducted under varied conditions. An assessment of hardness across the width and of the microstructure was carried out. The evolution of microstructure in the HR band at different locations from the edge of the strip and the genesis for the resulting hardness profile across the width of the HR coil were examined in detail. The influence of grain size on hardness was also analyzed. The paper outlines the role of finish rolling temperature, coiling temperature, chemistry, and grain size in restricting the hardness to values below 55 HR^sub B^.PUBLICATION ABSTRACT
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