Slab Heating Process Research Articles

Modeling effects of skid buttons and dislocated skids on the heating quality of slabs in an industrial walking-beam reheating furnace

The slab heating process inside a walking-beam reheating furnace is critical for slab quality. This paper presents a comprehensive CFD model simulating the fuel combustion, flow field, temperature distribution, and heating process of walking slabs in an industrial-scale furnace. It explicitly considers the effects of dislocated skids and skid buttons. After the model validation through industrial measurements, the model is used to analyze the influences of skid buttons and dislocated skids on the flow and temperature field and the slab heating process. The results show that the dislocated skids and skid buttons significantly affect the flow field and furnace temperature distribution. The simplifications on the structures of skid buttons and dislocated skids cause the neglect of shielding radiation of skids in the modeling. Overcoming this problem by the present model reduces the difference between the measured and predicted slab temperature by more than 20 K. Overall, the skid buttons reduce the sheltered area for slab heating by 86%, and the dislocated skids change the sheltered region of the slabs. These together favor a more uniform temperature of slabs. The results suggest that the CFD model can offer convenience to understanding, designing, controlling, and optimizing the slab heating process in a walking-beam reheating furnace.

Modeling approach and numerical analysis of a roller-hearth reheating furnace with radiant tubes and heating process optimization

Precise knowledge of the heat transfer in a reheating furnace is important for optimizing the slab production process. In the present work, a new comprehensive CFD (Computational Fluid Dynamics) model for simulating the gas flow, combustion and heat transfer in a roller-hearth reheating furnace with radiant tubes was developed. In the model, the slab dynamic heating process was performed based on the steady-state gas phase combustion in the furnace. The movement of slabs in the furnace was achieved by dynamic mesh. The radiant tubes and the furnace were coupled into a whole and the indirect heat transfer in the furnace was achieved by radiant tubes. The slab temperature predicted by the model showed a good agreement with the experimental results through the validation of “Black Box”. According to the simulation results, the temperature field in the furnace and the slab heating process were reasonably evaluated. Compared with the heating process with the slab residence time of 60min in actual production, the new heating process was determined by the simulating time for the whole slab reaching the austenitizing temperature and the holding time, and the slab residence time is 67min.

Multi‐Objective Optimization of Slab Heating Process in Walking Beam Reheating Furnace Based on Particle Swarm Optimization Algorithm

The unreasonably high heating process temperature of slab in furnace leads to many heating defects. To avoid these, a multi‐objective optimization method is proposed for furnace temperature setting based on particle swarm optimization (PSO) algorithm. A 2D model of the finite difference scheme, in which the thickness and width were unequally partitioned, is investigated. The distance between two neighbouring nodes increased with the thickness and width, and the effects of a more detailed grid on the surface or side are observed along with influence of a rough grid in the core. Then, a multi‐objective optimization function of the temperature setting, from which energy consumption and the oxidation and burning loss should be minimized, is established. The PSO algorithm is implemented to calculate the optimal value of the multi‐objective optimization function. The application results show that average temperature differences at the quarter and midpoint thicknesses between the predicted model and measured values decrease from 53.4 to 8.5 °C and 43.6 to 11.4 °C, respectively; furthermore, the average oxidation and burning loss rate decrease from 0.93% to 0.79%. Average energy consumption decreases from 1.57 to 1.33 GJ t−1, thereby considerably reducing the energy consumption of the reheating furnace and minimizing the production cost.

Performance of fuel-air combustion in a reheating furnace at different flowrate and inlet conditions

Abstract A geometry model for simulating the gas circulation, heat transfer and slab heating process in a reheating furnace was developed with numerical simulation. The slabs are heated in the furnace and the temperature of the slabs become above more than 1500 K, and then they are transported to the rolling mill. The slab heating in a reheating furnace is influenced by many factors, such as gas velocity, the movement speed of the slab, the height and spacing of the burners and others. The slab heating characteristics in the walking beam type reheating furnace were studied by considering the slab movement. The movement of the slabs was processed by transferring temperature data from the previous location to the next location. It was assumed that no time is spent for moving the slabs. Especially, the effects of different inlet boundaries of the burners were investigated. Results show that the entrainment effect from the inner air flow results in a larger coverage area of the flames, and there is an increase of more than 28.5% in the slab temperature over the whole furnace.

Steady State model of a Reheating Furnace for determining slab boundary conditions

The slab reheating process in a reheating furnace is a very energy intensive process with many operating parameters that can be optimized. Numerical methods are therefore applied to generate models which can be used in an optimization strategy. This paper presents the first step in the creation of these models: obtaining the boundary conditions for the slab model from a steady state model of the furnace. The slab heating process itself is a transient phenomenon and an accurate cross-sectional slab temperature cannot be obtained using a steady state model. The furnace however, operates in a narrow range of temperatures and steady state operation is a suitable approximation. The steady state model is calibrated with data from a working reheating furnace at the ArcelorMittal Gent site. The numerical results show a good agreement with the experimental data with an average relative error of 3.1%. This gives confidence in using this model to determine the furnace heating boundary conditions of the slab model which will be implemented in future work.

Finite element analysis and experiment on induction heating process of slab continuous casting-direct rolling

To reduce the energy consumption of reheating billets between the continuous casting and hot rolling processes, the continuous casting-direct rolling (CC-DR) process is developed, of which one of the key technologies in CC-DR is compensative heating between the processes. Considering the compensative heating technology requirements in the actual production of slab CC-DR, the finite element models of longitudinal flux induction heating (LFIH) and transverse flux induction heating (TFIH) are established to analyse the slab heating process. The results show that LFIH is good for heating surfaces of the slab, but cannot solve the problem of low temperature on the edges, which can effectively be heated with TFIH. The temperature distribution of the slab can be made more uniform by choosing the appropriate current and moving speed. Besides, induction-heating prototypes are developed to inspect the effect of induction heating. The measured results are consistent with the simulated ones. The results of the analysis have direct significance on the induction heating process in the actual production of slab CC-DRs.

CFD modeling and validation of a dynamic slab heating process in an industrial walking beam reheating furnace

Comprehensive numerical modeling and validation on an industrial walking beam slab reheating furnace were conducted. A transient three-dimensional Computational Fluid Dynamics (CFD) model was developed to simulate the flow characteristics, combustion process and multi-scale heat transfer inside the reheating furnace. The actual geometry of the furnace was used and typical operating conditions were simulated. Specific walking speeds of slabs in production were modeled using a dynamic mesh model which is controlled by a user defined function (UDF) solved using ANSYS Fluent. Fuel variations at different zones with time were also considered. The model was validated with instrumented slab trials conducted at the SSAB Mobile mill. The temperature field in the furnace and the temperature evolution of a slab predicted by the CFD model are in good agreement with those obtained from the instrumented slab trials. Based on the simulation results, the slab reheating process and the temperature uniformity of a slab at discharge were able to be properly evaluated.

Modeling of the slab heating process in a walking beam reheating furnace for process optimization

A new methodology involving the integration of a three-dimensional (3D) Computational Fluid Dynamics (CFD) model and a two-dimensional (2D) heat transfer model for the study of the slab reheating process in a walking beam reheating furnace has been proposed. A comprehensive 3D CFD model has been developed to simulate the flow characteristics, combustion process and multi-mode heat transfer phenomena inside an industrial slab reheating furnace. A customized 2D heat transfer model for the slab reheating process has also been developed based on the finite difference method. The simulation results from the 3D CFD model provide detailed heat transfer boundary conditions for the 2D heat transfer model. Instrumented slab trials were conducted under typical operating conditions of the furnace and the results were used to calibrate the 2D model. By comparing the slab temperatures measured from the instrumented slab trials and those predicted using the models, it was demonstrated that the 3D CFD and 2D heat transfer models predict the reheating process reasonably well. The proposed methodology is fairly easy to be used by mill engineers for trouble shooting and optimizing of the slab reheating process.

Numerical simulation of slab heating process in a regenerative walking beam reheating furnace

A simplified method is described to study the slab heating process in a regenerative walking beam reheating furnace. The boundary conditions of the furnace are matched with the burner properties in different zones to simulate the slab heating process and consider both the regenerative reversing combustion process and the slab movement. The simulated results agree well with the experimental results. The predicted results show that the slab temperature increases rapidly in the furnace preheating and heating zones. The slab surface temperature rises faster than the central point of the slab. The section temperature difference of the slab increases until the maximum value is reached in the heating zone. The slab temperature along its length is distributed unevenly, which is slightly higher near the burner and lower near the center of the furnace. The slab charging temperature has a great influence on its heating process. An increase in charging temperature reduces the section temperature difference, and the slab whole heating time is significantly shortened for satisfying the emission conditions.

Исследование процесса нагрева заготовки при газовой листовой штамповке

Исследование процесса нагрева заготовки при газовой листовой штамповке

Thermal Stress Field Simualtion Research in Heating Process Based on FEM

For increasing heat efficiency and preventing crack resulting in thermal stress, the laws of heating slab must be accurately studied. The thermal stress field distribution in slab heating process is researched, which adopts FEM and bases on the transient non-linear heat analysis theory. The 3500 slab heating model is established in according to the heating technique in mills. The factor of conduction coefficient and specific heat changing with temperature also are considered. The heating process is simulated and the influence laws of furnace temperature and heating rate are drawn, which is very significant in engineering.

Research on Thermal Stress of Slab Heating Process Based on Transient Non-Linear Analysis

Polycrystalline α-HgI2 films have been grown through combining vertical deposition method with hot wall vapor phase deposition (HWPVD) method. The influence of the α-HgI2 seed layers on the structural and electrical properties of the polycrystalline α-HgI2 films was investigated. It is found that the α-HgI2 seed layers play an important role in reducing the grain sizes, increasing the density improving the crystallographic orientation and electrical properties of the polycrystalline α-HgI2 films.

FUZZY NEURAL NETWORK'S APPLICATION IN FURNACE TEMPERATURE COMPENSATION BASED ON ROLLING INFORMATION FEEDBACK

In hot rolling process, reheating furnace and roughing mill are controlled separately in general, and the transfer of production information between the two facilities is very limited, so rolling information of roughing mill can not be fed back to reheating furnace to adjust slab's heating process dynamically, which leads to exceeding energy consumption. In this paper, fuzzy neural network (FNN) is used to deal with the feedback of rolling information, and then real-time compensation of furnace temperature setting can be obtained. Simulation results show that by using this method slab's heating process can be optimized dynamically, and energy consumption of hot rolling process can be reduced greatly, and rolling security of roughing mill can be guaranteed at the same time.

Development of a simulator to calculate an optimal slab heating pattern for reheat furnaces

To improve energy consumption and to meet quality requirements for the slab heating process of reheat furnaces in hot strip mills, a new optimal slab heat pattern calculation simulator has been developed. The simulator consists of the following functions; (1) two-dimensional (slab thickness direction and slab length direction) slab temperature calculation function, which is capable of calculating skidmarks along the length of a slab, (2) furnace heat balance calculation function, (3) optimizing calculation function of slab heat pattern using a linear programming method. The simulator developed has been installed into a furnace computer control system for an actual plant. This paper describes the functions of the simulator and simulation results using the simulator. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 120(3): 42–53, 1997

Development of an optimal slab heat pattern calculation simulator for reheat furnaces.

To improve energy consumption and to meet quality requirement for slab heating process of reheat furnaces in hot strip mills, a new optimal slab heat pattern calculation simulator has been developed.The simulator consists of the following functions;(1) two-dimensional (slab thickness direction and slab length direction) slab temperature calculation function, which is capable of calculating skidmark along the length of a slab, (2) furnace heat balance calculation function, (3) optimizing calculation function of slab heat pattern using linear programming method.The developed simulator has been installed into a furnace computer control system for actual plant.This paper describes the functions of the simulator and simulation results using the simulator.