Slab Heating Research Articles

3-D Transient Heat Transfer Analysis of Slab Heating Characteristics in a Reheating Furnace in Hot Strip Mills

3-D Transient Heat Transfer Analysis of Slab Heating Characteristics in a Reheating Furnace in Hot Strip Mills

Optimization of a slab heating pattern for minimum energy consumption in a walking-beam type reheating furnace

A two-dimensional mathematical heat transfer model for the prediction of the temperature history of steel slabs was performed in order to obtain the optimal heating pattern of these slabs with minimum energy consumption in a walking-beam type reheating furnace. An algorithm developed with a simplified conjugated-gradient method combined with a shooting method, was used as an optimizer to design the furnace temperature distribution, including the preheating zone, heating zone and soaking zone temperatures. Comparison with the in-situ experimental data indicated that the present heat transfer model works well for the prediction of the thermal behavior of a slab in the reheating furnace. The effect of the furnace temperature distribution on the design requirements, such as energy required for heating a slab, slab temperature uniformity at the furnace exit and slab discharging temperature, were investigated. The parametric study results indicated that energy consumption significantly decreases with reductions in the preheating zone temperature. The optimal design also resulted in lower energy consumption for heating a slab as compared to the original operational conditions in the steel plant.

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

Evolution of Austenite Grain Structure and Microalloying Element Precipitation During Heating of Steel of Strength Class K65 (X80) for Rolling

The effect of temperature and soaking time during slab heating for rolling on austenite structure size and uniformity, and dissolution of microalloying element precipitates, is considered. It is shown that the heating regime has a strong effect on austenite structure uniformity. With an increase in heating temperature, there is anomalous growth of individual grains, and this is a consequence of gradual microalloying element dissolution. As a result of this, boundaries acquire mobility, thus leading to generation of secondary recrystallization and significant inhomogeneity, and embrittlement of the structure. It is also shown that austenite grain size and distribution after heating is inherited during roughing rolling.

Parallel computations of the step response of a floor heater with the use of a graphics processing unit. Part 1: models and algorithms

Abstract The article presents a method of computing the step response of an air floor heater. The method implements parallel algorithms on a graphics processing unit. In the analyzed concrete slab heating ducts are placed. Hot air is transferred through them, thanks to which the heat penetrates into the slab. Heat transfer into the environment takes place on the top surface of the floor by natural convection and radiation. The bottom surface of the slab is thermally insulated. A two-dimensional heat equation was discretized with the use of the implicit finite difference method. In order to solve the obtained system of equations, the conjugate gradient method was used. Moreover, in order to examine the possibility of shortening the computations time, the algorithm of this method was implemented on a graphics processing unit. A computer program, using the CUDA parallel computing platform and linear algebra libraries CUBLAS and CUSPARSE, was developed

Energy-saving potential and process optimization of iron and steel manufacturing system

SUMMARY Thermodynamic models for iron and steel manufacturing system are established to analyze the equilibriums of mass and energy and the characteristics of energy consumption. Based on the analysis of theoretical and practical energy consumptions, energy-saving potentials of the processes are obtained. Thermo-analysis software for iron-making process is developed and used to investigate the theoretical mechanisms and practical effects of some focused energy-saving technologies. For steel-making section, thermodynamic models of hot metal pretreatment, converter steel-making, secondary refining, and ladle transporting are established to simulate temperature and composition of liquid metal. Energy-saving measures are summarized by analyzing the effects of the operating parameters on energy-consuming process in the section. An integrated scheduling model of slab hot rolling section is established, which concerns the processes of slab transmitting, slab heating, and hot rolling. Production scheduling software and furnace control system are developed. As a result of practical application, the number of rolling units and energy consumption of reheating furnaces are minimized through the systematic optimization. Based on the physical model of dynamic ordered production, simulation platform of production and network model of energy flow are developed for iron and steel manufacturing system. The optimal operating parameters and energy distribution scheme of the main processes are obtained by using the platform and the model. Copyright © 2013 John Wiley & Sons, Ltd.

Research of Dynamic Forecasting Model of Temperature Field in Slab and ANSYS Analysis

In view of the practical significance of the establishment of model database of slab heating, the dynamic forecasting model of temperature field in slab is established by the numerical solution according to the energy conservation in this paper. The ANSYS simulation has been successfully introduced to the modeling simulation of slab heating based on the character of slab heating. The simulation results emerge the temperature field and heat transfer of slab heating, and offer investigative instrument for the more analyse of slab heating and heating system. The temperature field in slab and energy saving would be achieved by using the model database of slab heating.

Optimizing the Process of Steel Slab Reheating in Pusher Type Reheat Furnace Prior to Hot Working

Steel reheating prior to hot rolling is a process which is necessary to achieve sound mechanical and chemical properties of the finished steel products. Heating of steel works in reheat furnaces takes place gradually and with specific rates in order to avoid the development of structural defects due to the development thermal stresses. A mathematical two dimensional heat transfer model was constructed in order to calculate steel slab heating profile through the reheat furnace with actual temperature set points of the furnace zones being used as an input to this model. Calculated slab temperatures indicated aggressive heating of the steel in the early stages of heating and that slabs remain at temperatures close to rolling temperatures for longer period of time than necessary. This finding necessitates a readjustment of slab heating strategy in order to protect furnace components and steel from overheating.

Radiative slab heating analysis for various fuel gas compositions in an axial-fired reheating furnace

A transient radiative slab heating analysis was performed to investigate the effect of various fuel mixtures on the performance of an axial-fired reheating furnace. The various fuel mixtures tested were assumed to be attained by mixing COG (coke oven gas) and BFG (blast furnace gas), which are the two main byproduct gases found in the integrated steel mill industry. The numerical prediction of radiative heat transfer was calculated using an FVM radiation solving method, which is a well-known and efficient method for curvilinear coordinates. The WSGGM (weighted sum of gray gas model) was also adopted to calculate the radiative heat transfer in composition dependent media. The entire furnace was divided into fourteen sub-zones to calculate the radiative thermal characteristics of the furnace without flow field calculations. Each sub-zone was assumed to have homogeneous media and wall temperatures. All of the medium and wall temperatures were computed by calculating the overall heat balance using some relevant assumptions. The overall heat balance was satisfied when the net heat input equaled the three sources of heat loss in each sub-zone, wall loss, skid loss, and slab heating loss.

Global variations in H2O/Ce: 1. Slab surface temperatures beneath volcanic arcs

We have calculated slab fluid temperatures for 51 volcanoes in 10 subduction zones using the newly developed H2O/Ce thermometer. The slab fluid compositions were calculated from arc eruptives, using melt inclusion‐based H2O contents, and were corrected for background mantle contributions. The temperatures, adjusted to h, the vertical depth to the slab beneath the volcanic arc, range from ∼730 to 900°C and agree well (within 30°C on average for each arc) with sub‐arc slab surface temperatures predicted by recent thermal models. The coherence between slab model and surface observation implies predominantly vertical transport of fluids within the mantle wedge. Slab surface temperatures are well reconciled with the thermal parameter (the product of slab age and vertical descent rate) andh. Arcs with shallow h (∼80 to 100 km) yield a larger range in slab surface temperature (up to ∼200°C between volcanoes) and more variable magma compositions than arcs with greater h (∼120 to 180 km). This diversity is consistent with coupling of the subducting slab and mantle wedge, and subsequent rapid slab heating, at ∼80 km. Slab surface temperatures at or warmer than the H2O‐saturated solidus suggest that melting at the slab surface is common beneath volcanic arcs. Our results imply that hydrous melts or solute‐rich supercritical fluids, and not H2O‐rich aqueous fluids, are thus the agents of mass transport to the mantle wedge.

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.

Numerical simulation and experimental study on electrothermal properties of carbon/glass fiber hybrid textile reinforced concrete

Carbon/glass fiber hybrid textile reinforced concrete is a relatively new composite material with good mechanical capacity and excellent electrical conductivity. Both small-scale slab heating experiments and numerical simulation are presented in this paper. Temperature variation curves obtained during heating indicate the effects of environmental temperature, heat-conducting layer thickness and electric heating power. Comparison of temperature rising between the situations with and without thermal isolation layer is given as well. The results indicate that the textile can form a good conductive heating network and generate enough heat to raise the temperature in the concrete when connected to a power supply, while the resistance of the slab remains stable during the heating. Numerical results are in good accordance with the experiments. Real time snow-melting experiment was conducted to verify the feasibility of deicing. The electrothermal properties of textile can be utilized for deicing and snow melting in a safe, environmentally friendly and efficient way.

Efficiency analysis of radiative slab heating in a walking-beam-type reheating furnace

Abstract The thermal efficiency of a reheating furnace was predicted by considering radiative heat transfer to the slabs and the furnace wall. The entire furnace was divided into fourteen sub-zones, and each sub-zone was assumed to be homogeneous in temperature distribution with one medium temperature and wall temperature, which were computed on the basis of the overall heat balance for all of the sub-zones. The thermal energy inflow, thermal energy outflow, heat generation by fuel combustion, heat loss by the skid system, and heat loss by radiation through the boundary of each sub-zone were considered to give the two temperatures of each sub-zone. The radiative heat transfer was solved by the FVM radiation method, and a blocked-off procedure was applied to the treatment of the slabs. The temperature field of a slab was calculated by solving the transient heat conduction equation with the boundary condition of impinging radiation heat flux from the hot combustion gas and furnace wall. Additionally, the slab heating characteristics and thermal behavior of the furnace were analyzed for various fuel feed conditions.

Investigation of the slab heating characteristics in a reheating furnace with the formation and growth of scale on the slab surface

In this work, the development of a mathematical heat transfer model for a walking-beam type reheating furnace is described and preliminary model predictions are presented. The model can predict the heat flux distribution within the furnace and the temperature distribution in the slab throughout the reheating furnace process by considering the heat exchange between the slab and its surroundings, including the radiant heat transfer among the slabs, the skids, the hot combustion gases and the furnace wall as well as the gas convection heat transfer in the furnace. In addition, present model is designed to be able to predict the formation and growth of the scale layer on the slab in order to investigate its effect on the slab heating. A comparison is made between the predictions of the present model and the data from an in situ measurement in the furnace, and a reasonable agreement is found. The results of the present simulation show that the effect of the scale layer on the slab heating is considerable.

A numerical analysis of slab heating characteristics in a walking beam type reheating furnace

Numerical analysis of slab heating characteristics in a reheating furnace has been accomplished using FLUENT, a commercial software. The phenomena in the furnace are periodically transient because the slabs are transported toward a rolling mill with every time interval controlled. Unsteady calculation has been performed to obtain a periodically transient solution. A User-Defined Function (UDF) program has been developed to process the movement of slabs because FLUENT cannot handle the movement using its default functions. When the mean temperature of a slab emitted to the rolling mill does not change, calculation is considered to have converged and is stopped. This convergence criterion is appropriate for achieving an analytical solution. With the boundary and initial conditions given, over 55 new slabs are inserted to get a converged solution. Skid posts and beams are included in the calculation because they disturb radiation heat transfer from hot combustion gas to the slabs. This article examines what the slabs experience in the furnace before they are emitted to the rolling mill and whether a slab emitted to the rolling mill satisfies the required slab conditions, such as target temperature and skid severity.

Simulation of slab heating in continuous furnaces

Simulation of slab heating permits assessment of the influence of the hearth pipes and riders on the thermal state of the slabs and the scope for furnace redesign to improve heating and productivity.

A Two-Phase Heuristic for the Production Scheduling of Heavy Plates in Steel Industry

In this paper, the production scheduling of heavy plates is considered. Different from general hot rolling mill, the reheating furnace scheduling shares the same importance with the hot rolling scheduling due to the special characters of heavy plates such as the large differences in weight and dimension. One major characteristic of the reheating furnace is that it can simultaneously process multiple slabs. When the furnace is full, a slab can be drawn in only if the head slab in the furnace has been drawn out. Therefore, the practical heating time of a slab is variable and besides the weight and dimension, is also dependent on not only the slab heating sequence but also the furnace capacity. Since there is no buffer between the reheating furnace and the hot rolling line, a finished slab will reside in the furnace until the hot rolling line is available. To solve this problem, a two-phase heuristic is proposed. In the first phase, only the hot rolling scheduling problem is considered and a scatter search is developed for it. In the second phase, a decision tree-based heuristic is constructed to obtain the corresponding reheating furnace schedule. The experimental results on real production data show that the two-phase heuristic outperforms the current manual scheduling system.

Control characteristics and heating performance analysis of automatic thermostatic valves for radiant slab heating system in residential apartments

Computer simulations and experiments are carried out to research the control characteristics and heating performances for a radiant slab heating system with automatic thermostatic valves in residential apartments. An electrical equivalent R–C circuit is applied to analyze the unsteady heat transfer in the house. In addition, the radiant heat transfer between slabs, ceilings and walls in the room is evaluated by enclosure analysis method. Results of heating performance and control characteristics were determined from control methods such as automatic thermostatic valves, room air temperature-sensing method, water-temperature-sensing method, proportional control method, and On–Off control method.