Walking Beam Furnace Research Articles

Инженерная методика определения температурного состояния металла при его нагреве

Currently, the determination of the temperature profile of the furnace required to ensure the specified heating parameters of the metal is carried out using the temperature measurement method or mathematical models. They are most based on solution of the differential equation of non-stationary thermal conductivity. Previously, the thermal diagram method of I.D. Semikin was widely used. It allows us, under given heating conditions, to determine heating duration. In practice, it is important to develop a simple engineering method that would allow the temperature field of the metal to be determined with sufficient accuracy under given heating conditions. The development is based on the thermal diagram method of I.D. Semikina. But at the same time, the final equation describing the heat balance of the metal within the furnace zone is solved relative to the enthalpy of the metal at the exit from the zone. The specified heating conditions (productivity, zone temperature) are used to determine the quantities of the right-hand side of the equation (time heating, average heat flux density). The authors have proposed the method for continuous furnaces of various types (push-type and with a mechanized hearth) that allows us for a given productivity and temperature profile of the furnace to calculate the change in the temperature state of the metal for all heating zones, from the moment of loading to the release of metal. The adequacy of the proposed methodology has been tested for two types of furnaces. For methodical push-type furnaces, the results obtained have been compared to the results of modeling the temperature state of the metal using a numerical method. The discrepancy between the results after passing the inertial heating period does not exceed 1 %. For a walking-beam furnace the calculated value of the metal surface temperature after the furnace has been compared with the results of operational measurements. The discrepancy is less than 2 %. The totality of the results obtained ensures the achievement of the research goal. The proposed method is based on the heat balance equation and allows us to consider it to be correct. It is an engineering method and quite simple to implement. The method is recommended to be used to design furnaces and to calculate the temperature profile of furnaces by engineering departments of metallurgical enterprises.

Сontinuous walking beam furnace without water cooling for reheating copper alloy blanks

It takes a special technique to heat up round blanks cast of copper alloys in conformance with applicable process specification, which implies maintaining a low oxidizing atmosphere in a gas furnace. This paper describes a continuous furnace with walking beams that are not watercooled designed to heat up round blanks to the maximum temperature of 1,000 ºC. The furnace, which stands before the pipe press for making pipes of different sizes, is fueled by natural gas burned in high-speed burners with the air flow rate of α = 0.98 in hot zones and that of α = 1.05–1.1 in preheating zones. The side walls of the furnace are equipped with high-speed burners which serve to intensify the convective heat transfer inside the furnace. The burners ensure a transverse/countercurrent flow of gases with an intense transverse jet circulation. The furnace is equipped with a panel roof lined with ribbed ceramic fiber blocks (original design by UralTermoKompleks) which serves to intensify the radiation heat transfer without raising the temperature. A larger interior surface of the furnace roof leads to an increased radiation heat flow density and hence higher heating rates. It means that the furnace has better performance at the same temperature. The furnace is equipped with charging and discharging systems. An eccentric is responsible for moving the walking beams. An integrated control system controls heat in each of the five zones of the furnace guided by thermocouples and charging and discharging modes. The furnace has been fully commissioned.

Steady-State Heat Flux Prediction to Slabs in a Walking Beam Furnace

After casting steel slabs are reheated in a reheat furnace to temperatures in the range 1200-1250 °C in order to be suitable for rolling. The high energy requirements and the importance of reheating for quality control are the motivation behind numerically modeling the furnace. Computational fluid dynamics allows us to understand the fundamental physics with great detail. It is however unclear how assumptions of such models influence the results of the simulations. In this work a steady-state model was analyzed, and it was found that the chosen slab temperature profile can underestimate the average heat flux on the slab surface by 30%. A slab model was employed to simulate the transient slab temperatures which results in an underestimation of the average slab temperatures by about 500 °C for the case with reduced fluxes. The uniform slab temperature assumption also results in the overestimation of heat fluxes on its front and side face.

Modeling of Energy Consumption and Reduction of Pollutant Emissions in a Walking Beam Furnace Using the Expert Method—Case Study

This paper presents an algorithm for modeling electricity and natural gas consumption in a walking furnace with the use of artificial intelligence and simulation methods, depending on the length of the rolling campaign and the established rolling program. This algorithm is the basis for the development of a proposal for a set of minimum requirements characterizing the Best Available Techniques (BAT) for beam furnaces intended for hot rolling, taking into account the requirements set out in national regulations and the recommendations described in the BREF reference documents. This information should be taken into account when drawing up an application for an integrated permit, as well as when setting emission limit values. Based on the constructed algorithm, it was shown that depending on their type and technical specification, the analyzed projects will offer measurable economic benefits in the form of reducing the amount of energy consumed by 1,076,400 kWh during the implementation of 50 rolling campaigns to reduce gas by 14,625 GJ and environmental benefits in the form of reduction of pollutant emissions into the atmosphere 80–360 g/Mg. The constructed algorithm was validated in the Dosimis-3 program, based on a discrete event-driven simulation. Thanks to this representation of the model, its user can interactively participate in changes that take place in the model and thus evaluate its behavior. The model, verified in real conditions, can be the basic source of information for making effective operational technological decisions related to the preparation of production at the rolling mill as part of planning and long-term activities.

Statistical modeling of temperature operating modes of heating furnaces for hot strip mills

The article provides a method of mathematical modeling to improve temperature operating modes of heating furnaces for hot strip mills. The object of the research is the thermal operation of a continuous walking beam furnace for heating slabs before rolling. The subject of the research is statistical modeling of metal heating in furnaces of this type. The creation of a statistical model consists of factors selection, construction of regression model, correlation analysis and assessment of the variables significance, adjustment of factors and obtaining regression equations. The main part of the research refers to a statistical model based on a comprehensive analysis. This model is based on the results of 15 automated industrial experiments on Russian heating furnaces of hot strip mills and describes the heating process in walking-beam furnace with acceptable accuracy. The adaptation of the statistical model and error calculation has been carried out. The article contains graphs comparing real temperatures and temperatures calculated on the basis of mathematical and statistical models for one of the experiments. The main conclusions are formulated based on the results of the research done. For the first time in metallurgical practice, a statistical model has been developed that describes the process of metal heating in a five-zone continuous furnace with eight heating subzones. Since the regression function is defined, interpreted and justified, and the assessment of the accuracy of the regression analysis meets the requirements, it can be assumed that the model and predicted values have sufficient reliability.

Continuous walking-beam furnace 3D zonal model and direct thermal-box barrier based temperature measurement

Numerical simulation of industrial reheating furnaces belongs to important procedures for an optimization of their design and processing parameters. A 3D numerical model of a continuous gas burners heated walking-beam furnace is introduced in this paper. The main benefit of the model is a compromise between its complexity and computing speed. The model connects numerical procedures and empirical knowledge. It is based on a Hottel zonal method and a compartment based solution of heat transfer process in solids. It allows specifying charge, heating system and furnace parameters. The solution includes convective and radiative heat transfer in the furnace including a participation of a semi-transparent gaseous furnace atmosphere. A direct measurement of charge temperature course in a walking-beam furnace using thermocouples and thermal box-barrier are introduced. Comparisons of the measurement results with results of numerical simulations are presented. Connection between direct measurement in the furnace and the numerical simulation parameters is discussed. A good agreement between the theoretical and measured data shows, that the model includes the most important physical process.

Design and Research of Energy-saving Hydraulic System for Walking Beam Furnace

Design and Research of Energy-saving Hydraulic System for Walking Beam Furnace

Characteristics of skid pipe failure in walking beam reheating furnace of an integrated steel plant

Moving beam of S355J0 grade seamless steel pipe of EN 10025 specification was failing frequently particularly below the retainer ring of skid pipe, which is located under the hearth level of walking beam furnace in an integrated steel plant. The pipe samples both at unaffected and affected regions were examined using scanning electron microscopy (SEM) and light optical microscopy. The oxidized layer and scale deposits were analyzed using X-ray fluorescence spectrometer (XRF) and X-ray diffractometer (XRD). The microstructure of the affected region changed to ferrite pearlite away from the rupture, degenerated pearlite towards rupture and widmanstatten ferrite at the tip of the rupture. The dynamic transformation of ferrite has been attributed to overheating coupled with cyclic stress. On the other hand, the unaffected region of pipe revealed original spherodized annealed microstructure consisting of dispersed carbides in ferrite matrix. The scale deposit constituents were inferred as oxides of Ca, Mg and Si from XRF study, which were confirmed as CaMgSi2O6 and (Mg, Ca)CO3 and the oxidized scales consisted of FeO, Fe2O3 and Fe3O4. While the hardness of makeup water (89.0 mg/L) was moderately soft and well suited for industrial use, the re-circulating water in skid pipe showed much higher hardness (142.4 mg/L). The oxidation of metal and increase in hardness of water resulting in scale deposits have been attributed to the exposure of skid pipe to high temperature, which finally led to its rupture.

Secondary steel mill furnace performance.

Energy in a steel re-rolling mill is mainly consumed in furnaces. Therefore, furnace performance is very important and its contribution in the cost of product is very high. Data has been collected for two different furnaces in Stackle mill and analyzed for performance of furnace. In this paper, effect of furnace performance on secondary steel sector is analyzed. These data about performance is collected on Walking beam furnace in Stackle mill and Re-heating furnace.

Modeling of a walking beam furnace using CFD – methods

In steel industry the walking beam furnace is used to heat up and reheat steel slabs for the rolling process. In order to meet the demands for high quality steel a very homogeneous temperature profile in the slabs is required. Using Computational Fluid Dynamics (CFD) in ANSYS Fluent 15, a walking beam furnace was investigated to analyze the causes of inhomogeneous temperature distribution in the steel slabs. Due to different sizes in length scale, starting with burner nozzles with a diameter of about 10 mm to dimensions of the whole oven with over 50 meters, about 220x106 tetrahedron cells were necessary to resolve the geometry. On the basis of this model size it is unavoidable to find strategies to reduce the calculation time and consumption of computational power. Therefore the walking beam furnace was modeled as a steady state process. To avoid high requirements of computational power for solving chemical reactions a steady laminar flamelet model for non-adiabatic combustion was used [1]. For this purpose a flamelet was generated for the specific mixture of natural gas, blast furnace gas and air as oxidizer. In order to avoid the need of a dynamic mesh or a complex movement algorithm for the slab motion and a transient model of the oven the steel girder were mapped as a continuous band. The motion of the band was modeled by a Multi Reference Frame (MRF) with a specific velocity, resulting in a mass flow through the furnace similar to the real one. To describe turbulent effects the realizable k-ε-model was used with one modification. For a more accurate description of the flame acceleration the turbulent constant C2ε was edited according to literature data from 1.9 to 1.8 [2, 3]. For this purpose the Discrete Ordinate Model (DOM) was used in combination with a Weighted Sum of Gray Gases Model (WSGGM) to describe the emissivity and absorption of radiation from CO, CO2, H2O und CxHy [4,5]. To set the boundary conditions for thermal properties of the oven wall a User Defined Function (UDF) was developed and implemented into the ANSYS Fluent 15 calculation [6]. The model should be used to start an improvement process to analyze the impacts of different operating conditions to get a better insight into the process.

The Effect of Boron and Titanium Microalloying on the Scale Formation of AISI 304 Austenitic Stainless Steel in Simulated Walking Beam Furnace Conditions

The effect of microalloying boron and titanium on AISI 304 austenitic stainless steel scale formation is studied. Thermogravimetric tests simulating walking beam furnace conditions are performed at temperatures of 800, 1100, and 1300 °C for 3 h on samples of AISI 304 steels with different alloying amounts of B and Ti. Scaling at 800 °C is negligible on all the samples, while scaling is clear at 1100 and 1300 °C. The thermogravimetric results show that even in small amounts, boron and titanium have an effect on scale growth rate. FESEM microscopy and accompanying EDS analyses are used to study oxidation area element composition. The FESEM images are also used to compare the oxidation zones’ area fractions of metal, pores, and oxide between different alloying amounts for the samples of 1300 °C tests. Calculations for scale formation activation energy are done based on the thermogravimetric data. The steel sample with the lowest alloying of boron and titanium shows a noticeably different growth rate, which is nearly linear in both the 1100 and 1300 °C tests. Differences between alloying amounts in accumulated scale during the 180 min period in kg m−2 are greater at 1100 °C than they are at 1300 °C.

Operation Optimization of Slab Reheating Process Based on Differential Evolution

In the slab reheating process, the temperature distribution of walking beam furnace is critical for the temperature of slab, as well as the subsequent hot rolling. Besides, this process is dynamic, nonlinear, and time varying due to coupling with complex physical and chemical reactions. In this paper, we focus on an operation optimization problem of tuning furnace temperature to optimize the slab reheating process, which considers the reheating quality and production cost. For this purpose, we develop a novel operation optimization method. Specifically, first, from the view of mechanism, a heat transmit model based on the heat-exchange of slab and furnace, an energy consumption function, and especially, an oxidation loss function are established. Therefore, incorporating the mechanism models, we build an optimization model to minimize temperature deviation of slab, energy consumption, and oxidation loss to describe our problem. Then, based on the features of the problem, we propose a modified differential evolution algorithm, which includes a space contraction scheme, a new self-adaptive parameter strategy, and a new mutation operator. Finally, to evaluate the performance of our method, extensive numerical experiments are implemented by comparing it with other well-known evolutionary algorithms based on practical data. The experimental results demonstrate the effectiveness of proposed operation optimization method on solving our problem.

Short-term and long-term thermal prediction of a walking beam furnace using neuro-fuzzy techniques

The walking beam furnace (WBF) is one of the most prominent process plants often met in an alloy steel production factory and characterized by high non-linearity, strong coupling, time delay, large time-constant and time variation in its parameter set and structure. From another viewpoint, the WBF is a distributed-parameter process in which the distribution of temperature is not uniform. Hence, this process plant has complicated non-linear dynamic equations that have not worked out yet. In this paper, we propose one-step non-linear predictive model for a real WBF using non-linear black-box sub-system identification based on locally linear neuro-fuzzy (LLNF) model. Furthermore, a multi-step predictive model with a precise long prediction horizon (i.e., ninety seconds ahead), developed with application of the sequential one-step predictive models, is also presented for the first time. The locally linear model tree (LOLIMOT) which is a progressive tree-based algorithm trains these models. Comparing the performance of the one-step LLNF predictive models with their associated models obtained through least squares error (LSE) solution proves that all operating zones of the WBF are of non-linear sub-systems. The recorded data from Iran Alloy Steel factory is utilized for identification and evaluation of the proposed neuro-fuzzy predictive models of the WBF process.

Influence of Temperature Change on the Energy Parameters during Round Bars Rolling Process

The paper presents results of experimental studies on the effect of non-uniform temperature distribution over the metallic charge length on the energy parameters change during round bars rolling process. Experimental tests were conducted on the D370 Continuous Shape Mill in industrial works. From the tests carried out, it has been found that the main cause of occurrence of the non-uniform distribution of temperature over the charge length is the process of heating the metallic charge in the walking beam furnace. During rolling of bars from metallic charge with non-uniform temperature distribution over its length, changes in friction conditions in the zone of contact between the band and the rolls and in the plastic properties of steel being rolled occur. For decrease temperature during metallic charge rolling process about 100 °C (Fig. 2) in walking beam furnace, increase of rolling torque and total rolling power about 30% during rolling process metallic charge in first continuous shape mill stand was observed.

The Description of a Distributed Parameter Process through a Finite Discrete Dimensional System

This article analyses the process of warming a metal by using a walking beam furnace. This process is meant to offer the technologist objective information that may allow him to produce eventual modifications of the temperature references from the furnaces zones. Thus making the metals temperature at the furnaces exit to have an imposed distribution, within precise limits, according to the technological requests. This industrial process has a geometrical parameters distribution, more precisely it can be described through a partial differential equation, by being attached to dynamic infinite dimensional systems (or with distributed parameters). Using a procedure called geometric-time discretization (in the condition of the solutions convergence), we have managed to obtain a representation under the form of a finite discrete dimensional linear system for a process with distributed parameters.

Introduction of a Level-2 Automated System as Part of the Reconstruction of a Walking-Beam Furnace in the Rail-Beam Shop

Engineers and scientists in Russia and abroad are giving a considerable amount of attention to improving the quality of the rails being made by metallurgical plants. Rolling 100-m-long rails requires proper preheating of the continuous-cast semifinished products with a minimal temperature gradient along and across the products. A heating operation of the requisite quality is assured by the use of a level-2 automation system to heat the metal in the furnace.

Numerical Simulation and Experiment Research on Temperature Field of Steel Slab in Walking Beam Furnace

This paper presents a study of the temperature fields of steel slab in a walking beam furnace. To simulate the temperature distribution in the slab of heating-up process in heating furnace, a two-dimensional mathematical model was developed. The heat transfer in the furnace was very complex, so the model was developed on the assumptions that the temperature of each section of the furnace was unchangeable, the slab moved in the furnace in even velocity, the heat transfer between the slab and the walking beam was out of consideration, the longitudinal heat conduction of the slab and the effect of the scale on the heat conduction were neglected. The equations were calculated by the finite difference method. A black box experiment research was carried out to measure the temperature history of the slab as it passed through the furnace. The comparison of the calculated results with the measured results showed that the model worked well for simulating the temperature distribution of the slab in walking beam furnace. With this developed model, the optimizing of hot rolling and heating processes of steel slab can be investigated in the future.

Research of Furnace Temperature Optimization Control Method in Hot Rolling Process

To effectively solve the problems of high energy consumption, low control accuracy and time control-delay for furnace, this paper proposes the intelligent control strategies based on the process feature of walking beam furnace, namely fuzzy-RBF network self-learning and self-optimizing function, which is combined with dynamic PID feedback compensation strategy. The experiment shows that the system not only guarantees the furnace temperature control accuracy and increases the temperature up and down rate under working condition fluctuation, which reduces unit fuel consumption, unit electricity consumption and billet burning loss, but also improves the furnace production capacity.

Hot repair of refractory blocks on walking beams for slabs reheating furnace by means of ceramic welding (RPR technology)

The repair of a walking beam furnace is usually achieved by replacing the damage block or by gunning a wet refractory mix on the hot surface. A new alternative is introduced, based on the ceramic welding technology. It has been successfully applied by Industeel in their slab reheating furnaces.

제어압연.제어냉각기술로 제조된 냉간성형용 비조질강의 소재특성

The main purpose of the present study has been placed on investigating the mechanical properties and microstructures of C-Si-Mn-V steels for cold forming manufactured by controlled rolling and cooling technology. The steels were manufactured in electric arc furnace (EAF) and casted to <TEX>$160{\times}160mm$</TEX> billet. The billets were reheated in walking beam furnace and rolled to coil, the stocks were rolled by Controlled Rolling and Cooling Technology (CRCT), so rolled at low temperature by water spraying applied in rolling stage and acceleratly cooled before coiling. Rolled coils were cold drawed to the degree of 16%, 27% of area reduction respectively without heat treatment. Microstructual observation, tensile test, compression test and charpy impact tests were conducted. The mechanical properties of the steels were changed by area reduction of cold drawing and it is founded that there are optimum level of cold drawing to minimize compression stress for these steels. From the result of this study, it is conformed that <TEX>$80kg_{f}/mm^{2},\;90kg_{f}/mm^{2}$</TEX> grade high strength microalloyed steel for cold forming are developed by accelerated cooling and optimum cold drawing.