This paper presents an efficient thermo-elastoplastic method for the prediction of welding-induced distortions in a large panel structure. It is based on a shell/3D modeling technique which was proposed and experimentally validated in the authors’ previous study. Two numerical examples are analyzed to evaluate the accuracy and efficiency of the present method. In the first example, the recommendations for the estimation of the minimum 3D zone size in the shell/3D model reported in the authors’ previous work are verified, in comparison with the full 3D model, on a T-joint model consisting of plates with different thicknesses. It is shown that the shell/3D modeling technique provides a significant reduction in the computational time needed for the simulation of the welding process and thus enables efficient thermo-elastoplastic analyses on large structures. In the second example, the proposed model is validated on a large panel structure by corresponding the experimental data and inherent strain solutions from the literature.

Water spray quenching distinguished itself as a promising method for industry production, especially for the parts which require good mechanical strength while simultaneously retaining the initial toughness. Studies have shown that the heat transfer process during the spray quenching is mostly influenced by the spray impingement density, particle velocities and sizes. The application of advanced numerical methods still plays insufficient role in the development of the production process, in spite of the fact that industry today is facing major challenges that can be met only by development of new and more efficient systems using advanced tools for product development, one of which is CFD. Taking the above stated, the object of this research is numerical simulation of spray quenching process in order to determine validity of mathematical models implemented within the commercial CFD code Fire, especially droplet evaporation/condensation and droplet-wall heat transfer model. After review of the relevant literature suitable benchmark case was selected and simulated by employing discrete droplet method for the spray treatment and Eulerian approach for the gas phase description. Simulation results indicated that existing droplet/wall heat transfer model is not able to reproduce heat transfer of dense water spray. Thus, Lagrangian spray model was improved by implementing experimental correlation for heat transfer coefficient during spray quenching. Finally, verification of the implemented model was assessed based on the conducted simulations and recommendations for further improvements were given.

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Steel and iron making industries have been driven by the requirements of maintaining or improving product quality and minimization of production costs. Within these requirements the overall energy management and energy efficiency play important role. Since the rotating-hearth furnace in the seamless pipe rolling mill has the nominal heating capacity of 27 t/h, and the real needs are of an average 13 t/h, the aim of the conducted study was to investigate whether it is possible by decreasing the height of rotating-hearth furnace workspace to reduce fuel consumption. In the article's introduction, a short description of the furnace with the measured values of heating regime, which served as the basis for calculations, is given. Namely, for the purposes of calculation is necessary along the furnace to know the temperatures of flue gases and the surfaces of linings and heated charge. The intensity of the charge heating depends on the radiation heat transfer from the flue gases and the linings onto the charge and the convection heat transfer from the flue gases onto the charge. It was established with the calculations to what extent the decrease in the furnace space height affects the coefficients of heat transfer by radiation and convection, and on the other hand, the heat loss through the furnace linings on the environment. In the end of the article, the suggested solutions are explained.Keywords: rotary hearth furnace, steel charge, heat transfer, furnace efficiency 1 Introduction During the last decades, global energy and market conditions have motivated energy users to improve energy utilization -this means reducing the fuel consumption -in order to remain competitive. For this reason, a research in the thermal processing industry has been directed toward one or more of the following: improving process productivity, improving thermal efficiency, increasing process temperature, improving process temperature uniformity, improving process quality and reducing the pollutant production [1][2][3][4][5][6][7][8]. The goal of a reheating furnace is to heat the steel charge to the minimum temperature consistent with achieving the correct temperature and metallurgical properties at the finishing stands of the mill. Uniformity of the temperature within the load, minimisation of local temperature gradients, avoidance of surface defects such as skid marks, overheating marks and oxidation scale represent the characteristics of the ideal product of the reheating operation [9][10][11][12][13][14]. The rotary-hearth furnace of the nominal heating capacity (throughput capacity) of 27 t/h is located before the rolling stand of type "pilger" in the line for seamless pipe production. Because of the lower production capacity of the seamless tube mill in the relation to the furnace heating capacity, the furnace works with the decreased furnace output of 13-15 t/h. For this reason, the preheated zone is not fired.

In this paper, thermomechanical processing of niobium microalloyed steel was performed with the purpose of determining the interaction between niobium precipitates and dislocations, as well as determining the influence of the temperature of final deformation on the degree of precipitation and dislocation density. Two variants of thermomechanical processing with different final rolling temperatures were carried out. Samples were studied using electrochemical isolation with an atomic absorption spectrometer, transmission electron microscopy, X-ray diffraction analysis, and universal tensile testing with a thermographic camera. The results show that the increase in the density of dislocations before the onset of intense precipitation is insignificant because the recrystallization process takes place simultaneously. It increases with the onset of strain-induced precipitation. In this paper, it is shown that niobium precipitates determine the density of dislocations. The appearance of Lüders bands was noticed as a consequence of the interaction between niobium precipitates and dislocations during the subsequent cold deformation. In both variants of the industrial process performed on the cold deformed strip, Lüders bands appeared.