A modified network approach for modeling solidification of complex-shaped domains

The finite-difference method is widely used in the formulation of a mathematical representation of the solidification process in metal/mold systems. When complex geometries have to be analyzed, precision of simulations will depend on a multigrid computational scheme covering the spatial domain, which can represent a significant increase in computational time. The present work proposes an approach that modifies the finite-difference network from thermal to electrical elements, permitting a flexible and versatile representation and connection between grid patterns, and consequently an easier transmittal of information at these boundaries, Results of simulations have shown that the proposed approach provides good numerical accuracy and substantial savings in computational time and computer storage requirements, dare mainly to the significant reduction of number of elements within the computational domain.381759

Numerical analysis of solidification of complex shaped bodies: coupling of mesh elements of different geometries

In the present work a three dimensional mathematical model has been developed permitting the integral analysis of solidification of complex shaped castings. The model enables a flexible connection among different kinds of geometrical elements from the numerical mesh permitting the full geometry of the physical body to be analyzed. Model predictions were compared with experimental results obtained in industrial plants for the cases of gray cast iron and stainless steel shaped castings and with laboratory results concerning the solidification of a 7075 aluminum alloy. In all cases a quite good agreement has been observed. (C) 2000 Elsevier Science S.A. All rights reserved.2774167119820

Modeling of solidification in twin-roll strip casting

Twin-roll continuous casting combines solidification and hot rolling into a single operation to produce thin strips that are directly coilable. It offers advantages of low capital investment and low operational cost, and the strips produced have a refined solidification microstructure, which has attracted interest of global metal producers. This is evidenced by numerous pilot-scale casters constructed. The successful development of near-net-shape casting depends critically on an understanding of the fundamental knowledge of heat and fluid flow. Despite sophisticated instrumentation technology, information critical to the understanding of the casting region cannot be measured directly, therefore it is necessary to develop efficient numerical tools to control the process. This paper presents a numerical model for the two-dimensional solidification problem in the twin-roll continuous casting system by using a finite difference technique. The thermal analysis results give valuable insight into the thermal characteristics of solidification and processing for the strip casting. Results of subsequent simulations are compared with data from the Literature. (C) 2000 Elsevier Science S.A. All rights reserved.10241699333

Numerical modeling and optimization of zone refining

The purification of materials by zone refining has been analyzed theoretically and investigated experimentally with a view to establishing operational parameters and optimum processing conditions. A numerical model capable of predicting the solute redistribution at any stage of a multi-pass zone refining is proposed. Experimental work was carried out using tin of commercial grade purity as the starting material. Axial impurity profiles have been determined experimentally for equilibrium distribution coefficients less, as well as higher, than unity. These results are compared with theoretical results furnished by the proposed model in order to validate its predictions. A reasonably good agreement was observed in all cases examined. The efficiency of zone refining as a function of the number of passes and zone length has been modelled. Analysis of solute profiles after a significant number of molten zone passes shows that the model can establish an optimum combination of initial long zones followed by shorter ones, providing improvement in purification efficiency without the technical difficulties which arise with the process that allows a continuous variation of zone size. (C) 2000 Elsevier Science S.A. All rights reserved.2984167129930

The use of artificial intelligence technique for the optimisation of process parameters used in the continuous casting of steel

The productivity and quality of a continuous caster depend mainly on process parameters, i.e. casting speed, casting temperature, steel composition and cleanliness of the melt, water flow rates in the different cooling zones, etc. This work presents the development of an algorithm, which incorporates heuristic search techniques for direct application in metallurgical industries, particularly those using continuous casting process for the production of steel billets and slabs. This is done to determine the casting objectives of maximum casting rate as a function of casting constraints. These constraints are evaluated with the aid of a heat transfer and solidification model based on the finite difference technique, which has been developed and integrated with a genetic algorithm. The essential parts of continuous casting equipment, which must be subjected to monitoring, as well as a methodology of mathematical model and physical settlements in each cooling region, are presented. The efficiency of the intelligent system is assured by the optimisation of the continuous casting operation by maximum casting rate and defect-free products. This approach is applied to the real dimension of a steel continuous caster, in real conditions of operation, demonstrating that good results can be attained by using heuristic search, such as: smaller temperature gradients between sprays zones, reduction in water consumption and an increase in casting speed. (C) 2002 Elsevier Science Inc. All rights reserved.26111077109

Application of a solidification mathematical model and a genetic algorithm in the optimization of strand thermal profile along the continuous casting of steel

This work presents an optimization method based on a genetic algorithm applied to continuous casting process. A simple genetic algorithm was developed, which works linked to a mathematical model permitting the determination of optimum values for the water flow rates in the secondary cooling zones. First, experimental data (industrial) were compared with simulated results obtained by the solidification mathematical model, to determine the metal/cooling heat transfer coefficients along the machine by the inverse heat conduction problem method. The industrial data concerning surface strand temperature were obtained by using infrared pyrometers along a continuous caster machine during casting of both SAE 1007 and 1025 steels. In a second step, these results were used by a numerical code based on a genetic algorithm for determining optimum settings of water flow rates in the different sprays zones, which are conducive to the best quality of the solidified strand. The simulations were carried out by analyzing the solidification process during continuous casting to attain metallurgical restrictions concerning the reheating of strand surface temperature and metallurgical length.20342143

Application of a heuristic search technique for the improvement of spray zones cooling conditions in continuously cast steel billets

The process of casting occupies an important place in the metallurgical industry, and the entire world of the metal user. In the past, the ingot casting-rolling (slabbing, blooming, or billeting) process was commonly used. The continuous casting process has largely replaced this earlier method because of the inherent advantages of energy savings, enhanced productivity, higher yield and reduced costs. However, continuous casting process is not without of its problems. Considerable effort has been made by many researches to establish adequate design, operation and maintenance of continuous casting machine to ensure metallurgical quality of the final product. One of the most severe defects in continuous casting products is concerned with the cracks provoked by improper design of the spray cooling system. The aim of this work is to develop a two dimensional heat transfer model based on the finite difference method in order to calculate the strand temperatures and the solid shell profile along the machine. An Artificial Intelligence heuristic search procedure interacts with the numerical model to determine the improved cooling conditions for the sprays zones of a real continuous caster for the production of quality billets. (c) 2005 Elsevier Inc. All rights reserved.30110411

A solidification heat transfer model and a neural network based algorithm applied to the continuous casting of steel billets and blooms

This work presents the development of a computational algorithm applied to improve the thermal behaviour in the secondary cooling zone of steel billets and blooms produced by continuous casting. A mathematical solidification heat transfer model works integrated with a neural network based algorithm (NNBA) connected to a knowledge base of boundary conditions of operational parameters and metallurgical constraints. The improved strategy selects a set of cooling conditions (in the secondary cooling zone) and metallurgical criteria established to attain high product quality, which are related to a more homogeneous thermal behaviour during solidification. Initially, the results of simulations performed by using the mathematical model are validated against experimental industrial data, and good agreement is observed, in any case examined, permitting the determination of nominal heat transfer conditions by the inverse heat conduction method. By using the numerical model linked to a NNBA results have been produced determining a set of casting conditions, which has permitted better strand surface temperature profile and metallurgical length to be attained during the continuous casting of SAE 1007 billets and SAE 1025 blooms.1371071108

The Interrelation between Casting Size, Steel Grade, and Temperature Evolution Along the Mold Length and at the Strand Surface during Continuous Casting of Steel

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)The present work focuses on the investigation of thermal profiles in copper molds and at the strand surface during continuous casting of different steel grades in an industrial plant. Thermocouples embedded in the mold walls were used to measure temperatures along the mold length. Noncontact pyrometers positioned at different locations along the machine monitored the strand surface temperatures. The experimental results permitted an interrelation between steel grade, mold section (240x240mm, 180x180mm, and 150x150mm), and mold wall, and strand surface temperatures to be established as a function of casting operating conditions. It is shown that the mold outer face (external curved wall) has the highest temperature distribution from the meniscus to the bottom of the mold followed by the inner and side faces, respectively. The deepest meniscus is shown to occur for the 150-mold, and the 180-mold is shown to have the highest temperature profiles along the mold length in all faces examined. Low carbon steels present the highest strand surface temperatures along the machine when compared with those of medium and high carbon steels. When the steel composition is parameterized, it is shown that the 150-mold has the smaller strand surface temperature close to the mold exit when compared with the 180 and 240 molds, and it is shown that this behavior changes after the unbending point.261113126Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq