Papers by Keyword: CET

Abstract: The effects of forced convection on grain refinement of S32205 duplex stainless steel (DSS) were investigated using a continuous casting simulation setup. The sample, which was called slab simulating unit here, was solidified in the continuous casting simulation setup, whose temperature was controlled according to the cooling curve of a DSS slab center, with the bottom cooled by running water to simulate the solidification process of slab. Forced convection was generated by square-wave mechanical stirring. The CET (columnar to equiaxed transition) was gradually promoted by forced convection when the rotation of the crucible speeded up, the microstructure was refined significantly. The average columnar zone length was reduced from 8.2 cm to 4.8 cm, the equiaxed grain average size decreased from 9.5 mm to 1.7 mm, and the microstructure was refined from Widmänstatten plates to island-shaped pieces.

Abstract: This paper presents the implementation of CETPayment system which is an online payment system against CET (College English test). Hierarchical design is used to increase the flexibility of the system development. Althrough the workload of system design and implementation increased significantly, it can respond to rapidly changing business needs. Because of the use of hierarchical design, the system can be modified and adjusted quickly when it faced two major adjustments in the business logic. LINQ to SQL is used to make the system development process more automatic and effective, and avoid SQL injection attacks. A third-party payment company is chosen to process the payment requests of the candidates. A synchronous Reconciliation strategy is used to solve the problem of "single out". CET-CETPayment system can effectively reduce the work pressure of exam organization and management.

Abstract: Concurrent engineering has been used in many OEMs in order to face up to the fierce competition situation. Modular development teams develop common modules which are applied in the same platform-based variants and its product family in order to save design costs and reduce development time. The R&D department should construct a concurrent engineering team to quicken the pace of new product development and to ensure product quality by means of open-loop and close-loop cycle, and frame a platform to frequent communication and quick decision for the concurrent engineering team.

Abstract: In the fragmentation theory of T. Campanella et al, the local remelting of dendrite arms is induced by the solute-rich fluid flow. Based on this theory, the effects of linear EMS intensity and solute content on CET of steel are investigated. The conclusions are as follows: The criterion for dendrite fragmentation under linear EMS is derived based on dendrite fragmentation theory by T. Campanella et al. And the criterion is verified with steel experiments. It is valid for steel under the Linear EMS. Investigation is carried out on relation between critical volume fraction of solid and solute content at the time of dendrite fragmentation (CET occurrence). It is concluded that critical volume fraction of solid is small with low EMS intensity and it decreases with the increase of solute content (C, Mn). The reason is that it causes that flow in the mushy zone becomes small which leads to CET occurrence difficult.

Abstract: A macroscopic model of Columnar-to-Equiaxed Transition (CET) formation is presented. The growth of a columnar zone and an equiaxed zone are treated separately and modeled on a fixed grid. The model uses a columnar Front Tracking (FT) formulation to compute the motion of the columnar front and the solidification of the dendritic columnar mushy zone. The model for the equiaxed zone calculates the average growth of equiaxed grains within the control volumes of undercooled liquid. The proposed model, which calculates the average equiaxed growth, is different from previous FT models which consider each equiaxed grain envelope separately. A lognormal size distribution model of seed particles is used for the equiaxed nucleation in the undercooled liquid zone. After nucleation, average equiaxed growth is computed by considering the equiaxed envelopes as spherical. The extended volume concept is used to deal with grain impingement. The Scheil equation is used to calculate the solid fraction and latent heat release. When the equiaxed fraction is great enough, advancement of the columnar front is halted and the CET position is determined. CET formation was simulated for directional solidification of an aluminium-silicon alloy. The results were compared with a previous FT-CET prediction model as well as with experimental data. Agreement was found in both cases.

Abstract: The columnar to equiaxed transition (CET) has been widely studied for many years [1] because this phenomenon is observed in metallurgical applications like castings. In non refined alloys, detachment of dendrite fragments is the most probable mechanism responsible for the formation of an equiaxed microstructure [1]. In this frame, melt convection influences the grain structure evolution by playing a role in the fragmentation phenomena [2].

Abstract: A series of Al-Si hypoeutectic alloy ingots were prepared by centrifugal casting (CC) both with and without an external electromagnetic field (EMF). The effects the EMF on grain refinement and on the solidification mechanism during centrifugal casting have been investigated using optical microscopy, scanning electron microscopy (SEM) and electron backscattering diffraction (EBSD) orientation measurements. The electromagnetic stirring effect caused by the EMF promotes the columnar-equiaxed transition (CET) resulting in a finer cast grain size. The silicon and aluminum nucleate and grow independently both with and without EMF

Abstract: This paper deals with the characterization of solidification, cooling and expected properties of continuously cast slabs. Semi-empirical models based on theoretical consideration and on the results of heat transfer model are used for characterization of the following: surface and inner temperature distribution of the cast semis, liquid sump depth and shape, liquid motion intensity resulting in centerline segregation, parameters of the primary dendritic structure (primary and secondary dendritic spacings, columnar to equiaxed transition position, CET). This method provides an opportunity to make a realistic comparison between the solidification and final properties of semis with different chemical compositions as a function of applied casting technologies. The final goal of this research activity in the future is to define a comprehensive quality function for optimizing continuous casting technology.

Abstract: Two computer programs were used for simulation of continuous steel casting processes in frame of this work. In the same time industrial experiments by isotope technics were carried out for observation of solidification and shell thickness. The comparison of calculations and experimental results mutually verified the applicability of methods for more sophisticated control of continuous casting procedure.