Materials Science Forum Vols. 475-479

Abstract: ZA27 alloy solidifies in the way of paste-solidification, and results in gravity segregation. The two-phase flow model was developed on the basis of the solidification characteristic of the ZA 27 alloy. And the governing equations of the solidification process were differentiated and computed in a 3-D cylindrical coordinate system through a heat and fluid simulation software package (PHOENICS). The computation of the concentration field indicated a segregation of Al, and is in good agreement with the experiments. This model could simulate the convection and the gravitational segregation during the solidification.

Abstract: A 3-D coupled numerical model for flowing distribution and temperature distribution in twins strip roll-casting process is developed, and the influence of technological parameter on roll-casting process is studied. As a result, lower superheat can get more homogeneity structure in thickness direction, but the metal will solidify in the casting system if the superheat is too low, which doesn’t benefit the slag inclusion floating up. When the velocity is between 6m/mim and 8m/min, the end-point will be at 2~8mm above the anastomotic point. The model can provide the theory to the control on strip roll-casting process.

Abstract: In the present paper, applied the experiential correlation, the gas holdup and distribution of two phase zone which formed by argon blown were determined. The flow variables of molten steel and turbulence parameters in the Ladle Furnace were estimated utilizing the results of frontal calculation and through numerically solution momentum Navier-Stokes equation in conjunction with k-εturbulence model. Several different spray styles including blowing through single hole, double holes, top lance were simulated and compared in this project.

Abstract: The distribution of velocity field in single outlet tundish has been simulated through numerical solution of turbulent Navier-Stokes equation in conjunction with e − k turbulence model. The theoretical predicted results have compared with experimental ones, and excellent agreement between them has been achieved. Through comparing the computational data using coupled heat and flow method with that of using uncoupled method, it indicated that it’s necessary to utility the coupled heat and flow method in big size tundish since the thermal buoyance should not be ignored in the calculation.

Abstract: An Eulerian finite element analysis for the steady state rolling process is addressed. This analysis combines the crystal plasticity theory for texture development as well as the continuum damage mechanics for growth of micro voids. Although an Eulerian analysis for steady state rolling has many advantages, it needs an initial assumption about the shape of control volume. However, the assumed control volume does not match the final shapes. To effectively predict the correct shape in an assumed control volume, a free surface correction algorithm and a streamline technique are introduced. Applications to plate rolling, clad rolling, and shape rolling will be given and the results will be discussed in detail.

Abstract: A computational model for roll pressing of powder was developed based on an elastoplastic finite element method, and was applied to predict the alligatoring behavior at roll nip during powder compacting process. The yield criterion for powder has been implanted for the simulation of the roll pressing of Direct Reduced Iron powder with both flat roller and indentationtype roller. Calculated results could well explain the experimental observation that the indentationtype roller is more useful to hinder in alligatoring.

Abstract: An analysis for non steady state heat transfer of a hot pressing roller was suggested in 1-dimensional model. The surface temperature on hot pressing roller was predicted by using surface contact heat transfer coefficient calculated with induced analytic solution. We calculated the size of iron powder, influencing on surface contact heat transfer coefficient. Since coarse iron powder has reduced heat transfer coefficient during contacting on roll surface with smaller contact area, temperature on roller surface has been expected to decrease. This predicted temperature by the analytic model was fairly reasonable in comparison with experimental data and finite element model.

Abstract: The dissimilar channel angular pressing (DCAP) process by rolling was numerically modeled and analyzed by the rigid-plastic two-dimensional finite element method in order to optimize the strain state of the DCAP process. Three distinct deformation mechanics during DCAP by rolling includes rolling, bending, and shearing. AA 1100 aluminum alloy was selected as a model material for the analysis of DCAP process. Difference in the friction conditions between the upper and lower roll surfaces led to large variation of shear strain component throughout the thickness of sample. Strain accompanying bending turned out to be negligible because of a large radius of curvature by relatively large roll diameter. The concentrated shear deformation was monitored at the corner of the DCAP-channel where the abrupt change in the direction of material flow occurred. The strain state at the upper and lower surfaces was observed to vary strongly from that of the center layer of the sheet.

Abstract: In general micro alloy steel have the higher strength relative to conventional steels, which limits the utilization of conventional plastic forming processes. Incremental forming processes are more suitable for cold forming of such a high strength material. In particular, cold cross wedge rolling (CWR) can be a potential tool to fabricate axi-symmetric components with multi steps using high strength micro alloy steel. Obviously, optimization of die shape design is a crucial factor to apply cold cross wedge rolling to micro alloy steels. In this regards, a simulation-based process design using an elasto-plastic FEM has been carried out in order to obtain an optimum die shape for cold cross wedge rolling in this paper. Analysis results provided that the stretching angle and the shoulder angle at knifing and guiding zones were significant parameters for the stable forming process. It was demonstrated that proper stretching and shoulder angles reduced an excessive slip between a work piece and die in CWR process despite the condition of the low friction coefficient.

Abstract: This paper presents the plastic deformation behavior of bimetal composite rods during the axisymmetric and steady-state extrusion process through a conical die. In this study, the finite element code, DEFORM commercial package, considering frictional contact problem was used to analyze the effects for the diameter ratio of the core to sleeve layer on the material flow. Different cases of initial composite material are simulated under different conditions of extrusion process, which includes the semi-die angle, reduction in area and end distance, from the end of sleeve to the end of core, with constant value of reduction area, die corner radius and die land. The main design parameters influencing on deformation pattern are diameter ratio of the composite components and semi-die angle. Simulation results indicate that there is an obvious difference of forming pattern with various diameter ration and semi-die angle. The predicted forming load, the end distance and outer radius of sleeve of the rods are also obtained from numerical results. The analysis in this paper is concentrated on the evaluation of the design parameters on the deformation pattern of composite rod.