[en] In an effort to minimize costs and to obtain optimum designs, computer simulation of shape casting processes is more and more used as a development tool. Accurate predictions are possible by means of three dimensional fluid flow and solidification modelling. The bases of the model are the transient laminar Navier-Stokes-equations for a Newtonian fluid including the tracking of the free surface. They are describing the melt flow pattern during the mold filling sequence. Simultaneously, the temperature development in the alloy and mold is calculated using Fourier's heat transfer equation. At OEGI, a commercial software package (MAGMAsoft) with a finite difference equation solver is used for improvement of casting processes. Different examples of industrial applications will be shown. (author)

[en] Full Text: A transient interferometric technique to measure thermal expansion of pure metals and alloys during rapid heating is presented. The metallic specimen is resistively heated from room temperature to a high temperature close to melting within approximately 500 ms by the passage of an electrical high current pulse. The time dependent temperature of the specimen is measured by a fast pyrometer, the thermal expansion is obtained by a high-speed laser-interferometer. The device used is a modified polarized-beam Michelson-type interferometer with a phase quadrature detector that allows to distinct between expansion and contraction. Details of its principle, the construction, adjustment and operation are described. Furthermore, thermal expansion measurements performed an molybdenum and tungsten standard reference materials (SRM) are presented and compared with results obtained by other researchers. (author)

[en] Published in summary form only

[en] Full Text: The specific enthalpy and the temperature of the titanium alpha-beta phase transformation were measured by a pulse-heating system, operating in the millisecond time regime. The measurement technique is based on self-heating of a tube-shaped specimen from room temperature to the beta phase of titanium in approximately 300 ms and measuring the current through the specimen, the voltage drop along a defined portion of the specimen, and the temperature of the specimen every 0.5 ms. From current, voltage drop and mass, the specific enthalpy as a function of temperature is calculated. The comparison between the measured phase transition temperature during heating and cooling of the specimen shows a difference of approximately 20 K. The temperature measured during the heating period is higher than the value obtained from the cooling cycle of the specimen. This is probably due to the high heating rate of approximately 4000 Kxs^-1. For the evaluation of the specific enthalpy of the alpha-beta transformation, the specific enthalpy versus temperature function of the beta phase of the heating period was extrapolated to the transition temperature obtained from the cooling cycle (1153 K). A total of 12 measurements on 3 tube-shaped specimens was made, a value of 89900 Jxkg^-1 was obtained for the specific enthalpy of the transformation. The reproducibility of the measured specific enthalpy at the begin and at the end of the transformation was 0.5 %, the reproducibility of the phase transformation enthalpy as difference was 3 %. The extended measurement uncertainty (at a confidence level of 95 %) is estimated to be 6 % for the specific enthalpy of the transformation and ±5 K for the transformation temperature. (author)

No abstract available

[en] A numerical simulation model for the horizontal centrifugal pipe casting process was developed with the commercial simulation package Flow3D. It considers - additionally to mass, energy and momentum conservation equations and free surface tracking - the fast radial and slower horizontal movement of the mold. The iron inflow is not steady state but time dependent. Of special importance is the friction between the liquid and the mold in connection with the viscosity and turbulence of the iron. Experiments with the mold at controlled revolution speeds were carried out using a high-speed camera. From these experiments friction coefficients for the description of the interaction between mold and melt were obtained. With the simulation model, the influence of typical process parameters (e.g. melts inflow, mold movement, melt temperature, cooling media) on the wall thickness of the pipes can be studied. The comparison to results of pipes from production shows a good agreement between simulation and reality.

[en] Two individual high-pressure die-casting geometries were developed in order to study the influence of process parameters and different alloys on the distortion behaviour of castings. These geometries were a stress lattice and a V-shaped sample tending to form residual stress due to different wall thickness respectively by a deliberate massive gating system. In the experimental castings the influence of the most important process parameters such as die temperature and die opening time and the cooling regime was examined. The time evolution of process temperatures was measured using thermal imaging. The heat transfer coefficients were adapted to the observed temperature distributions. Castings were produced from the two alloys AlSi12 and AlSi10MnMg. The distortion of the castings was measured by means of a tactile measuring device. For the alloy AlSi10MnMg thermo-physical and thermo-mechanical data were obtained using differential scanning calorimetry, laser flash technique, dilatometry and tensile testing at elevated temperatures. These data were used for modelling the material behaviour of the AlSi10MnMg alloy in the numerical model while for the alloy AlSi12(Fe) literature data were used. Process and stress simulation were conducted using the commercial FEM software ANSYS Workbench. A survey on the results of the comparison between simulation and experiment is given for both alloys.

[en] Published in summary form only

[en] This is the sixth of a series of workshops on both experimental and theoretical aspects of thermophysical behavior of matter (such as ceramics, graphite, liquid alloys and metals, refractories, tungsten and uranium oxides among others) in the millisecond to picosecond time regimes. It includes rapid resistive or inductive heating (volume), pulse laser heating (surface) and levitation techniques. The emphasis was on the measurements of thermopysical properties (emissivity, melting points, phase transition temperatures, specific heat, surface tension, thermal diffusivity and thermal expansion) at high temperatures. In this region, pulse-heating techniques are a unique approach to study the behavior of matter. (nevyjel)

[en] This work presents two three-dimensional solidification models, which were solved by several commercial solvers (MAGMASOFT, FLOW-3D, ProCAST, WinCast, ANSYS, and OpenFOAM). Surprisingly, the results show noticeable differences. The results are analyzed similar to a round-robin test procedure to obtain reference values for temperatures and their uncertainties at selected positions in the model. The first model is similar to an adiabatic calorimeter with an aluminum alloy solidifying in a copper block. For this model, an analytical solution for the overall temperature at steady state can be calculated. The second model implements additional heat transfer boundary conditions at outer faces. The geometry of the models, the initial and boundary conditions as well as the material properties are kept as simple as possible but, nevertheless, close to a realistic solidification situation. The gained temperature results can be used to validate self-written solidification solvers and check the accuracy of commercial solidification programs. (paper)