Papers by Keyword: Thin-Walled Casting

Abstract: Investment casting is one of main precision casting processes to realize near net shape castings. For the castings with thin-walled cross section or complicated shape, it is easy to generate casting stress such as thermal stress, mechanical stress and phase transformation stress, resulting in casting deformation due to the uneven cooling and hindered contraction. Once three-dimensional deformation is formed, it is very hard to correct. In this paper the finite element method (FEM) was used to analyze the stress and deformation of thin-walled lost wax casting. The results show that the temperature and stress distributions are uneven in the casting and the tendency to deform is higher even with insulating shell mold. And based on the results, the technical measures of adding supporting ribs are adopted to restrain deformation. The practice of volume production indicates that no casting was rejected due to deformation defects.

Abstract: A commercial software, MAGMASOFT, was used to simulate the ZM5 shell with different materials of chills. The calculated results of solidification are obtained. Shrinkage porosity is predicted by means of a built-in porosity criterion. It shows that using the different materials of chills, such as copper, gray iron and steel, a large amount of shrinkage porosity defects are formed in ZM5 shell. However, with graphite as the material of chills, shrinkage porosity defects of ZM5 shell can be effectively reduced.

Abstract: This work aims to develop flow and thermal control methods for the high pressure die casting (HPDC) of very thin-walled aluminium components where thicknesses are predominantly less than 1 mm. One specific aim includes developing advanced modelling capability using CFD software to predict the complex structure of the metal flow in the die and the casting solidification. The modelling based on FLOW-3D started initially with a fluidity die study to establish several key parameters in HPDC modelling through experimental validation. A new test casting geometry has been designed in the form of a shallow tray with other features such as changes in curvature, fins and bosses. The casting thickness can be made variable in the die. The experimental work was conducted on a 250-tonne HPDC machine. Initial models of molten metal flow in the die cavity based on a runner design for casting thicknesses between 1.5 mm and 1 mm are presented. The detailed model required a very large mesh of very small elements, and more accurate physical parameters which may not have been previously available.

Abstract: The optimal alloy design and microstructure for the high temperature (around 800oC) constrained cyclic thermal fatigue applications in thin-section ductile irons have been established previously by the authors. This study intends to investigate the effect of graphite morphology on the thermal fatigue property of thin-section (2mm ~ 6mm) graphitic cast irons. The results show that to produce carbide-free spheroidal graphite irons in relatively thin sections of 2-mm or 3-mm in the as cast conditions is feasible. However, for compacted graphite cast irons, graphite particles largely in nodular form always occurs in rather thin sections, and acceptable compacted graphite structure can only be obtained when the section thickness exceeds about 6-mm. Regarding the constrained cyclic thermal fatigue property (20 ~ 800oC), cast irons with spheroidal graphite exhibit the best thermal fatigue life, which is followed by irons with compacted graphite, and then flake graphite cast irons, even though flake graphite cast irons show least swelling or distortion after cyclic thermal fatigue test. Furthermore, adding some 0.5%Mo to the irons significantly improves the thermal fatigue property, in some cases even by a factor of 2, implying that the role of Mo outweighs the influence of graphite structure in promoting thermal fatigue property.