Papers by Keyword: Permanent Mold Casting

Abstract: The demand for lightweight and high-strength materials in automotive applications has been a driving force for research and development of ductile iron. This study investigates the influence of casting parameters on the nodule count of ultrafine spheroidal graphite iron, as nodule count is the major factor for enhancing mechanical properties. Several heats of ductile iron were produced using an induction furnace, varying silicon content, carbon equivalent, mold preheating temperature, and inoculation levels. Optical Emission Spectrometry (OES) and image analysis were used to determine chemical composition and nodule count, respectively. Results showed that silicon content significantly affects graphite fineness (e.g. nodule count) and carbide formation, with a minimum of 3.7% silicon required to prevent carbide formation. Higher mold preheating temperatures and increased inoculation levels promote higher nodule counts by slowing down the cooling rates and promoting the heterogeneous nucleation of graphite. Microstructural analysis revealed that increasing silicon increased ferrite fraction and decreased pearlite. The results suggest optimal casting parameters to maximize nodule count and enhance the strength and ductility of ultrafine spheroidal graphite iron.

Abstract: Permanent mold cast (PMC) AJ62 magnesium alloy exhibits a fine-grained microstructure in the thin section and a coarse-grained microstructure in the thick section. Microstructure of the PMC AJ 62 alloy was analyzed by using the Scanning Electron Microscopy (SEM). Potentiodynamic polarization experiments were performed to investigate the corrosion resistances of the PMC AJ62 alloys in salt solutions and engine coolant. The corrosion behaviors in the fine- and coarse-grained AJ62 alloys were compared. The results show that the AJ62 alloy with fine microstructure presents enhanced corrosion resistance.

Abstract: Melt flow and casting solidification are essential parts of the permanent mold casting process and affect significantly the quality of castings．For this reason, accurate prediction of mold filling pattern and temperature field in permanent mold castings plays on an important role in producing sound castings. In this paper, the model filling and solidification of a box casting produced from an aluminum alloy is studied. Different casting processes are employed, simulated and optimized to obtain sound castings. Simulation results reveal that with appropriate gating system, pouring rate, cooling line, a smooth mold filling, reduced shrinkages and other defects are available and desired sound castings can be produced.

Abstract: To adapt to the trend of lightweight of vehicles, and optimize the structure of vehicle components, the former overturned support of a medium-duty truck cab was optimized by lightweight design. The 3d model of the cabin former overturned support was firstly established, and then finite element analysis method was used to analyze the distributions of stress and displacement, with the support under extreme work conditions. And then a lightweight design was made basing on the analysis. The support blank is produced by permanent mold casting method. To meet the requirement of actual production, this paper, analyzed the casting defects of the structure by lightweight design, and then had a further modification basing on the actual casting technique. The results indicate that the weight of the cab support is reduced 23.2%, with lightweight design reducing the support weight effectively under safety. And the modifications of the structure casting performance meet better the structural optimization objective, and make the production of the cab support more efficient.

Abstract: For thin-walled casting development of austempered ductile iron (ADI), permanent mold casting and accompanied heat treatment practice were systematically investigated to suppress and/or remove chill defects of ductile cast iron (DCI) with various thickness of 2 to 9 mm and to ensure mechanical properties of the final ADI casting. Si content was increased up to 3.8% to reduce the chill formation tendency under a high cooling rate. The residual Mg content remarkably affected the nodule count, while the nodule size and spherodization were proven to have weak relationships. Austenitizing process followed by austempering was very sensitive to chemical compositions (Si and Sn) and heat treatment temperature. As a practical application, the steel bar coupler for a structural frame was tried to produce without subsequent machining.

Abstract: Hot cracking of ternary Mg-Al-Ca alloys in permanent mold casting was studied. The alloys are the base of some potential creep-resistant Mg alloys. The Mg-xAl-yCa alloys included Mg-4Al-1Ca, Mg-4Al-2Ca, Mg-4Al-3Ca, Mg-4Al-4Ca, Mg-5Al-3Ca, and Mg-6Al-3Ca. Constrained-rod casting was conducted with a steel mold. Rods were cast with their ends enlarged to act as anchors, which kept the rods from free contraction and thus induced tension in the rods to cause cracking during solidification. The susceptibility to hot cracking was evaluated based on both the widths and locations of cracks in the resultant castings. Both binary Mg-4Al and commercial alloy AZ91E, which is known to have a low susceptibility to hot cracking, were also included for comparison. It was found that within the composition range studied, the crack susceptibility decreased significantly with increasing Ca content (y) but did not change much with the Al content (x).