Interplay among Coating Thickness, Strip Size, and Thermal and Solidification Characteristics in A356 Lost Foam Casting
- PDF / 3,551,663 Bytes
- 12 Pages / 593.972 x 792 pts Page_size
- 11 Downloads / 177 Views
foam casting (LFC) is already considered to transfigure a new era in the development of casting processes, and its applications are expected to increase in the future.[1,2] The main advantages of this process are cost-effective and environmentally friendly casting of complex products widely used in transport and automotive market applications, such as for diesel engine cylinder heads, crank shafts, differential cases, compressor bodies, and motor vehicles.[3,4] This process is determined by using expendable polystyrene (EPS) patterns of the component to be produced.[5] This pattern is covered with a refractory material, located in a flask, and surrounded with sand condensed by a vibrating system. Molten metal is then poured into the
S.G. SHABESTARI, M. DIVANDARI, M.H. GHONCHEH, and V. JAMALI are with the Center of Excellence for High Strength Alloys Technology (CEHSAT), School of Metallurgy and Materials Engineering, Iran University of Science and Technology (IUST), Narmak, Tehran 16846-13114, Iran. Contact e-mail: [email protected] Manuscript submitted June 22, 2016.
METALLURGICAL AND MATERIALS TRANSACTIONS B
flask, which vaporizes the polystyrene pattern and replaces it, to form its finalized shape.[6,7] The coating layer overspread on the pattern foam is a significant factor in achieving high-quality castings. It was proposed that in the LFC, the covering refractory coating on the pattern surface is requisite in order to provide support against the weight of the sand before the solidification of liquid metal as well as to tolerate the high temperature of molten metal.[3] Recently, it was expressed that the coating also provides an insulation obstacle to retain the molten metal from losing too much heat, which may result in imperfect solidification.[3,4] One of the important technical challenges in the LFC is to recognize the connection between the crucial parameters of feeding setup, and the solidification characteristics have a direct effect on the preparation of sound samples.[8,9] Recent developments in the LFC have focused on controlling the process parameters that affect the casting accuracy and metallurgical quality, the dimensional tolerance of products, and the compaction of the sand mold.[9] For instance, dendrite arm spacing (DAS) is the microstructural parameter that plays an important role in the mechanical and physical properties of solidified samples; e.g., tensile strength, toughness, and solidification defects mainly progressed during late
stages of mushy zone, such as microsegregation, shrinkage pores, and hot tearing. The DAS is significantly influenced by the value of cooling rate (CR), which can be easily detected through measuring the slope of the cooling curve in the mushy zone plotted by the thermal analysis technique.[10,11] Toward this end, Flemings concluded that increasing the CR improved not only the soundness but also the refinement in the dendritic structure.[12] He derived a correlation between the DAS and the CR for a wide variety of alloys. These equations obeyed the DAS = B(CR)n formula
Data Loading...
