Examining Lost Foam beads. (Lost Foam).The Lost Foam Div. provided Congress attendees with six presentations and one panel focused on lost foam patterns and molding. In their presentation "Influence of Bead Chemistry on Metal Velocity and Defect Formation in Aluminum Lost Foam Casting" (03-105), D. Hess, D. Askeland and C. Ramsay, Univ. of Missouri-Rolla, examined the effect of three foam characterisitics (bead type, bead fusion and nominal pattern density on metal velocity and defect formation. Two chemistries of expanded polystyrene polystyrene (pŏl'ēstī`rēn), widely used plastic; it is a polymer of styrene. Polystyrene is a colorless, transparent thermoplastic that softens slightly above 100°C; (212°F;) and becomes a viscous liquid at around 185°C; beads were examined, including untreated beads and those treated with a bromide-based additive. Both beads had a molecular head weight of 280,000 and an average size of 350 microns. The bromide bromide, any of a group of compounds that contain bromine and a more electropositive element or radical. Bromides are formed by the reaction of bromine or a bromide with another substance; they are widely distributed in nature. additive was found to be effective in reducing the incidence of pyrolysis-related defects in aluminum lost foam castings, nearly eliminating folds and blisters. The fusion of the beads during blowing of the patterns also influenced the severity of the pyrolysis py·rol·y·sis n. Decomposition or transformation of a chemical compound caused by heat. pyrolysis (pīrol´isis), n defects, with fewer defects observed when the beads were well fused. Compared with the bead type and fusion level, the effect of nominal pattern density, liquid infiltration infiltration /in·fil·tra·tion/ (in?fil-tra´shun) 1. the pathological diffusion or accumulation in a tissue or cells of substances not normal to it or in amounts in excess of the normal. 2. infiltrate (2). rate and permeability permeability /per·me·a·bil·i·ty/ (per?me-ah-bil´i-te) the property or state of being permeable. per·me·a·bil·i·ty n. 1. The property or condition of being permeable. 2. of the coating on the incidence of pyrolysis defects was almost negligible. High pattern density did slightly reduce metal velocity (as expected), while liquid infiltration rate and permeability had no effect. In their presentation "Effect of Foam Pattern Fusion on the Quality of Lost Foam Aluminum Castings: Real Time and Digital X-ray Observations" (03-083), W. Sun, H. Littleton and C. Bates Bates , Katherine Lee 1859-1929. American educator and writer best known for her poem "America the Beautiful," written in 1893 and revised in 1904 and 1911. , Univ. of Alabama-Birmingham, examined the variability in lost foam patterns and how it affects casting quality. The research found that castings poured with patterns having a low degree of fusion exhibited more surface defects. In addition, castings poured with patterns having a nominal degree of fusion were found to contain more internal anomalies. Last, when the lost foam pattern was modified with a pattern pre-coat, the number of fold defects decreased while a porosity porosity /po·ros·i·ty/ (por-os´it-e) the condition of being porous; a pore. po·ros·i·ty n. 1. The state or property of being porous. 2. line developed, indicating the presence of internal defects. |
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