Green strength adequate strength and plasticity after

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Unformatted text preview: Green strength: adequate strength and plasticity after mixing water and sand 2.Dry strength: strength, erosion resistance against metallostatic pressure after pouring the metal 3.Hot strength: After moisture evaporation, sand should resist erosion, breakage during metal flow 4.Permeability: should permit the steam/gases to pass off 5.Thermal stability: Heat from the casting causes rapid expansion of silica 6. Refractoriness 7. Flowability 8. Produces good casting finish 9. Reusable 10.Collapsibility: The mold should collapse easily after the liquid metal/ alloy has solidified. Hard/rocklike sand mold cause tear/crack of the casting upon contraction during solidification. 11. Remove heat from the casting during solidification 12.Offer ease of sand preparation and control Shape and size of sand grains Size AFS grain fineness number/ sieve analysis 15 min If the clay content in the pan is estimated to be 0.4 g, calculate the AFS grain fineness number. Molding materials other than silica steel no PT, rapid heat extr. Features of molding processes 1. Use of pattern 2. Mixtures/aggregate comprising of granular refractory and binders 3. A method of forming the aggregate around the pattern 4. Hardening of the aggregate-development of bonds in mold 5. Withdrawal of the pattern 6. Liquid metal/alloy is poured into the mold (assemble of mold+ core pieces+ etc) Parameters Method of forming molds<-> granular refractory<-> method of bonding Forming of molds 1. Compaction of the aggregate around the pattern 2. Free flow of the dry aggregate around the pattern (shell molding) 3. Free flow of a slurry / fluid aggregate (investment/plaster molding) 4. Variants of mold forming methods Sand molding methods Flask molding: hand ramming/ machine ramming-molding jolt ramming squeezing sand slinger Loam molding: large savings of the patter making cost All-core molding: Shell molding: Flask Molding Classification of the molding processes 1. Sand molding (or sand casting) a) green-sand molding b) dry-sand molding c) core-sand molding d) shell molding e) Miscellaneous sand molding (pitfloor molding, cement bonded sand, air-set sand, loam molding, CO2 processes, hot box) 2. Inv...
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This note was uploaded on 10/11/2012 for the course MINING 101 taught by Professor K.dey during the Spring '11 term at Indian Institute of Technology, Kharagpur.

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