MIT 2 008 - Metal Casting (11 pages)

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Metal Casting



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Metal Casting

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Lecture Notes


Pages:
11
School:
Massachusetts Institute of Technology
Course:
2 008 - Design and Manufacturing II

Unformatted text preview:

Outline 2 008 Metal Casting Some Facts First casting 5000 3000 BC Bronze iron age light metal age Versatility Many types of metals Rapid production Wide range of shapes and sizes Complex parts as an integral unit Introduction Process Constraints Green Sand Casting Other Processes Example Sand Casting Example Die Casting Casting Process Physics and Constraints Phase Change Density Solubility Diffusion rates High melting temperature Chemical activity High latent heat Handling Example Investment Casting Analysis of Casting Processes Fluid mechanics for mold filling Heat transfer for solidification Thermodynamics mass transfer and heat transfer for nucleation and growth Materials behavior for structure property relationships Mold Filling Cooling for Sand Mold Bernoulli s equation h P v2 const g 2 g AIR MOLD SOLID LIQUID h v 2 gh 1 5 m s TEMPERATUR E Tw Reynold s number Re vD 5 10 4 T METAL MOLD INTERFACE T MOLD AIR INTERFACE T0 Turbulence Injection Molding Re 10 4 DISTANCE Conductivity Diffusivity Conductivity W mK Cu 400 Al 200 Sand 0 5 PMMA 0 2 Sand Casting sand metal Die Casting tool metal metal Injection Molding tool metal polymer Solidification Time Sand Casting Transient 1 D heat transfer T 2T s 2 t x Solution T TM x erf To TM 2 st Solidification time 2 V ts C A Chvorinov s rule Comparison Sand Mold vs Metal Mold Solidification Time Die Casting Transient 1 D heat transfer mC p T Ah T To t Solution t Tinject Tsp Tmold ln Ah Teject Tmold mC p Solidification time V ts C A Sand Mold Metal Mold Sand casting Die casting ts V A 2 ts V A 1 1 Microstructure Formation Formation of Dendrites Liq L S Solid So uid TL us T S S L lid us Temperature Liquid Solid Solid Schematic illustration of three basic types of cast structures a Columnar dendritic b equiaxed dendritic c equiaxed nondendritic Liquid Mushy zone Alloying element Mold wall Dendrites Liquid T CL CS LIQUID SOLID LIQUID COMPOSITION Constitutional Supercooling Green Sand Casting SOLUTE ENRICHED LAYER IN FRONT OF



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