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1、1. Metal casting,1.1 Concept of casting 1.2 Casting process 1.3 Fluid flow 1.4 Casting defects 1.5 Sand casting 1.6 Investment casting 1.7 Foundry and automation,Please refer to chapters 10 and 11,Metal casting-key words,Casting Mold Grain Fluidity Sand casting/ die casting Investment casting Foundr
2、y Pattern/core/porosity/ shrinkage,1.1 Concept of casting,Casting: process which involves pouring molten metal into a mold cavity, then obtains the shape of the cavity.,1.1 Concept of casting,Advantages: Complex shapes with internal cavities or hollow sections Very large parts Almost all metals, sui
3、table for workpiece materials difficult to process by other means Competitive with other processes,1.1 Concept of casting,Applications: Many parts and components, for examples,1.1 Concept of casting,Trends: Mechanization and automation of the casting process Increasing demand for high-quality castin
4、gs with close dimensional tolerances and no defects,1.2 Casting process,Casting process: Pouring molten metal into a mold patterned after the part to be manufactured; Allowing it to cool; Removing the metal from the mold.,1.2 Casting process,Solidifications of metals: Pure metals Alloys,1.2 Casting
5、process,Influence of grain size on casting properties: Strength ductility micro-porosity tendency for the casting to crack.,1.3 Fluid flow,Casting system,1.3 Fluid flow,Fluidity: the capability of the molten metal to fill mold cavities. Influence factors of fluidity （1）Characteristics of the molten
6、metal （2）Casting parameters page 249 for detail Castability: the ease with a metal can be cast to obtain a part with good quality. Test method for castability：,1.4 Casting defects,Main influence factors: Materials, part design, processing techniques Seven categories: （1）metallic projections （2）cavit
7、ies - - porosity （3）discontinuities (4) defective surface (5) Incomplete casting (6) Incorrect dimension or shape (7) Inclusions,1.4 Casting defects,See Fig.10.11,1.4 Casting defects,Porosity: may be caused by shrinkage or gases or both. Methods to reduce or eliminate porosity avoid cavities by shri
8、nkage (1) Adequate liquid metal (2) Internal or external chills,1.4 Casting defects, Reading program: P.256, example.,1.5 Sand casting,Advantages and limitations: - See Table 11.1, (P.8); Table 11.2, (P.9) Process of sand casting: (1) Place a pattern having the shape of the desired casting in sand t
9、o make an imprint; (2) Incorporating a gating system (3) Filling the resulting cavity with molten metal (4) Allowing the metal to cool until it solidifies (5) Breaking away the sand mold (6) Remove the casting,1.5 Sand casting,1.5 Sand casting,Why sand is used for casting? reading See P.264 Componen
10、ts of sand molds and their functions: (1) Flask - - cope and drag; (2) Pouring basin (3) Sprue (4) Running system (5) Riser (6) Core (7) Vent,1.5 Sand casting,Patterns: are used to mold the sand mixture into the shape of the casting. pattern materials: Table 11.3, See P.267,1.5 Sand casting,Cores: F
11、or casting with internal cavities or passages, cores are used. Core are placed in the mold cavity before casting to form the interior surfaces of the casting and removal from the finished part during shakeout and further processing.,1.5 Sand casting,Sand- operation: p.271,1.6 Investment casting,Home
12、work-questions： State the sequences of investment casting operation. Explain the meaning of “investment”. In the operation of “pattern meltout”, mold is fired to 650-1050 C for 4 hours, why? Describe the advantages and limitations of investment casting,1.7 Foundry and automation,Advantages of foundr
13、y automation: Wide variety and sizes of casting at high production, at low cost, and with good quality control. Two groups of casting activities: 1. Pattern and mold making- CAD, CAM, RPM 2. Melting the metals, pouring molten metal into mold -automated machinery, industry robot,1.7 Foundry and automation,1.7 Foundry and automation,Safety in foundry: Dust, fumes from molten metal, fuel for furnaces,
