Common Castings Considerations Greater Flexibility In Designing Complex Shapes. Dissipate Stress That Cause Fatigue Cracking. Blending Shapes That Adhere To Clearance Issues. Move Fabrication / Weld Joints To Low- Stress Areas Or Eliminate Fab Joints! Provide Durability Resistance To Impact Loads. Weight Enhancement

Most of the common alloys can be cast using expendable molds of some kind. But their use in reusable mold depends on their melting points. A reusable mold process can't be used if the melting point of the alloy is higher.

Each alloy has its own strengths and weaknesses with regard to cost, reliability, dimensions held, metallurgical quality, volume production and competitive situation. Things to be considered, while selecting an alloy, are as follows:

• Cost
• Cost
• Strength
• Hot strength
• Hardness
• Density (weight limitations)
• Bearing qualities (galling resistance)
• Machinability
• Weldability
• Brazability
• Brazability
• Abrasion resistance
• Corrosion resistance
• Oxidation resistance
• Fatigue properties
• Resistance to crack propagation
• Electrical conductivity
• Magnetic properties
• Thermal conductivity

Followings are the two tables that may be useful in Selecting a Casting Alloy :


Followings are the two tables that may be useful in Selecting a Casting Alloy :

Base Maximum Strength (1000s psi) Reusable Mold Zinc 61 Yes Aluminum 60 Some alloys Magnesium 40 Yes Copper 150 Some alloys Cast iron 60 Some alloys Cobalt 110 No Nickel 130 No Stainless steel 200 No Tool steel 220 No Maraging steel 240 No Low alloy steel 220 No Carbon steel 150 No Titanium 160 No Comparison Chart For Various Alloys Aluminum Alloys Second most plentiful metal on earth Hall-Heroult process electrolytic reductionof Al2O3 to liquid metal One-third the density of Steel Aluminum alloys can be up to 30 times stronger than pure Aluminum Wrought & Casting Alloys Al Li Alloys Magnesium Alloys Extracted electrolytically from concentrated magnesium chloride in seawater Density = 1.74g/cm3 (lighter then Al) Specific strength comparable to Al Poor corrosion resistance in a marine environment Beryllium Alloys Modulus of Elasticity = 42 x 106 psi (stiffer then steel) Density = 1.848 g/cm3 (light then Al) Expensive , complicated production It can be toxic, BeO is a carcinogenic material for some people. Copper Alloys Heavier then Steel, lower specific strength then Aluminum Many copper alloys are excellent electrical conductors Brass - Copper-Zinc alloys w/ < 40% Zn Bronze - Copper-Tin alloys w/ < 10% Sn Copper-Beryllium alloys are non-sparking Nickel Alloys High temperature alloys Great corrosion resistance Supperalloys - Nickel, iron-nickel, and cobalt. (high strength at high temperatures) Solid solution, dispersion strengthening and precipitation hardening Titanium Alloys The Kroll process - conversion of TiO2 to TiCl4 which is then reduced to titanium metal Higher specific strength then aluminum Excellent corrosion resistance and high temperature properties Alpha (a) and Beta (b) titanium alloys Refractory Metals Exceptionally high melting temperatures Tungsten (W) – 3,410oC Molybdenum (Mo) – 2,610oC Tantalum (Ta) – 2,996oC Niobium or Columbium (Nb) - 2,468oC