Materials

Die casting typically makes use of non-ferrous alloys. The four most common alloys that are die cast are shown below, along with brief descriptions of their properties. (Follow the links to search the material library).

Materials Properties
Aluminum alloys
  • Low density
  • Good corrosion resistance
  • High thermal and electrical conductivity
  • High dimensional stability
  • Relatively easy to cast
  • Requires use of a cold chamber machine
Copper alloys
  • High strength and toughness
  • High corrosion and wear resistance
  • High dimensional stability
  • Highest cost
  • Low die life due to high melting temperature
  • Requires use of a cold chamber machine
Magnesium alloys
  • Very low density
  • High strength-to-weight ratio
  • Excellent machinability after casting
  • Use of both hot and cold chamber machines
Zinc alloys
  • High density
  • High ductility
  • Good impact strength
  • Excellent surface smoothness allowing for painting or plating
  • Requires such coating due to susceptibility to corrosion
  • Easiest to cast
  • Can form very thin walls
  • Long die life due to low melting point
  • Use of a hot chamber machine

The selection of a material for die casting is based upon several factors including the density, melting point, strength, corrosion resistance, and cost. The material may also affect the part design. For example, the use of zinc, which is a highly ductile metal, can allow for thinner walls and a better surface finish than many other alloys. The material not only determines the properties of the final casting, but also impacts the machine and tooling. Materials with low melting temperatures, such as zinc alloys, can be die cast in a hot chamber machine. However, materials with a higher melting temperature, such as aluminum and copper alloys, require the use of cold chamber machine. The melting temperature also affects the tooling, as a higher temperature will have a greater adverse effect on the life of the dies.

 

Possible Defects

Defect Causes
Flash
  • Injection pressure too high
  • Clamp force too low
Unfilled sections
  • Insufficient shot volume
  • Slow injection
  • Low pouring temperature
Bubbles
  • Injection temperature too high
  • Non-uniform cooling rate
Hot tearing
  • Non-uniform cooling rate
Ejector marks
  • Cooling time too short
  • Ejection force too high

Many of the above defects are caused by a non-uniform cooling rate. A variation in the cooling rate can be caused by non-uniform wall thickness or non-uniform die temperature.

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Category: Die casting

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