Low Expansion 42

UNS #K94101

Low Expansion 42 is a 42% nickel-iron alloy with a consistently low rate of thermal expansion at temperatures up to approximately 650°F (343°C). It is often used as core rod material uniformly coated with an 18 to 28 volume % copper sheath by manufacturers of copper coated wire. The thermal expansion of the composite wire provides a suitable match for glass sealing to soft glass.

Type Analysis

  • Carbon (Maximum) 0.05
  • Silicon (Maximum) 0.2
  • Nickel (Nominal) 42
  • Manganese (Maximum) 1
  • Iron (Nominal) Balance


Thermostat bimetal applications, glass seal lead wires

Applicable Specifications

  • ASTM F29



Technical Information


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