Alloy 42 UNS K94100: Properties and Applications

# Alloy 42 UNS K94100: Properties and Applications

## Introduction to Alloy 42 UNS K94100

Alloy 42, also known as UNS K94100, is a nickel-iron alloy with a controlled coefficient of thermal expansion. This unique property makes it particularly valuable in applications where dimensional stability is critical across a range of temperatures.

## Chemical Composition

The chemical composition of Alloy 42 UNS K94100 typically includes:

– Nickel: 41-42.5%
– Iron: Balance
– Manganese: 0.8% max
– Silicon: 0.3% max
– Carbon: 0.05% max
– Sulfur: 0.025% max
– Phosphorus: 0.025% max

## Physical Properties

Alloy 42 exhibits several notable physical properties:

– Density: 8.11 g/cm³
– Melting Range: 1420-1465°C (2590-2670°F)
– Thermal Expansion Coefficient: ~5.3 μm/m·°C (20-300°C)

– Electrical Resistivity: 75 μΩ·cm
– Curie Temperature: ~360°C (680°F)

## Mechanical Properties

The mechanical properties of Alloy 42 can vary depending on heat treatment and processing:

– Tensile Strength: 450-600 MPa (65-87 ksi)
– Yield Strength: 275-450 MPa (40-65 ksi)
– Elongation: 30-45%
– Hardness: 70-90 HRB (annealed condition)

## Key Characteristics

Several characteristics make Alloy 42 particularly valuable:

– Low thermal expansion coefficient similar to glass and ceramics
– Excellent dimensional stability
– Good corrosion resistance
– High strength and ductility
– Excellent magnetic properties at room temperature

## Heat Treatment

Alloy 42 can be heat treated to optimize its properties:

– Annealing: Typically performed at 790-900°C (1450-1650°F)
– Stress Relieving: 425-540°C (800-1000°F)
– Rapid cooling from annealing temperature is recommended

## Applications of Alloy 42 UNS K94100

Due to its unique properties, Alloy 42 finds use in various industries:

### Electronics Industry

– Lead frames for integrated circuits
– Glass-to-metal seals
– Thermostatic bimetals
– Electronic packaging components

### Aerospace Industry

– Precision instruments
– Gyroscope components
– Satellite components
– Temperature-sensitive devices

### Other Applications

– Medical devices
– Telecommunications equipment
– Watchmaking components
– Scientific instruments

## Fabrication and Machining

Alloy 42 can be fabricated using standard methods:

– Machining: Can be machined using standard techniques, though work hardening may occur
– Forming: Can be cold worked but requires annealing between heavy working operations
– Welding: Can be welded using conventional methods, with post-weld heat treatment recommended
– Joining: Suitable for brazing and soldering

## Comparison with Other Alloys

Compared to other nickel-iron alloys:

– Lower expansion coefficient than Invar (Alloy 36)
– Better machinability than some similar alloys
– More cost-effective than some specialty alloys
– Better strength than pure nickel alloys

## Conclusion

Alloy 42 UNS K94100 offers a unique combination of properties that make it indispensable in applications requiring dimensional stability across temperature variations. Its controlled thermal expansion characteristics, combined with good mechanical properties and fabricability, ensure its continued use in precision engineering applications across multiple industries.