# Alloy 36 (UNS K93600) Overview and Applications

## Introduction to Alloy 36

Alloy 36, also known by its UNS designation K93600, is a nickel-iron alloy with a controlled low coefficient of thermal expansion. This unique property makes it particularly valuable in applications where dimensional stability is critical across a wide temperature range.

## Composition and Properties

The chemical composition of Alloy 36 typically includes:

– Nickel: 36%
– Iron: Balance
– Small amounts of carbon, manganese, silicon, and sulfur

Key properties of Alloy 36 include:

– Low coefficient of thermal expansion (approximately 1.2 × 10-6/°C between 20-100°C)
– Good mechanical strength
– Excellent dimensional stability
– Good corrosion resistance in various environments
– Magnetic properties similar to iron

## Thermal Expansion Characteristics

One of the most remarkable features of Alloy 36 is its thermal expansion behavior. The alloy exhibits minimal dimensional changes with temperature fluctuations, making it ideal for precision applications. This characteristic is particularly valuable in:

– Precision measuring instruments
– Aerospace components
– Cryogenic applications
– Electronic packaging

## Mechanical Properties

Alloy 36 offers a combination of strength and workability:

– Tensile strength: 517-655 MPa (75-95 ksi)
– Yield strength: 276-414 MPa (40-60 ksi)
– Elongation: 35-45%
– Hardness: 70-90 HRB

These properties can be further enhanced through cold working or heat treatment processes.

## Applications of Alloy 36

### Aerospace Industry

In aerospace applications, Alloy 36 is used for:

– Satellite components
– Cryogenic fuel tanks
– Instrumentation housings
– Structural components requiring dimensional stability

### Electronics and Semiconductor

The electronics industry utilizes Alloy 36 for:

– Lead frames
– Semiconductor packaging
– Thermocouple components
– Precision resistors

### Scientific Instruments

Scientific applications include:

– Laser components
– Optical measurement devices
– Telescope mounts
– Precision gauges

### Other Industrial Applications

Additional uses of Alloy 36 span various industries:

– Glass-to-metal seals
– Bimetallic thermostats
– Molds for composite materials
– Nuclear reactor components

## Fabrication and Machining

Alloy 36 can be readily fabricated using standard techniques:

– Machining: Similar to austenitic stainless steels but with better chip breaking
– Welding: Can be welded using conventional methods
– Forming: Good cold working properties
– Heat treatment: Typically annealed at 871-982°C (1600-1800°F)

## Comparison with Other Low Expansion Alloys

Alloy 36 offers distinct advantages over other low expansion materials:

– More cost-effective than superalloys
– Better machinability than ceramics
– More consistent expansion properties than some composite materials
– Greater strength than pure nickel alloys

## Environmental Resistance

Alloy 36 demonstrates good resistance to:

– Atmospheric corrosion
– Fresh and salt water
– Alkaline solutions
– Many organic compounds

However, it is not recommended for strongly acidic environments or high-temperature oxidizing conditions.

## Conclusion

Alloy 36 (UNS K93600) remains a critical material for applications requiring exceptional dimensional stability across temperature ranges. Its unique combination of properties continues to make it indispensable in aerospace, electronics, and precision instrumentation industries. As technology advances, new applications for this versatile alloy continue to emerge, ensuring its ongoing relevance in modern engineering.