Expansion Alloy

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Expansion alloys are specialized materials designed to exhibit controllable thermal expansion properties. These alloys are widely used in applications where the thermal expansion needs to match or remain stable with other materials, such as glass, ceramics, or specific industrial components, or when a specific expansion must be met over a certain temperature range.

Available grades: 4J29, 4J32, 4J33, 4J50, 4J42

Some expansion alloys, such as Invar alloys, expand almost not at all with temperature changes, while other types can be engineered to have a specific expansion rate.
These alloys maintain shape and size stability, even in environments with significant temperature fluctuations.
They typically offer enough strength and toughness, making them suitable for complex structural components.
They are easy to process with cold and hot working, welding, and other forming techniques.
Many expansion alloys also exhibit excellent corrosion resistance.

Precision instruments and measuring devices: such as balances, microscopes, and laser interferometers
Electronics and semiconductors: integrated circuit boards, connectors, resistors, etc.
Aerospace: navigation systems, control systems on aircraft and satellites
Automotive industry: engine sensors, exhaust system components
Energy industry: sensitive equipment in nuclear power plants, thermal power stations, such as instrument panels and controllers
Watchmaking: precision components such as gears and mainsprings in high-end watches
Lighting industry: metal brackets and connectors in light bulbs and LED lighting fixtures

Product Forms

Expansion Alloy Rod

Expansion Alloy Strip

Plate / Sheet

Thickness: 0.1mm-50mm

Width: 50mm-1000mm

Length: 1000mm-6000mm
Strip

Thickness: 0.02mm-1mm

Width: 3mm-500mm

Delivery Forms: Bright shiny surface or anodized surface, supplied in spools or cut-to-length
Rod

Diameter: Ø3mm-Ø100mm

Length: 100mm-2000mm

Delivery Forms: Hot rolled, forged or turned
Wire

Diameter: Ø0.03mm-Ø6mm

Delivery Forms: Bright shiny or anodized, supplied in spools
Tube

Outer Diameter: Ø3mm-Ø200mm

Wall Thickness: 0.5mm-10mm

Length: 100mm-6000mm

Chemical Composition

Elements		4J29	4J36
Carbon (C)	Not greater than	0.03	0.05
Sulfur (S)		0.02	0.02
Phosphorus (P)		0.02	0.02
Manganese (Mn)		≤0.50	0.20-0.60
Silicon (Si)		≤0.30	≤0.30
Nickel (Ni)		28.5-29.5	35.0-37.0
Chromium (Cr)		-	-
Cobalt (Co)		16.8-17.8	-
Iron (Fe)		Rest	Rest
Other Elements

Thermal Expansion Properties

Alloy Grade	20°C-100°C	20°C-300°C	20°C-500°C
4J36 Invar Alloy	1.2×10⁻⁶ /°C	2.5×10⁻⁶ /°C	-
4J29 Kovar Alloy	4.6×10⁻⁶ /°C	5.5×10⁻⁶ /°C	6.2×10⁻⁶ /°C

Mechanical Properties

Alloy Grade	4J36 Invar Alloy	4J29 Kovar Alloy
Density (g/cm³)	8.1	8.2
Tensile Strength (MPa)	500-600	600-700
Yield Strength (MPa)	250-350	300-400
Hardness (HV)	150-200	200-250

Electrical Properties

Alloy Grade	4J36 Invar Alloy	4J29 Kovar Alloy
Electrical Resistivity (10⁻⁶ Ω·cm)	80	50
Thermal Conductivity (W/m·K)	10-12	16-18

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