INVAR alloy is an iron-based high-nickel alloy with a nickel content of up to 36%. It has a very low coefficient of linear expansion below 100°C. It is also called non-expandable steel. The INVAR trademark was first held by the French Inferno Alloy Company. Invar is the abbreviation of Invariability, meaning that the volume remains unchanged.
Application: Due to the advantages of low expansion, 4J36 is an indispensable structural material for precision instruments. It is widely used in the electronics industry, precision instrument industry and other fields sensitive to size requirements, such as: bimetallic materials, magnetic materials, measuring instruments Jigs, astronomical telescope components, optical instruments, CFRP metal molds, antenna parts, FPD shielding frames, high-precision printing frames, semiconductor inspection jigs, semiconductor processing jigs, etc.
Material characteristics:
Most metals and alloys expand in volume when heated and shrink in volume when cooled. However, due to its ferromagnetism, Invar has abnormal thermal expansion with Invar effect within a certain temperature range, and its expansion coefficient is extremely low. , Sometimes even zero or negative values. Its characteristics are summarized as follows:
1. Small expansion coefficient
The average expansion coefficient of Invar alloy is generally 1.5×10-6/℃, and the volume does not change at room temperature -80℃~+100℃.
2. The strength and hardness are not high
The carbon content of Invar alloy is less than 0.05%, the hardness and strength are not high, the tensile strength is about 517Mpa, the yield strength is about 276Mpa, and the Vickers hardness is about 160. Generally, the strength can be improved by cold deformation, while the strength is improved. Still has good plasticity.
3. Low thermal conductivity
The thermal conductivity of Invar alloy is 10W/m·K, which is only ?~? of the thermal conductivity of 45 steel.
4. High plasticity and toughness
Plasticity, toughness, elongation, reduction of area and impact toughness are all high, elongation δ=30~45%, shrinkage δ=50~70%. Impact toughness αK=130~310 J/cm2.
5. Other properties
Due to the high nickel content of Invar alloy, the hardenability and hardenability of steel are improved, and the gas resistance, corrosion resistance and wear resistance of steel are improved.