Introduction

• UNS K93500(ASTM F1684), also known as Super Invar 32-5, is a low-expansion iron-nickel-cobalt alloy. Its main chemical composition is FeNi32Co4Cu (nominally about 32% Ni and 4% Co, with the balance Fe plus minor Cu), Super Invar Alloy exhibits minimum thermal expansion at room temperatures (one half of Invar Alloy), as well as thermal expansion properties less than that of Invar Alloy in the 67/203°F (-55/95°C) temperature range. By further optimizing its chemistry, this family of alloys achieves superior dimensional stability in specific low-temperature environments.
• Super-Invar 32-5 soft-magnetic alloy exhibit good magnetic permeability and low magnetic reluctance, enabling efficient conversion of electrical energy into magnetic energy during electromagnetic processes and thereby improving device operating efficiency. In addition, its high saturation magnetic flux density helps the alloy maintain stable magnetic performance even in strong magnetic fields.
• UNS K93500 (also referenced as Super Invar 32-5, Invar, or FeNi32Co4Cu) offers excellent oxidation and corrosion resistance, allowing it to retain stable performance over long periods in harsh operating conditions. This makes it suitable for use in environments with high humidity, elevated temperatures, or aggressive corrosive agents while still maintaining good magnetic properties and long service life.

Chemical Composition

• Ni: 32%
• Co: 4%
• Cu: 0.6%
• Fe: Remainder

Alloy Standard

• ASTM: K93500 / ASTM F1684
• France: Invar / Surperieur
• USA: Super-Invar32-5 / Super Nilvar
• Japan: SI
• Russia: 32НКД / 32НК-ВИ

Average Coefficient of Linear Expansion

• max. 1.0 10⁻⁶/℃ (20～100°C)
• To heat the semi-finished products samples to 840±10°C, hold for1hour, and quench in the water. Machine the samples to finished samples. And heat at 315±10℃ for 1h, furnace or air cool.

Application

• Precision instruments & metrology
  4J32 (Super Invar 32-5) provides extremely low thermal expansion for high-precision, low-temperature measurement and reference devices.
• Electronic packaging & sealing
  Used where stable dimensions are needed to preserve hermetic seals and tight tolerances in specialized electronic packages.
• Thermal bimetal layers & resonant cavities
  Applied to bimetal passive layers and resonant cavities to maintain frequency and alignment under temperature changes.
• Power electronics (inductors, transformers, sensors)
  Its good magnetic properties improve efficiency and stability in inductors, transformers, and sensors.
• Communications (antennas, filters, microwave)
  Used in antennas, RF filters, and microwave parts where dimensional stability affects performance.
• Aerospace (satellites, rockets)
  Used for critical lightweight components that require long-term dimensional reliability in space environments.
• Renewable energy & EV motors
  Employed in high-performance motor cores and generators for EVs and wind turbines to boost efficiency and durability.
• Medical devices (MRI, imaging)
  Helps maintain stable magnetic circuits and mechanical structures in high-precision imaging equipment.

Alloy Forms

• Strip
• Sheet
• Rod / Bar
• Wire