Precision iron-nickel alloys engineered for exceptionally low and controlled thermal expansion. The definitive choice for electronics packaging, aerospace structures, scientific instruments, and hermetic glass-to-metal seals.
Invar and Kovar are precision iron-nickel alloys engineered for their exceptionally low and controlled thermal expansion coefficients. Invar 36 has the lowest expansion of any metal at room temperature, while Kovar's expansion precisely matches borosilicate glass and alumina ceramics, enabling hermetic glass-to-metal and ceramic-to-metal seals. These alloys are indispensable in electronics, aerospace, scientific instruments, and precision measurement equipment.
FountainHead Alloys supplies Invar and Kovar in bars, sheets, wires, and custom forms. With over 25 years of experience and exports to 60+ countries, we deliver these critical low-expansion alloys to the most demanding electronics, aerospace, and scientific instrument projects worldwide.
Request a QuoteInvar and Kovar alloys available in all standard and custom product forms to meet your project specifications.
Hot rolled, cold drawn, forged. 6mm to 300mm dia.
Hot rolled, cold rolled. 0.1mm to 50mm thick.
Seamless & welded. 6mm to 300mm OD.
Precision rolled strip and foil. 0.01mm to 3mm thick.
Cold drawn wire, welding wire. 0.1mm to 12mm dia.
Forgings, machined parts, lead frames, and stampings.
Invar 36 is a 36% nickel-iron alloy renowned for possessing the lowest coefficient of thermal expansion (CTE) of any commercially available metal. Discovered by Swiss physicist Charles Édouard Guillaume in 1896 (earning him the Nobel Prize in Physics), Invar 36 exhibits a near-zero CTE from cryogenic temperatures up to approximately 200°C. This remarkable dimensional stability makes it essential for precision instruments, laser systems, LNG storage, and aerospace structures where thermal distortion cannot be tolerated.
| Ni | Fe | C | Mn | Si | Co | Se | S | P |
|---|---|---|---|---|---|---|---|---|
| 35.0 - 37.0 | Balance | 0.05 max | 0.60 max | 0.35 max | 0.50 max | 0.025 max | 0.025 max | 0.025 max |
| Property | Value |
|---|---|
| Tensile Strength | 450 - 585 MPa |
| Yield Strength (0.2% Offset) | 240 - 275 MPa |
| Elongation (in 50mm) | 30 - 45% |
| Hardness | 140 - 160 HB |
| Property | Value |
|---|---|
| Density | 8.10 g/cm³ |
| Melting Range | 1427 - 1445 °C |
| Thermal Conductivity (at 20°C) | 10.5 W/m·K |
| Coefficient of Thermal Expansion (20-100°C) | 1.2 x 10⁻&sup6;/°C |
| Standard | Designation |
|---|---|
| UNS | K93600 |
| W.Nr (DIN) | 1.3912 |
| ASTM | F1684 |
| AMS | 5550 |
| DIN | 1.3912 |
| BS | 3981 NA36 |
| JIS | PB |
Invar 42 (Alloy 42) is a 42% nickel-iron controlled-expansion alloy with a CTE specifically designed to match soft glasses, silicon, and certain ceramic substrates used in electronic packaging. While its expansion is higher than Invar 36, it provides the precise CTE match required for reliable glass-to-metal seals with soft (soda-lime) glass and is the dominant lead frame material for integrated circuit (IC) packaging in the semiconductor industry.
| Ni | Fe | C | Mn | Si | S | P | Cr |
|---|---|---|---|---|---|---|---|
| 41.0 - 43.5 | Balance | 0.05 max | 0.80 max | 0.30 max | 0.025 max | 0.025 max | 0.25 max |
| Property | Value |
|---|---|
| Tensile Strength | 490 - 540 MPa |
| Yield Strength (0.2% Offset) | 275 - 310 MPa |
| Elongation (in 50mm) | 30 - 40% |
| Hardness | 150 - 180 HB |
| Property | Value |
|---|---|
| Density | 8.12 g/cm³ |
| Melting Range | 1425 - 1450 °C |
| Thermal Conductivity (at 20°C) | 12.1 W/m·K |
| Coefficient of Thermal Expansion (20-300°C) | 4.4 - 5.3 x 10⁻&sup6;/°C |
| Standard | Designation |
|---|---|
| UNS | K94100 |
| W.Nr (DIN) | 1.3917 |
| ASTM | F30 |
| AMS | 5550 |
| DIN | 1.3917 |
Kovar (ASTM F15) is a nickel-cobalt-iron controlled-expansion alloy whose coefficient of thermal expansion is precisely matched to borosilicate glass (such as Corning 7052 and 7056) and alumina ceramics. This CTE matching enables the production of reliable, hermetically sealed glass-to-metal and ceramic-to-metal joints that maintain vacuum-tight integrity over wide temperature ranges. Kovar is the industry-standard material for electronic packaging, microwave tubes, power tubes, and aerospace electronic enclosures.
| Ni | Co | Fe | C | Mn | Si | Cr | Mo | Cu | Al |
|---|---|---|---|---|---|---|---|---|---|
| 29.0 - 30.0 | 16.5 - 17.5 | Balance | 0.04 max | 0.50 max | 0.20 max | 0.20 max | 0.20 max | 0.10 max | 0.10 max |
| Property | Value |
|---|---|
| Tensile Strength | 517 - 540 MPa |
| Yield Strength (0.2% Offset) | 345 - 365 MPa |
| Elongation (in 50mm) | 30 - 35% |
| Hardness | 150 - 210 HB |
| Property | Value |
|---|---|
| Density | 8.36 g/cm³ |
| Melting Range | 1440 - 1460 °C |
| Thermal Conductivity (at 20°C) | 17.3 W/m·K |
| Coefficient of Thermal Expansion (20-400°C) | 5.1 - 5.5 x 10⁻&sup6;/°C (matches borosilicate glass) |
| Standard | Designation |
|---|---|
| UNS | K94610 |
| W.Nr (DIN) | 1.3981 |
| ASTM | F15 |
| AMS | 7727 |
| DIN | 1.3981 |
| MIL | MIL-I-23011 |
India's trusted source for precision low-expansion and glass-sealing alloys.
ISO certified with full mill test certificates (EN 10204 3.1), ASTM and AMS compliance, and third-party inspection available on request for all Invar and Kovar grades.
Extensive inventory of Invar 36, Invar 42, and Kovar in round bars, sheets, strips, wires, and custom forms for immediate dispatch from our Mumbai warehouse.
Exporting Invar and Kovar alloys to 60+ countries across the Middle East, Europe, Southeast Asia, Africa, and the Americas with reliable logistics support.
Common questions about Invar and Kovar alloys answered by our technical team.
Invar 36 is a 36% nickel-iron alloy with the lowest thermal expansion coefficient of any commercial metal (1.2 x 10⁻&sup6;/°C), designed for applications requiring extreme dimensional stability. Kovar is a 29% nickel-17% cobalt-iron alloy whose CTE (5.1 x 10⁻&sup6;/°C) is specifically engineered to match borosilicate glass and alumina ceramics, enabling reliable hermetic seals. Invar is used in precision instruments and measurement, while Kovar dominates electronic packaging and glass-to-metal seal applications.
Invar 36's anomalously low CTE is due to the "Invar effect" or magnetostriction. At the 36% nickel composition, the alloy sits at a critical magnetic transition point where the normal thermal expansion is almost exactly cancelled by a spontaneous volume magnetostriction (magnetic ordering causes a slight contraction). This delicate balance produces a near-zero CTE from -60°C to about 200°C. Above the Curie temperature (~230°C), the Invar effect diminishes and expansion returns to normal values.
These alloys serve highly specialized industries: Electronics and semiconductors (Kovar for IC packages, hermetic seals, lead frames), aerospace (Invar for satellite structures, telescope mirrors, composite tooling), scientific instruments (Invar for precision gauges, laser cavities, geodetic survey equipment), energy (Invar for LNG tank membranes), telecommunications (Kovar for microwave and power tube components), and defense (both alloys in avionics and radar systems). The global push for smaller, more reliable electronics and precision instruments continues to drive demand.
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