Invar 42 (4J42) · UNS K94100 · GB 4J42
Invar 42 (4J42) (K94100): composition, properties, fittings and flanges
Invar 42 (4J42) (K94100, GB 4J42) is Iron-nickel controlled-expansion alloy. Invar 42 (4J42) is specified at Nickel 41.0 - 43.0, Cobalt 0.50 max. Invar 42 raises nickel to 42 % so the expansion coefficient matches soft glass and some ceramics, filling the gap between Invar 36 and Kovar in sealing and thermostat applications.…
- UNS
- K94100
- W. Nr.
- -
- Density
- 8.15 g/cm³ (0.294 lb/in³)
- Key strength
- 490 MPa / 71 ksi
Identification and standards
| Short form | Invar 42 (4J42) · UNS K94100 · GB 4J42 |
|---|---|
| Classification | Iron-nickel controlled-expansion alloy |
| UNS | K94100 |
| Werkstoff number | - |
| Material family | Precision Alloys |
Chemical composition
| Element | Composition (wt %) | Why it is there |
|---|---|---|
| Iron (Fe) | Balance | Matrix |
| Nickel (Ni) | 41.0 - 43.0 | Sets the expansion curve |
| Manganese (Mn) | 0.80 max | Deoxidation |
| Silicon (Si) | 0.30 max | Deoxidation |
| Carbon (C) | 0.05 max | - |
| Cobalt (Co) | 0.50 max | - |
| Phosphorus (P) | 0.020 max | - |
| Sulphur (S) | 0.020 max | - |
Note Single figures are maximum limits unless shown as a range. Always confirm against the heat-specific EN 10204 3.1 certificate supplied with your order.
Mechanical properties
| Tensile strength, min (annealed) | 490 MPa / 71 ksi |
|---|---|
| 0.2 % yield strength, min | 275 MPa / 40 ksi |
| Elongation in 2 in, min | 30 % |
| Typical hardness, annealed | 140 - 180 HB |
| Mean coefficient of thermal expansion, 20-300 °C | 4.5 - 5.5 x 10⁻⁶ /°C |
Warning Values depend on product form, section thickness and heat treatment. Larger sections generally achieve lower strength than thin product; always design against the applicable code allowable stress rather than these figures.
Physical properties
| Density | 8.15 g/cm³ (0.294 lb/in³) |
|---|---|
| Melting range | 1425 °C (2600 °F) |
| Modulus of elasticity | 145 GPa (21.0 x 10⁶ psi) |
| Thermal conductivity at 20 °C | 13.7 W/m·K |
| Curie temperature | About 320 °C |
| Specific heat capacity | 450 J/kg·K |
Specifications by product form
| Forgings & flanges | To order against GB/T 15018 (4J42) |
|---|---|
| Butt weld fittings | Not normally supplied |
| Seamless pipe & tube | To order |
| Plate / sheet / strip | GB/T 15018 / ASTM F30 family |
| Bar / rod | GB/T 15018 / ASTM F30 family |
| Welding consumables | Matching Invar 42 filler |
| UNS / EN / China | UNS K94100 · GB 4J42 |
Product forms available
Hangbo supplies this grade in the following forms. Sizes outside the listed range can often be produced to order.
- Forged flanges blanks and finished flanges to ASME B16.5, B16.47 Series A/B and B16.36
- Butt weld elbows, tees, reducers, caps and stub ends to ASME B16.9 and MSS SP-43
- Seamless pipe and tube to the applicable ASTM / ASME pipe specification
- Forged rings, discs and hubs machined to your drawing
Typical applications
- Soft glass and ceramic sealing components
- Thermostat bimetals and temperature compensation strips
- Precision instrument frames and measuring standards
- Electronic lead frames and relay components
Welding, forming and machining
- Welding
- Weld with matching filler under controlled atmosphere. Keep heat input low to limit the heat affected zone where the expansion behaviour changes.
- Heat treatment
- Anneal at 850 - 900 °C in a protective atmosphere, then stabilise at 600 °C and slow cool.
- Hot and cold forming
- Hot work in the range stated by the mill for this grade, then re-solution or re-age before final machining so that the delivered condition matches the certificate.
- Machining
- Machine with sharp carbide or high-speed steel tooling, positive rake, constant feed and ample coolant. Never dwell - the surface work-hardens quickly.
Buy Invar 42 (4J42) from Hangbo
Material is supplied with full heat-number traceability, solution annealing or ageing performed under calibrated furnace control, and an EN 10204 3.1 certificate covering chemical analysis, mechanical properties, heat treatment records and the agreed NDT scope. Positive material identification and third party inspection and test reports from SGS are available for critical service.