Expansion Alloy 4J50 · UNS K94500 · GB 4J50
Expansion Alloy 4J50 (K94500): composition, properties, fittings and flanges
Expansion Alloy 4J50 (K94500, GB 4J50) is Iron-nickel 50 % controlled-expansion and sealing alloy. Expansion Alloy 4J50 is specified at Nickel 49.0 - 51.0, Cobalt 0.50 max. 4J50 is the 50 % nickel expansion alloy whose coefficient matches certain hard glasses and mica, used for sealing and for components that must expand in…
- UNS
- K94500
- W. Nr.
- -
- Density
- 8.20 g/cm³ (0.296 lb/in³)
- Key strength
- 520 MPa / 75 ksi
Identification and standards
| Short form | Expansion Alloy 4J50 · UNS K94500 · GB 4J50 |
|---|---|
| Classification | Iron-nickel 50 % controlled-expansion and sealing alloy |
| UNS | K94500 |
| Werkstoff number | - |
| Material family | Precision Alloys |
Chemical composition
| Element | Composition (wt %) | Why it is there |
|---|---|---|
| Iron (Fe) | Balance | Matrix |
| Nickel (Ni) | 49.0 - 51.0 | 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) | 520 MPa / 75 ksi |
|---|---|
| 0.2 % yield strength, min | 290 MPa / 42 ksi |
| Elongation in 2 in, min | 30 % |
| Typical hardness, annealed | 150 - 190 HB |
| Mean coefficient of thermal expansion, 20-400 °C | 9.2 - 10.0 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 | 8.20 g/cm³ (0.296 lb/in³) |
|---|---|
| Melting range | 1430 °C (2610 °F) |
| Modulus of elasticity | 158 GPa (22.9 x 10⁶ psi) |
| Thermal conductivity at 20 °C | 14.5 W/m·K |
| Curie temperature | About 500 °C |
| Specific heat capacity | 460 J/kg·K |
Specifications by product form
| Forgings & flanges | To order against GB/T 15018 (4J50) |
|---|---|
| Butt weld fittings | Not normally supplied |
| Seamless pipe & tube | To order |
| Plate / sheet / strip | GB/T 15018 |
| Bar / rod | GB/T 15018 |
| Welding consumables | Matching 4J50 filler |
| UNS / EN / China | UNS K94500 · GB 4J50 |
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
- Hard glass and mica sealing components
- Ceramic substrate and hybrid circuit packages
- Precision measuring instruments and standards
- Thermostatic and compensation elements
Welding, forming and machining
- Welding
- Weld with matching filler in a protective atmosphere. Control the chemistry across the joint because the expansion coefficient moves quickly with nickel content.
- Heat treatment
- Anneal at 850 - 950 °C in a protective atmosphere and slow cool to stabilise dimensions.
- 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 Expansion Alloy 4J50 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.