Stainless 440C · UNS S44004 · W. Nr. 1.4125
Stainless 440C (S44004): composition, properties, fittings and flanges
Stainless 440C (S44004, W. Nr. 1.4125) is High-carbon martensitic chromium stainless steel. Stainless 440C is specified at Chromium 16.00 - 18.00, Molybdenum 0.75 max. 440C reaches 58 - 60 HRC, the hardest of the standard stainless grades, which is why it is used for bearing races, knife blades, valve balls and seats where wear…
- UNS
- S44004
- W. Nr.
- 1.4125
- Density
- 7.80 g/cm³ (0.282 lb/in³)
- Key strength
- 758 MPa / 110 ksi
Identification and standards
| Short form | Stainless 440C · UNS S44004 · W. Nr. 1.4125 |
|---|---|
| Classification | High-carbon martensitic chromium stainless steel |
| UNS | S44004 |
| Werkstoff number | 1.4125 |
| Material family | Stainless Steel |
Chemical composition
| Element | Composition (wt %) | Why it is there |
|---|---|---|
| Chromium (Cr) | 16.00 - 18.00 | Corrosion resistance and carbide formation |
| Carbon (C) | 0.95 - 1.20 | Maximum hardness |
| Molybdenum (Mo) | 0.75 max | Temper resistance |
| Manganese (Mn) | 1.00 max | - |
| Silicon (Si) | 1.00 max | - |
| Phosphorus (P) | 0.040 max | - |
| Sulphur (S) | 0.030 max | - |
| Iron (Fe) | Balance | Matrix |
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) | 758 MPa / 110 ksi |
|---|---|
| 0.2 % yield strength, min (annealed) | 448 MPa / 65 ksi |
| Elongation in 2 in, min (annealed) | 14 % |
| Typical hardness, hardened | 58 - 60 HRC |
| Wear resistance vs 420 | Substantially better |
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 | 7.80 g/cm³ (0.282 lb/in³) |
|---|---|
| Melting range | 1425 - 1510 °C (2600 - 2750 °F) |
| Modulus of elasticity | 200 GPa (29.0 x 10⁶ psi) |
| Thermal conductivity at 20 °C | 24.2 W/m·K |
| Mean coefficient of thermal expansion, 20-100 °C | 10.2 µm/m·°C |
| Specific heat capacity | 460 J/kg·K |
Specifications by product form
| Forgings & flanges | To order against ASTM A276 chemistry |
|---|---|
| Butt weld fittings | Not recommended - welds crack |
| Seamless pipe & tube | Not normally supplied |
| Plate / sheet / strip | ASTM A276 / A756 family |
| Bar / rod | ASTM A276 / A756 (UNS S44004) |
| Welding consumables | Welding not recommended |
| UNS / EN / China | UNS S44004 · W. Nr. 1.4125 · GB 102Cr17Mo |
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
- Ball bearing races, balls and rolling elements
- Knife blades, scissors and precision cutting tools
- Valve balls, seats and nozzle components
- Measuring instruments, gauges and wear pads
Welding, forming and machining
- Welding
- Fusion welding is not recommended: the high carbon content produces a brittle untempered martensite zone. Parts are machined and heat treated, not welded.
- Heat treatment
- Anneal at 840 - 885 °C and furnace cool, or austenitise at 1010 - 1065 °C, oil quench and temper at 150 - 260 °C. Deep cryogenic treatment between quench and temper improves dimensional stability.
- 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 Stainless 440C 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.