N50 ASTM A276 Stainless Steel – High Strength
N50 Stainless Steel is an austenitic, nitrogen strengthened steel providing a combination of corrosion resistance and strength not found in types 316 and 317. Unlike many other austenitic stainless steels, N50 remains non-magnetic even after severe forming operations or when it is cooled to sub zero temperatures.
N50 is generally used for applications requiring high strength and corrosion resistance such as downhole equipment in the oil and gas industry, valves, fittings and pumps in the marine and pulp and paper industries.
National Specification
| ASTM | UNS | SEA AMS | British Standard | Other |
|---|---|---|---|---|
| A276 | S20910 | - | - | Type XM-19 As Hot Finished |
Material may also be released to Customer Specifications, subject to enquiry.
Technical Data
Nominal Composition by Percent
| C | Mn | Cr | Ni | Mo | N | Nb | Fe | - | |
|---|---|---|---|---|---|---|---|---|---|
| Min | - | 4.0 | 20.5 | 11.5 | 1.50 | 0.20 | 0.10 | - | % |
| Max | 0.06 | 6.0 | 23.5 | 13.5 | 3.0 | 0.40 | 0.30 | Bal | % |
Typical Tensile Properties at Ambient Temperature
| Diameter mm | Yield Strength MPa min. |
UTS MPa min. |
Elongation % min. |
Reduction of Area min % |
|---|---|---|---|---|
| Up to 50.8mm | 725 | 930 | 20 | 50 |
| 50.8mm to 76.2mm | 515 | 795 | 25 | 50 |
| 76.2mm to 203.2mm | 415 | 690 | 30 | 50 |
Physical Properties
| Density | 7880 kg/m3 |
| Magnetic Permeability | < 1.05 |
| Electrical resistivity at 20°C | 0.82μΩm |
| Thermal Conductivity at 20°C | 13.3 W.m-1.k-1 |
Hot Working
Heat to 1090°C, soak to equalise, then heat to 1175°C and equalise prior to forging.
Heat Treatment
Anneal at 1066°C - 1121°C for a time dependent on section thickness followed by either air or water cooling. Annealing towards the lower end of the temperature range provides a higher level of mechanical properties along with excellent corrosion resistance.
Machining
N50 is more susceptible to cold work hardening than types 304 and 316 stainless steel. Slow speeds, positive feeds, coated carbides, rigid tool and work holders and plenty of resulphurised lubricant are essential.
| Condition | Tool Type | Cut Depth mm | Speed m/min. | Feed mm/rev. |
|---|---|---|---|---|
| Annealed | Carbide | 3.0 roughing | 27 – 42 | 0.2 – 0.38 |
| 0.5 finishing | 35 – 60 | 0.13 – 0.20 |