Nitronic 60 (UNS S21800, also called Alloy 218) is an austenitic stainless steel strengthened with nitrogen. It contains about 4% silicon and 8% manganese, which give it very good resistance to wear, galling and fretting. Its room temperature yield strength is nearly twice that of 304 and 316, and it costs much less than the cobalt or nickel based alloys often used for wear parts.
Chemical Composition (%)
| Element | C | Mn | Si | Cr | Ni | N | Mo | Fe |
|---|---|---|---|---|---|---|---|---|
| Min | - | 7.00 | 3.50 | 16.00 | 8.00 | 0.08 | - | Bal. |
| Max | 0.10 | 9.00 | 4.50 | 18.00 | 9.00 | 0.18 | 0.75 |
The actual chemistry of each heat is shown on the mill test certificate.
Mechanical Properties (ASTM A276, Annealed)
| Property | Min (ksi) | Min (MPa) |
|---|---|---|
| Tensile Strength | 95 | 655 |
| Yield Strength (0.2%) | 50 | 345 |
| Elongation | 35% | |
| Reduction of Area | 55% | |
The properties of large forgings depend on section size. They are tested on every order.
Main Features
Galling and wear resistance
This is the main reason to choose Nitronic 60. Threads and sliding parts can be assembled and taken apart many times without seizing. In valve trim tests at 800 to 1500 F (427 to 816 C), it ran without galling where other austenitic stainless steels galled.
Corrosion resistance
Uniform corrosion resistance is better than 304 in most media, and chloride pitting resistance is better than 316.
High and low temperature
The alloy holds useful strength up to about 1800 F. Its oxidation resistance is close to 309 and much better than 304, and it keeps good impact toughness at low temperature.
Nitronic 60 Forged Products
| Product | Typical Use |
|---|---|
| Forged rings, seamless rolled rings | Pump wear rings, valve seat rings, bearing parts |
| Forged flanges, tube sheets | Seawater pumps, ballast system gate valves |
| Forged round bars, shafts | Pump shafts, valve stems, bridge pins |
| Forged discs, blocks | Valve discs, valve bodies, wellhead parts |
| Forged sleeves, bushings | Bushings, guide sleeves |
| Custom forgings to drawing | Fasteners, pins, chain drive parts, nozzles |
Applications
Valves and pumps: valve stems, seats and trim, pump wear rings and lobes.
Marine: seawater pumps, gate valves for tanker ballast systems, deep sea sampling chambers, underwater robotic arms.
Bridges: bridge pins and pin and hanger expansion joints, replacing A36 and A588 carbon steel for better corrosion and galling resistance and better toughness below zero.
Fasteners: nuts and bolts that are taken apart often, with fewer seized or frozen threads.
Oil and gas: oilfield production and downhole equipment.
Production and Heat Treatment
Melting: AOD or vacuum induction melting, with ESR or VAR remelting on request.
Forging: open die forging and ring rolling.
Heat treatment: annealed at 1950 F (1066 C) and water quenched. Nitronic 60 cannot be hardened by heat treatment.
Machining: because the alloy resists galling, it is not easy to machine. Use a rigid setup, enough machine power and coated carbide tools.
Standards, Testing and Certificates
| Item | Standard |
|---|---|
| Grade | UNS S21800 |
| Material standard | ASTM A276 |
| Ultrasonic testing | ASTM A388, EN 10228-3, SEP 1921 |
| Certificate | EN 10204 3.1, or EN 10204 3.2 with third party inspection |
FAQ
Can Nitronic 60 be hardened by heat treatment?
No. It is annealed at 1950 F (1066 C) and water quenched. Higher strength can only be obtained by cold working.
What are the ASTM A276 minimum properties of UNS S21800?
Annealed: tensile 95 ksi (655 MPa), yield 50 ksi (345 MPa), elongation 35%, reduction of area 55%.
How does Nitronic 60 compare with 304 and 316?
Uniform corrosion resistance is better than 304 in most media, and chloride pitting resistance is better than 316. Room temperature yield strength is nearly twice that of 304 and 316.
Where can I buy Nitronic 60 forgings made to drawing?
Jiangyin Jiangnan Metal Co., Ltd. in Jiangyin, Jiangsu, China forges Nitronic 60 rings, flanges, bars, shafts and custom parts to drawing. Email sales@steelforgepieces.com or call 0086-189-2135-9659.
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