Specifications
Surface Treatments
Certifications
- ISO 9001 - 2015 Certified
- PED 2014/68/EC
- NACE MR0175/ISO 15156-2
- NORSOK M-650
- DFAR
- MERKBLATT AD 2000 W2/W7/W10
UNS S21800 Datasheet, Nitronic 60 Composition, Properties, Equivalents
UNS S21800 is the Unified Numbering System designation for the high-manganese, high-silicon, nitrogen-strengthened austenitic stainless steel commonly known as Nitronic 60. The same chemistry is also marketed as Alloy 218, 218-SMO, or under the legacy ASTM designation XM-31. The defining property is the highest galling resistance among austenitic stainless steels commercially produced, plus approximately 2x the yield strength of 304 and 316L in the annealed condition.
NITRONIC Trademark Attribution
NITRONIC® is a registered trademark of Electralloy, a division of G.O. Carlson Inc. (Cleveland-Cliffs Steel). TorqBolt is not affiliated with Electralloy. References to "Nitronic 60" elsewhere on this site use the alloy descriptor; the equivalent UNS designation S21800 is always trademark-safe in body usage and purchase-order language.
Equivalent Designations
| Designation | Issuing Body | Notes |
|---|---|---|
| UNS S21800 | SAE / ASTM (UNS) | Primary trademark-safe identifier |
| NITRONIC® 60 | Electralloy / Cleveland-Cliffs | Registered trademark of mill |
| Alloy 218 / 218-SMO | generic | Common trade reference |
| XM-31 | ASTM (legacy) | Pre-UNS designation |
| Pyromet® 218 | Carpenter Technology | Mill brand for the same chemistry |
| S-21800 | variant spelling | Sometimes seen on European data sheets |
International Cross-Reference
There is no exact ISO or EN equivalent for UNS S21800. The closest European chemistry is DIN 1.3815 (X8CrMnN18-18-10), which has higher manganese and lower silicon and is partial overlap only, not an exact substitute. Order to UNS S21800 chemistry windows directly. JIS SUSXM27 is sometimes referenced but covers a different family. Verify per-application acceptance with the end-user spec before substituting.
Composition Spec Window (UNS S21800)
| Element | Min % | Max % | Role |
|---|---|---|---|
| Chromium (Cr) | 16.00 | 18.00 | Corrosion resistance + austenite stabilization |
| Manganese (Mn) | 7.00 | 9.00 | Galling resistance + nitrogen solubility |
| Nickel (Ni) | 8.00 | 9.00 | Austenite stabilization |
| Silicon (Si) | 3.50 | 4.50 | Galling resistance + oxidation resistance |
| Nitrogen (N) | 0.08 | 0.18 | Solid-solution strengthening |
| Carbon (C) | , | 0.10 | Carbide control (kept low) |
| Phosphorus (P) | , | 0.040 | Residual |
| Sulfur (S) | , | 0.030 | Residual |
| Iron (Fe) | balance | Matrix | |
Mechanical Property Spec Window (Annealed)
| Property | Annealed (min) | Cold-Worked HS (typical) |
|---|---|---|
| Tensile strength | 690 MPa (95 ksi) | 965 MPa (140 ksi) |
| Yield strength 0.2% | 380 MPa (55 ksi) | 830 MPa (120 ksi) |
| Elongation in 50 mm | 35% min | 15% typical |
| Hardness | 95 HRB max | up to 30 HRC |
| Density | 7.62 g/cm³ (0.275 lb/in³) | |
| Modulus of elasticity | 196 GPa (28.4 x 10³ ksi) at 20 C | |
| CTE 20-100 C | 16.2 µm/m·K | |
Hardness, Magnetic Permeability
Annealed Nitronic 60 is essentially non-magnetic with relative magnetic permeability typically below 1.005. Heavy cold work induces small permeability rises (typically 1.02-1.10), still well below ferritic or martensitic stainless levels. The fully austenitic gamma matrix is stable and does not undergo strain-induced martensitic transformation under moderate cold work, which is part of why galling resistance stays high even after surface-finishing operations.
Heat Treatment, Solution Anneal Only
UNS S21800 is supplied solution-annealed at 1010-1120 C (1850-2050 F) followed by water quench. There is no aging step, no gamma-prime precipitation, no martensitic transformation. Strength comes from solid-solution effects (Mn, Si, N) plus optional cold work. Do not pair Nitronic 60 with 17-4 PH or A286 service patterns.
Standards Coverage
- ASTM A193 Gr B8R / B8RA, bolting
- ASTM A194 Gr 8R / 8RA, nuts
- NACE MR0175 / ISO 15156-3, sour service
- API 6A, subsea wellhead and trim
- ASME B&PV Section II Part D, allowable stress
- ASME B16.34, valve materials
Form Availability
TorqBolt supplies UNS S21800 in round bar, hex bar, square bar, flat bar, sheet, plate, forging, wire, tubing, plus the full fastener portfolio and Helicoil thread inserts.
Sister UNS Designations (Nitronic Family)
| UNS | Trade Name | Differentiator |
|---|---|---|
| S21800 | Nitronic 60 (this datasheet) | Highest galling resistance |
| S20910 | Nitronic 50 / XM-19 | Higher yield (55 ksi annealed, 75-100 ksi HS), better corrosion; lower galling resistance than 60 |
| S24100 | Nitronic 32 / XM-28 | Lower-cost lean austenitic, work hardening |
| S24000 | Nitronic 33 / XM-29 | Mn-N strengthened, magnetic-property control |
Sister grades are not interchangeable. Nitronic 50 wins on yield strength and pitting; Nitronic 60 wins decisively on galling. See Nitronic 60 vs Nitronic 50 for the trade-off matrix.
Mill Source Cross-Reference
UNS S21800 is produced by Electralloy (NITRONIC® trademark holder), Carpenter Technology (Pyromet® 218), Cleveland-Cliffs Steel (formerly AK Steel / Armco), Eagle Stainless Industrial Alloys, HP Alloys, and other qualified mills. TorqBolt sources from these mills under their respective UNS S21800 chemistry compliance and issues independent EN 10204 3.1 / 3.2 MTC documentation traceable through final inspection. TorqBolt is not an authorized distributor of any specific mill brand; mill cross-reference is provided for buyer reference only.
Request a Quote
For Nitronic 60 in any product form, sized to spec, with EN 10204 MTC documentation, Contact the TorqBolt QA-QC team at info@torqbolt.com or +91-22-66157017. We respond within 24 hours with sized stock availability, lead time, and 3.1 / 3.2 MTC documentation samples.
Frequently Asked Questions
What does S21800 mean?
UNS S21800 is the Unified Numbering System code for the alloy commonly known as Nitronic 60 / Alloy 218 / 218-SMO / XM-31. All four refer to the same Cr-Mn-Si-Ni-N chemistry.
Is NITRONIC a trademark?
Yes. NITRONIC(R) is a registered trademark of Electralloy, a division of G.O. Carlson Inc. (Cleveland-Cliffs Steel). TorqBolt is not affiliated with Electralloy. The equivalent UNS designation S21800 is always trademark-safe.
What is the EN / ISO equivalent of UNS S21800?
There is no exact equivalent. DIN 1.3815 (X8CrMnN18-18-10) is partial overlap only and not a direct substitute. Order to UNS S21800 chemistry windows directly.
Is UNS S21800 the same as Nitronic 50?
No. Nitronic 50 is UNS S20910 / XM-19 with different chemistry and a different property profile. Nitronic 50 wins on yield strength and pitting; Nitronic 60 wins decisively on galling resistance. They are sister grades, not interchangeable.
Can I substitute Carpenter Pyromet 218 for Electralloy NITRONIC 60?
Yes for chemistry. Both meet the UNS S21800 spec window. Verify the end-user spec accepts the alternate mill brand; some aerospace and nuclear specs name a single mill source.
Satisfaction Survey
