Nitronic Fasteners
Manufacturer
India · Mumbai
Nitronic Alloys — High Nitrogen Austenitic SS with 2× the Yield of 316L
Nitronic is a family of high-nitrogen austenitic stainless steels originally developed by Armco Steel (now AK Steel). The defining characteristic is a high interstitial nitrogen content — 0.20–0.40% N in Nitronic 50 (S20910) compared with 316L’s ≤0.10% N. This elevated nitrogen performs two simultaneous functions: it is a powerful austenite-stabilising element (replacing the more expensive nickel), and it is a highly effective solid-solution strengthener that dramatically raises yield strength without requiring cold work or heat treatment.
The yield strength increase is the key selection driver: Nitronic 50 achieves ≥380 MPa yield strength in the annealed condition — compared with 316L’s ≥170 MPa. This 2+ times yield advantage allows bolt count reduction (the same joint can be achieved with fewer or smaller diameter fasteners), weight reduction (lighter structural sections), and higher bolt preload for the same fastener size. In offshore structural connections, LNG plant support structures, and marine engineering where weight and bolt count are design constraints, Nitronic 50 provides the strength of duplex stainless with the fully austenitic non-magnetic microstructure.
The two main grades serve different primary needs: Nitronic 50 (S20910, also called XM-19) is the high-strength, high-corrosion-resistance grade with PRE≈37 and excellent cryogenic toughness — the specification for marine, offshore, and cryogenic applications where 316L lacks both strength and corrosion resistance. Nitronic 60 (S21800) is the anti-galling specialist — 8–9% silicon dramatically reduces wear and galling, making it the standard specification for fasteners that must be repeatedly assembled and disassembled in stainless-to-stainless connections without thread destruction.
| Property | Value |
|---|---|
| Min Yield Strength | ≥ 380 MPa (annealed) |
| vs SS 316L Yield | ~2.2× (316L ≥170 MPa) |
| Min UTS | ≥ 690 MPa |
| Elongation | ≥ 35% |
| PRE (nominal) | ≈ 37 |
| Nitrogen (N) | 0.20–0.40% |
| Non-magnetic | Yes (fully austenitic) |
| Cryogenic toughness | Excellent to −196°C |
| Anti-galling | Moderate (use N60 for galling) |
Grade Profiles — Nitronic 50 (Strength + Corrosion) vs 60 (Anti-Galling)
Nitronic 50 and Nitronic 60 solve different problems. Specify by primary engineering requirement — corrosion + strength, or anti-galling thread behaviour.
Nitronic 50
Nitronic 60
Why Nitronic — The Four Properties That Set It Apart
2× Yield of 316L — Annealed Condition, No Cold Work
Nitronic 50 achieves ≥380 MPa yield in the annealed condition through interstitial nitrogen solid-solution strengthening — no cold work, no precipitation hardening, no loss of corrosion resistance. Standard 316L achieves only ≥170 MPa annealed. This 2.2× yield advantage: fewer bolts for same joint preload, lighter bolt weight, thinner flanges in weight-critical offshore and marine structures, and higher clamping force in small-diameter fasteners where 316L reaches its strength limit at the required preload.
Nitronic 60 — The Stainless Anti-Galling Specialist
Austenitic stainless steels (304, 316L) are notorious for galling — cold-welding of thread surfaces that destroys bolt and nut threads in a single over-tightened assembly. Nitronic 60’s uniquely high silicon content (3.5–4.5%) creates an oxide surface layer that prevents the metallic contact required for cold welding. Where 316L stud bolts gall in 316L valve body threads, Nitronic 60 stud bolts in the same connection release cleanly after years of service. For chemical plant valve gland bolts, marine maintenance hardware, and any repeated-disassembly stainless connection, Nitronic 60 is the anti-galling specification.
PRE≈37 — Between Duplex and 904L, Fully Non-Magnetic
Nitronic 50’s PRE≈37 places it at the same chloride pitting resistance as Duplex 2205 (PRE≈35) but with a critical difference: Nitronic 50 is fully austenitic with zero ferrite — so it is completely non-magnetic. Duplex 2205 is slightly magnetic due to its ferritic phase. For offshore structural bolts near sensitive instruments, subsea vehicle fasteners, MRI room construction hardware, and marine magnetic compass equipment, Nitronic 50 provides duplex-level corrosion resistance with zero magnetic signature.
Cryogenic Toughness — Excellent to −196°C
Nitronic 50 maintains exceptional impact toughness at cryogenic temperatures — no ductile-brittle transition. The high nitrogen and austenitic structure provide superior cryogenic performance compared with duplex (which has reduced cryogenic toughness due to its ferritic phase). For LNG plant structural fasteners, liquid nitrogen equipment, cryogenic pressure vessel connections, and any application requiring both high strength and verified cryogenic toughness in a stainless fastener, Nitronic 50 is the specification that avoids the need to move to Inconel 625.
Nitronic Fastener Types — Both Grades
Nitronic 50 (S20910) and Nitronic 60 (S21800) from ASTM A276-certified bar stock. PMI-confirmed N content before machining. M4–M36.
Stud Bolts
Fully threaded and equal-end stud bolts in Nitronic 50 (S20910) and Nitronic 60 (S21800). M6–M36, lengths to 500mm. Nitronic 50 for offshore structural flanges, marine seawater connections, LNG cryogenic flanges, and any ASME B16.5 connection where 316L lacks both strength and chloride resistance. Nitronic 60 for valve body studs, pump cover studs, and any flanged connection with repeated maintenance disassembly.
Hex Bolts
Full thread and partial thread hex bolts in Nitronic 50 and Nitronic 60. M4–M36. Offshore platform structural hex bolts (Nitronic 50), marine deck and hull connections, chemical plant valve gland bolts (Nitronic 60), subsea structural hex bolts, MRI room construction hex bolts, and all applications where 316L lacks sufficient strength or chloride resistance and duplex’s slight magnetism is unacceptable.
Hex Nuts
Standard hex nuts in Nitronic 50 and Nitronic 60. M4–M36. Matched from same ASTM A276-certified bar as stud bolts for single-alloy assembly documentation. For Nitronic 60 anti-galling service, specify Nitronic 60 nuts matched to Nitronic 60 stud bolts — the anti-galling benefit requires both mating surfaces to be the Si-rich alloy, or one surface matched to a dissimilar harder alloy.
Washers
Plain flat washers in Nitronic 50 and Nitronic 60. M4–M36. For complete Nitronic stud bolt assembly documentation — stud bolt, nut, and washer from the same ASTM A276 certified heat. Nitronic 50 washers for LNG and cryogenic assembly sets; Nitronic 60 washers for anti-galling maintenance bolting where all three contact surfaces (washer-nut, nut-bolt, washer-flange face) must have anti-galling characteristics.
Socket Cap Screws
Hex socket cap screws in Nitronic 50 and Nitronic 60. M4–M24. Offshore instrument housing screws (Nitronic 50, non-magnetic), chemical plant valve internal fixture screws (Nitronic 60, anti-galling), subsea equipment internal screws, marine navigation instrument housing screws requiring non-magnetic + high-strength + corrosion-resistant combination.
Custom Nitronic
Non-standard head forms, inch UNC/UNF thread, precision machined Nitronic 60 anti-galling components, and drawing-specific configurations in Nitronic 50 or Nitronic 60. Contact sales@akbarfasteners.in with UNS designation (S20910 or S21800), form, dimensions, and documentation requirement.
Nitronic 50 vs 316L vs Duplex 2205 vs Inconel 625
Nitronic 50 occupies a unique position — higher strength than 316L, comparable corrosion to Duplex 2205, fully non-magnetic unlike duplex, and significantly lower cost than Inconel 625.
| Criterion | Nitronic 50 This Page | SS 316L | Duplex 2205 | Inconel 625 |
|---|---|---|---|---|
| STRENGTH | ||||
| Min yield (annealed) | ≥380 MPa | ≥170 MPa | ≥448 MPa | ≥414 MPa |
| Strengthening mechanism | N solid solution | Annealed only | Dual phase | Ni-Cr-Mo solid soln. |
| CORROSION RESISTANCE | ||||
| PRE (pitting resistance) | ≈37 | ≈24 | ≈35 | ≈51 |
| Seawater / chloride | ✔ Good | Pitting risk | ✔ Good | ✔ Excellent |
| SPECIAL PROPERTIES | ||||
| Fully non-magnetic | ✔ Yes (austenitic) | ✔ Yes | Slightly magnetic | ✔ Yes |
| Cryogenic toughness (−196°C) | ✔ Excellent | ✔ Excellent | Reduced (ferrite) | ✔ Excellent |
| Anti-galling | Moderate | Poor (galls) | Moderate | Good |
| COST POSITION | ||||
| Relative cost vs 316L | 2.5–3.5× | Baseline 1× | 1.8–2.5× | 10–15× |
| Optimal niche | High-strength non-magnetic seawater + cryo | Non-chloride service | Chloride + strength (slight mag ok) | Aggressive acid + all-environment |
Anti-galling without strength req: Duplex or phosphor bronze · Heavy chloride: Hastelloy C276
Nitronic Fasteners Application Areas
Offshore structural, cryogenic LNG, non-magnetic MRI, anti-galling valve hardware, marine, and subsea — where 316L lacks strength and duplex’s magnetic properties are unacceptable.
Offshore Structural
non-magnetic + high-strength
LNG / Cryogenic
LNG plant structural
Anti-Galling Valves
anti-galling repeated service
Marine / Seawater
PRE≈37 non-magnetic
MRI / Non-Magnetic
medical imaging hardware
Chemical Processing
process flanges N50/N60
Subsea / ROV
ROV structural hardware
Defence / Naval
magnetic mine clearance equip
Nitronic Standards Coverage
Same ISO 9001:2015 quality system as our complete stainless range. PMI XRF confirms nitrogen presence and Mn content — the key differentiators between Nitronic and standard austenitic stainless (standard SS has ≤2% Mn; Nitronic 50 has 4–6% Mn; Nitronic 60 has 7–9% Mn).
Complete Documentation Package
A276 S20910 / S21800
Tensile · Hardness
Grade Confirmed
Conformance
Non-Magnetic (on req.)
Related High-Strength Corrosion-Resistant Grades
Nitronic for non-magnetic high-strength chloride service. Duplex when slight magnetic permeability is acceptable. 904L for H₂SO₄. Hastelloy C276 for aggressive acids.
Duplex 2205 Fasteners
When slight magnetic permeability from the ferritic phase is acceptable — Duplex 2205 provides comparable PRE≈35 and ≥448 MPa yield at a lower cost than Nitronic 50 (1.8–2.5× 316L vs 2.5–3.5× for Nitronic). For offshore applications where non-magnetic is not a constraint, duplex is typically the more cost-effective specification.
View Duplex Range →SS 316L Fasteners
The grade below Nitronic — when the application’s chloride and strength requirements are within 316L’s PRE≈24 and ≥170 MPa yield capability, 316L is the lower-cost correct choice. Nitronic represents a significant cost premium over 316L that is only justified when 316L is demonstrably insufficient.
View SS 316L →Hastelloy C276 Fasteners
When Nitronic 50’s PRE≈37 is insufficient — concentrated HCl, mixed acids, or extreme chloride concentrations. Hastelloy C276 (PRE≈66) handles environments that destroy all stainless steels including Nitronic 50, at 3–4× the cost of Nitronic and 10–15× the cost of 316L.
View C276 →Inconel 625 Fasteners
When both PRE and strength requirements exceed Nitronic 50 — Inconel 625 (PRE≈51, ≥414 MPa yield) also non-magnetic, also cryogenic, with superior corrosion resistance to Nitronic in aggressive offshore chemical environments. At 10–15× 316L cost, significantly more expensive than Nitronic 50.
View Inconel Range →Need Nitronic
Fasteners?
Grade (Nitronic 50/60) · form · size · non-magnetic requirement · documentation. Akbar Fasteners Pvt. Ltd. responds within 24 hours.
Export: +91 8696 32 4646 · Support: +91 800 9315 333 · export@akbarfasteners.in