Stainless Steel N08366
UNS N08366 · ASTM B676/B677
N08366 is an early 6% molybdenum superaustenitic stainless (20Cr-24Ni-6Mo), developed by Allegheny Ludlum as the predecessor to AL-6XN and covered by ASTM B676/B677.
Reference datasheet — N08366 is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the Annealed condition
N08366 tempers and conditions
N08366 is supplied in 4 conditions, soft to hard. Annealed is the default FabDigit quotes; the values on this page are for it.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
AnnealedDefault solution annealed and water quenched (plate/sheet/tube) | Standard stocked condition for plate, sheet, pipe and tube; maximum corrosion resistance and ductility. | 305 | 655 | 45 | 170 HB | — |
As-welded deposit | Reference condition for welded tube and fabrication; expect some Mo segregation unless overalloyed Ni-base filler is used. | 320 | 640 | 35 | 185 HB | 1.7 % IACS |
Cold drawn | Choose for bar and fastener stock needing better straightness, surface finish and higher yield strength. | 480 | 760 | 30 | 19 HRC | 1.7 % IACS |
Quarter hard | Use for springy strip, gaskets and diaphragms where higher yield strength is needed and forming is minimal. | 620 | 860 | 20 | 25 HRC | 1.7 % IACS |
What is N08366?
N08366 is an early 6% molybdenum superaustenitic stainless (20Cr-24Ni-6Mo), developed by Allegheny Ludlum as the predecessor to AL-6XN and covered by ASTM B676/B677. Engineers specify it for chloride pitting and crevice corrosion resistance well beyond 316L, usually as tube, pipe, plate and sheet; annealed material runs 305 MPa yield, 655 MPa tensile and 45% elongation. It work-hardens strongly, machinability is roughly 25% of 1212, and welds need over-alloyed Ni-base filler to keep weld molybdenum up. Maximum service temperature is 425 °C; AL-6XN (N08367) is the modern, more widely stocked equivalent. N08366 has a density of 8.08 g/cm³ (0.292 lb/in³), heavier than 99% of stainless steel grades. It melts at 1,320°C (2,408 °F). N08366 has a yield strength of 305 MPa (44.2 ksi) and a tensile strength of 655 MPa (95 ksi) — weaker than 66% of stainless steel grades. Elongation at break is 45% and the elastic modulus is 196 GPa (28.4 Msi).
What is N08366 used for?
- seawater piping
- pulp and paper bleach equipment
- flue-gas desulfurization components
- chemical process tanks
Advantages
- Good corrosion resistance — 82/100, better than 90% of stainless steel grades
- Ductile — tolerates forming and impact — 45%, better than 76% of stainless steel grades
Limitations
- Poor heat conductor — 11.5 W/m·K (6.64 BTU/hr·ft·°F), worse than 97% of stainless steel grades
- Difficult to machine — 22/100, worse than 95% of stainless steel grades
- Low electrical conductivity — 1.7 % IACS, worse than 93% of stainless steel grades
- High embodied carbon — 6.5 kg CO₂/kg, worse than 93% of stainless steel grades
N08366 properties
Typical room-temperature values for N08366-Annealed; bars are the position among stainless steel grades.
Physical3
N08366 has a density of 8.08 g/cm³ (0.292 lb/in³), heavier than 99% of stainless steel grades. It melts at 1,320°C (2,408 °F).
Mechanical14
N08366 has a yield strength of 305 MPa (44.2 ksi) and a tensile strength of 655 MPa (95 ksi) — weaker than 66% of stainless steel grades. Elongation at break is 45% and the elastic modulus is 196 GPa (28.4 Msi).
Thermal5
N08366 is rated for continuous service to 425°C (797 °F). It conducts heat at 11.5 W/m·K (6.64 BTU/hr·ft·°F), worse than 97% of stainless steel grades. Thermal expansion is 15.3 µm/m·K (8.5 µin/in·°F).
Electrical3
N08366 conducts electricity at 1.7 % IACS, worse than 93% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is very good (82/100), better than 90% of stainless steel grades.
Sustainability4
Producing a kilogram of N08366 takes about 80 MJ of energy and emits 6.5 kg of CO₂ — more than 89% of stainless steel grades. Typical recycled content is 45%.
Manufacturability7
N08366's machinability is poor (22/100, worse than 95% of stainless steel grades); weldability very good (70/100); formability good (60/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the stainless steel family
Yield strength against density for every stainless steel grade FabDigit runs. N08366 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with N08366
Is N08366 easy to machine?
Slow speeds, heavy positive-rake carbide tooling, rigid setups and flood coolant; it work-hardens strongly and must be cut, not rubbed (~25 % of 1212).
Can N08366 be welded?
GTAW/GMAW/SMAW with overalloyed Ni-base filler (ERNiCrMo-3/-4) to keep weld Mo up; no preheat, low heat input, interpass below ~150 °C, no post-weld heat treat needed for thin sections.
Can N08366 be formed, bent or molded?
Cold forms well but needs ~1.5–2× the press force of 304 with allowance for springback; hot work 1150–1200 °C followed by rapid cooling to avoid σ/χ phase.
N08366 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| Cmax per ASTM B688 | ≤ 0.04 | 0.02 |
| Mn | ≤ 2 | 1 |
| P | ≤ 0.03 | 0.02 |
| S | ≤ 0.03 | 0.01 |
| Si | ≤ 1 | 0.5 |
| Cr | 20 – 22 | 21 |
| Ni | 23.5 – 25.5 | 24.5 |
| Mosource of pitting/crevice resistance | 6 – 7 | 6.5 |
| Cu | ≤ 0.75 | 0.2 |
| Feremainder, ~46 % | balance |
What surface finishes work on N08366?
Pickle in HNO₃-HF and passivate after hot work or welding to restore the passive film; electropolish or mechanically polish for sanitary service — no anodizing.
Surface treatments FabDigit runs on stainless steel parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Passivation
Organic Coating
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Stainless Steel N08366 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- ASTM
- B676/B677
- Trade names
- AL6X
How much does N08366 cost?
N08366 is a high-cost stainless steel ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
N08366 — frequently asked
What is N08366 used for?
N08366 is typically used for seawater piping, pulp and paper bleach equipment, flue-gas desulfurization components and chemical process tanks. In short: first-generation 6Mo superaustenitic; chloride pitting resistance; AL-6XN predecessor grade.
What is the yield strength of N08366?
N08366 has a typical yield strength of 305 MPa (44.2 ksi) and a tensile strength of 655 MPa (95 ksi) — weaker than 66% of stainless steel grades. Strength varies by condition: see the 4 listed tempers.
Is N08366 easy to machine?
Not especially — machinability is rated poor (22/100, worse than 95% of stainless steel grades). Slow speeds, heavy positive-rake carbide tooling, rigid setups and flood coolant; it work-hardens strongly and must be cut, not rubbed (~25 % of 1212).
Can N08366 be welded?
Yes — weldability is rated very good (70/100). GTAW/GMAW/SMAW with overalloyed Ni-base filler (ERNiCrMo-3/-4) to keep weld Mo up; no preheat, low heat input, interpass below ~150 °C, no post-weld heat treat needed for thin sections.
What surface finishes work on N08366?
Pickle in HNO₃-HF and passivate after hot work or welding to restore the passive film; electropolish or mechanically polish for sanitary service — no anodizing.
Can N08366 be formed, bent or molded?
Cold forms well but needs ~1.5–2× the press force of 304 with allowance for springback; hot work 1150–1200 °C followed by rapid cooling to avoid σ/χ phase.
What is the maximum service temperature of N08366?
N08366 is rated for continuous use to about 425°C (797 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between N08366 Annealed and N08366-CD?
Annealed is the default condition — standard stocked condition for plate, sheet, pipe and tube; maximum corrosion resistance and ductility. CD: choose for bar and fastener stock needing better straightness, surface finish and higher yield strength. Yield strength is 305 MPa in Annealed versus 480 MPa in CD.
How much does N08366 cost?
N08366 is a high-cost stainless steel ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Sources
- ASTM B688 — Chromium-Nickel-Molybdenum-Iron (UNS N08366/N08367) Plate, Sheet, and Strip — ASTM International (2018)
- ASTM B676 / B677 — Welded and Seamless UNS N08366/N08367 Tube and Pipe — ASTM International (2019)
- ASTM B691 — UNS N08366/N08367 Rod, Bar, and Wire — ASTM International (2016)
- AL-6X / AL-6XN Alloy Technical Data — Allegheny Ludlum / ATI (2010)
- ASM Handbook Vol. 1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol. 13B — Corrosion: Materials — ASM International (2005)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.