Stainless Steel AL-6XN
UNS N08367 · ASTM A240/B688 · EN 1.4529
High-performance 6Mo superaustenitic alloy developed by Allegheny Technologies, providing outstanding resistance to chloride pitting, crevice corrosion, and stress corrosion cracking, comparable to 254SMO.
Values for the Solution Annealed condition
AL-6XN tempers and conditions
AL-6XN is supplied in 7 conditions, soft to hard. Solution Annealed is the default FabDigit quotes; the values on this page are for it.
Compare all 7 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Hot Finished / Forged + Solution Annealed | Choose for heavy bar, flanges and valve forgings per ASTM A479/B691 where full annealed corrosion performance is required. | 350 | 720 | 45 | 175 HB | 1.9 % IACS |
Solution AnnealedDefault 1100–1180 °C, water quenched | Standard supply condition for plate, sheet, pipe, tube and forgings — maximum corrosion resistance and ductility. | 365 | 745 | 45 | 180 HB | — |
As-welded deposit | Reference condition for weldments; autogenous welds suffer Mo segregation and should be over-alloyed with ERNiCrMo-3 or re-annealed. | 400 | 700 | 30 | 190 HB | 1.9 % IACS |
Cold drawn | Pick for close-tolerance shafting and fasteners needing higher yield strength and better surface finish than hot-finished bar. | 620 | 860 | 25 | 24 HRC | 1.9 % IACS |
1/4 Hard | Use where moderate strength increase is needed but some bending/forming remains, e.g. springs-back-tolerant strip parts. | 690 | 900 | 20 | 27 HRC | 1.9 % IACS |
1/2 Hard | Choose for high-strength flat springs, clips and diaphragms in chloride service where forming is limited to simple bends. | 830 | 1,030 | 12 | 32 HRC | 1.9 % IACS |
Full Hard | Highest strength condition, for wire, wedge wire screens and spring elements; essentially no formability left. | 1,100 | 1,250 | 5 | 38 HRC | 1.9 % IACS |
What is AL-6XN?
High-performance 6Mo superaustenitic alloy developed by Allegheny Technologies, providing outstanding resistance to chloride pitting, crevice corrosion, and stress corrosion cracking, comparable to 254SMO. AL-6XN has a density of 8.06 g/cm³ (0.291 lb/in³), heavier than 98% of stainless steel grades. It melts at 1,320°C (2,408 °F). AL-6XN has a yield strength of 365 MPa (52.9 ksi) and a tensile strength of 745 MPa (108 ksi) — weaker than 51% of stainless steel grades. Elongation at break is 45% and the elastic modulus is 195 GPa (28.3 Msi).
What is AL-6XN used for?
- Seawater cooling pipework
- Pharmaceutical reactors and vessels
- Heat exchanger tube and tubesheets
- Flue-gas desulfurization ducting
- Desalination plant piping
- Chemical process tanks
- Power plant condenser tubing
Advantages
- Good corrosion resistance — 88/100, better than 97% of stainless steel grades
- Polishes to a fine finish — 80/100, better than 89% of stainless steel grades
- Tough — resists crack growth — 200 MPa·√m (182 ksi·√in), better than 86% 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 — 25/100, worse than 88% of stainless steel grades
- High embodied carbon — 6 kg CO₂/kg, worse than 88% of stainless steel grades
- Low electrical conductivity — 1.9 % IACS, worse than 84% of stainless steel grades
AL-6XN properties
Typical room-temperature values for AL-6XN-Solution Annealed; bars are the position among stainless steel grades.
Physical3
AL-6XN has a density of 8.06 g/cm³ (0.291 lb/in³), heavier than 98% of stainless steel grades. It melts at 1,320°C (2,408 °F).
Mechanical15
AL-6XN has a yield strength of 365 MPa (52.9 ksi) and a tensile strength of 745 MPa (108 ksi) — weaker than 51% of stainless steel grades. Elongation at break is 45% and the elastic modulus is 195 GPa (28.3 Msi).
Thermal6
AL-6XN 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
AL-6XN conducts electricity at 1.9 % IACS, worse than 84% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is excellent (88/100), better than 97% of stainless steel grades.
Sustainability4
Producing a kilogram of AL-6XN takes about 85 MJ of energy and emits 6 kg of CO₂ — more than 92% of stainless steel grades. Typical recycled content is 40%.
Manufacturability7
AL-6XN's machinability is poor (25/100, worse than 88% of stainless steel grades); weldability very good (75/100); 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. AL-6XN is highlighted; hover a dot for its name, or open the interactive family chart.
Working with AL-6XN
Is AL-6XN easy to machine?
Machines like a nickel alloy: rigid setups, positive-rake sharp carbide, heavy depth of cut, 20–35 m/min, flood coolant — never dwell or rub, since it work-hardens instantly.
Can AL-6XN be welded?
GTAW/GMAW/SMAW with over-alloyed Ni filler (ERNiCrMo-3 / ENiCrMo-3, or ERNiCrMo-10) to offset Mo segregation; low heat input, interpass <100 °C, no preheat, no PWHT normally required.
Can AL-6XN be formed, bent or molded?
Cold forms well but needs ~50% more press force than 304 and generous bend radii; hot work 1150–1200 °C and always re-solution anneal + water quench afterwards.
Manufacturability
The process limits FabDigit applies to AL-6XN. Every AL-6XN part is priced by an engineer; design inside these and the quote comes back without a redesign loop.
CNC machining
| Machinability | Poor25 / 100 |
|---|---|
| ISO material group | M.1 |
| Cutting speed (rough / finish) | 150 / 180 m/min |
| Minimum wall | 0.8 mm |
| Minimum internal radius | 1.5 mm |
| Drill depth limit | 4× diameter |
| Best surface (machined / polished) | Ra 1.6 / — |
| Hardenable after machining | No |
Sheet metal
| Formability | Better60 / 100 |
|---|---|
| Weldability | Better75 / 100 |
| Bendable | Yes |
AL-6XN 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 |
|---|---|---|
| C | ≤ 0.03 | 0.02 |
| Mn | ≤ 2 | 0.4 |
| Si | ≤ 1 | 0.4 |
| P | ≤ 0.04 | 0.02 |
| S | ≤ 0.03 | 0 |
| Cr | 20 – 22 | 20.8 |
| Ni | 23.5 – 25.5 | 24.2 |
| Mo | 6 – 7 | 6.3 |
| N | 0.18 – 0.25 | 0.22 |
| Cu | ≤ 0.75 | 0.2 |
| Febalance, ≈47% | balance |
What surface finishes work on AL-6XN?
Pickle in HNO₃-HF or bead-blast plus passivation to restore the Mo-rich passive film; electropolishing gives the best pitting performance for pharma/seawater service.
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).
Plating
Organic Coating
CVD Coating
Black / Phosphate
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Stainless Steel AL-6XN in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- N08367
- ASTM
- A240/B688
- EN / DIN / Werkstoff-Nr.
- 1.4529
- Also called
- 6XN
How much does AL-6XN cost?
AL-6XN is a premium-cost stainless steel ($$$), cheaper than about 58% 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.
AL-6XN — frequently asked
What is AL-6XN used for?
AL-6XN is typically used for seawater cooling pipework, pharmaceutical reactors and vessels, heat exchanger tube and tubesheets, flue-gas desulfurization ducting, desalination plant piping and chemical process tanks. In short: super-austenitic seawater stainless.
What is the yield strength of AL-6XN?
AL-6XN has a typical yield strength of 365 MPa (52.9 ksi) and a tensile strength of 745 MPa (108 ksi) — weaker than 51% of stainless steel grades. Strength varies by condition: see the 7 listed tempers.
Is AL-6XN easy to machine?
Not especially — machinability is rated poor (25/100, worse than 88% of stainless steel grades). Machines like a nickel alloy: rigid setups, positive-rake sharp carbide, heavy depth of cut, 20–35 m/min, flood coolant — never dwell or rub, since it work-hardens instantly.
Can AL-6XN be welded?
Yes — weldability is rated very good (75/100). GTAW/GMAW/SMAW with over-alloyed Ni filler (ERNiCrMo-3 / ENiCrMo-3, or ERNiCrMo-10) to offset Mo segregation; low heat input, interpass <100 °C, no preheat, no PWHT normally required.
What surface finishes work on AL-6XN?
Pickle in HNO₃-HF or bead-blast plus passivation to restore the Mo-rich passive film; electropolishing gives the best pitting performance for pharma/seawater service.
Can AL-6XN be formed, bent or molded?
Cold forms well but needs ~50% more press force than 304 and generous bend radii; hot work 1150–1200 °C and always re-solution anneal + water quench afterwards.
What is the maximum service temperature of AL-6XN?
AL-6XN 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 AL-6XN Solution Annealed and AL-6XN CW-FH?
Solution Annealed is the default condition — standard supply condition for plate, sheet, pipe, tube and forgings — maximum corrosion resistance and ductility. CW-FH: highest strength condition, for wire, wedge wire screens and spring elements; essentially no formability left. Yield strength is 365 MPa in Solution Annealed versus 1,100 MPa in CW-FH.
How much does AL-6XN cost?
AL-6XN is a premium-cost stainless steel ($$$), cheaper than about 58% 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.
Can FabDigit make parts in AL-6XN?
Yes — AL-6XN is available for CNC machining and sheet metal; every part is priced by an engineer rather than instantly. Upload a STEP file to get a price and a DFM check.
Sources
- AL-6XN Alloy (UNS N08367) Technical Data Sheet — ATI (Allegheny Technologies) (2020)
- ASTM A240/A240M — Chromium and Chromium-Nickel Stainless Steel Plate, Sheet and Strip — ASTM International (2023)
- ASTM B688 / B691 / B675 / B676 — UNS N08367 plate, bar, pipe and tube — ASTM International (2021)
- ASM Handbook Vol.13B — Corrosion: Materials — ASM International (2005)
- AL-6XN alloy data and corrosion tables — Rolled Alloys (2022)
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.