Stainless Steel N08320
UNS N08320
N08320 (20Mo-4) is a titanium-stabilized, high-molybdenum superaustenitic stainless steel developed for severe reducing-acid chemical process environments, with pitting and crevice corrosion resistance above standard 6% Mo grades.
Reference datasheet — N08320 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
N08320 tempers and conditions
N08320 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 |
|---|---|---|---|---|---|---|
Hot Finished + Annealed | Choose for heavy sections, forgings and thick plate where hot working precedes the anneal; properties essentially the same as annealed with slightly lower strength in very heavy sections. | 255 | 565 | 45 | 150 HB | 1.7 % IACS |
AnnealedDefault solution annealed ~1010–1120 °C, rapid quench | Standard supply condition for plate, sheet, bar and tube in corrosive chemical process service; maximum corrosion resistance and ductility. | 265 | 585 | 45 | 160 HB | — |
Cold drawn | Choose for fasteners, shafts and pump/valve parts needing higher strength and better dimensional tolerance than annealed bar; slightly reduced ductility and corrosion margin. | 550 | 760 | 25 | 220 HB | — |
Quarter hard | Choose for springs, diaphragms and formed strip parts where extra strength is needed and full annealed ductility is not; sensitive to stress corrosion in hot chloride service. | 620 | 860 | 18 | 25 HRC | 1.7 % IACS |
What is N08320?
N08320 (20Mo-4) is a titanium-stabilized, high-molybdenum superaustenitic stainless steel developed for severe reducing-acid chemical process environments, with pitting and crevice corrosion resistance above standard 6% Mo grades. It is used as annealed plate, sheet, pipe and tube in acid plants and scrubbers, with typical values of 265 MPa yield, 585 MPa tensile, 45% elongation and 160 HB (83 HRB) and service to 500 °C. It welds readily (score 80) with matching or Ni-base filler, but machinability is low (28) and mill availability is limited; N08031 is the step up for hot sulfuric acid. N08320 has a density of 8.08 g/cm³ (0.292 lb/in³), heavier than 99% of stainless steel grades. It melts at 1,370°C (2,498 °F). N08320 has a yield strength of 265 MPa (38.4 ksi) and a tensile strength of 585 MPa (84.8 ksi) — weaker than 81% of stainless steel grades. Elongation at break is 45% and the elastic modulus is 196 GPa (28.4 Msi).
What is N08320 used for?
- sulfuric and phosphoric acid handling
- chemical reactor vessels
- scrubber and pollution control equipment
- heat exchangers in aggressive media
Advantages
- Good corrosion resistance — 78/100, better than 84% of stainless steel grades
- Forms and bends easily — 72/100, better than 84% of stainless steel grades
- Readily welded — 80/100, better than 80% 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
- Low electrical conductivity — 1.7 % IACS, worse than 93% of stainless steel grades
- High embodied carbon — 6.2 kg CO₂/kg, worse than 90% of stainless steel grades
- Low strength — 265 MPa (38.4 ksi), worse than 81% of stainless steel grades
N08320 properties
Typical room-temperature values for N08320-Annealed; bars are the position among stainless steel grades.
Physical3
N08320 has a density of 8.08 g/cm³ (0.292 lb/in³), heavier than 99% of stainless steel grades. It melts at 1,370°C (2,498 °F).
Mechanical13
N08320 has a yield strength of 265 MPa (38.4 ksi) and a tensile strength of 585 MPa (84.8 ksi) — weaker than 81% of stainless steel grades. Elongation at break is 45% and the elastic modulus is 196 GPa (28.4 Msi).
Thermal6
N08320 is rated for continuous service to 500°C (932 °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 14.6 µm/m·K (8.11 µin/in·°F).
Electrical3
N08320 conducts electricity at 1.7 % IACS, worse than 93% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is very good (78/100), better than 84% of stainless steel grades.
Sustainability4
Producing a kilogram of N08320 takes about 85 MJ of energy and emits 6.2 kg of CO₂ — more than 92% of stainless steel grades. Typical recycled content is 40%.
Manufacturability7
N08320's machinability is poor (28/100, worse than 79% of stainless steel grades); weldability very good (80/100); formability very good (72/100).
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. N08320 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with N08320
Is N08320 easy to machine?
Gummy and work-hardening like other high-Ni austenitics: use rigid setups, positive-rake sharp carbide, heavy positive feeds, low-to-moderate speeds (~20–35 m/min turning) and copious sulfochlorinated or emulsion coolant; never dwell or rub.
Can N08320 be welded?
Readily welded by GTAW/GMAW/SMAW with matching N08320 filler or over-alloyed Ni-base filler (ERNiCrMo-3); keep interpass below ~150 °C, low heat input, no preheat, and avoid post-weld sensitizing exposures — Ti stabilization protects HAZ.
Can N08320 be formed, bent or molded?
Cold forms well in the annealed condition but work-hardens rapidly, so allow 40–60% more press force than 304 and plan interstage anneals at 1010–1120 °C with rapid quench; hot work 1150–1230 °C, do not finish below ~950 °C.
N08320 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 | ≤ 0.05 | 0.03 |
| Mn | ≤ 2.5 | 1 |
| Si | ≤ 1 | 0.5 |
| P | ≤ 0.04 | |
| S | ≤ 0.03 | |
| Cr | 21 – 23 | 22 |
| Ni | 25 – 27 | 26 |
| Mo | 4 – 6 | 5 |
| Cu | ≤ 0.4 | 0.2 |
| Ti4×C minimum (stabilization against sensitization) | ≤ 0.6 | 0.3 |
| Febalance, approx. 42–46% | balance |
What surface finishes work on N08320?
Pickle (HNO₃-HF) or grit-blast plus passivation after hot work/welding to restore the passive film; electropolishing gives the best surface for acid-service vessels — anodizing is not applicable.
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 N08320 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- Trade names
- 20Mo-4
How much does N08320 cost?
N08320 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.
N08320 — frequently asked
What is N08320 used for?
N08320 is typically used for sulfuric and phosphoric acid handling, chemical reactor vessels, scrubber and pollution control equipment and heat exchangers in aggressive media. In short: reducing-acid superaustenitic; ti-stabilized against HAZ sensitization; weldable high-Mo austenitic.
What is the yield strength of N08320?
N08320 has a typical yield strength of 265 MPa (38.4 ksi) and a tensile strength of 585 MPa (84.8 ksi) — weaker than 81% of stainless steel grades. Strength varies by condition: see the 4 listed tempers.
Is N08320 easy to machine?
Not especially — machinability is rated poor (28/100, worse than 79% of stainless steel grades). Gummy and work-hardening like other high-Ni austenitics: use rigid setups, positive-rake sharp carbide, heavy positive feeds, low-to-moderate speeds (~20–35 m/min turning) and copious sulfochlorinated or emulsion coolant; never dwell or rub.
Can N08320 be welded?
Yes — weldability is rated very good (80/100). Readily welded by GTAW/GMAW/SMAW with matching N08320 filler or over-alloyed Ni-base filler (ERNiCrMo-3); keep interpass below ~150 °C, low heat input, no preheat, and avoid post-weld sensitizing exposures — Ti stabilization protects HAZ.
What surface finishes work on N08320?
Pickle (HNO₃-HF) or grit-blast plus passivation after hot work/welding to restore the passive film; electropolishing gives the best surface for acid-service vessels — anodizing is not applicable.
Can N08320 be formed, bent or molded?
Cold forms well in the annealed condition but work-hardens rapidly, so allow 40–60% more press force than 304 and plan interstage anneals at 1010–1120 °C with rapid quench; hot work 1150–1230 °C, do not finish below ~950 °C.
What is the maximum service temperature of N08320?
N08320 is rated for continuous use to about 500°C (932 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between N08320 Annealed and N08320-CD?
Annealed is the default condition — standard supply condition for plate, sheet, bar and tube in corrosive chemical process service; maximum corrosion resistance and ductility. CD: choose for fasteners, shafts and pump/valve parts needing higher strength and better dimensional tolerance than annealed bar; slightly reduced ductility and corrosion margin. Yield strength is 265 MPa in Annealed versus 550 MPa in CD.
How much does N08320 cost?
N08320 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 B620 — Ni-Fe-Cr-Mo Alloy (UNS N08320) Plate, Sheet, and Strip — ASTM International (2019)
- ASTM B621 — Ni-Fe-Cr-Mo Alloy (UNS N08320) Rod and Bar — ASTM International (2019)
- ASTM B622 — Seamless Nickel and Nickel-Alloy Pipe and Tube — ASTM International (2021)
- Carpenter 20Mo-4 Alloy Technical Data — Carpenter Technology (2020)
- ASM Handbook Vol. 13B — Corrosion: Materials — ASM International (2005)
- ASM Specialty Handbook: Stainless Steels — ASM International (1994)
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.