Stainless Steel 27-7Mo
UNS S31277 · ASTM A240/A312
A high-performance nitrogen-enhanced superaustenitic stainless with elevated Cr, Ni and Mo for superior localized-corrosion resistance in hot chloride and acid process streams beyond 904L/AL-6XN capability.
Reference datasheet — 27-7Mo 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
27-7Mo tempers and conditions
27-7Mo is supplied in 2 conditions, soft to hard. Annealed is the default FabDigit quotes; the values on this page are for it.
Compare all 2 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
AnnealedDefault solution annealed (≈1120–1180 °C) and rapid quenched | Standard supply condition for plate, sheet, pipe and bar; maximum corrosion resistance and ductility. | 405 | 800 | 50 | 200 HB | — |
cold drawn / cold worked bar and wire | Use where higher strength and closer tolerance bar are needed (fasteners, shafts) and slight loss of ductility is acceptable. | 730 | 950 | 25 | 30 HRC | 1.7 % IACS |
Supply forms, finishes and certifications
Ways 27-7Mo is supplied — form, process route, surface or paperwork — without a datasheet of their own. The property values above apply.
| Option | What it is | Type |
|---|---|---|
Annealed Bar | Solution annealed hot-finished bar/forging stock | Supply form |
CW Tube | Cold worked seamless tubing, bright annealed or as-drawn | Supply form |
Welded Pipe | Welded and solution annealed pipe/tube | Supply form |
CRA 2B | Cold rolled, annealed and pickled sheet/strip, 2B finish | Surface finish |
HRAP | Hot rolled, solution annealed and pickled plate | Surface finish |
What is 27-7Mo?
A high-performance nitrogen-enhanced superaustenitic stainless with elevated Cr, Ni and Mo for superior localized-corrosion resistance in hot chloride and acid process streams beyond 904L/AL-6XN capability. 27-7Mo has a density of 8 g/cm³ (0.289 lb/in³), heavier than 92% of stainless steel grades. It melts at 1,320°C (2,408 °F). 27-7Mo has a yield strength of 405 MPa (58.7 ksi) and a tensile strength of 800 MPa (116 ksi) — stronger than 60% of stainless steel grades. Elongation at break is 50% and the elastic modulus is 195 GPa (28.3 Msi).
What is 27-7Mo used for?
- FGD absorber systems
- chemical process piping
- pulp bleach plants
- seawater desalination equipment
Advantages
- Good corrosion resistance — 88/100, better than 97% of stainless steel grades
- Ductile — tolerates forming and impact — 50%, better than 90% of stainless steel grades
- Tough — resists crack growth — 200 MPa·√m (182 ksi·√in), better than 86% of stainless steel grades
Limitations
- Difficult to machine — 18/100, worse than 99% of stainless steel grades
- Poor heat conductor — 11.5 W/m·K (6.64 BTU/hr·ft·°F), worse than 97% of stainless steel grades
- High embodied carbon — 6.8 kg CO₂/kg, worse than 95% of stainless steel grades
- Low electrical conductivity — 1.7 % IACS, worse than 93% of stainless steel grades
- Limited service temperature — 400°C (752 °F), worse than 78% of stainless steel grades
27-7Mo properties
Typical room-temperature values for 27-7Mo-Annealed; bars are the position among stainless steel grades.
Physical3
27-7Mo has a density of 8 g/cm³ (0.289 lb/in³), heavier than 92% of stainless steel grades. It melts at 1,320°C (2,408 °F).
Mechanical14
27-7Mo has a yield strength of 405 MPa (58.7 ksi) and a tensile strength of 800 MPa (116 ksi) — stronger than 60% of stainless steel grades. Elongation at break is 50% and the elastic modulus is 195 GPa (28.3 Msi).
Thermal5
27-7Mo is rated for continuous service to 400°C (752 °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 14.5 µm/m·K (8.06 µin/in·°F).
Electrical3
27-7Mo conducts electricity at 1.7 % IACS, worse than 93% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is excellent (88/100), better than 97% of stainless steel grades.
Sustainability4
Producing a kilogram of 27-7Mo takes about 85 MJ of energy and emits 6.8 kg of CO₂ — more than 92% of stainless steel grades. Typical recycled content is 40%.
Manufacturability7
27-7Mo's machinability is poor (18/100, worse than 99% of stainless steel grades); weldability good (65/100); 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. 27-7Mo is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 27-7Mo
Is 27-7Mo easy to machine?
Machine like a nickel alloy: rigid setups, positive-rake carbide, low speed with heavy feed, generous flood coolant, and avoid dwelling to prevent severe work hardening.
Can 27-7Mo be welded?
GTAW/GMAW/SMAW with no preheat, low heat input and interpass below ~150 °C using overmatching Ni-base filler (ERNiCrMo-3/-4 or ERNiCrMo-13); autogenous welds should be avoided in critical corrosion service.
Can 27-7Mo be formed, bent or molded?
Hot work 1150–1200 °C followed by solution anneal and rapid quench; cold forming needs roughly 1.5–2× the force of 316L with springback allowance and interstage annealing on severe draws.
27-7Mo 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 |
|---|---|---|
| Clow carbon for weld corrosion resistance | ≤ 0.02 | 0.01 |
| Si | ≤ 0.5 | 0.3 |
| Mnaids nitrogen solubility | ≤ 3 | 1.5 |
| P | ≤ 0.03 | 0.02 |
| S | ≤ 0.01 | 0 |
| Cr | 26 – 28 | 27 |
| Nistabilizes austenite, SCC resistance | 30 – 32 | 31 |
| Mopitting/crevice resistance | 7 – 8 | 7.5 |
| Cuimproves resistance in reducing acids | 0.5 – 1.5 | 1 |
| Nstrength + pitting resistance | 0.3 – 0.4 | 0.35 |
| Fe | balance |
What surface finishes work on 27-7Mo?
Pickle in nitric-hydrofluoric or fully solution anneal after hot work to remove heat tint, then passivate per ASTM A967; electropolishing gives the cleanest surface for high-purity or scrubber duty.
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 27-7Mo in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- S31277
- ASTM
- A240/A312
How much does 27-7Mo cost?
27-7Mo 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.
27-7Mo — frequently asked
What is 27-7Mo used for?
27-7Mo is typically used for FGD absorber systems, chemical process piping, pulp bleach plants and seawater desalination equipment. In short: beyond AL-6XN corrosion resistance; highest strength superaustenitic here; hot chloride and acid service.
What is the yield strength of 27-7Mo?
27-7Mo has a typical yield strength of 405 MPa (58.7 ksi) and a tensile strength of 800 MPa (116 ksi) — stronger than 60% of stainless steel grades. Strength varies by condition: see the 2 listed tempers.
Is 27-7Mo easy to machine?
Not especially — machinability is rated poor (18/100, worse than 99% of stainless steel grades). Machine like a nickel alloy: rigid setups, positive-rake carbide, low speed with heavy feed, generous flood coolant, and avoid dwelling to prevent severe work hardening.
Can 27-7Mo be welded?
Yes — weldability is rated good (65/100). GTAW/GMAW/SMAW with no preheat, low heat input and interpass below ~150 °C using overmatching Ni-base filler (ERNiCrMo-3/-4 or ERNiCrMo-13); autogenous welds should be avoided in critical corrosion service.
What surface finishes work on 27-7Mo?
Pickle in nitric-hydrofluoric or fully solution anneal after hot work to remove heat tint, then passivate per ASTM A967; electropolishing gives the cleanest surface for high-purity or scrubber duty.
Can 27-7Mo be formed, bent or molded?
Hot work 1150–1200 °C followed by solution anneal and rapid quench; cold forming needs roughly 1.5–2× the force of 316L with springback allowance and interstage annealing on severe draws.
What is the maximum service temperature of 27-7Mo?
27-7Mo is rated for continuous use to about 400°C (752 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does 27-7Mo cost?
27-7Mo 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 A240/A240M — Chromium and Chromium-Nickel Stainless Steel Plate, Sheet, and Strip (S31277) — ASTM International (2023)
- ASTM A312/A312M — Seamless, Welded and Heavily Cold Worked Austenitic Stainless Steel Pipes — ASTM International (2022)
- ASTM A479/A276 — Stainless Steel Bars and Shapes — ASTM International (2022)
- ATI 27-7MO Superaustenitic Stainless Steel Technical Data Sheet — ATI (Allegheny Technologies) (2020)
- 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.