Alloy 27-7MO / UNS S31277 Forgings: 7% Molybdenum Super-Austenitic Stainless Steel

Published: 5 September 2022 · Last updated: 11 August 2026 · Technically reviewed by the Jiangyin Jiangnan Metal Co., Ltd. Metallurgical Engineering Team · Property data verified against Special Metals publication SMC-092 and the ASTM/ASME specifications cited in Technical References.

What Forged Shapes Are Available in Alloy 27-7MO / UNS S31277?

Jiangyin Jiangnan Metal Co., Ltd. manufactures UNS S31277 by three routes, selected by geometry and quantity. Seamless ring rolling is the primary route and produces rings from 200 mm to 2,600 mm outside diameter, the usual choice for scrubber shell courses, flange blanks, pressure-housing rings and pump casing rings. Open-die forging covers shafts, blocks, sleeves and large discs where the section is too heavy or too long for ring rolling. Upset forging is used for short, large-diameter discs, hubs and tube sheets.

27-7MO is harder to forge than a 300-series stainless. Its 0.34% nitrogen and 7.2% molybdenum raise the hot flow stress substantially and narrow the usable hot-working window to roughly 170 °C, so the size envelope for this grade is smaller than our general factory capacity. The figures below are the tested limits for UNS S31277 specifically.

What Is Alloy 27-7MO / UNS S31277 Stainless Steel?

Alloy 27-7MO (UNS S31277) is an advanced 7% molybdenum super-austenitic stainless steel that offers corrosion resistance superior to the 6% molybdenum super-austenitic grades in most environments. The name encodes the chemistry: approximately 27% nickel and 7% molybdenum. Chromium sits at about 22% and nitrogen at 0.34%, with a deliberate 0.5–1.5% copper addition and iron as the balance.

The alloy earns its performance from a balanced quartet of elements rather than from any single one. Molybdenum and chromium together with nitrogen give the resistance to pitting and crevice corrosion that defines the grade. The high nickel content plus nitrogen and molybdenum handle reducing media, while the 22% chromium handles oxidizing media, which is why 27-7MO performs unusually well in mixed acid environments where an oxidizing and a reducing acid appear together. The nickel and nitrogen also stabilize the austenite completely, so the microstructure is fully austenitic with no ferrite and the material is essentially non-magnetic.

Two consequences follow from that chemistry and matter more than any datasheet number:

• It sits in the gap between super-austenitic stainless and nickel-base alloys. In many environments its resistance approaches alloys 625, 622 and C-276 at a materially lower alloy cost, because iron is doing work that would otherwise be done by nickel. That price-to-performance position is the commercial reason the grade exists.
• It is not a drop-in replacement for 6Mo in fabrication. Like all super-austenitics it loses corrosion resistance when welded autogenously or with matching filler; it work-hardens; and its hot-working window is narrow. Getting the metallurgy right during forging and welding matters more than it does for 316L or even 904L.

Typical service is anywhere a 6Mo grade is being outrun but a nickel-base alloy is hard to justify: flue gas desulfurization scrubbers on high-sulfur coal, seawater and brine handling, chemical process equipment in mixed acids, pulp and paper bleach plants, and oil and gas components in chloride-bearing and sour environments.

How Did Alloy 27-7MO Develop? A Short Timeline

What Designations and Specifications Cover UNS S31277?

Unlike older stainless grades, 27-7MO has a short and clean designation list. There is no AISI number, no widely used EN 10088-3 designation and no JIS equivalent. The alloy postdates those numbering systems. In practice every purchase order should carry UNS S31277 plus the ASTM or ASME product specification appropriate to the form.

What Is the Chemical Composition of Alloy 27-7MO / UNS S31277?

The limiting chemical composition below is the published UNS S31277 specification. Note the two unusual features: nitrogen carries a minimum of 0.30%, which is what lifts the PREN so far above a 6Mo grade, and copper is deliberately added at 0.5–1.5% to improve resistance in reducing acids, particularly sulfuric. Carbon is held to 0.020% maximum to keep chromium carbide precipitation out of the heat-affected zone.

What Are the Mechanical Properties of Alloy 27-7MO?

UNS S31277 is supplied and used in the solution-annealed condition. It is not precipitation hardened and there is no aging cycle, a point that trips up engineers coming from 17-4PH or A286. Strength comes from nitrogen in solid solution, which is why the yield strength is roughly double that of 316L while ductility stays at 50% elongation.

The practical reading of that table: 27-7MO carries about 33% more yield strength than a 6Mo grade and sits within a few percent of alloy 625. On a pressure-retaining part designed by allowable stress, that difference translates directly into thinner walls, often enough to offset the alloy premium over 6Mo on the finished component. For ASME Section VIII design, allowable stresses come from Code Case 2458, not from the typical values above.

The alloy work-hardens at a rate similar to 25-6MO, meaningfully faster than carbon steel or 304, and this governs both machining and cold forming. Cold work raises hardness steeply; heavily cold-drawn wire reaches well above 400 HV, which is why the grade found a niche in oilfield armor wire.

What Are the Physical and Thermal Properties of UNS S31277?

How Corrosion-Resistant Is Alloy 27-7MO? PREN, CPT and CCT

Pitting Resistance Equivalent Number, and Why the Formula Matters

PREN ranks alloys by their resistance to localized chloride attack. The trap is that at least two PREN formulas are in common use and they give very different numbers for the same alloy. Comparing a value from one formula against a value from the other is meaningless, and it happens constantly in supplier literature.

Read the two right-hand columns separately. Under PREN₁₆, the formula most widely used for stainless steels and the one behind the familiar "PREN 40 for seawater" rule of thumb, 27-7MO reaches about 51, comfortably ahead of every 6Mo grade and every duplex. Under the Special Metals formula, which weights tungsten and niobium and is intended for cross-comparison with nickel-base alloys, 27-7MO scores 43 against 45.2 for C-276 and 40.8 for alloy 625. Either way the ranking of 27-7MO against the 6Mo grades is the same, and that ranking is the commercially relevant one.

Critical pitting and crevice temperatures (ASTM G48)

PREN is a calculation. CPT and CCT are measurements, and they are the numbers to put in a specification. In ASTM G48 the test solution becomes unstable above 85 °C, so ">85 °C" is a ceiling of the method rather than a property of the alloy.

The line worth noticing is the comparison with alloy 625: 27-7MO matches 625 on pitting and beats it on crevice corrosion (45 °C against 35 °C) at a substantially lower alloy cost. Crevice corrosion, not pitting, is what usually kills flanged and gasketed equipment, so that ten-degree margin is more valuable in the field than the headline PREN suggests.

In the more aggressive "green death" solution (11.9% H₂SO₄ + 1.3% HCl + 1% FeCl₃ + 1% CuCl₂), 27-7MO records a CPT of 75 °C and a CCT of 60 °C, against 60 °C and 45 °C for 25-6MO and 75 °C and 55 °C for alloy 625. Tested to ASTM G28 Method A, annealed wrought 27-7MO shows a typical corrosion rate of 15 mpy (0.38 mm/a).

How Does Alloy 27-7MO Perform in Acids and FGD Scrubbers?

Mixed-acid performance is where 27-7MO separates itself from the 6Mo grades most clearly. Molybdenum handles the reducing acids, chromium handles the oxidizing acids, and the copper addition helps in sulfuric, so the alloy does not have the "good in one, poor in the other" behaviour that forces material changes partway along a process line.

Three readings stand out. In chloride-contaminated dilute sulfuric acid: the exact chemistry of a wet scrubber liquor, 27-7MO is essentially unattacked while a 6Mo grade corrodes at 26 mpy: a factor of fifty or more. In boiling 85% phosphoric acid it outperforms alloy 625 by nearly seven to one, which is why it appears in fertilizer and phosphoric-acid plants. But in concentrated 95% sulfuric acid it is worse than 25-6MO and far worse than C-276, concentrated sulfuric is the one place this alloy should not be assumed adequate.

Simulated flue gas desulfurization environment

Wet scrubbers on high-sulfur coal are the application the alloy was designed around. The environment inside the absorber is typically sulfuric acid at pH 1 or below, carrying significant chloride and fluoride, at temperatures up to 80 °C. Testing in a standard FGD ranking solution (60% H₂SO₄ + 2.5% HCl + 0.2% HF + 0.5% flyash at 80 °C for one week) produced these rates:

How Does Alloy 27-7MO Behave in Seawater and Sour Service?

Seawater

In a crevice-corrosion programme run at the LaQue Center for Corrosion Technology in Wrightsville Beach, North Carolina, sheet specimens with PTFE crevice devices attached were exposed to flowing natural seawater at 30 °C for 60 days:

Zero measurable crevice attack under a deliberately severe artificial crevice, in real flowing seawater, over two months, matching alloy 625 and marginally better than C-276 in this particular test. For seawater cooling, desalination, offshore firewater and ballast systems this is the headline result. The alloy also resists chloride stress-corrosion cracking in sodium chloride at all concentrations up to saturation at the boiling point, a claim 316L and 904L cannot make.

Sour service (H₂S)

U-bend specimens of 27-7MO exposed for two months in boiling saturated sodium chloride showed no stress-corrosion cracking and no pitting. In armor-wire qualification testing on cold-worked 0.031 in wire, samples stressed by wrapping the wire upon itself survived a battery of sour and chloride tests without cracking, and were not attacked in the G48-D crevice test at 25 °C. Established oilfield applications include wireline, armor wire, sand screens and subsea banding.

When Should You Choose 27-7MO Over 6Mo, 904L, Super Duplex or a Nickel Alloy?

* Austenitic grades retain strength above these temperatures, but prolonged exposure in the 600–930 °C range precipitates sigma phase in 27-7MO and embrittles it. The figure quoted is a practical continuous-service ceiling for corrosion service, not a scaling or creep limit.

How Is Alloy 27-7MO Forged and Heat Treated?

This is the section that decides whether a UNS S31277 forging is sound or scrap. Three parameters govern everything.

Catastrophic oxidation, the failure mode nobody warns you about

Our production sequence for UNS S31277 forgings

1. Raw material. Billet or bar to the ASTM A479 chemistry, heat-number traced, chemistry verified by optical emission spectrometry on receipt. High-cleanliness routes (ESR, or VIM + ESR + VAR for critical work) are used where the project requires them.
2. Preheat and soak. Slow, uniform heating to 1150 °C. Because electrical resistivity is high and thermal conductivity low, heavy sections need generous soak time, a thermal gradient during the first blow is a common cause of centre bursts.
3. Forging. Reduction in the 980–1150 °C window, forging ratio 4:1 or better to break down the cast structure. Multi-step incremental reduction with reheats whenever surface temperature approaches 1000 °C.
4. Ring rolling (where applicable). Radial–axial rolling to final ring geometry, finishing above 980 °C.
5. Solution anneal. 1121–1177 °C, hold approximately 30 minutes per 25 mm of section, then rapid water quench. On thin rings a forced air quench is acceptable; on anything above roughly 60 mm section, water.
6. Pickling and passivation. Descale and remove heat tint. Heat tint left on a surface measurably reduces local pitting resistance, so this step is functional, not cosmetic.
7. Machining. Rough or finish machining to drawing.
8. NDT and testing. Ultrasonic examination to ASTM A388, liquid penetrant to ASTM E165, tensile and hardness testing, plus ASTM G48 or A262 corrosion testing when specified. Magnetic particle testing is not applicable. The alloy is non-magnetic.
9. Certification and dispatch. EN 10204 3.1 as standard, or 3.2 with a nominated third-party witness. Marking with heat number, specification and drawing number.

How Do You Weld Alloy 27-7MO / UNS S31277?

UNS S31277 welds readily by GTAW, GMAW, SMAW, SAW and PAW using conventional equipment. There is one rule that overrides everything else, and getting it wrong is the single most common cause of premature failure in super-austenitic equipment.

How Do You Machine Alloy 27-7MO?

Machining characteristics are similar to other austenitic alloys, and the alloy is machined in the annealed condition. Three behaviours drive the parameters: it work-hardens quickly, it has low thermal conductivity so heat stays in the cutting zone rather than leaving in the chip, and it produces tough, stringy chips.

• Never dwell or rub. A tool that stops feeding while still in contact glazes the surface into a work-hardened layer the next pass cannot cut. Maintain positive, continuous feed and withdraw under power.
• Take deep enough cuts to get under the previous pass's hardened layer. Light spring passes are the classic way to ruin a super-austenitic part.
• Flood coolant, generously. Low thermal conductivity means the tool tip carries the heat.
• Rigid setups, sharp positive-rake carbide. Chatter accelerates work hardening and tool failure.
• Peck-drill deep holes and clear chips aggressively to prevent packing and re-cutting.

Production Capability, UNS S31277 Forging Manufacturer

Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory located at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China. The company employs approximately 460 people, including 9 senior engineers and 32 intermediate engineers, and has been producing open-die forgings and seamless rolled rings since 2008 for customers in more than 40 countries.

UNS S31277 size envelope

Where a project needs sizes beyond this envelope, our general factory capability extends to 6,000 mm ring diameter, 12,000 mm length and 15,000 kg single-piece weight in more readily forged grades. Send the drawing and we will confirm feasibility in UNS S31277 specifically.

Which Standards and Quality Documents Apply?

Quality gates and non-conformance handling

Every UNS S31277 order passes six mandatory hold points at which production cannot continue without quality sign-off: incoming chemistry verification, forging temperature compliance, post-forging ultrasonic examination, heat-treatment chart approval, mechanical and corrosion test acceptance, and final NDE plus dimensional inspection. Customer-witnessed hold points can be added at no charge. Any out-of-specification finding raises a formal non-conformance report within 24 hours, with root-cause analysis completed within five working days and the proposed disposition sent to the customer before any action is taken. Shipping and test documentation is retained for ten years.

How Do You Specify an Alloy 27-7MO Forging Order?

1. State the generic designation. Write UNS S31277 plus the governing product specification, ASTM A182 for flanges and fittings, ASTM A479 for bar and forging stock, ASTM A240 where plate chemistry is the reference. Do not order under a trademarked brand name.
2. Define the forged shape and envelope. Outside diameter, inside diameter, height or length, wall thickness, finished weight, and machining allowance if the part is supplied rough machined.
3. Specify the delivery condition. "Solution annealed at 1121–1177 °C, rapid water quench." There is no aging or hardening condition to choose. If a supplier offers you one, they have confused this grade with a precipitation-hardening alloy.
4. Specify corrosion testing where it matters. ASTM G48 Method C or D with a stated acceptance temperature for chloride service; ASTM A262 Practice E or ASTM G28 Method A for intergranular attack. Consider adding a minimum PREN clause, since the specification band spans roughly nine PREN points.
5. Specify NDT correctly. Ultrasonic to ASTM A388 with the acceptance class, liquid penetrant to ASTM E165. Do not specify magnetic particle inspection: the alloy is non-magnetic and the requirement cannot be met.
6. Specify certification. EN 10204 3.1 as standard, or 3.2 with a nominated third-party witness (DNV, BV, Lloyd's Register, ABS, TÜV). Add NACE MR0175 / ISO 15156 compliance and your full H₂S, chloride, pH and temperature envelope if the service is sour.
7. Give quantity, date and destination. Piece count, required delivery date, port and Incoterm. Typical lead time is 8–12 weeks; add 2–4 weeks for third-party witnessed release.

Top 10 Mistakes When Specifying Alloy 27-7MO Forgings

1. Quoting a PREN without saying which formula. The same heat is "PREN 51" or "PREN 43" depending on the equation. Purchasing teams compare across suppliers and reach the wrong conclusion. Fix: write the formula next to the number on every document.
2. Ordering the grade name and nothing else. A heat at the bottom of the composition band computes to PREN ≈ 47; one at the top reaches ≈ 56. Fix: state a minimum PREN, or minimum Mo and N, on the purchase order for critical chloride service.
3. Specifying magnetic particle inspection. UNS S31277 is fully austenitic and non-magnetic; MPI cannot be performed. Fix: specify liquid penetrant to ASTM E165.
4. Asking for an age-hardened or "H-condition" delivery state. This is not a precipitation-hardening alloy. Fix: specify solution annealed and quenched.
5. Allowing matching or autogenous welds. Molybdenum segregation makes a matching-composition weld the weakest corrosion link in the assembly. Fix: mandate ERNiCrMo-10 or ERNiCrMo-14 overmatching filler in the weld procedure specification.
6. Leaving heat tint on the back of welds. Back-face heat tint is invisible from the inspection side and is a routine cause of premature pitting. Fix: require argon purging plus mechanical or chemical removal of heat tint on both faces.
7. Stacking parts in the annealing furnace. Stagnant oxidizing conditions above 925 °C cause catastrophic oxidation at the contact faces. Fix: require spacers and forced atmosphere circulation in the heat-treatment procedure.
8. Slow cooling from the solution anneal. Time between 600 °C and 930 °C precipitates sigma phase and sensitizes the alloy. Fix: require rapid water quench on heavy sections and verify with a heat-treatment chart, not a verbal assurance.
9. Assuming it replaces C-276 everywhere. In concentrated sulfuric acid, and in the most severe FGD zones, it does not. Fix: match the alloy to the zone rather than the plant.
10. Treating published sour-service test data as a NACE compliance statement. Qualification depends on the annex listing and your specific environmental envelope. Fix: require the qualification route in writing before ordering.

Drawing Callout Template for UNS S31277 Forgings

MATERIAL:      UNS S31277 super-austenitic stainless steel
               per ASTM A182 (forged flanges/fittings)
               [or ASTM A479 for bar and forging stock]

CHEMISTRY:     Ni 26.0-28.0 / Cr 20.5-23.0 / Mo 6.5-8.0
               N 0.30-0.40 / Cu 0.5-1.5 / C 0.020 max
               MINIMUM PREN 50 (PREN = %Cr + 3.3x%Mo + 16x%N)

CONDITION:     Solution annealed 1121-1177 C, rapid water quench
               No aging or precipitation-hardening treatment

FORGING:       Hot work 980-1150 C only. Forging ratio >= 4:1.
               Forced atmosphere circulation in furnace; do not stack.

CORROSION:     ASTM G48 Method C, CPT >= 65 C, no pitting
               ASTM A262 Practice E - pass, no fissures
               [state acceptance temperature for your service]

NDE:           UT per ASTM A388, acceptance class [state class]
               PT per ASTM E165 Type I Method C
               MT NOT APPLICABLE - material is non-magnetic

WELDING:       Overmatching filler only - ERNiCrMo-10 (622)
               or ERNiCrMo-14. Interpass max 150 C.
               Matching or autogenous welds NOT permitted.
               Argon purge root side; remove all heat tint.

SURFACE:       Pickled and passivated. No heat tint permitted
               on any wetted surface.

CERTIFICATE:   EN 10204 3.1  [or 3.2 with witness by ______ ]

MARKING:       Heat number, UNS S31277, specification,
               drawing number - low-stress stamp or vibro-etch

Where Is Alloy 27-7MO / UNS S31277 Used?

Request a Quote: Alloy 27-7MO / UNS S31277 Forgings

Send a drawing or the dimensions, the governing specification and your certification requirement, and Jiangyin Jiangnan Metal Co., Ltd. will reply within 24 hours with price, lead time and confirmation of the applicable standards. For complex enquiries, use the RFQ generator above to produce a complete specification sheet first.

Frequently Asked Questions, Alloy 27-7MO / UNS S31277

Glossary

UNS S31277

The generic Unified Numbering System designation for the 27Ni-22Cr-7.2Mo-0.34N super-austenitic stainless steel commonly called Alloy 27-7MO. This is the correct designation for purchase orders and drawings.

Super-austenitic stainless steel

A fully austenitic stainless steel with molybdenum above roughly 4% and deliberate nitrogen additions, giving chloride pitting resistance far beyond the 300-series. The class includes 904L, the 6Mo grades and, at the top, 27-7MO.

PREN

Pitting Resistance Equivalent Number, a calculated index ranking alloys by resistance to localized chloride attack. Two formulas are in common use: %Cr + 3.3 × %Mo + 16 × %N, and %Cr + 1.5 × (%Mo + %W + %Nb) + 30 × %N. They give different numbers and must never be mixed in a comparison.

CPT, Critical Pitting Temperature

The lowest temperature at which measurable pitting occurs in a standard test, typically ASTM G48 Method C in 6% ferric chloride plus 1% hydrochloric acid. The method has a practical ceiling of 85 °C because the solution becomes unstable above it.

CCT, Critical Crevice Temperature

As CPT, but with a crevice device attached to the specimen (ASTM G48 Method D). CCT is always lower than CPT and is usually the governing number for flanged, gasketed and tube-to-tube-sheet joints.

Sigma phase

A hard, brittle chromium- and molybdenum-rich intermetallic that precipitates at grain boundaries when high-alloy stainless steels dwell between roughly 600 °C and 930 °C. It destroys toughness and corrosion resistance. The rapid quench after solution annealing exists specifically to avoid it.

Sensitization

Precipitation of chromium carbides at grain boundaries, leaving adjacent metal chromium-depleted and vulnerable to intergranular attack. The 0.020% maximum carbon limit in UNS S31277 is set to suppress it.

Catastrophic oxidation

Rapid, non-protective oxidation of molybdenum-bearing alloys under stagnant oxidizing conditions above about 925 °C, where molybdenum oxides become liquid or volatile instead of forming a passive scale. Prevented by forced furnace atmosphere circulation and by not stacking parts.

Overmatching filler metal

A welding consumable with higher molybdenum content than the parent metal, used so the weld's corrosion resistance is not the weak link after solidification segregation. For UNS S31277 this means ERNiCrMo-10 or ERNiCrMo-14, never matching composition.

Heat tint

The coloured oxide film formed on stainless steel adjacent to a weld. It is chromium-depleted underneath and locally reduces pitting resistance, so it must be removed mechanically or by pickling, including on the back face of the joint.

Solution annealing

Heating to put all alloying elements into solid solution (1121–1177 °C for UNS S31277) followed by rapid cooling to hold them there. The standard and only delivery condition for this alloy.

ASME Code Case 2458

The ASME Boiler and Pressure Vessel Code case that establishes allowable design stresses for UNS S31277, required for pressure-vessel construction in this alloy.

EN 10204 3.1 / 3.2

Types of inspection document. A 3.1 certificate is issued by the manufacturer's own independent quality department; a 3.2 certificate is countersigned by an independent third party such as DNV, BV, Lloyd's Register, ABS or TÜV.

Trepanned billet

A billet with the centre bored out before forging, used for hollow parts with bores above roughly 100 mm. It reduces raw-material input and drilling time, significant on an alloy of this cost.

Technical References

1. Special Metals Corporation, Publication SMC-092, INCOLOY® alloy 27-7MO, December 2005. Source of the limiting chemical composition, physical and mechanical property data, PREN values, ASTM G48 critical temperatures, acid and seawater corrosion results, and the hot-working, annealing and welding parameters cited on this page.
2. ASTM A479/A479M, Standard Specification for Stainless Steel Bars and Shapes for Use in Boilers and Other Pressure Vessels, ASTM International, West Conshohocken, PA.
3. ASTM A182/A182M, Standard Specification for Forged or Rolled Alloy and Stainless Steel Pipe Flanges, Forged Fittings, and Valves and Parts for High-Temperature Service, ASTM International.
4. ASTM A240/A240M, Standard Specification for Chromium and Chromium-Nickel Stainless Steel Plate, Sheet, and Strip for Pressure Vessels and for General Applications, ASTM International.
5. ASTM A312/A312M, Standard Specification for Seamless, Welded, and Heavily Cold Worked Austenitic Stainless Steel Pipes, ASTM International.
6. ASTM A213/A213M and ASTM A249/A249M, seamless and welded austenitic stainless steel tube specifications, ASTM International.
7. ASME Boiler and Pressure Vessel Code, Code Case 2458, allowable design stresses for UNS S31277, American Society of Mechanical Engineers.
8. ASTM G48, Standard Test Methods for Pitting and Crevice Corrosion Resistance of Stainless Steels and Related Alloys by Use of Ferric Chloride Solution, ASTM International. Method C for critical pitting temperature, Method D for critical crevice temperature.
9. ASTM G28, Standard Test Methods for Detecting Susceptibility to Intergranular Corrosion in Wrought, Nickel-Rich, Chromium-Bearing Alloys, ASTM International.
10. ASTM A262, Standard Practices for Detecting Susceptibility to Intergranular Attack in Austenitic Stainless Steels, ASTM International.
11. ASTM A388/A388M, Standard Practice for Ultrasonic Examination of Steel Forgings, ASTM International.
12. ASTM E165/E165M, Standard Practice for Liquid Penetrant Testing for General Industry, ASTM International.
13. ANSI/NACE MR0175 / ISO 15156-3, Petroleum and natural gas industries — Materials for use in H₂S-containing environments in oil and gas production — Part 3: Cracking-resistant CRAs and other alloys, International Organization for Standardization.
14. EN 10204, Metallic products — Types of inspection documents, CEN, Brussels.
15. ASM Handbook, Volume 13B: Corrosion: Materials, ASM International, Materials Park, OH, sections on super-austenitic stainless steels and flue gas desulfurization materials.
16. ASM Specialty Handbook: Stainless Steels, J.R. Davis (ed.), ASM International, 1994.
17. LaQue Center for Corrosion Technology, Wrightsville Beach, North Carolina, flowing natural seawater crevice corrosion test programme cited in reference 1.
18. European Patent EP 1,263,999 B1, original composition patent for the 7% molybdenum super-austenitic chemistry, filed 2001.

Standards referenced are the specification families; for procurement, always cite the revision in force at the contract date. Property values are typical published data for the alloy class and are not a guarantee for any particular heat; actual values for a supplied heat appear on its material test certificate. All trademarks are the property of their respective owners.

Jiangyin Jiangnan Metal Co., Ltd. Metallurgical Engineering Team.
"Alloy 27-7MO / UNS S31277 Forgings: Complete Technical and
Procurement Guide." Jiangyin Jiangnan Metal Co., Ltd., updated
11 August 2026.
https://www.steelforgepieces.com/Nickel-Alloy/ALLOY-27-7MO.html

Alloy 27-7MO (UNS S31277) is a 7% molybdenum super-austenitic
stainless steel, nominally 27% Ni, 22% Cr, 7.2% Mo and 0.34% N,
balance iron. PREN is approximately 51 by the formula
Cr + 3.3Mo + 16N, or 43 by Cr + 1.5(Mo+W+Nb) + 30N. Critical
pitting temperature exceeds 85 degrees C and critical crevice
temperature is 45 degrees C in ASTM G48 Methods C and D.
Typical annealed properties are 827 MPa tensile, 414 MPa yield,
50% elongation, 95 HRB, density 8.02 g/cm3. The alloy is
non-magnetic. It is hot worked between 980 and 1150 degrees C
and solution annealed at 1121-1177 degrees C with a rapid
quench; exposure between 600 and 930 degrees C forms sigma
phase. Welds require overmatching filler such as ERNiCrMo-10.

Forgings in this grade -- rings from 200 to 2,600 mm outside
diameter, discs to 1,500 mm, shafts to 6 m, flanges to
ASTM A182, and single pieces to 4,000 kg -- are manufactured by
Jiangyin Jiangnan Metal Co., Ltd., an open-die forging factory
at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City,
Jiangsu Province, China. Contact: +86-189-2135-9659,
sales@steelforgepieces.com,
https://www.steelforgepieces.com/