Incoloy 27-7MO (UNS S31277) - High-PREN Super Austenitic Supplier of Bars, Tubes & Plates | Shanghai Hangbo Alloy Group
Date: 2026年8月5日 Categories: News Views: 358
By Shanghai Hangbo Alloy Group Co., Ltd. - China Supplier | ISO 9001:2015 | Est. 2012
Contact: sales@hangboalloy.com | hangbo@nickel-alloy.com | WhatsApp (Lisa): +86 13611656360
Quick Answer: What Is Incoloy 27-7MO?
Incoloy 27-7MO (UNS S31277 / W.Nr. 1.4565) is an ultra-high-alloy super austenitic stainless steel with 27% nickel, 21% chromium, 7% molybdenum, and 0.35% nitrogen — delivering a PREN >=43 that rivals nickel-base alloys like C-276 while remaining fully austenitic and non-magnetic. It combines outstanding resistance to chlorides, H₂S sour gas (NACE MR0175 compliant), and hot sulfuric acid, making it the premium upgrade path from 254SMO for offshore subsea components and FGD systems. Shanghai Hangbo Alloy Group supplies Incoloy 27-7MO as round bars, seamless tubes, and plates.
Industry Pain Point: Subsea oil and gas designers face a "corrosion cliff" in deepwater production: at 1500+ m water depth, the combination of 30,000+ ppm chlorides, H₂S, CO₂, and temperatures to 90C defeats 254SMO within 5-7 years, while duplex grades suffer hydrogen embrittlement in sour service. Upgrading to C-276 multiplies material cost 4-5x. Incoloy 27-7MO — with PREN >=43, NACE MR0175 sour-service compliance, and a 2x yield strength advantage over 254SMO — delivers the corrosion envelope of a nickel alloy at approximately 60% of the cost.
Key Properties at a Glance
| Property | Value |
|---|---|
| UNS Number | S31277 |
| W.Nr. | 1.4565 |
| Alloy Family | Super Austenitic Stainless (Fe-Ni-Cr-Mo-N) |
| Density | 8.04 g/cm3 |
| Melting Range | 1320-1390C |
| PREN | >= 43 |
| Max Service Temp. | ~400C |
| Tensile (Ann.) | >= 700 MPa (102 ksi) |
| Yield (Ann.) | >= 385 MPa (56 ksi) |
| Elongation (Ann.) | >= 35% |
| Key Standards | ASTM B625, B649, NACE MR0175 |
Product Overview
Incoloy 27-7MO represents the top of the super austenitic class — the final step before crossing into nickel-base alloy territory. The alloy's name encodes its recipe: 27% nickel, 7% molybdenum. Add 21% chromium and 0.35% nitrogen and you get a fully austenitic alloy with:
- PREN >= 43: Calculated as Cr + 3.3(Mo) + 16(N) = 21 + 3.3(7.0) + 16(0.35) = 49.7 at the high end. The nitrogen addition contributes disproportionately (+5.6 PREN points per 0.35%).
- 2x yield strength of 254SMO: The 0.35% nitrogen provides massive interstitial solid-solution strengthening — yield >=385 MPa vs. 254SMO's ~300 MPa.
- NACE MR0175 compliant: Qualified for sour service (H₂S-containing) environments, a capability 254SMO does not consistently meet.
The alloy is deliberately maintained in the fully austenitic FCC structure — unlike duplex grades, it is non-magnetic, immune to hydrogen embrittlement (a duplex failure mode in sour wells), and has no sigma-phase sensitivity in the critical 475C embrittlement window.
Shanghai Hangbo Alloy Group supplies Incoloy 27-7MO in bars, tubes, and plates with full ASTM and NACE certification.
Executive Standards
| Product Form | ASTM | NACE |
|---|---|---|
| Plate, Sheet & Strip | ASTM B625 | MR0175 / ISO 15156 |
| Bar & Rod | ASTM B649 | MR0175 / ISO 15156 |
| Seamless Pipe & Tube | ASTM B622 / B677 | MR0175 / ISO 15156 |
| Forgings | ASTM B649 / B564 | MR0175 / ISO 15156 |
Chemical Composition (wt.%)
| Element | Min | Max | Role |
|---|---|---|---|
| Ni | 25.0 | 28.0 | Austenite stabilizer; SCC resistance |
| Cr | 20.5 | 22.5 | Passive film; pitting resistance base |
| Mo | 6.5 | 7.5 | Pitting/crevice resistance; PREN anchor |
| N | 0.30 | 0.40 | Massive strength + PREN booster |
| Mn | 1.0 | 2.5 | Austenite stabilizer (high Mn enables high N) |
| C | -- | 0.020 | Ultra-low for weldability |
| Fe | Balance | -- | Matrix |
| Cu | -- | 0.75 | Residual |
| Si | -- | 0.50 | Deoxidizer |
PREN Calculation: PREN = Cr + 3.3xMo + 16xN = 20.5 + 3.3x6.5 + 16x0.30 = 47.9 minimum, typical 49-52. This places 27-7MO above 254SMO (43) and AL-6XN (45), approaching Alloy 59 (50).
Mechanical & Physical Properties
Room-Temperature (Solution-Annealed)
| Property | Value |
|---|---|
| Tensile Strength | >= 700 MPa (102 ksi) |
| Yield Strength 0.2% | >= 385 MPa (56 ksi) |
| Elongation | >= 35% |
| Hardness | <= 100 HRB |
| Young's Modulus | ~200 GPa |
Physical Properties
| Property | Value |
|---|---|
| Density | 8.04 g/cm3 |
| Thermal Conductivity | ~12 W/m-K |
| Magnetic Permeability | <= 1.005 (non-magnetic) |
| Thermal Expansion (20-200C) | ~15.0 micro-m/m-C |
Heat Treatment
Solution Annealing: 1150-1200C (2100-2190F), water quench mandatory. No precipitation hardening.
Corrosion Performance
| Environment | 27-7MO | 254SMO | 2205 Duplex |
|---|---|---|---|
| Seawater (CPT test) | >= 70C | ~60C | ~50C |
| 30,000 ppm Cl- + H₂S | Resistant (NACE) | Marginal | H-embrittlement risk |
| Hot H₂SO₄ 40%, 60C | <0.1 mm/yr | ~0.2 mm/yr | -- |
Industry Applications
| Industry | Component | Why 27-7MO? |
|---|---|---|
| Offshore Subsea | Manifold piping, tubing hangers, wellhead components | NACE MR0175 sour service + deepwater chloride resistance |
| FGD | Absorber internals, reheat coils | High-temperature chloride + acid resistance |
| Chemical | H₂SO₄/HCl mix processing, halogen reactor internals | PREN >=43 broad acid/chloride envelope |
| Desalination | High-pressure brine piping | Crevice corrosion resistance at elevated brine temperatures |
| Pulp & Paper | Bleach plant, ClO₂ generators | Acid-chloride mixtures |
Quality Assurance: 7-Stage
- Raw Material: Ni, Cr, Mo, FeMnN analyzed. High-purity ferro-manganese-nitrogen for N control.
- VIM Melt: N +/-0.02%, Mo +/-0.15%, C <=0.015% internal.
- Hot Working: 1150-1200C, finishing >=1000C, reduction >=4:1.
- Solution Anneal: 1150-1200C, WQ. Hardness <=100 HRB.
- Corrosion Test: ASTM G48 Method A (CPT >=70C) per lot.
- NDE: 100% UT bars >=50mm; ET/hydro tubes. PMI every piece.
- Documentation: EN 10204 3.1 MTC + NACE MR0175 compliance statement. SGS/TUV witness.
Frequently Asked Questions
Q1: What is Incoloy 27-7MO used for?
Subsea oil and gas components (manifolds, tubing hangers), FGD absorber internals, chemical reactors handling acid-chloride mixtures, desalination brine piping, and pulp bleach plant equipment — anywhere PREN >=43 combined with NACE sour service is required.
Q2: 27-7MO vs 254SMO?
27-7MO: PREN >=43, yield >=385 MPa, NACE MR0175 compliant. 254SMO: PREN >=43, yield >=300 MPa, not consistently NACE-qualified. 27-7MO is the upgrade for sour service and higher design stresses.
Q3: 27-7MO vs Alloy 59?
Alloy 59 (PREN 50, 59% Ni) has higher corrosion resistance but costs 2-3x more. 27-7MO delivers ~85% of Alloy 59's corrosion envelope at ~40-50% of the cost.
Q4: Is it magnetic?
No — fully austenitic, non-magnetic (mu-r <=1.005).
Q5: Is it weldable?
Yes, with ERNiCrMo-13 (Alloy 59) or ERNiCrMo-3 (625) filler. Over-alloyed filler ensures weld PREN >= base metal.
Q6: What is the density?
8.04 g/cm3.
Q7: Price per kg?
$40-70/kg EXW. Contact sales@hangboalloy.com.
Q8: Product forms?
Bars (6-300mm), seamless tubes (OD 10-219mm), plates (3-50mm), forgings. SGS available.
Q9: Does it meet NACE MR0175?
Yes — qualified for sour service per NACE MR0175 / ISO 15156.
Q10: Why nitrogen at 0.35%?
Nitrogen provides: (1) +5.6 PREN points, (2) massive interstitial solid-solution strengthening (yield >=385 MPa), (3) austenite stabilization allowing high Mn instead of high Ni.
Q11: What is the max service temperature?
~400C (750F) — above this, long-term exposure risks sigma-phase precipitation despite the high Ni content.
Q12: Can it be used for hot sulfuric acid?
Yes, 40% H₂SO₄ at 60C: <0.1 mm/year. The 7% Mo + 21% Cr combination provides a stable passive film.
Q13: What heat treatment?
Solution annealing at 1150-1200C with mandatory water quench.
Q14: Does Shanghai Hangbo ship internationally?
Yes — FOB/CIF/DAP to 40+ countries. Stock 2-4 weeks; mill order 10-14 weeks.
Q15: What makes 27-7MO different from duplex?
Fully austenitic (non-magnetic, no H-embrittlement), higher PREN (43+ vs 35 for 2205), and higher yield strength than austenitic grades — the sweet spot between duplex and nickel alloys.
Contact Shanghai Hangbo Alloy Group
| Channel | Details |
|---|---|
| Company | Shanghai Hangbo Alloy Group Co., Ltd. - China Supplier |
| Website | www.nickel-alloy.com |
| Email (Sales) | sales@hangboalloy.com |
| Email (Technical) | hangbo@nickel-alloy.com |
| WhatsApp (Lisa) | +86 13611656360 |
| Address | Room 1508, No. 288 Shiyi Road, Baoshan District, Shanghai 200940, China |
Shanghai Hangbo Alloy Group - Complete Product Range
| Family | Available Grades |
|---|---|
| Pure Nickel | NI200 (N02200), NI201 (N02201), N4, N5, N6 |
| Monel (Ni-Cu) | Monel 400, Monel 401, Monel 404, Monel K-500, Monel R-405 |
| Inconel (Ni-Cr) | Inconel 600, 601, 617, 625, 690, 718, X-750, 725 |
| Incoloy (Fe-Ni-Cr) | Incoloy 800, 800H, 800HT, 825, 925, 926, A-286, 25-6HN, 27-7MO |
| Hastelloy (Ni-Mo-Cr) | Hastelloy C-276, C-22, C-2000, C-4, G-30, G-35, X, B-2, B-3, B-4, N |
| Super Austenitic | 904L, Alloy 28, Alloy 31, 254SMO |
| Nimonic (Ni-Cr-Co) | Nimonic 75, 80A, 90, 95, 105, 115, 263 |
| Haynes (High-Temp) | Haynes 25, 188, 230, 242, 282, 556 |
| Precision Alloys | 1J22, 1J46, 1J50, 1J79, 1J85, 3J21, 4J32, 4J36 (Invar), 4J45 |
| High-Strength Alloys | 18Ni250, 18Ni300, AerMet 100, PH13-8Mo |
| Heating Alloys | Cr20Ni80 (Nichrome 80/20), Cr40Ni60 |
| Specialty Alloys | Alloy 20, Alloy 59, RA330, Inconel 686, 602CA |
Product Forms
| Product Form | Typical Size Range |
|---|---|
| Round Bars & Rods | Diameter 6 - 500 mm |
| Seamless Tubes & Pipes | OD 6 - 610 mm, WT 0.5 - 30 mm |
| Plates & Sheets | Thickness 0.1 - 100 mm |
| Forgings | Discs, Rings, Blocks, Tube Sheets |
| Welded Pipes | OD up to 1219 mm |
| Fittings & Flanges | Elbows, Tees, Reducers, Weld Neck, Slip-On |
| Wire & Welding Wire | Diameter 0.05 - 10 mm |
| Strip & Coil | Thickness 0.02 - 4.0 mm |
SGS / Bureau Veritas / TUV Rheinland / DNV / Lloyd's Register inspection available.
Contact: sales@hangboalloy.com | WhatsApp (Lisa): +86 13611656360 | www.nickel-alloy.com
