Hastelloy C276 Stainless Steel Flanges

Universal Corrosion Resistance: Resists both reducing and oxidizing acids, wet chlorine, chlorides, hypochlorite, and mixed acids – the most versatile corrosion-resistant alloy for flange applications.

Highest Pitting Resistance (PRE ≥ 65): Outstanding pitting and crevice corrosion resistance, the highest among all commercial flange materials, with PREN calculated as %Cr + 3.3 × (%Mo + 0.5 × %W) + 16 × %N ≥ 65.

No Sensitization: Extremely low carbon content (≤0.010%) plus Mo/W content prevents carbide precipitation – can be used as-welded without post-weld heat treatment.

Excellent Resistance to Wet Chlorine and Hypochlorite: Hastelloy C276 is the premier material for handling wet chlorine gas, chlorine dioxide, and hypochlorite solutions, where most other alloys fail rapidly.

Superior Hydrochloric Acid Resistance: Excellent performance in hydrochloric acid (HCl) across all concentrations and temperatures, making C276 the standard for HCl handling systems.

NACE MR0175 / ISO 15156 Compliant: Fully qualified for sour service with the highest allowable H₂S partial pressures and lowest pH values, documented HIC and SSC test reports available.

Excellent Resistance to Mixed Acids: Outstanding performance in mixed acid environments (HNO₃/HCl, H₂SO₄/HCl) where other alloys experience rapid attack.

Good High-Temperature Strength: Maintains excellent mechanical properties up to 400°C (752°F) in corrosive service and up to 540°C (1000°F) in non-corrosive service.

Excellent Weldability: No preheat or post-weld heat treatment required. Can be welded using matching filler metals (ERNiCrMo-4).

Full Range of Types: Weld neck (WN), slip-on (SO), blind (BL), socket weld (SW), threaded (TH), lap joint (LJ), plate flanges, and orifice flanges.

Pressure Ratings: Available in Class 150, 300, 600, 900, 1500, and 2500 (PN6 to PN400 in metric equivalents).

Low Carbon Content (≤0.010%): Eliminates sensitization and intergranular corrosion concerns, even in severe service.

International Certifications: Flanges can be certified by ABS, BV, DNV, LR, GL, RINA, CCS, KR, and NK, and comply with NORSOK M-650, NACE MR0175, ASME, PED, and EN standards.

These standards ensure that our Hastelloy C276 stainless steel flanges meet global requirements for chemical composition, mechanical properties, dimensional tolerances, and pressure-temperature ratings for extreme corrosive service.

Hastelloy C276 (UNS N10276) is a nickel-chromium-molybdenum-tungsten alloy with the highest molybdenum content (15-17%) among commercial flange materials. The combination of high molybdenum and tungsten (3-4.5%) gives C276 the highest PREN of any commercial alloy (≥65). The extremely low carbon content (≤0.010%) ensures no sensitization and eliminates the need for post-weld heat treatment, even in severe service conditions.

Comparison of PREN (Pitting Resistance Equivalent) Values:

High-Temperature Tensile Properties (Annealed Condition, Typical Values):

NACE MR0175 / ISO 15156 Compliance:
Hastelloy C276 is fully qualified for sour service applications up to the highest limits specified in NACE MR0175/ISO 15156 for nickel-based alloys. The alloy exhibits exceptional resistance to sulfide stress cracking (SSC) and hydrogen induced cracking (HIC) in H₂S-containing environments, even at high H₂S partial pressures and low pH levels. Maximum sour service temperature: 232°C (450°F).

Maximum Recommended Service Temperatures:

Critical Note: Hastelloy C276 must be water quenched after solution annealing. Air cooling may result in precipitation of intermetallic phases (mu phase, P phase) that can reduce corrosion resistance. The extremely low carbon content (≤0.010%) ensures that sensitization is not a concern. Unlike many stainless steels, C276 can be used in the as-welded condition without any risk of intergranular attack due to its extremely low carbon content.

Heat Treatment Condition:
All Hastelloy C276 flanges are solution annealed at 1120–1175°C followed by immediate water quenching (delay must be kept under 30 seconds). This heat treatment:

l  Dissolves precipitated carbides and intermetallic phases.

l  Relieves internal stresses from forging.

l  Restores optimum corrosion resistance and ductility.

l  Ensures the alloy's exceptional resistance to corrosive attack.

Critical Note: Hastelloy C276 must be water quenched after solution annealing. Air cooling may result in precipitation of intermetallic phases (mu phase, P phase) that can reduce corrosion resistance. The extremely low carbon content (≤0.010%) ensures that sensitization is not a concern.

Delivery Condition: Flanges normally supplied in annealed and pickled condition, providing a clean, smooth surface and exceptional corrosion resistance. Bright annealing is not recommended for Hastelloy C276 due to the water quenching requirement.

Reference: Based on ASME B16.5 for nickel alloys. For concentrated HCl or wet chlorine service at elevated temperatures, pressure ratings may require additional derating; consult project specifications.

Standard Dimensions: ASME B16.5 for sizes up to 24″, and ASME B16.47 Series A/B for large diameters up to 60″. EN 1092-1 dimensions available upon request.

Raw Material Selection: High-quality Hastelloy C276 (UNS N10276) nickel alloy billets from certified premium mills (Haynes International, VDM Metals, Special Metals) with certified chemical composition (Ni ≥57%, Cr 14.5-16.5%, Mo 15-17%, W 3-4.5% verification) and traceability. Material is VIM-VAR (Vacuum Induction Melted – Vacuum Arc Remelted) for optimal cleanliness.

Cutting & Heating: Material is cut to precise weight using band saws, then induction-heated to forging temperature (1150–1200°C). Temperature control is critical for high-molybdenum nickel alloys.

Forging: Hot forged using hydraulic presses (3000–8000 tons) with strict temperature control. Extremely careful reduction rates required due to high alloy content.

Heat Treatment – Solution Annealing: Heat treatment at 1120–1175°C followed by immediate water quenching (<30 seconds delay) to dissolve carbides and restore properties. This is the most critical step in C276 flange manufacturing.

Machining: CNC lathes and milling machines produce precise dimensions, bolt holes, and facing surfaces. High-alloy C276 requires specialized tooling, slower cutting speeds, and rigid setups.

Surface Finishing: Raised face serration, flat facing, or RTJ groove machining per ASME B16.5 requirements.

Marking: Laser engraving or stamping with grade (N10276/C276), size (NPS), class, heat number, heat treatment condition (solution annealed + water quenched), heat treatment records reference, manufacturer identification, and standard.

Inspection & Testing: Dimensional check, PMI, hardness test, NDT, and corrosion testing as required.

Surface Treatment: Pickling using specialized pickling acids optimized for high-molybdenum nickel alloys (careful control to avoid hydrogen pickup); thorough rinsing required.

Note: Bright annealing is not possible for Hastelloy C276 due to the mandatory water quenching requirement. All C276 flanges from Womic Steel are supplied in the annealed and pickled condition.

Each Hastelloy C276 flange face is inspected for surface roughness, concentricity, and absence of defects.

Chemical Analysis: PMI 100% verification using handheld XRF spectrometer for Ni, Cr, Mo, W (tungsten verification critical for C276).

Mechanical Testing: Tensile strength (≥690 MPa), yield strength (≥310 MPa), elongation (≥40%), hardness (≤250 HBW).

Intergranular Corrosion Test: ASTM G28 Method A – validates resistance to intergranular corrosion (mandatory for C276).

Pitting Corrosion Test: ASTM G48 Method A – ferric chloride pitting test for C276 (typically no pitting at 40-50°C).

Dimensional Inspection: OD, ID, bolt circle, bolt hole alignment, thickness, flatness using calibrated gauges and CMM.

Thread Inspection: NPT thread verification using GO/NO-GO gauges per ANSI B1.20.1.

NDT – Liquid Penetrant Testing (PT): 100% for surface defects.

NDT – Ultrasonic Testing (UT): For internal flaws upon request.

NDT – Radiographic Testing (RT): For critical applications upon request.

Sour Service Qualification (upon request): HIC per NACE TM0284, SSC per NACE TM0177.

Third-Party Inspection: SGS, BV, DNV, TUV, LR, or ABS on customer request.

Chemical Processing (Acid Service – Extreme): Hydrochloric acid (HCl) piping flanges – all concentrations and temperatures, sulfuric acid (H₂SO₄) coolers and heaters, mixed acid (HNO₃/HCl, H₂SO₄/HCl) process flanges, acetic acid reactor flanges, chlor-alkali heat exchanger flanges, vinyl chloride monomer (VCM) processing flanges.

Wet Chlorine & Hypochlorite Service: Chlorine gas drying tower flanges, chlorine dioxide heat exchanger flanges, hypochlorite cooler flanges, chlorinated hydrocarbon processing flanges, bleaching chemical system flanges, pulp & paper bleach plant flanges.

Pharmaceutical (High-Purity Aggressive): High-purity API reactor flanges, sterile aggressive chemical transfer line flanges, clean steam system flanges for corrosive services, high-purity HCl handling flanges.

Flue Gas Desulfurization (FGD): Reheater flange connections, gas-gas heater (GGH) flanges, slurry heat exchanger flanges, absorber tower flanges, quench nozzle flanges – in high-chloride, low-pH, high-temperature zones.

Oil & Gas (Severe Sour Service): Sour gas pipeline flanges with extreme H₂S partial pressure, high-pressure HP/HT sour gas manifolds, produced water cooler flanges, amine regenerator flanges for sour gas processing (NACE MR0175 compliant, highest H₂S limits).

Waste Incineration: Flue gas heat exchanger flanges, acid gas condenser flanges, scrubber reheat flanges – for high-chlorine, high-acid flue gases.

Offshore (Severe Sour Service): Offshore HP sour gas flanges, deepwater subsea sour service manifolds (ABS, BV, DNV, LR certified, NORSOK M-650 qualified).

Hydrometallurgy: Pressure acid leaching (PAL) flanges, high-temperature solvent extraction flanges, electrowinning solution flanges – for concentrated acid and high-chloride environments.

Pickling Plants: Acid recovery system flanges, spent acid heater flanges, pickling line circulation flanges for steel mills.

Semiconductor Manufacturing: High-purity gas line flanges, aggressive chemical delivery flanges for semiconductor wet processing equipment.

Small flanges (≤4″): Heavy-duty cartons with moisture barrier paper on pallets, individual plastic bagging for high-purity flanges.
Medium flanges (6″–12″): Wooden crates with foam padding dividers, each flange wrapped in VCI paper.
Large flanges (≥14″): Individual wooden crates or steel-framed pallets with foam padding.

All shipments:

VCI paper interleaving between flanges

Plastic end caps for bore protection

Bolt hole protectors for RTJ facings

Individual tagging: Grade (Hastelloy C276/N10276), size, class, heat number, heat treatment condition (solution annealed + water quenched), heat treatment records reference, standard, PO number

Waterproof shipping marks for export containers

Moisture barrier wrapping for sea freight

Strict avoidance of contamination from carbon steel or other alloys

Womic Steel's Delivery Strengths:

Ready stock: Class 150 and 300 Hastelloy C276 flanges in sizes 1/2″–8″ – dispatch within 48-72 hours.

Direct cooperation with global shipowners for the most competitive freight rates.

Professional loading by in-house teams using non-metallic slings and padded supports.

Complete documentation package including EN 10204 3.1 MTR, PMI reports, IGC test reports (ASTM G28), ASTM G48 corrosion test reports, NACE certificates, heat treatment charts, and mechanical test reports.

Continuous cargo tracking and after-sales follow-up with destination agent support.

1. What makes Hastelloy C276 different from Alloy 625 for flange applications?
Hastelloy C276 has significantly higher molybdenum (15-17% vs 8-10%) and contains tungsten (3-4.5%), giving it PRE ≥65 vs ≥45 for Alloy 625. C276 offers superior resistance to hydrochloric acid (all concentrations), wet chlorine, and mixed acids where Alloy 625 may be marginal. For seawater applications, Alloy 625 is generally sufficient and more cost-effective. For HCl and wet chlorine service, C276 is the preferred material.

2. Is Hastelloy C276 resistant to hydrochloric acid (HCl)?
Yes. Hastelloy C276 has excellent resistance to hydrochloric acid across the entire concentration range at temperatures up to 400°C (752°F). It is considered the premier material for HCl handling systems, including piping, valves, and flanges.

3. Can Hastelloy C276 flanges be used in wet chlorine service?
Yes. Hastelloy C276 is the premier material for wet chlorine service. Unlike most alloys that fail rapidly in wet chlorine due to pitting or SCC, C276 has outstanding resistance and is the industry standard for chlorine drying and handling systems.

4. What is the maximum temperature for C276 flanges in HCl service?
Up to 400°C (752°F) for general corrosive service. For concentrated HCl at elevated temperatures, consult corrosion charts. Above 540°C (1000°F) in non-corrosive service, C276 remains stable but pressure ratings must be derated significantly.

5. Do Hastelloy C276 flanges require post-weld heat treatment (PWHT)?
No. Due to extremely low carbon content (≤0.010%), C276 can be used in the as-welded condition without any risk of sensitization or intergranular corrosion. This is a significant advantage for field fabrication.

6. What facing is recommended for high-pressure HCl service flanges?
Ring Type Joint (RTJ) facing with octagonal ring gasket (PTFE-coated or PTFE encapsulated) is recommended for high-pressure HCl service (Class 600 and above) to ensure leak-tight sealing in aggressive acid conditions.

7. Can you supply Hastelloy C276 flanges with NACE MR0175 documentation?
Yes. We supply full NACE MR0175 / ISO 15156 compliance documentation including material certification for the highest H₂S partial pressure limits with optional HIC/SSC test reports upon request.

8. Are Hastelloy C276 flanges available in EN 1092-1 dimensions?
Yes. We can manufacture Hastelloy C276 flanges to EN 1092-1 Type 01, 02, 05, 11, 12 with PN6 to PN400 pressure ratings. Please specify your standard.

9. What is the typical lead time for Hastelloy C276 flanges?
Stock sizes (1/2″–8″, Class 150/300 WN RF): 2-4 days. Non-stock or special facings (RTJ, T&G): 4-6 weeks. Large diameter B16.47 flanges (≥26″): 6-8 weeks depending on thickness and facing.

10. How is Hastelloy C276 flange corrosion resistance verified?
ASTM G28 Method A intergranular corrosion test (mandatory) and ASTM G48 Method A pitting resistance test (standard for NORSOK M-650). Test reports include weight loss measurement and microscopic examination.

Complete Product Range: Weld neck, slip-on, blind, socket weld, threaded, lap joint, and plate flanges – one-stop sourcing for extreme chemical and sour gas projects.

Strict Quality Control: ISO 9001:2015, PED 2014/68/EU, and API Q1 certified facilities.

Premium Mill Sources: Haynes International, VDM Metals, Special Metals certified raw materials – 100% traceable with VIM-VAR melt.

NORSOK M-650 Qualified: Complete documentation packages available for offshore and FGD projects.

NACE MR0175 / ISO 15156 Compliant: Highest H₂S partial pressure tolerance, with HIC/SSC test reports on request.

ASTM G28 and ASTM G48 Corrosion Testing: In-house corrosion testing capability with documented reports.

Advanced Forging & Machining: 3000–8000 ton hydraulic presses and CNC machining centers with specialized tooling for C276.

Full Traceability: Heat number stamped on each flange – traceable back to original mill certificate.

Extremely Low Carbon Verified: ≤0.010% carbon content documented on MTR for each heat.

Water Quenching Verified: Heat treatment records include time-temperature charts validating water quenching (<30 second delay).

Flexible Customization: Special facing types (RTJ, T&G, M&F), custom bolt drilling, and non-standard sizes available.

Pharmaceutical & Chemical Certified: Suitable for high-purity, high-corrosion applications.

Global Delivery: Exported to major chemical plants, FGD systems, and pharmaceutical facilities worldwide.

Tel / WhatsApp:
Victor: +86 15575100681
Jack: +86 18390957568

E-mail: info@womicstainless.com

Website: www.womicsteel.com

Contact Womic Steel today for a competitive quote on Hastelloy C276 stainless steel flanges. We offer certified quality, NORSOK M-650 documentation, NACE MR0175 compliance, ASTM G28 and ASTM G48 corrosion testing, fast production lead times, and reliable global delivery to keep your extreme chemical processing, wet chlorine, HCl handling, and FGD projects running smoothly.

Stock Examples (Class 150 WN RF – Hastelloy C276, Annealed + Water Quenched):

Stock Examples (Class 300 WN RF – Hastelloy C276, Annealed + Water Quenched):

Stock Examples (Class 600 and above – RTJ facing – Hastelloy C276, Annealed + Water Quenched):

Common Stock Examples for HCl Service (Hastelloy C276, Class 150, RF):

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