ASTM B564 Monel 400 Flanges (UNS N04400) • Monel K500 Flanges (UNS N05500) • ASME SB564 • Nickel-Copper Alloy Flanges — Weld Neck, Blind, Slip-On, Socketweld, Threaded, Lap Joint, Spectacle Blind
BROWSE BY MATERIAL
Monel flanges are manufactured from nickel-copper alloys whose exceptional resistance to seawater, hydrofluoric (HF) acid, alkalis, and reducing acids makes them indispensable in marine engineering, offshore oil & gas, chemical processing, and HF alkylation refinery units. Tesco Steel & Engineering produces ASTM B564 Monel flanges in both standard grades — Monel 400 (UNS N04400) and Monel K500 (UNS N05500) — with full dimensional control under ASME/ANSI B16.5, B16.47, and DIN standards, supplied with EN 10204 3.1 or 3.2 mill test reports.
Unlike austenitic stainless steels, Monel alloys are immune to chloride stress corrosion cracking (SCC) — a critical distinction for offshore and marine piping where seawater chlorides attack 316L at elevated stress. Monel 400 also performs without degradation at cryogenic temperatures down to −196°C, making it suitable for liquefied gas service where LTCS grades would be under-specified. No post-weld heat treatment (PWHT) is mandatory for Monel 400 field welds, simplifying onsite installation compared to alloy steel flanges.
Two ASTM B564 grades cover the full range of Monel flange applications — from general corrosion-resistant service to high-strength marine and rotating equipment applications.
⚓ Monel 400 — Primary Alloy for HF Acid & Seawater Service
In refinery HF alkylation units, Monel 400 is the mandated material for flanges, valves, and piping per API RP 751. RTJ face flanges are specified to minimise fugitive HF emissions. In marine and offshore applications, Monel 400 is immune to chloride SCC that disqualifies 316L stainless — both grades also resist biofouling due to the Cu content.
| Grade | UNS | Ni (min) | Cu | Fe (max) | Mn (max) | Si (max) | C (max) | Al | Ti |
|---|---|---|---|---|---|---|---|---|---|
| Monel 400 | N04400 | 63.0 | 28.0–34.0 | 2.50 | 2.00 | 0.50 | 0.30 | — | — |
| Monel K500 | N05500 | 63.0 | 27.0–33.0 | 2.00 | 1.50 | 0.50 | 0.25 | 2.30–3.15 | 0.35–0.85 |
MINIMUM ULTIMATE TENSILE STRENGTH (MPa)
MINIMUM YIELD STRENGTH (MPa)
Source: ASTM B564 Table 1 mechanical requirements. K500 values after solution anneal + age at 595°C / 8 h minimum.
| Parameter | Monel 400 (N04400) | Monel K500 (N05500) |
|---|---|---|
| AWS Filler Wire | ERNiCu-7 (Monel FM 60) | ERNiCu-7 (with matching base) |
| AWS Covered Electrode | ENiCu-7 (Monel Electrode 190) | ENiCu-7 |
| Process | GTAW (TIG), SMAW, GMAW, SAW | GTAW preferred |
| Preheat | Not required | Not required |
| Max Interpass Temp | 150°C | 150°C |
| PWHT | Not required as standard | Solution anneal + age if full strength needed |
| ASME P-Number | P42 | P43 |
| Heat Input | Low to moderate; avoid excessive | Low; no restrike on K500 welds |
Note: Monel 400 does not require PWHT — a significant advantage over Cr-Mo alloy steels in field construction. Monel K500 flanges in full-strength service may require solution anneal + re-ageing after welding, but most piping specifications accept the HAZ softening.
| ASME/ANSI B16.5 | WN, SO, SW, BL, TH, LJ, RTJ — Class 150 / 300 / 400 / 600 / 900 / 1500 / 2500 |
| ASME/ANSI B16.47 | WN, Blind [Series A & B] — Class 75 / 150 / 300 / 400 / 600 / 900 |
| ASME/ANSI B16.36 | Orifice flanges — WN, SO, TH — Class 300 / 600 / 900 / 1500 / 2500 |
| DIN Flanges | DIN 2527, 2566, 2573, 2576, 2631–2638, 2641, 2642, 2655, 2656, 2673 — PN6 to PN100 |
| BS 4504 | WN, Slip-On, Plate, Blank — PN 2.5 to PN400 |
| BS 1560 / BS 10 | WN, SO, SW, BL, Screwed — Tables D / E / F / H |
| Face Types | Raised Face (RF), Flat Face (FF), Ring Type Joint (RTJ) |
| Size Range | NPS ½″ to 60″ |
Monel 400 is mandated by API RP 751 for all piping, flanges, and valves in refinery HF alkylation units. RTJ face flanges minimise fugitive HF emissions at flange joints.
Seawater piping, heat exchanger nozzles, pump flanges, desalination plant headers — Monel 400 immune to chloride SCC and marine biofouling. Monel K500 for propeller shafts and pump impellers.
Hydrochloric acid (non-oxidising), sulfuric acid (reducing), phosphoric acid, caustic soda production — Monel resists a wide range of acids and alkalis better than stainless steel.
Upstream sour gas environments, subsea Christmas tree flanges, wellhead connections — Monel 400 resists H₂S under NACE MR0175 / ISO 15156 at defined conditions.
Monel 400 maintains toughness down to −196°C — suitable for LN₂ and some LPG applications where LTCS LF2/LF3 and austenitic SS would compete. No impact test requirement at cryogenic temp for Ni alloys under ASME.
Multi-Stage Flash (MSF) and Reverse Osmosis (RO) desalination — Monel used in brine heater nozzles, seawater intake flanges, and heat exchanger headers where high chloride + temperature conditions exist.
What is the ASTM standard for Monel flanges?
Monel flanges are manufactured to ASTM B564 (Standard Specification for Nickel Alloy Forgings) and the ASME boiler-code equivalent ASME SB564. Two grades are available: Monel 400 (UNS N04400) for general corrosion-resistant service, and Monel K500 (UNS N05500) for high-strength applications via age hardening.
What is the difference between Monel 400 and Monel K500?
Monel 400 is the solution-annealed standard grade (UTS ≥517 MPa, YS ≥207 MPa). Monel K500 adds aluminium (2.3–3.15%) and titanium (0.35–0.85%) that form gamma-prime precipitates during age hardening at ~595°C, tripling yield strength to ≥586 MPa while retaining identical corrosion resistance. K500 is preferred for pump shafts, propeller shafts, and valve stems in offshore service.
Are Monel flanges immune to chloride stress corrosion cracking?
Yes. Unlike austenitic stainless steels (316L, 321), Monel 400 and K500 are immune to chloride SCC — a critical advantage in marine, offshore, and seawater service. The high nickel content (≥63%) provides this immunity, making Monel the preferred choice where seawater chlorides are present alongside elevated stress and temperature.
Is Monel 400 the best material for HF acid service?
Yes. Monel 400 is the primary material specified for hydrofluoric (HF) acid service per API RP 751. It resists anhydrous and aqueous HF at virtually all concentrations and temperatures with minimal corrosion rates. In refinery HF alkylation units, all flanges, valves, and piping must be Monel 400 with RTJ facing to prevent fugitive HF emissions at flange joints.
What welding consumable is used for Monel 400 flanges?
The matching consumable is ERNiCu-7 (AWS A5.14) bare wire (commercially Monel Filler Metal 60 / FM 60) for GTAW/GMAW, and ENiCu-7 (AWS A5.11) covered electrode (Monel 190) for SMAW. No preheat is required; interpass temperature should be kept below 150°C.
Does Monel 400 require PWHT after welding?
No — Monel 400 does NOT require post-weld heat treatment (PWHT) as standard practice. This is a significant advantage over Cr-Mo alloy steels (which require mandatory PWHT) and simplifies field installation. Optional solution annealing at 871–982°C may be specified for cold-worked components to restore ductility.
What is the maximum temperature for Monel 400 flanges?
Monel 400 can be used up to approximately 480°C in oxidising environments and up to ~550°C in reducing environments. Monel K500 should not exceed 480°C service temperature to prevent overageing and strength loss. Both grades remain fully usable at cryogenic temperatures down to −196°C with no impact testing requirements under ASME BPVC.
What ASME P-Number is assigned to Monel flanges?
Under ASME BPVC Section IX: Monel 400 (UNS N04400) = P-Number 42; Monel K500 (UNS N05500) = P-Number 43. Separate WPS/PQR qualifications are required for P42 and P43. This is relevant for all pressure vessel and piping weld qualifications in offshore, marine, and refinery construction.
Can Monel flanges be used in sour service (H₂S)?
Yes. Monel 400 is listed in NACE MR0175 / ISO 15156 Part 3 for use in H₂S-containing environments at defined hardness and strength limits. It is not susceptible to hydrogen-induced cracking (HIC) or sulfide stress cracking (SSC) at the hardness levels produced in standard ASTM B564 forgings, making it suitable for sour gas upstream and refinery service.
What pressure classes are available for ASTM B564 Monel flanges?
ASTM B564 Monel flanges are available in ASME B16.5 pressure classes 150, 300, 400, 600, 900, 1500, and 2500 for NPS ½″ to 24″, and ASME B16.47 Series A & B for larger diameters. DIN pressure classes from PN6 to PN100 are also available. Face types: RF, FF, RTJ. Tesco Steel manufactures sizes from NPS ½″ to 60″ to order.
ASTM B564 • UNS N04400 / N05500 • All Types & Pressure Classes • Exported to 96 Countries
Inquiry Form WhatsAppEvery Monel 400 and Monel K500 flange dispatched by Tesco Steel & Engineering is individually protected before packing — bore caps and face protectors preserve machined surfaces, plastic stretch film shields against moisture and contact corrosion during sea freight, and large-diameter flanges receive heavy-duty foam or non-woven wrapping. Finished goods are packed in sea-worthy wooden export crates or palletised in woven bags for container loading. All packages carry packing lists, heat numbers, material certificates (EN 10204 3.1/3.2), and country-of-origin declarations for smooth customs clearance across all 96 countries we export to.
Countries we export Monel flanges to: USA, UK, Germany, France, Italy, Netherlands, Belgium, Spain, Norway, Sweden, Finland, Denmark, Poland, Czech Republic, Russia, Ukraine, Kazakhstan, Turkey, Saudi Arabia, UAE, Kuwait, Qatar, Bahrain, Oman, Iraq, Iran, Jordan, Israel, Egypt, Libya, Algeria, Tunisia, Morocco, Nigeria, Ghana, Kenya, Tanzania, South Africa, Angola, Mozambique, Namibia, Botswana, Zambia, Zimbabwe, Canada, Mexico, Brazil, Argentina, Colombia, Venezuela, Peru, Chile, Ecuador, Bolivia, Trinidad & Tobago, Australia, New Zealand, Singapore, Malaysia, Indonesia, Thailand, Philippines, Vietnam, South Korea, Japan, China, India, Bangladesh, Sri Lanka, Pakistan and 40+ more destinations.
Major Exporting Hubs: Houston, Aberdeen, Dubai, Abu Dhabi, Al Khobar, Dammam, Jubail, Doha, Kuwait City, Muscat, Singapore, Rotterdam, Oslo, Stavanger, Lagos, Port Harcourt, Jakarta, Bangkok, Kuala Lumpur, Montreal, Calgary, São Paulo, Buenos Aires, Cairo, Nairobi.
