Specifications
Surface Treatments
Certifications
- ISO 9001 - 2015 Certified
- PED 2014/68/EC
- NACE MR0175/ISO 15156-2
- NORSOK M-650
- DFAR
- MERKBLATT AD 2000 W2/W7/W10
Monel 400 Washers - UNS N04400 Flat, Spring Lock & Structural
Monel® 400 washers (also called UNS N04400 washers, nickel-copper alloy washers and NiCu30Fe washers) carry the bolt-head and nut bearing load on Monel 400 flange and structural joints where chlorides, hydrofluoric acid, sour gas or seawater rule out carbon-steel hardened washers. The washer body is blanked from ASTM B127 annealed plate; the alloy registers as UNS N04400. Flat washer dimensions follow ASME B18.22.1 type A and DIN 125; spring lock washers follow ASME B18.21.1 and DIN 127B; structural washers meet the ASTM F436 dimensional envelope on Monel 400 material. Monel is a registered trademark of Special Metals Corporation; TorqBolt is not authorized by, affiliated with or endorsed by Special Metals.
Monel 400 Washer Types
Five washer families are produced in Monel 400 against the ASTM F468 bolt and ASTM F467 nut sets. Plain flat washers distribute the seating load and protect the soft annealed Monel 400 nut bearing surface. Spring lock washers (helical split, DIN 127B) provide an axial spring reaction against vibration loosening on machinery joints. Fender washers (DIN 9021) carry an oversize outside diameter for slotted holes and tank-skin clamping. Structural flat washers meet ASTM F436 dimensions on Monel 400 material for A325-equivalent connections in chemical-plant steel. Belleville disc washers (DIN 6796) carry a coned-disc spring rate for thermal-cycling joints where bolt elongation must be absorbed without re-torque.
Dimensional Standards (ASME B18.21.1, DIN 125, DIN 127, ASTM F436)
ASTM does not publish a UNS N04400 washer specification; ASTM F468 covers nonferrous bolts and ASTM F467 covers nonferrous nuts, leaving washer dimensions to the carbon-steel and metric standards. The dimensional call-outs Monel 400 washers ship against:
| Standard | Family | Pattern | Typical use |
|---|---|---|---|
| ASME B18.22.1 type A | Plain flat | Narrow + wide series, inch sizes | Under nut and head on F468 bolts, UNC / UNF threads |
| ASME B18.21.1 | Helical spring lock | Regular, heavy, extra-duty, hi-collar | Vibration loosening on machinery, inch sizes |
| ASTM F436 | Structural flat | Hardened-steel envelope, met on dimension only | Structural connections, A325-equivalent steel joints |
| DIN 125 (ISO 7089 / 7090) | Plain flat | Metric form A (chamfered) + form B | Under nut on metric Monel 400 bolts, M5 to M48 |
| DIN 127B | Spring lock | Helical split, square section | Vibration joints on metric bolting |
| DIN 9021 (ISO 7093) | Fender / large diameter | OD up to 3.5 x bolt diameter | Slotted holes, sheet metal, marine fittings |
| DIN 6796 | Belleville disc | Conical disc spring | Thermal-cycling joints, gasket relaxation |
Size Range (Metric M5 to M48, Imperial 3/16 to 1-1/2 inch)
Standard production covers Monel 400 washers M5 to M48 metric and 3/16 inch to 1-1/2 inch imperial, with M52 to M64 and 1-3/4 inch to 2 inch supplied on indent. Imperial sizes blank to ASME B18.22.1 type A narrow and wide series; metric sizes follow DIN 125 form A as the default with form B on request. Inside diameter clears the nominal bolt; outside diameter and thickness follow the series tabulated below.
| Bolt size | Pattern | ID (mm) | OD (mm) | Thickness (mm) |
|---|---|---|---|---|
| M6 | DIN 125 A | 6.4 | 12 | 1.6 |
| M8 | DIN 125 A | 8.4 | 16 | 1.6 |
| M10 | DIN 125 A | 10.5 | 20 | 2.0 |
| M12 | DIN 125 A | 13 | 24 | 2.5 |
| M16 | DIN 125 A | 17 | 30 | 3.0 |
| M20 | DIN 125 A | 21 | 37 | 3.0 |
| M24 | DIN 125 A | 25 | 44 | 4.0 |
| M30 | DIN 125 A | 31 | 56 | 4.0 |
| M36 | DIN 125 A | 37 | 66 | 5.0 |
| M48 | DIN 125 A | 50 | 92 | 8.0 |
| 1/2 in | B18.22.1 wide | 13.5 | 34.9 | 3.4 |
| 3/4 in | B18.22.1 wide | 20.6 | 50.8 | 4.3 |
| 1 in | B18.22.1 wide | 27.0 | 63.5 | 4.6 |
| 1-1/4 in | F436 structural | 34.9 | 63.5 | 4.6 |
| 1-1/2 in | F436 structural | 41.3 | 76.2 | 4.6 |
Material per ASTM B127 (Plate Cut and Punched)
Monel 400 washers blank from ASTM B127 nickel-copper plate, sheet or strip in the annealed condition (UNS N04400). Chemistry is identical across B127, B164, B564, F467 and F468; the form name follows the cross-section. Heavy-section washers above 16 mm thickness source from B564 forging stock. Free-machining UNS N04405 is not used for washers.
| Element | UNS N04400 (% by mass) | Source |
|---|---|---|
| Nickel + Cobalt | 63.0 min | ASTM B127 Table 1 |
| Copper | 28.0 to 34.0 | ASTM B127 Table 1 |
| Iron | 2.5 max | ASTM B127 Table 1 |
| Manganese | 2.0 max | ASTM B127 Table 1 |
| Carbon | 0.30 max | ASTM B127 Table 1 |
| Silicon | 0.50 max | ASTM B127 Table 1 |
| Sulphur | 0.024 max | ASTM B127 Table 1 |
Hardness for Structural Washers
Structural-dimension washers blanked from B127 hot-rolled annealed plate carry 60 to 80 HRB Rockwell as supplied, well below the 25 HRC F468 bolt ceiling and well below the NACE MR0175 35 HRC nickel-copper sour-service cap. The bearing surface stays softer than the bolt head and nut, so the seating load distributes across the washer face. Spring lock washers receive a stress-relief at the end of the form sequence to lock in the spring rate; flat washers ship in the as-blanked annealed condition. Hardened carbon-steel F436 washers reach 38 to 45 HRC; the Monel 400 equivalent stays soft by design to preserve corrosion behaviour and is not a substitute for hardened steel on high-tension steel-on-steel structural connections.
Applications (HF Flange Bolting, Marine, Naval, Sour Service)
Monel 400 washers ride under F468 bolts and F467 nuts on the same HF-wetted flanges, seawater piping and sour-gas bolting that drive bolt selection. On HF alkylation units per API RP 751 the washer takes the seating crush on a Monel flange face where carbon steel would corrode out under acid drip. On naval and offshore marine bolting, Monel 400 washers preserve the non-magnetic and seawater behaviour of the joint and prevent the galvanic discontinuity that a stainless or carbon-steel washer would create against a Monel flange. On sour-service NACE MR0175 joints, the 60 to 80 HRB washer sits well inside the 35 HRC nickel-copper limit and ships with the same EN 10204 type 3.2 MTC as the bolt. HF acid service at 70 to 95 percent and seawater at flowing velocities up to 4 m/s sit inside the Monel 400 alloy envelope.
Companion Fasteners (Monel 400 Bolts F468 + Nuts F467)
Specify the washer against the same line item as the bolt and nut to keep chemistry consistent across the joint. Monel 400 bolts to ASTM F468 Class A pair with Monel 400 nuts to ASTM F467 Class A and with Monel 400 washers cut from ASTM B127 plate. Mixing a carbon-steel washer into a Monel bolt-nut stack creates a galvanic couple at the bearing surface; the carbon-steel washer corrodes first and the joint relaxes. Companion lines: hex bolts, heavy hex, stud bolts, anchor bolts, hex nuts, heavy hex nuts, lock nuts, threaded rod. All ship with EN 10204 type 3.1 by default and 3.2 on order for NACE MR0175, PED 2014/68/EC, NORSOK and nuclear procurement.
FAQ
What Monel 400 washer types does TorqBolt supply? Plain flat to ASME B18.22.1 and DIN 125, spring lock to ASME B18.21.1 and DIN 127B, fender to DIN 9021, structural flat to the ASTM F436 envelope, and Belleville disc to DIN 6796. All blanked from ASTM B127 plate or ASTM B564 forging stock in UNS N04400.
What is the material specification? ASTM B127 nickel-copper alloy plate, sheet and strip in the annealed condition (UNS N04400). ASTM F436 is a dimensional specification for carbon-steel and alloy-steel structural washers; the F436 envelope is met on Monel 400 material, with the chemistry call-out staying on B127.
Flat washer or spring lock washer for a flange joint? Plain flat under nut on every Monel 400 flange bolt to spread the seating load. Spring lock washers belong on vibration-loosening machinery joints, not on pressure-flange bolting; ASME PCC-1 calls correctly-tensioned plain bolting on flanges in place of spring lock washers. For thermal cycling, Belleville disc washers absorb bolt elongation without re-torque.
Related Pages and Request a Quote
Related: Monel 400 bolts, Monel 400 nuts, ASTM B127, ASTM F468, fasteners hub. Send pattern (flat / spring / fender / structural / Belleville), nominal bolt size, ID / OD / thickness if non-standard, and quantity to info@torqbolt.com or WhatsApp +91-22-66157017. Ex-Mumbai price and lead time returned within one working day. Domestic India 3 to 7 working days; export through JNPT.
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