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 Hex Nuts - UNS N04400 ASTM F467 / DIN 934
Monel 400 hex nuts, also listed as Monel 400 hex nut, UNS N04400 hex nut, Ni-Cu Alloy 400 hex nut and NiCu30Fe hex nut per DIN 17743, are governed by ASTM F467 for chemistry and proof load, with head dimensions to ASME B18.2.2 in imperial and DIN 934 / ISO 4032 in metric. Threads are ASME B1.1 Class 2B (UNC, UNF, 8UN) or ISO 965 6H. The alloy is UNS N04400, a nickel-copper bolting grade specified for HF alkylation, marine, sour gas and demagnetised naval joints. Monel® is a registered trademark of Special Metals Corporation; TorqBolt is not authorized by, affiliated with or endorsed by Special Metals.
Head Dimensions (ASME B18.2.2 / DIN 934)
F467 section 7.1 defers dimensions to ASME B18.2.2 for imperial finished hex nuts and to DIN 934 / ISO 4032 for metric. Width across flats and nut thickness drive wrenching and grip. Style 2 (taller) nuts raise DIN 934 thickness by approximately 10 percent for higher proof load. Heavy hex sizes are covered separately on the heavy hex nuts page.
| Nominal size | Width across flats (mm) | Thickness DIN 934 (mm) | Imperial equivalent | Width across flats (in) | Thickness ASME B18.2.2 (in) |
|---|---|---|---|---|---|
| M5 | 8.00 | 4.00 | -- | -- | -- |
| M6 | 10.00 | 5.00 | 1/4 | 7/16 | 7/32 |
| M8 | 13.00 | 6.50 | 5/16 | 1/2 | 17/64 |
| M10 | 16.00 | 8.00 | 3/8 | 9/16 | 21/64 |
| M12 | 18.00 | 10.00 | 1/2 | 3/4 | 7/16 |
| M16 | 24.00 | 13.00 | 5/8 | 15/16 | 35/64 |
| M20 | 30.00 | 16.00 | 3/4 | 1-1/8 | 41/64 |
| M24 | 36.00 | 19.00 | 1 | 1-1/2 | 55/64 |
| M30 | 46.00 | 24.00 | 1-1/4 | 1-7/8 | 1-3/64 |
| M36 | 55.00 | 29.00 | 1-1/2 | 2-1/4 | 1-7/32 |
| M42 | 65.00 | 34.00 | -- | -- | -- |
| M48 | 75.00 | 38.00 | -- | -- | -- |
Thread Types and Fits
F467 section 7.2 sets the default thread fit at Class 2B internal threads per ASME B1.1; Class 3B is available on indent. Metric nuts ship 6H to ISO 965-1 unless 5H is specified. Thread forms: UNC coarse, UNF fine, 8UN (above 1 inch), and ISO metric coarse M6 through M48. Left-hand threads are produced on indent. Stress relief per F467 section 4.2.3 is at manufacturer option for Ni 400 and Ni 405 and is invoked where residual stress could affect sour service.
Size Range - M5 to M48 / 1/4 to 1-1/2 inch
F467 Table 4 covers nominal sizes 1/4 inch through 1-1/2 inch. Metric range is M5 through M48 standard, M52 and M64 on indent. Stocked band is M6 through M36 and 3/8 through 1-1/4 inch; outside the band, made to order on 4 to 6 week lead time.
F467 Class A vs Class B (Weldable vs Free-Machining)
F467 Table 1 splits Monel 400 nut chemistry into two grades by sulfur. Class A is Ni 400 (UNS N04400), the weldable grade with sulfur 0.024 percent maximum, used wherever the joint sees post-installation seal welding, HF alkylation, sour service or marine fasteners under cathodic protection. Class B is Ni 405 (UNS N04405) with sulfur 0.025 to 0.060 percent for free machining, used on jam, slotted and castle nuts in unwelded joints. Both share the Ni 63 to 70 percent envelope with copper as balance.
| Class | UNS | Sulfur (%) | F467 marking | Use case |
|---|---|---|---|---|
| A (Ni 400) | N04400 | 0.024 max | F 467U | Weldable nuts; sour service; HF alky flanges; marine |
| B (Ni 405) | N04405 | 0.025 to 0.060 | F 467V | Free-machining jam, slotted and castle nuts (unwelded joints) |
Mechanical Properties - Proof Load and Hardness
F467 Table 2 sets the mechanical floor for Monel 400 hex nuts. Proof stress is the load the nut withstands without permanent thread deformation, applied through a hardened test mandrel per F606. Hardness minimum is enforced; F467 itself does not set a hardness maximum on Ni 400 (a NACE MR0175 sour-service ceiling of 35 HRC applies separately, see below). Heavy hex nut proof stress is 1.08 times the hex nut value per F467 Table 2 Note B. Source: ASTM F467/F467M-2013 Table 2.
| Alloy | F467 marking | Hardness min | Hex nut proof (ksi) | Hex nut proof (MPa) | Heavy hex proof (ksi) | Heavy hex proof (MPa) |
|---|---|---|---|---|---|---|
| Ni 400 (UNS N04400) | F 467U | 75 HRB | 80 | 552 | 86 | 593 |
| Ni 405 (UNS N04405) | F 467V | 60 HRB | 70 | 483 | 76 | 524 |
Hardness is measured per ASTM E18 / E92 on the top or bottom face. For sizes 1/4 through 7/16 inch one reading; for sizes 1/2 inch and larger the average of four readings 90 degrees apart per F467 section 13.2.2. Where both proof load and hardness are tested, proof load takes precedence per F467 section 6.2.
Companion Bolts (F468) and Washers
Pair F467 Ni 400 hex nuts with Monel 400 bolts to ASTM F468 Class A (F 468U marking) so the joint chemistry is matched across thread engagement. Mixing Class A nut with Class B bolt creates a sulfur step in the threaded interface and is rejected by sour-service buyers. Companion Monel 400 washers are produced from ASTM B127 plate stock to DIN 125 plain, DIN 9021 fender, DIN 127 spring or DIN 6798 serrated. For higher proof load duties switch to heavy hex nuts; for prevailing torque applications use lock nuts (DIN 985 nylon-insert or all-metal). Stud bolts pair with two F467 hex nuts per stud bolts page.
Applications and Sour Service
Monel 400 hex nuts are the default fastener on HF alkylation acid settler manways and flange joints per API RP 751 inspection, on naval bulkhead fasteners requiring magnetic permeability below 1.05, on seawater piping flanges in offshore platform topside service, and on sour gas wellhead bolting where NACE MR0175 / ISO 15156-3 applies. The 35 HRC sour-service ceiling on UNS N04400 is comfortably above the 75 HRB Ni 400 hardness minimum, so the F467 hex nut clears the NACE gate by design when shipped in the as-formed or stress-relieved condition. HF acid resistance derives from the protective nickel-fluoride film that forms in HF concentrations 70 to 95 percent, the band covering HF alkylation service. Marine joints in flowing seawater are covered on the marine applications and seawater corrosion pages. Sour-service shipments carry EN 10204 type 3.2 mill test certificate with the NACE MR0175 compliance statement.
FAQ
What standard governs Monel 400 hex nuts? ASTM F467 covers chemistry and proof load; ASME B18.2.2 sets head dimensions in imperial; DIN 934 and ISO 4032 are the metric dimensional standards; ASME B1.1 Class 2B governs UNC and UNF threads. Chemistry maps to DIN 17743 NiCu30Fe.
What is the difference between F467 Class A and Class B for Monel 400? Class A (Ni 400, F 467U, S 0.024 percent max) is weldable and used for sour service and HF alkylation. Class B (Ni 405, F 467V, S 0.025 to 0.060 percent) is free-machining and used where the joint stays unwelded.
What is the proof load of a Monel 400 hex nut? F467 Table 2 sets Ni 400 hex nut proof stress at 80 ksi (552 MPa) and heavy hex at 86 ksi (593 MPa). Ni 405 is 70 ksi (483 MPa) hex and 76 ksi (524 MPa) heavy hex.
Are Monel 400 hex nuts NACE MR0175 compliant? Yes. NACE MR0175 / ISO 15156-3 lists UNS N04400 as acceptable for sour service with a 35 HRC hardness ceiling. F467 Ni 400 nuts in the as-formed or stress-relieved condition clear that ceiling and ship with EN 10204 type 3.2 certificate.
What thread fit and finish do Monel 400 hex nuts ship with? Class 2B per ASME B1.1 (UNC, UNF, 8UN) or 6H per ISO 965 metric. Per F467 section 8.2 the nuts ship without additive chemical or metallic finish unless a coating (Xylan, Xylar, PTFE or zinc-nickel) is specified on the purchase order.
Related Pages
Browse the full nut catalogue at Monel 400 nuts. Higher proof load duties: heavy hex nuts. Prevailing torque joints: lock nuts. Companion bolting: Monel 400 bolts. Governing standard reference: ASTM F467.
Request a Quote
Send diameter, thread (UNC, UNF, 8UN, metric coarse, metric fine), nut style (hex, heavy hex, jam, slotted, castle), F467 class 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 to FOB Mumbai or CIF named port. Full Monel 400 alloy reference on the main reference.
Satisfaction Survey
