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 Bolts - UNS N04400 ASTM F468, DIN 931 / DIN 933
Monel 400 hex bolts (also called Monel 400 hex cap screws, UNS N04400 hex bolts or Alloy 400 hex bolts) are the most common form of nickel-copper bolting on HF alkylation flanges, NACE MR0175 sour-service joints, seawater intakes and naval non-magnetic structures. The bolt is governed by ASTM F468, the chemistry by ASTM B164 bar stock, and the alloy register entry is UNS N04400. Hex head dimensions follow ASME B18.2.1 (imperial) or DIN 933 fully threaded / DIN 931 partial thread (metric). Monel® is a registered trademark of Special Metals Corporation; TorqBolt is not authorized by, affiliated with or endorsed by Special Metals.
Hex Head Dimensions (ASME B18.2.1 / DIN 933)
Imperial Monel 400 hex bolts use the ASME B18.2.1 standard hex cap screw series. Metric bolts use the DIN 933 (fully threaded) hex head, which is dimensionally aligned with ISO 4017 and is the international default. Heads are forged from ASTM B164 hex bar with a washer-face on the bearing side. For larger preload or piping flanges, see heavy hex bolts; for internal-wrench applications use socket head cap screws.
| Size | Across flats F (mm) | Head height K (mm) | Standard | Wrench |
|---|---|---|---|---|
| M8 | 13 | 5.3 | DIN 933 / ISO 4017 | 13 mm |
| M10 | 17 | 6.4 | DIN 933 / ISO 4017 | 17 mm |
| M12 | 19 | 7.5 | DIN 933 / ISO 4017 | 19 mm |
| M16 | 24 | 10.0 | DIN 933 / ISO 4017 | 24 mm |
| M20 | 30 | 12.5 | DIN 933 / ISO 4017 | 30 mm |
| M24 | 36 | 15.0 | DIN 933 / ISO 4017 | 36 mm |
| M30 | 46 | 18.7 | DIN 933 / ISO 4017 | 46 mm |
| 1/2 in | 0.750 (3/4) | 0.323 | ASME B18.2.1 | 3/4 in |
| 5/8 in | 0.938 (15/16) | 0.403 | ASME B18.2.1 | 15/16 in |
| 3/4 in | 1.125 (1-1/8) | 0.483 | ASME B18.2.1 | 1-1/8 in |
| 1 in | 1.500 (1-1/2) | 0.627 | ASME B18.2.1 | 1-1/2 in |
Thread Types - UNC, UNF, Metric Coarse, Metric Fine
Imperial Monel 400 hex bolts are threaded UNC (coarse) or UNF (fine) to ASME B1.1 in class 2A fit. Metric bolts run metric coarse to ISO 261 (the default for DIN 933 and DIN 931). Metric fine threads to ISO 261 are available on indent for cyclic-load joints where finer pitch reduces self-loosening. DIN 933 carries a full thread up to the head; DIN 931 carries a partial thread with an unthreaded shank, giving better fatigue performance and shear capacity in flanged joints.
| Standard | Thread coverage | Typical use |
|---|---|---|
| DIN 933 / ISO 4017 | Fully threaded to head | Short bolts, structural clamping, tension joints |
| DIN 931 / ISO 4014 | Partial thread with shank | Long bolts, flange bolting, shear joints, fatigue service |
| ASME B1.1 UNC | Coarse, class 2A | General-purpose imperial bolting |
| ASME B1.1 UNF | Fine, class 2A | Vibration-sensitive joints, thin-section nuts |
Size Range (M6 to M40, 1/4 in to 1-1/2 in)
F468 covers nominal thread diameter 0.250 inch through 1.500 inch. Metric Monel 400 hex bolts span M6 through M40 in stock, with M48 through M64 produced on indent from ASTM B564 forging stock with F468 Heavy Forged Equivalent mechanicals. Lengths range from 1/2 inch (16 mm) through 20 inch (300 mm). Short stocked lengths are usually DIN 933 fully threaded; long lengths default to DIN 931 partial thread for fatigue and shear performance.
Mechanical Property Minima per ASTM F468
F468 sets the mechanical floor by nominal thread diameter and grade marking. Hardness is capped at 25 HRC across all diameters, well below the NACE MR0175 sour-service ceiling of 35 HRC for nickel-copper bolting. Values below are from ASTM F468/F468M-2016 Table 2.
| Marking | Diameter (in) | Hardness | Tensile (ksi) | Tensile (MPa) | Yield min (ksi) | Yield min (MPa) | Elongation |
|---|---|---|---|---|---|---|---|
| F 468U | 0.250 to 0.750 | 75 HRB to 25 HRC | 80 to 130 | 552 to 896 | 40 | 276 | 20% |
| F 468U | 0.875 to 1.500 | 60 HRB to 25 HRC | 70 to 130 | 483 to 896 | 30 | 207 | 20% |
| F 468U4 | 0.875 to 1.500 | 75 HRB to 25 HRC | 80 to 130 | 552 to 896 | 40 | 276 | 20% |
| F 468HF | all | 60 to 95 HRB | 70 to 120 | 483 to 827 | 30 | 207 | 20% |
| F 468V (Ni 405) | all | 60 HRB to 20 HRC | 70 to 125 | 483 to 862 | 30 | 207 | 20% |
Companion Nuts and Washers
Pair Monel 400 hex bolts with Monel 400 nuts to ASTM F467. Hex nuts match the standard hex bolt across-flats; heavy hex nuts are the piping-flange default. Lock nuts handle cyclic-load joints. Washers ship as DIN 125 plain, DIN 9021 fender, DIN 127 spring, or DIN 6798 serrated, all in matching Monel 400 chemistry to remove galvanic discontinuity in the clamped stack. For long-bolt stud configurations see stud bolts; for foundation work see anchor bolts and foundation bolts.
Applications and NACE Sour Service
Monel 400 hex bolts go onto HF alkylation flanges per API RP 751, sour gas wellhead and tree assemblies under NACE MR0175 / ISO 15156, seawater pump and heat-exchanger flanges, naval non-magnetic structural joints (magnetic permeability stays near 1.0), and process flanges where chloride stress corrosion cracking forces a step up from austenitic stainless. The F468 25 HRC cap clears the NACE MR0175 35 HRC ceiling for nickel-copper bolting by design; only H2S partial pressure and chloride concentration need to be checked against ISO 15156-3 Annex A.4. Sour-service shipments ship EN 10204 type 3.2 with the NACE compliance statement. Detail on HF acid resistance, HF alkylation, sour service and marine applications.
Head Marking Codes per F468
Per ASTM F468 Section 11, every Monel 400 hex bolt 1/4 inch (M6) and larger is stamped on the top of the head with the manufacturer identifier plus the F468 grade marking. The marking is forged or top-die stamped, never roll-stamped on the side. Class A weldable bolts carry F 468U or F 468U4; hot-finished equivalents carry F 468HF; Class B (Ni 405, free-machining) carries F 468V. Sour-service bolts carry both the F468 grade marking and the NACE MR0175 traceable stamp. The grade marking governs both chemistry and the mechanical floor; an unmarked bolt fails F468 acceptance.
FAQ
What is the difference between a Monel 400 hex bolt and a heavy hex bolt?
Standard hex uses the ASME B18.2.1 hex cap series with a smaller across-flats and washer face. Heavy hex uses the ASME B18.2.1 heavy-hex head with larger flats, thicker head and larger bearing area, and is the default for ASME B16.5 raised-face piping flanges. Standard hex is general-purpose; heavy hex is for high-preload flanged joints.
What size range is available?
Imperial 1/4 inch through 1-1/2 inch UNC and UNF to ASME B1.1, lengths 1/2 inch to 20 inch. Metric M6 through M40 to DIN 933 fully threaded or DIN 931 partial thread, lengths 16 mm to 300 mm. M48 through M64 on indent from B564 forging stock.
Are Monel 400 hex bolts suitable for sour service?
Yes. F468 caps hardness at 25 HRC, under the NACE MR0175 / ISO 15156-3 ceiling of 35 HRC for nickel-copper. Verify H2S partial pressure and chloride concentration against ISO 15156-3 Annex A.4 before final qualification.
Related Products
Full bolt family on the Monel 400 bolts hub. Adjacent forms: heavy hex bolts for piping flanges, stud bolts for B16.5 raised-face service, socket cap screws for internal-wrench joints, hex nuts for the matched nut, and ASTM F468 for the governing specification. Full alloy reference on the Monel 400 home page.
Request for Quote
Send diameter, length, thread series (UNC / UNF / DIN 933 / DIN 931), grade marking (F 468U / U4 / HF / V) 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 North Sea, Gulf, Middle East and Singapore.
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