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
Incoloy 800H Hex Bolts
Incoloy 800H hex bolts to DIN 931 / ISO 4014 are partially threaded head-and-shank fasteners machined from ASTM B408 round bar for high-temperature petrochemical, refinery and fired-heater service to 815 deg C (1500 deg F). The hex bolt carries a 6-sided head (across-flats per DIN 931), a plain shank for through-hole bearing and a partial thread for nut engagement. Standard diameter range is M12 to M48 with shank lengths cut to print. Across-flats dimensions follow the DIN 931 schedule (18 mm A/F on M12 through 75 mm A/F on M48). Every hex bolt ships with EN 10204 type 3.1 mill test certificate documenting heat number, Incoloy 800H chemistry per ASTM B408, solution-anneal cycle and ASTM grain size 5 verification. Type 3.2 third-party witness is supplied on PO call-out. The DIN 931 hex bolt is the standard alternative to heavy hex bolts (ASME B18.2.1) on European-spec petrochemical projects where DIN/ISO geometry is the controlling specification.
Hex Bolt Dimensions (DIN 931 / ISO 4014)
| Size designation | Across flats / OD | Head / nut height | Thread pitch | Standard reference |
|---|---|---|---|---|
| M12 | 12.0 mm OD | Head A/F 18 mm; Head height 7.5 mm | 1.75 mm | DIN 931 / ISO 4014 |
| M16 | 16.0 mm OD | Head A/F 24 mm; Head height 10 mm | 2.0 mm | DIN 931 / ISO 4014 |
| M20 | 20.0 mm OD | Head A/F 30 mm; Head height 12.5 mm | 2.5 mm | DIN 931 / ISO 4014 |
| M24 | 24.0 mm OD | Head A/F 36 mm; Head height 15 mm | 3.0 mm | DIN 931 / ISO 4014 |
| M30 | 30.0 mm OD | Head A/F 46 mm; Head height 18.7 mm | 3.5 mm | DIN 931 / ISO 4014 |
| M36 | 36.0 mm OD | Head A/F 55 mm; Head height 22.5 mm | 4.0 mm | DIN 931 / ISO 4014 |
| M42 | 42.0 mm OD | Head A/F 65 mm; Head height 26 mm | 4.5 mm | DIN 931 / ISO 4014 |
| M48 | 48.0 mm OD | Head A/F 75 mm; Head height 30 mm | 5.0 mm | DIN 931 / ISO 4014 |
Manufacturing Route at TorqBolt
Hex bolt manufacture from Incoloy 800H bar uses CNC turn-mill to machine the hex head in one setup, then thread roll the partial-thread section:
- Receive Incoloy 800H bar to ASTM B408; heat verification and PMI.
- Cut bar to overall length on bandsaw (head height + shank length + thread length).
- CNC turn the shank to print OD; face the head-end square.
- Mill hex head in one setup: 6-sided across-flats per DIN 931, with controlled head-height tolerance.
- Thread roll the partial-thread section: class 6g per ISO 965, ring + plug gauge verification.
- Solution anneal at 1149 deg C plateau followed by rapid quench; grain size 5 or coarser verified.
- Hardness band 120-184 HB on first piece and one per batch.
- Visual + dimensional + PMI inspection 100 percent; head-mark for heat number + grade.
- VCI wrap, kraft inner, plywood crate; ship with CoC + EN 10204 certificate.
Hex Bolt Sizes Stocked and Lead Times
| Diameter range | Length range | Stock status | Lead time |
|---|---|---|---|
| M12 - M20 | 30 mm - 200 mm | Stock + ex-stock | 7 working days |
| M24 - M30 | 50 mm - 300 mm | Made-to-order from stock bar | 10 to 14 working days |
| M36 - M42 | 75 mm - 400 mm | Made-to-order from stock bar | 14 to 21 working days |
| M48 | 100 mm - 500 mm | Made-to-order, large bar | 4 to 6 weeks |
Inspection and Heat Marking
EN 10204 type 3.1 mill test certificate is default. Hex bolt specific inspection points:
- Hex head across-flats verified with go / no-go gauge per DIN 931 schedule.
- Head height verified to DIN 931 tolerance band.
- Plain shank diameter measured at three points; OD per print.
- Thread engagement verified with class 6g ring + plug gauges.
- Hardness band 120-184 HB on first piece and one per batch.
- ASTM E112 grain-size etch verification (grain size 5 or coarser).
- PMI by X-ray fluorescence on first piece and one per batch.
- Head-marked: heat number + grade (800H) + TorqBolt mark.
Typical Service Conditions
DIN 931 hex bolts are the standard European-spec choice on high-temperature flange and structural bolting:
- European-spec pressure-vessel flange bolting on PED-certified equipment.
- Ethylene cracker radiant-section flange bolting on European petrochemical units.
- Heat exchanger shell flange bolting on European refinery service.
- Reformer pigtail outlet flange bolting on European hydrogen plant scope.
- Radiant tubes and furnace components structural fastening.
- Combustion-air ductwork flange bolting per European piping standards.
Incoloy 800H Alloy Considerations on This Fastener Form
Companion Fasteners and Related Pages
- Heavy Hex Bolts: ASME B18.2.1 alternative for US-spec scope.
- Hex Cap Screws: fully threaded variant per DIN 933.
- Hex Nuts: matched DIN 934 nuts for hex bolt assemblies.
- Socket Head Cap Screws: Allen-key drive alternative per DIN 912.
- Stud Bolts: no-head stud bolt alternative for through-flange bolting.
Frequently Asked Questions
Q. Are Incoloy 800H hex bolts available in inch sizes?
Yes. Standard supply is metric DIN 931 (M12-M48). Inch sizes 1/2 inch through 1-7/8 inch to ANSI / ASME B18.2.1 dimensions are machined on PO call-out.
Q. What is the difference between DIN 931 and DIN 933?
DIN 931 is a partially threaded hex bolt (head, plain shank, partial thread). DIN 933 is fully threaded (head, full-length thread, no plain shank). DIN 933 is also called a hex cap screw.
Q. Are Incoloy 800H hex bolts qualified to ASTM A193 grade B8 or B8M?
No. A193 B8 and B8M are 304 / 316 stainless. Incoloy 800H is a separate nickel-iron-chromium alloy specified under ASTM B408. The certificate references B408 chemistry, not A193 chemistry.
Q. What thread tolerance class is supplied?
ISO 965 class 6g (external) per DIN 931 default. Class 4g6g or 4h6h on PO call-out for high-precision assembly.
Q. Can hex bolts be supplied with through-shank reduced section?
Yes on call-out. Standard supply is full-OD shank. Reduced-shank waisted hex bolts for controlled-stretch flange bolting are machined to print on special order.
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