ASME B18.2.1 heavy series, ASTM A193 supplementary S6, NACE MR0175 sour-service
Procurement teams sourcing flange bolting for sour hydrocarbon, seawater, and chloride-rich chemical service usually arrive at super duplex when standard 22Cr duplex (S31803, S32205) fails the PREN ≥ 40 specification. Ferralium 255 (UNS S32550, EN 1.4507) is a Cu-bearing super duplex grade that meets ASTM A193 supplementary requirement S6 with hardness ≤ 32 HRC for NACE MR0175 / ISO 15156-3 sour-service compliance. The heavy hex pattern per ASME B18.2.1 provides a larger across-flats and head height than the regular hex series, suitable for ASME B16.5 raised-face flange joints class 600 and above. Each consignment ships with EN 10204 type 3.2 MTC. RFQ to info@torqbolt.com or WhatsApp +91-22-66157017.
Manufactured to ASME B18.2.1 heavy hex series for inch sizes 1/2 through 4 inch and ISO 4014 / DIN 6914 for metric M16 through M64. Across-flats is approximately 1/8 inch larger than the regular hex series for the same nominal diameter, and head thickness is 2/3 of the nominal diameter. Threading is class 2A UNC or 6g metric, single-point cut for sizes above 1-1/2 inch and rolled for smaller sizes where matched die hardness permits.
| Standard | Region | Diameter range | Length range |
|---|---|---|---|
| ASME B18.2.1 heavy hex | US, ASME flanges | 1/2" to 4" | 1" to 30" |
| DIN 6914 | EU, structural high-strength | M12 to M36 | 30 mm to 350 mm |
| ISO 4014 (full thread variant) | EU, ISO flanges | M16 to M64 | 40 mm to 500 mm |
| Property | Requirement |
|---|---|
| Tensile, min | 760 MPa (110 ksi) |
| Yield 0.2%, min | 550 MPa (80 ksi) |
| Elongation 4D, min | 15% |
| Hardness, max (NACE) | 32 HRC |
| Ferrite, range | 35 to 55% |
| Charpy V at -46 °C, typical | ≥ 45 J |
The heavy hex pattern is required by ASME B16.5 for raised-face flange joints class 600 and above where the higher bolt preload demands a larger bearing area under the bolt head. For class 150 and 300 service, regular hex per ASME B18.2.1 (see Ferralium 255 hex bolts) is adequate. For studded service in lieu of through-bolts, see Ferralium 255 stud bolts per ASTM A193 S6. Companion nuts ship as Ferralium 255 heavy hex nuts per ASTM A194 S7.
EN 10204 type 3.2 MTC (third-party witnessed) ships with each consignment, covering chemistry per ASTM A479, mechanical properties per ASTM E8 and A370, hardness traverse, ferrite-content point count per ASTM E562, Charpy at the qualifying temperature, and NACE MR0175 conformance with ISO 15156-3 Table A.10 reference. NORSOK M-650 QTR (MDS D55) and PED 2014/68/EC AD 2000 W2/W7/W10 conformance available on request.
