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
Hiduron 130 vs 191 Bolt Selection
Choosing between Hiduron 130 (UNS C72400, DTD 900/4805) and Hiduron 191 (UNS C72420, NES 835) is rarely a strength contest. The decision is forced by the controlling specification, the H2S partial pressure, the cathodic-protection regime and the hot-forged section thickness. This page is the working decision tree TorqBolt uses on procurement enquiries: a single 8-row matrix that maps each application class to the correct grade, plus the metallurgical driver behind each verdict.
When to Specify Hiduron 130
Pick Hiduron 130 (UNS C72400) when the governing design driver is high 0.2 percent proof strength in a non-sour, non-NACE service envelope. Typical 0.2 percent proof on aged Hiduron 130 sits between 730 and 850 MPa with hardness reading 290 to 320 HBW. This puts the grade in the same strength band as Monel K-500 but without the hydrogen embrittlement liability that K-500 carries under cathodic protection. The DTD 900/4805 UK Air Ministry specification holds Hiduron 130 against the original chemistry and heat-treatment cycle. Use 130 for subsea hydraulic connector bodies, valve spindles, mechanical seal faces and aerospace-legacy fasteners where the controlling spec names the 130 grade. Avoid 130 the moment H2S partial pressure exceeds 0.05 psia because the aged hardness exceeds the NACE MR0175 286 HBW ceiling.
When to Specify Hiduron 191
Pick Hiduron 191 (UNS C72420) when the bolting will see NACE MR0175 sour service, cathodic protection, splash zone wetting, naval procurement, or hot-forged section thickness above 150 mm. The lower aluminium loading and the manganese addition combine to hold aged hardness reliably below 280 HBW, which sits inside the NACE 286 HBW ceiling with margin. 191 is also the grade named in NES 835, DEF STAN 02-835 and DOD-C-24676 for Royal Navy and allied naval fastener procurement. The trade-off is roughly 100 to 200 MPa lower 0.2 percent proof than 130, but the hydrogen embrittlement immunity, the sour-service qualification and the larger forgable section more than offset the strength reduction for the applications that need them.
Selection Matrix by Application
| Application | Service envelope | Grade verdict | Driver |
|---|---|---|---|
| Subsea hydraulic connector body | Saline, non-sour, design stress > 700 MPa | Hiduron 130 | Higher proof; thinner forged section |
| Splash zone riser bolting (sweet) | Wet/dry tidal band, cathodic protection | Hiduron 191 | Hydrogen embrittlement immunity required |
| Sour service flange bolting | H2S partial pressure > 0.05 psia | Hiduron 191 | NACE MR0175 hardness ceiling 286 HBW |
| Royal Navy naval fastener | NES 835 / DEF STAN 02-835 | Hiduron 191 | Specification calls 191 explicitly |
| Aerospace / DTD legacy fastener | UK Air Ministry DTD 900/4805 | Hiduron 130 | Specification calls 130 explicitly |
| Mechanical seal face body | Tungsten carbide running face, marine | Hiduron 130 | Hardness for seal-face flatness retention |
| Naval propeller shaft | Submerged shaft, fatigue-driven | Hiduron 191 | Hot-forge to large section; non-magnetic |
| Subsea valve spindle | Cyclic, seawater wetted, non-sour | Hiduron 130 | Wear resistance from higher aged hardness |
The matrix above is the working procurement filter. Run a candidate bolting application through three questions in order: (1) does the spec name a grade explicitly (NES 835 names 191, DTD 900/4805 names 130, decision is made); (2) does the service envelope include H2S sour service or cathodic protection (yes forces 191); (3) is the design stress above 700 MPa with section below 150 mm (yes favours 130, no leaves 191 as the default). If the bolting passes through all three questions without a forced answer, 191 is the lower-risk default because it has both NACE and naval coverage.
Section Thickness and Forging Window
| Equivalent round section | Hiduron 130 | Hiduron 191 | Forging notes |
|---|---|---|---|
| up to 50 mm | routine | routine | Both grades hot-forge with no risk; either selection works on strength alone |
| 50 to 100 mm | routine | routine | 130 carries higher proof; 191 carries NACE coverage |
| 100 to 150 mm | practical limit | routine | 130 needs careful billet preheat; 191 is the default at this section |
| 150 to 250 mm | not recommended | routine | 130 hot-workability ceiling reached; specify 191 |
| above 250 mm | not available | case-by-case | Forging house consultation required on 191; consider 2-piece machined assembly |
Related Hiduron Pages
- Hiduron 130 vs Hiduron 191: Side-by-side comparison of mechanical and chemical bands.
- Hiduron 130 Datasheet: Consolidated chemistry, mechanicals, heat treatment.
- Hiduron 191 Datasheet: NACE qualified naval and subsea grade datasheet.
- NACE MR0175 Compliance: Hiduron 191 286 HBW hardness ceiling evidence.
- NES 835 Naval Spec: Royal Navy controlling spec on Hiduron 191.
- DTD 900/4805: UK Air Ministry spec naming Hiduron 130.
- Subsea Connectors: Hiduron 130 flying-lead and stab-plate bodies.
- Riser Bolting: Hiduron 191 splash-zone bolting on offshore platforms.
- Naval Fasteners: NES 835 and DEF STAN 02-835 procurement.
- Mechanical Seals: Hiduron 130 seal-face bodies.
Frequently Asked Questions
Q. Is Hiduron 130 ever specified for NACE MR0175 sour service?
No. NACE MR0175 qualification on the Cu-Ni-Al family is held against Hiduron 191 by virtue of its DEF STAN 02-835 hardness ceiling that sits below 286 HBW. Hiduron 130 in the fully aged condition typically reads 290 to 320 HBW and exceeds the NACE hardness limit. Specify Hiduron 191 whenever the bolting will see wet H2S partial pressure above 0.05 psia.
Q. Why pick Hiduron 130 over Hiduron 191 for subsea flying-lead bodies?
Hiduron 130 carries a higher 0.2 percent proof strength (730 to 850 MPa typical) than Hiduron 191 (550 to 750 MPa typical) because of the higher aluminium loading and the more aggressive gamma-prime Ni3Al precipitation. On a flying-lead stab plate or connector body where the design stress is the governing input and sour service is not in scope, Hiduron 130 is the higher-strength selection.
Q. Can I mix Hiduron 130 studs with Hiduron 191 nuts in one flange make-up?
Yes for marine non-sour service. The chemistries are close enough that the galvanic couple is negligible and the thermal expansion is matched. For NACE sour service the entire bolting set (stud, nut, washer) must be the Hiduron 191 grade because the 286 HBW hardness ceiling applies to every threaded part in the make-up.
Q. Does the 130-or-191 selection change between metric and imperial sizes?
No. The grade selection is driven by the service envelope (sour vs sweet, strength target, section thickness, naval certification), not by the thread series. The same selection logic applies to ASME B18.2.1 imperial heavy hex bolts and to DIN 931 metric hex bolts.
Q. What section thickness is the practical hot-forging limit on each grade?
Hiduron 191 hot-forges reliably to roughly 250 mm equivalent round section. Hiduron 130 is forging-limited to about 150 mm equivalent because the higher aluminium content narrows the hot-workability window. Above 150 mm section, default to Hiduron 191 even when the strength envelope would otherwise pick 130.
Request a Quote
TorqBolt supplies Hiduron 130 (UNS C72400, DTD 900/4805) and Hiduron 191 (UNS C72420, NES 835, DEF STAN 02-835, DOD-C-24676) in round bar, stud bolts, hex bolts, heavy hex bolts, nuts, washers, forgings and machined components. Standard fastener lead time is 4 to 8 weeks from order, subsea machined components quote project-specific lead time. Send an enquiry through TorqBolt Contact with the controlling specification, the form factor, the size envelope and the certification level (3.1 default, 3.2 on call-out, NACE on call-out).
Request a Quote on Hiduron 130 and Hiduron 191 Bolting Stock and Fasteners
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