Bolting is a small part of the value of an assembly and a large part of the consequence when it fails. Naval bolting adds two problems to the usual chloride attack and thread-root crevice corrosion.
Submarine service demands a low magnetic signature, and cathodically protected assemblies generate hydrogen, which embrittles many high strength grades. The alloys that survive all of this at once are few.
Hiduron® 191 was developed for naval service and is approved as a named alloy by leading navies. It meets DEF STAN 02-835, NES 835 and DOD-C-24676, and is specified for fasteners for ships and submarines, prized for its freedom from hydrogen embrittlement and its excellent anti-galling behaviour.
Hiduron® 130 covers naval fastening where seawater resistance and very low magnetic permeability are the drivers. And Hidurel® 5 is used for bolting for ships and submarines where bearing and anti-friction behaviour also matter.
Where the requirement is a high PREN with high strength rather than low magnetism, the super duplex grades - Alloy 32760, Alloy 32750 and Ferralium® 255 - clear a PREN above 40. And Fermonic® 50 gives a non-magnetic austenitic option.
Hiduron® 191 meets DEF STAN 02-835 and NES 835. Alloy 32760 is UNS S32760, also known as Zeron 100® (Rolled Alloys); Alloy 32750 is UNS S32750, also known as SAF 2507® (Alleima); Ferralium® 255 is UNS S32550. Fermonic® 50 is UNS S20910, known elsewhere as Nitronic® 50 (Cleveland-Cliffs). We supply bar to fastener manufacturers and specialist bolting houses.