NES 835 Hiduron 191 Specification

NES 835 is the UK Naval Engineering Standard that specifies chemistry, heat treatment, mechanical-property floor, hardness ceiling and inspection requirements for Hiduron 191 (UNS C72420) Cu-Ni-Al-Mn precipitation-hardened cupronickel bolting supplied to Royal Navy surface ship and submarine service. The standard fixes nickel at 14.0-15.5 percent, manganese at 4.0-5.0 percent, aluminium at 1.5-2.5 percent with balance copper, and demands tensile strength 820-1000 MPa, 0.2 percent proof stress above 580 MPa, elongation A5 above 15 percent, and hardness below 286 HBW (28 HRC) — the same ceiling that qualifies the material for NACE MR0175 sour-service bolting simultaneously. NES 835 was adopted by the UK Ministry of Defence as DEF STAN 02-835 and is cross-referenced by the US Department of Defense as DOD-C-24676 for US Navy procurement. Cross-procurement orders routinely carry all three document numbers on a single purchase order.

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Scope of NES 835

NES 835 specifies technical delivery conditions for round bar, forging stock, finished forgings, finished fasteners (bolts, screws, studs, nuts, washers, threaded rod) and machined components in the Cu-Ni-Al-Mn precipitation-hardened cupronickel family intended for Royal Navy surface and submarine bolting service. The standard governs chemistry ranges, the solution-anneal plus age heat treatment cycle, room-temperature mechanical-property floors, hardness ceiling for NACE MR0175 sour-service compliance, magnetic permeability ceiling for naval mine-countermeasures qualification, inspection categories to EN 10204, hydrogen-embrittlement test acceptance, and product marking.

Latest Revision and Sister Standards

NES 835 is maintained by the UK Ministry of Defence under the Defence Standardisation programme. The standard was adopted into the Defence Standards series as DEF STAN 02-835 with the same technical content, and the US Department of Defense maintains a sister specification under the document number DOD-C-24676 for US Navy procurement. Cross-procurement of Hiduron 191 stock and fasteners commonly cites all three documents on the same purchase order.

Grade Matrix Relevant to Hiduron

Chemistry to NES 835 (Hiduron 191)

NES 835 fixes the Hiduron 191 chemistry within tight Cu-Ni-Mn-Al-Fe windows that hold the gamma-prime precipitation response under repeated solution-anneal plus age cycles. The headline ranges are nickel 14.0 to 15.5 percent, manganese 4.0 to 5.0 percent, aluminium 1.5 to 2.5 percent, iron 0.5 to 1.5 percent, with balance copper and tight tramp limits on lead, sulphur and carbon. The detailed element-by-element table is in the shared Chemistry block below.

Mechanical-Property Floor (NES 835)

Hiduron 191 in the solution-annealed plus aged condition to NES 835 holds tensile strength 820 to 1000 MPa, 0.2 percent proof stress at least 580 MPa, elongation A5 at least 15 percent, and Charpy V impact at least 40 J at room temperature on longitudinal specimens. Hardness is controlled below 286 HBW (28 HRC) for NACE MR0175 sour-service compliance. Magnetic permeability is controlled below 1.005 mu_r for Royal Navy naval mine-countermeasures qualification. The detailed property table is in the shared Mechanicals block below.

Inspection Categories to EN 10204

NES 835 references the inspection-document categories defined in EN 10204: type 2.1 declaration of compliance, type 2.2 test report, type 3.1 mill test certificate issued by the manufacturer with heat-level traceability, and type 3.2 inspection certificate witnessed by Lloyd's Register, DNV, BV, SGS or TUV. Type 3.1 is the TorqBolt default for NES 835 supply; type 3.2 is standard practice for Royal Navy and allied naval procurement and is supplied on call-out with the witness body named on the purchase order.

Cross-References to Other Standards

NES 835 cross-references the UK Ministry of Defence variant DEF STAN 02-835 and the US Department of Defense variant DOD-C-24676. For sour-service compliance, NES 835 supply commonly carries a NACE MR0175 hardness certificate as a separate document on the same heat. For the Hiduron 130 mid-strength grade in the same family, the controlling specification is DTD 900/4805.

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