scope:

This Defence Standard defines the requirements for the manufacture, inspection and testing of gunmetal ingots, gunmetal sand castings to BS EN 1982 grade CC492K, gunmetal centrifugal castings, and continuous cast gunmetal to BS EN 1982 in grades CC491K and CC492K.

BS EN 1982 grade CC492K is a good, general purpose alloy for pressure tight castings with corrosion and erosion resistant duties in sea water e.g. medium strength components, lightly loaded bearings and gears. This is the most widely used grade of gunmetal where pressure tightness is required, and is widely used for pressure tight Class III castings on surface ships. For submarines, the use of gunmetal is limited to low integrity castings and unlubricated bearings.

Castings produced to this Standard shall not be used in systems where the operating temperature will exceed 230oC as the creep strength reduces above this temperature.

Joining Methods

BS EN 1982 alloys CC492K and CC491K may be soft soldered. Silver soldering and brazing are possible where restraint is absent.

Welding of alloy CC492K is not advised. Minor repairs only to sand castings are allowed, provided that suitably qualified weld procedures and welders are employed. Details of welding qualification requirements are given in Def Stan 02-863.

The welding of alloy CC491K with Shielded Metal Arc Welding (SMAW) and Gas Metal Arc Welding (GMAW) processes is only possible with specialist techniques.

Components made from these materials are classified as Class III in accordance with Defence Standard 02-863 unless otherwise explicitly stated in the contract.