Specifications

Chemical composition and mechanical properties

Nickel includes cobalt. Limits as given in ASTM B127, B164 and B165 (alloy 400) and B865 (alloy K-500).

Annealed condition. Hot-rolled, cold-worked and stress-relieved conditions have higher strength, with size limits as given in each standard.

Cold-drawn and stress-relieved bar has higher strength than annealed bar, with limits by size in ASTM B164. Background is on the Monel 400 page.

Choosing the condition

Annealed bar is the softest and most ductile, used where parts will be cold formed or where maximum resistance to stress corrosion cracking in hydrofluoric acid vapour is needed. Cold-drawn and stress-relieved bar has higher strength and machines better, because the chips break more cleanly; it is the usual choice for fasteners, shafts and machined parts. Hot-finished bar is used for larger diameters and forging stock. Where much higher strength is needed, Monel K500 bar is used.

How we manufacture Monel 400 bars

We manufacture Monel 400 round bars from certified billets by hot rolling or forging, followed by annealing, or by cold drawing for close tolerance and higher strength. Bright bars are peeled, turned or centreless ground. Every bar is marked with grade and heat number, and ultrasonic testing is carried out on request for bars that will be machined into pressure parts such as flanges and fittings.

Machining and welding

Monel 400 work-hardens during machining; use rigid set-ups, sharp tools with positive rake, steady feeds deep enough to cut beneath the hardened layer, and plenty of coolant. Cold-drawn bar gives better chip control than annealed bar. Welding uses ERNiCu-7 filler on clean joints free of sulphur and lead.

Corrosion resistance

Monel 400 bars resist flowing seawater and brackish water, hydrofluoric acid, caustic soda and many salts, and are not prone to chloride stress corrosion cracking. In stagnant seawater, pitting can occur under deposits, and Monel is not suitable for oxidising acids such as nitric acid. For sour service, bars can be supplied to NACE MR0175 / ISO 15156 on request.

Ordering Monel 400 round bars

Please give the specification, shape and size, tolerance, condition, surface, length, quantity and any testing or inspection requirement. Bars are packed in wooden boxes or bundles, with bright bars wrapped, and each piece is traceable to its mill test certificate.

Monel 400 in marine and chemical parts

On ships and offshore platforms, Monel 400 bars are machined into seawater pump shafts and sleeves, valve stems and seats, propeller and rudder fastenings, and fittings for seawater and firewater systems. In chemical and refinery plants, they are used for valve trim and fittings in hydrofluoric acid alkylation units, caustic soda plants and brine service. Where a higher-strength shaft or fastener is needed in the same service, Monel K500 bar is used.

Applications and related products

Monel 400 round bars are used for valve stems and trim, pump shafts and impellers, fasteners, fittings and flanges machined from bar, marine hardware and chemical-plant parts. Other Monel bars, including K500, are on the Monel round bars page, and other materials on the round bars, rods and wires page.