Monel is an alloy mostly comprised of nickel, copper and iron, as well as some trace elements. A brand trademark created by Special Metals Corporation, Monel was discovered by Robert Crooks Stanley in 1901 and patented in 1906. The name comes from company president of the International Nickel Co. at the time, Ambrose Monell.
The alloy is manufactured in five main grades: Monel 400, Monel 401, Monel 404, Monel K-500 and Monel R-405.
Highly resistant to corrosion and acid, Monel can withstand high temperatures. Monel 400, in particular, shows excellent anti-corrosion characteristics in a range of substances, including sea water, acids and alkalines. While Monel K-500 has the same properties, it is harder and stronger, due to the addition of aluminium and titanium.
Monel is more expensive to manufacture than stainless steel. The alloy is difficult to machine as it hardens quickly, so needs to be worked at low speeds and feed rates. Monel K-500 gains an advantage from double melting using Electro Slag Refining (ESR), which improves purity of the finished product.
While Monel 400 is formed into wire, rods, foil, sheets, tubes and pipes, K-500 is primarily used for rods, sheets and plates.
While more costly than other alloys, Monel clearly has a greater range of uses and is found commonly in all the following industries:
- Marine – piping systems, valves and seabird banding
- Aerospace – aircraft frames
- Petrochemical – drilling equipment
- Musical instruments – guitar strings
- Military – dog tags
During the 30s, Monel was used in the manufacture of an anti-thumb sucking device, known as the Baby Alice Thumb Guard.
Properties of Supplied Materials and Heat Treated Materials
|Condition of Supply||Heat Treatment (After Forming)|
|Annealed/Spring Temper||Stress relieve at 300-320°C (570-610°F) for 1 hour and air cool.|
|Condition||Approx Tensile Strength||Approx Service Temp.|
|Annealed||400 – 600 N/mm2||58 – 87 ksi||-200 to +230°C||-330 to +445°F|
|Spring Temper||850 – 1050 N/mm2||123 – 152 ksi||-200 to +230°C||-330 to +445°F|