What Is Monel (Nickel-Copper Alloy)

Monel is the name given to a group of alloys containing nickel (predominantly), copper and a few other substances that is known for its high corrosion resistance and tensile strength. It bears the trademark of Special Metals Corporation. Also known as nickel-copper alloy, it is manufactured in the form of wires, sheets, tubes, rods, bolts, plates, nuts, nails, rivets, screws, valves, tube fittings, fasteners, etc. Common types of the alloy are Monel 400, 405, K-500, etc ^[1]. It has the advantage of being easily brazed, welded and soldered ^[2].

Composition ^[2]

The compositions of Monel alloys being varied, we have given here that of Monel 400 only in detail.

Monel 400

Nickel	63% (minimum)
Copper	29-34%
Iron	2-2.5%
Manganese	1.5-2%

Besides the above, Monel 405 contains a maximum of 0.5% silicon and Monel K-500 has 2.3-3.15% aluminum and 0.35-0.85% titanium.

Properties and Characteristics of Monel

Physical Properties
Color/appearance	Gray [6]
Luster	Metallic [9]
Melting point	1300 – 1350°C [1]
Density	8.80X103 kg/m3 [2]
State of matter at room temperature (normal phase)	Solid [9]
Hardness	110-150 HB [7]
Thermal Conductivity	21.8 W/(m K) [1]
Resistivity	54.7X10-8 ohm-m [2]
Tensile strength (annealed)	550 MPa [2]
Specific heat capacity	427 J/(kg*K) [2]
Modulus of elasticity	179 GPa [2]

Uses

1. Resistance to deterioration makes Monel 400 ideal for use in equipment parts that remain in chemical and marine environments ^[2].
2. For producing hydrocarbon and chemical processing equipment ^[1].
3. In carburetor needle valves and sleeves, exhaust manifolds and other critical parts of aircraft ^[8].
4. Making screw machine products, heat exchangers, piping systems and wind instruments ^[2].

Is It Dangerous

The alloy is non-toxic in its solid form. However, welding, grinding or melting may produce hazardous fumes or dust the contact or inhalation of which should be avoided ^[9].

Interesting Facts

• Its property of work-hardening fast makes it very difficult to machine compared to steel ^[3].
• Some Monels are magnetic while others are non-magnetic ^[5].
• While Monel was one of the most popular metals in the market during the 1920s – 1940s, for manufacturing household goods like sinks, countertops, appliances, etc., it was largely replaced by stainless steel from the 1950’s onward due to its lower cost ^[2].

Monel Metal Cost

Though it is subject to price fluctuations, on an average, the alloy costs around $2.05 per pound ^[4].

References
1. Monel – Lenntech.com
2. Properties and Composition of Monel 400 – Thebalance.com
3. Monel Welding Overview – Welding-fabrication.com
4. Monel – Rockawayrecycling.com
5. Monel or Stainless? – Forum.woodenboat.com
6. Antique Jewelry University – Langantiques.com
7. Monel 400 – Espimetals.com
8. Monel and K-Monel – Aircraftsystemstech.com
9. Monel – Espimetals.com