High Strength, High Modulus Cupronickel Alloy

Nibron SPECIAL is a copper nickel alloy with extra high strength that improves corrosion resistance and strength. The Nibron alloy is also referred to as nickel bronze and contains small quantities of aluminium, manganese and iron that combine with nickel and copper to achieve its exclusive properties. The material is suited to an extensive range of differing industries due to its corrosion resistance, high strength, anti-galling, low magnetism, good fabrication characteristics and high conductivity. It is highly resistant to hydrogen embrittlement, sulphide, chloride, ammonia and amine stress corrosion cracking, while offering low magnetism and resistance to sparking, galling and seizure.

There is no need for complicated heat treatments for Nibron since it features high mechanical strength in the ‘as delivered’ condition. Nibron retains its properties from cryogenic temperatures up to ~300°C, with the mechanical properties including its impact strength being maintained, if not improved, at temperatures as low as at least –196°C.

Nibron’s corrosion resistance is excellent in a range of media and this is one of the key benefits over other alloys. It shows excellent marine corrosion resistance to aluminium bronzes and also 90/10 and 70/30 cupronickels. It has an electrode potential of – 0.3 V. It is found to be resistant to stress corrosion cracking in a number of marine environments including those contaminated with amine, sulfide and ammonia. In spite of having comparatively high alloying additions, Nibron retains electrical and thermal conductivity values. It also provides an exclusively low magnetic permeability less than 1.01 suitable for non-magnetic components and instruments.

Nibron has a good dimensional stability and machinability. It has a machinability rating of 30 (free cutting brass = 100) hence can be readily machined and possesses a greater resistance to galling and seizure when compared to other alloys such as duplex stainless steels and K500. Another fabricational benefit is that Nibron can be inherently welded both to 316 stainless steel and to itself using a traditional TIG welding process.

Composition of Nibron SPECIAL

The composition of Nibron SPECIAL is provided in the table below:

Element Percentage
Nickel, Ni 14.5
Aluminium, Al 3
Iron, Fe 1.5
Manganese, Mn 0.3
Copper, Cu Remaining

Key Features

The key features of Nibron SPECIAL are:

  • Excellent mechanical properties
  • Excellent galling resistance and wear
  • Excellent machinability and dimensional stability
  • Good thermal conductivity
  • High ductility and excellent resistance to marine corrosion and erosion
  • Properties are retained at cryogenic temperatures
  • Very low magnetic permeability

Mechanical Properties (Specification Minima)

The mechanical properties of Nibron SPECIAL are:

≤65mm dia inc. >65mm dia
Ultimate Tensile Strength (N/mm2) 850 770
0.2% Proof Strength (N/mm2) 630 555
Elongation (%) 12 12
Hardness (HB) 240 229

Typical Physical Properties (As delivered)

The physical properties of Nibron SPECIAL are:

Density (g/cm3) 8.50
Melting Range (°C) 1080 - 1100
Young's Modulus (GPa) 146
Thermal conductivity (20°C - W/m°K) 71
Coeff. Thermal Exp. (0-400°C - m/m°K x 10-6) 16.4
Electrical Resistivity (microhm/m) 0.17
Magnetic Permeability <1.01

Applications of Nibron SPECIAL

Nibron may be primarily suited to the extremes of marine or offshore oil and gas environments, however it is also useful for a number of critical components in several industrial sectors such as aerospace, electrical, chemical and automotive.

The applications of Nibron SPECIAL are listed below:

  • Offshore and Marine: Bearing bushes and marine shafts, offshore bolting, valve and pump trim.
  • Chemical processing: Pump and valve spindles and other trim, pipe fittings, flanges, plant components and clamps.
  • Aerospace: Aircraft landing gear bushes, actuating sleeves, steering gear, bearing bushes, non-magnetic bolts and control surface components.
  • Automotive: High performance engine shafts, gears, pinions, bearing bushes, and locking nuts, mechanical and electromechanical components, thrust washers and hydraulic equipment.

Conclusion

The distinct combination of properties offered by Nibron ensures it is an excellent choice for a number of critical mechanical engineering components where a “fit and forget” approach to material selection is required. Nibron features mechanical properties equivalent to B7 bolting steel and a very high corrosion resistance in a large number of different aggressive media, hence it is vastly superior to most other copper alloys and steels.

This information has been sourced, reviewed and adapted from materials provided by Columbia Metals.

For more information on this source, please visit Columbia Metals.

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