High Strength Cupronickel Marine Alloy

Columbia 835 is a high strength cupronickel that integrates the benefits of aluminium bronze and cupronickels. It is mainly a marine alloy with a proven resistance to corrosion and bio-fouling along with a good resistance to impingement. Its high strength is combined with a high impact strength and its composition is controlled tightly by the MoD (Navy) standard. Columbia 835® offers good machinability, a very low magnetic permeability, and it is readily weldable.

Columbia 835 alloy provides an excellent resistance to impingement, excellent antigalling properties, high impact strength and freedom from hydrogen embrittlement. The material can also be used for high strength critical components in the chemical processing, general engineering and automotive industries.

The optimum condition for this alloy is the stress relieved and heat-treated condition as it does not just help to enhance the toughness and strength of the material but also to bring down the risk of stress corrosion cracking. Additionally, this condition will enable close machining tolerances to be held during final manufacture.

Columbia 835 is known for its excellent marine corrosion resistance, outperforming the standard cupronickels 90/10 and 70/30 in fresh water, seawater, brackish water and also many polluted industrial waters. Also it has an excellent resistance to water line corrosion, bio fouling, crevice corrosion and pitting.

Columbia 835 is galvanically compatible with most other copper based alloys. Even though it is intrinsically less noble than austenitic or duplex stainless steels, the aluminium oxide film allows a certain protection against significant preferential corrosion; however, good design must be employed to reduce corrosion between dissimilar metals. Columbia 835 alloy is not subject to hydrogen embrittlement. Columbia 835 also offers a very low magnetic permeability of <1.01 and is resistant to galling both operating against itself and against other materials such as aluminium bronzes and duplex stainless steels. It can be fabricated well and can be readily machined, hot formed, brazed welded and soldered.

Composition

The composition of Columbia 835 is provided in the table below:

Element Percentage
Nickel, Ni 14.5
Manganese, Mn 4.5
Aluminium, Al 1.7
Iron, Fe 1.0
Copper, Cu Remaining

Key Features

The key features of Columbia 835 alloy are:

  • High strength
  • Spark resistant
  • Excellent corrosion and biofouling resistance
  • Low magnetic permeability
  • High impact strength retained down to cryogenic temperatures

Mechanical Properties (Specification Minima)

The mechanical properties of Columbia 835 alloy are:

  <15mm dia 15-125mm dia >125mm dia
Ultimate Tensile Strength (N/mm2) 725 725 710
0.2% Proof Strength (N/mm2) 430 430 400
Elongation (%) 18 18 18
Impact Strength - 40J 40J

Typical Physical Properties (as delivered)

The physical properties of Columbia 835 alloy are:

   
Density (g/cm3) 8.53
Melting Range (°C) 1030 - 1085
Thermal conductivity (20°C - W/m°K) 25
Coeff. Thermal Exp. (0-400°C - m/m°K x 10-6) 16.0
Electrical Resistivity (microhm/m) 0.35
Magnetic Permeability <1.01

Applications

Columbia 835 alloy finds applications in marine applications such as critical marine fasteners, gears, shafts, pipe couplings, offshore and shipboard applications in addition to its MoD (Navy) use. The alloy can also be used in many safety critical components including critical fasteners, valve and pump trim, gears, sonar equipment, shafts, connectors, pipe couplings, flanges and subsea components for offshore oil and gas production.

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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