Colsibro® is a precipitation hardening copper nickel silicon that offers an outstanding mixture of mechanical and physical attributes unparalleled by many other grades of copper alloy. Its combination of high strength, high thermal and electrical conductivity, spark resistance, corrosion resistance, excellent wear resistance, and good cryogenic properties has enabled Colsibro® to find a spot in almost every engineering field, from mechanical to electrical and marine to automotive. Colsibro® is a high copper alloy with small additions of silicon and nickel, which combine to boost the hardness, strength, and wear resistance of the material, while retaining many of the physical advantages of copper itself.
Columbia Metals stocks Colsibro® in the fully heat treated condition, which maximizes the mechanical strength levels. These are developed by a combination of heat treatment and cold work, with the heat treatment or aging process forming a nickel silicide precipitate that hardens the metal matrix. This provides Colsibro® an improved strength level than many stainless steels and low alloy steels. It also offers Colsibro® the advantage of a yield strength that is approximately 90% that of the ultimate tensile strength, while keeping a good level of ductility. Fully age hardened Colsibro® also gives a high hardness level, anti-friction properties, an outstanding wear resistance, and excellent bearing properties particularly under high loading against hardened steels.
Colsibro® has an extremely good corrosion resistance in many industrial and marine applications and is superior to numerous other copper-based alloys and copper itself. With a high corrosion resistance in sea water and fresh water, it offers superior resistance to wet sulfurous atmospheres and a freedom from hydrogen embrittlement and stress corrosion. Integrated with a very low magnetic permeability and outstanding cryogenic temperature properties, Colsibro® is a suitable choice for use in subsea connector applications, marine hardware, and for non-magnetic instrumentation both below and above the waterline.
The high copper content of Colsibro® guarantees it maintains an impressive electrical and thermal conductivity value. This, mixed with its resistance to softening up to ~300 °C, a high wear resistance and its mechanical strength makes Colsibro® the ideal selection for high performance engine components such as valve seats, gears, valve guides, and bushes. The high conductivity values are also vital to the specification of Colsibro® in several other components including welding electrodes, current-carrying electrical components and connectors, resistance welding wheels, rotary contacts and heavy duty switchgear.
Colsibro® offers good fabrication properties and is easily machined particularly in the heat treated condition where close machining tolerances can be held. Forming is possible either cold or hot but both processes are better performed in the solution treated condition with any age hardening treatment being applied to the finished component. It can be brazed, soldered, and welded by conventional TIG and MIG techniques.
Colsibro® can be used for bearing cages, bushes, short circuit rings, slip rings, high strength fasteners, mechanical seals, valve bodies, thrust pads, plugs and sockets, as well as resistance welding components including flash butt welding dies, wheels and electrodes, masonry fixings and spark resistant safety tools.
- High electrical conductivity
- High mechanical strength
- Proof strength 90% of UTS
- Readily machinable
- High thermal conductivity
- Excellent wear resistance
- Low magnetic permeability
- Very good corrosion resistance
- Spark resistant
- Good ductility and formability
Nominal Composition (%)
||1.6 - 2.2
||0.4 - 0.8
Mechanical Properties (specification minima)
||≤30 mm dia
||30 ≤ 50 mm dia
||50 ≤ 90 mm dia
|Ultimate Tensile Strength (N/mm2)
|0.2% Proof Strength (N/mm2)
Typical Physical Properties
|Melting Range (°C)
||1040 - 1060
|Thermal conductivity (20 °C; W/m°K)
|Coeff. Thermal Exp. (0-400 °C; m/m°K x 10-6)
|Electrical Conductivity (IACS)
Round Bar Weight and Stock Sizes
|0.500” - 3.000” A/F
in a comprehensive range
|Flat: wide range of sizes
Square: 1.000” - 3.000”
NB Weight data for guidance only