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How do I select a consumable for welding cast iron?


Frequently Asked Questions

Many factors affect choice of consumable for cast iron, and the relative importance of each depend on the user's priorities. The most popular consumables for arc welding are nickel and nickel-iron alloys, which, while expensive, offer the most manageable weld metal properties. Copper-tin alloys are used for bearing and surfacing applications because of their good sliding properties.

The best colour match with the casting is achieved by depositing a cast iron weld metal. Oxy-acetylene welding is most effective in this respect, though it is possible to use arc welding successfully. Good colour matching is also possible with nickel-copper fillers.

Recommended applications for each filler type are:

Filler typeTypical application
Cast iron Oxyacetylene and arc welding of grey, ductile and blackheart malleable irons where good colour match is required. Different consumables give either a flake or a nodular graphite structure.
Ni Joining and repair of grey irons and for surfacing high dilution welds in stronger grades. Produces a soft peenable deposit. Special electrode coverings are available to help repair deep cavities and blow holes.
NiFe Joining and repair of ductile, blackheart malleable and higher strength grey irons. Also used to join cast iron to dissimilar metals and for welding austenitic irons. Can also be used on irons with high sulphur and phosphorus levels.
NiFeMn Similar applications to NiFe fillers, but a stronger more crack resistant deposit is produced.
NiCu Used when a soft peenable deposit with good colour match is required on grey, nodular and blackheart malleable irons. Also useful for welding castings of unknown type and composition.
CuSn Mostly used for its good sliding and anti-seizing properties, i.e. for surfacing applications, particularly on grey irons.
CuAl Similar applications to CuSn but with poorer surfacing properties, but higher strength.
CuMnNiAl Similar application to CuAl fillers, but used where higher strength is required.

See also Welding of cast irons - a guide to best practice , from which this FAQ is extracted.

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