Dissimilar Joints

In industry today alloy steels are frequently welded to carbon steels, stainless steels, and nickel alloys. Less frequently there is a need to weld alloy steel to cast irons, copper alloys, or aluminium alloys.

The term 'alloy steel' includes a wide variety of materials and some of them are difficult to weld. The metallurgy of the alloy steel must always be considered when a dissimilar joint is required. Preheat may be needed with many alloy steels whatever other material they are to be welded to depending on their carbon equivalents.

Welding alloy steel to carbon steel, other alloy steels, stainless steel, and nickel alloys may be carried out using most welding processes. The consumable used for fusion welding one type of alloy steel to a carbon or other alloy steel must be compatible with both steels.

Welding to stainless steels usually requires the use of specially formulated Cr-Ni-Mo or Ni alloy consumables to maintain a suitable, crack-free weld metal microstructure.

Nickel alloy consumables are recommended to fusion weld alloy steels to nickel alloys, the choice of which to use depending on the nickel alloy involved.

If welding alloy steel to cast iron a Ni alloy consumable is normally used but the main problem is the low ductility and poor weldability of the cast iron.

Welding to copper alloys by friction welding or other non-fusion techniques is possible. Fusion welding requires use of complicated techniques, although acceptable results can be achieved with some alloys using aluminium bronze type fillers.

Welding to aluminium with any process but friction or other non-fusion technique is not recommended.