Alloy 28 possesses good weldability. Suitable welding methods are manual metal-arc with covered electrodes and gas shielded arc welding, such as TIG and MIG. The heat input should be 1 kJ/mm maximum and the interpass temperature 150°C (300°F) maximum. A stringer bead welding technique should be used. Welding should be undertaken without preheating and, if correctly performed, there will be no need for any subsequent heat treatment. To maintain full corrosion resistance of the weld joint, welding must be followed by thorough cleaning to ensure removal of all oxides and slag particles.
In common with all austenitic stainless steels, Alloy 28 has low thermal conductivity and high thermal expansion. Welding should, therefore, be carefully planned in advance so that distortion of the welded joint can be minimized.
The welding of fully austenitic steels usually involves the risk of hot cracking in the weld metal, particularly if the weldment is under constraint. However, since Alloy 28 is an alloy with a very low impurity content, it is not particularly prone to this type of cracking.
As a filler metal for gas shielded arc welding, 27.31.4.LCu wire is recommended. For manual metal-arc welding, covered electrodes of the 27.31.4.LCuR type are recommended.
When Alloy 28 is welded to carbon steel, it is also possible to use nickel base filler metals, such as Sanicro 60.