Both tungsten inert gas (TIG/GTAW) and plasma arc welding have been used for cast irons. The results achieved were comparable with less costly processes and are not likely to be used except for applications where they have special advantages.
Both metal inert/active gas (MIG, MAG or GMAW) and flux cored wire welding have been used for a wide range of cast irons with a variety of filler materials. The processes are readily mechanised and are, therefore, ideal for repetitive work.
Oxy-acetylene gas welding has been practised successfully for many years and involves extensive preheating to 600-800°C and welding with a filler wire and flux followed by slow cooling. Although this process is slower than arc welding, the slow thermal cycles tend to give good mechanical properties.
Variations on the process include bronze welding (more properly, brazing), where a brass filler wire is used and the cast iron is not melted, and powder welding, where low heat input is achieved by using a powder filler instead of a filler rod.
Friction welding has been utilised in the automobile industry for joining tubular driveshafts to malleable iron flanges and flash-butt welding has been carried out on flange/tube joints.
The selection of an alternative welding process requires care. If in doubt, contact an experienced practitioner.
Further information on welding of cast iron is available in:
Welding of cast irons - a guide to best practice
C.L.M.Cottrell, 'Welding cast irons', published by TWI, Abington, Cambridge, UK, 1986 and available from Woodhead Publishing, Abington, Cambridge, UK. e-mail: firstname.lastname@example.org
ISBN 0 85300 176 6
Guide for Welding Iron Castings - ANSI/AWS D11.2-89, American Welding Society, Miami, Florida, USA.
ISBN 0 87171 295 4