Fusion welding
involves a heat source and may involve the use of a filler material
such as a consumable electrode or a wire fed into the weld pool.
These processes also use a protective layer between the atmosphere
and the molten metal, either in the form of gas shielding or a
flux
which melts to give a viscous slag on the weld metal that eventually
solidifies and can be removed. There are several different types of
fusion welding processes that can be used. The table below gives
some typical applications for the different procedures and the
typical characteristics of technique.
|
Cost |
Cleanness of the weld |
HAZ width |
Level of automation |
Thickness of plate |
Comments and typical applications
|
Manual Metal Arc (MMA) |
Low |
Poor - OK |
5 - 6 mm |
Not |
Any - multipass |
Only use for relatively short runs, for example car repair
welds, small repair welds on bridges, oil rigs etc. |
Submerged arc welding (SAW)
|
Medium |
Poor |
7 - 10 mm |
Very high |
Any - multipass |
Only use horizontally, used for high production runs for
example pipelines. |
Metal inert gas (MIG)
|
Low - Med |
OK |
3 - 4 mm |
Medium |
Any - multipass |
Used for production runs on thinner sections than SAW |
Tungsten inert gas (TIG)
|
Low - Med |
Good |
2 - 3 mm
|
Medium |
Any - multipass |
Used for similar applications as MIG but for longer
production runs |
Laser
|
Very high |
Very good |
< 0.5 mm for 12 mm thick plate |
Very high |
up to 30 mm |
Used for reasonably higher specification welds, becoming
more widespread as cost comes down, for example automotive
bodies. Low distortion process, requires good fit up no filler
wires (reduces cost). |
Electron Beam |
Very high |
Very good |
< 0.5 mm for 12 mm thick plate |
Low |
up to 250 mm |
Requires a vacuum, very expensive, used in aerospace
industry predominantly can be used for welding Al, Ti, Cu,
stainless steels and reactive metals. Low distortion process,
requires good fit up no filler wires (reduces cost). |