There are three groups of tubular electrodes are available for common use:
- The first group of wires are called gas shielded flux cored wires and these are meant to
be used with an external gas shield following the original developments in the 1950s.
- The first major variation of the gas shielded flux cored wire was the self-shielded flux
cored wire. With these wires, as the name implies, no external gas shield is used
(Figure 4.22) and instead all the required shielding of the arc and the weld pool is
provided by the gases formed by the break down of flux ingredients in the core and the
slag cover on the weld metal. A certain amount of nitrogen pick-up from the atmosphere
is unavoidable and therefore denitriders or nitrogen fixers such as aluminum are added
to the core ingredients.