Page 122 - Welding of Aluminium and its Alloys

TIG welding 107

6.11 Modern TIG torch. Courtesy of TPS-Fronius.

Table 6.3 Suggested nozzle sizes and gas flow rates

Material thickness Gas nozzle diameter Shield gas flow rates
(mm) (mm)
Argon Helium
(l/min) (l/min)
up to 1 9.5 3.4 7.5
1 to 3 9.5 4.5 9.5
3 to 5 12.5 5.6 11.8
5 to 9 12.5 7.0 14.2
9 to 12 16.0 8.0 16.5
12 and above 25.0 12.0 21.0

the correctly rated torch is selected for the current to be used in produc-
tion. The manufacturer’s rating for a torch may be based on DC-positive
current and a torch rated in this way will need to be de-rated when used
with AC.
Most of the torches can be fitted with either metal or ceramic gas shrouds
although the ceramic shrouds are the most popular. They are, however,
rather more easily damaged than the metal shrouds. Nozzle sizes for a range
of thicknesses and gas flow rates are given in Table 6.3. It is recommended
that a device known as a gas lens is fitted to welding torches. This is a mesh
disc inserted into the torch which assists in providing a more efficient,
laminar flow gas shield with better coverage. The beneficial effect of a gas
lens is illustrated in Fig. 6.12.