Tig Welding Of Aluminium In Alternating Current - Selco Genesis G 200 TLH Instruction Manual

9.2.3 TIG welding of aluminium in alternating
current (only G 200/202 AC/DC)
The process can be applied to all the positions, but, given the
difficulties in bath support, flat welding is preferable.
Cleaning of edges of welding material is essential for successful
weldings. A brushing operation, eliminating part of the alumi-
nium formed on the surface, also proves to be useful.
In full penetration joints, it is important to use stainless steel rests
that enable the bath to be supported on reverse and protect it
against oxidising. The bests results in protecting the bath on the
reverse are gained by causing the inert gas to flow along the wel-
ding.
Preparing the edges
An accurate cleaning and preparation of the edges are requi-
red.
Setting up and use of electrode
Since the electrode is subjected to
high heat supply in alternating cur-
rent TIG welding, it cannot have
conical tip; it is rounded as shown
in the figure. In order to obtain the
indicated appearance, you simply
need to round off the sharp edges
of the electrode, the arc will then
ensure that a circular head is formed. If the tip acquires a drop
shape during welding, this indicates overloading, the electrode is
replaced with one having a wider diameter. Otherwise, you can
operate the Balance control by moving it to 20%.
In the following table we give the electrode selection criteria on
the basis of the maximum amperage with Balance equal to 50%.
Electrode diameter Amperage for pure
(mm) tungsten
(green colour) (A)
1.0
1.6
2.4
3.2
4.0
4.8
6.0
Amperage for tung-
sten+zirkonium
(white colour) (A)
30 30
70 55
120 100
170 150
220 210
280 280
400 400
Welding material
The welding material is selected in accordance with the base
material on which you have to work. On the market there are
bars made of silicon alloy aluminium (Si = 5%) for welding AI-
Si alloys and AI-Mg-Si alloys with 10% and bars made of alloy
with base magnesium composed of corrosion-resistent AI-Mg
alloys.
Protective Gas
Both argon and helium can work when welding aluminium. The
recommended gas outputs are:
Current (A) Argon (l/min)
50
100
150
200
250
300
Elio (l/min)
7 14
7 14
8 20
9 20
10 25
12 25
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