20 |
of the current, polarity, type of basic material and
composition of protective gas.
4. sharpening of tungsten electrodes - sharpening the
tip of the electrode should be done in traverse/
horizontal direction. the tinier the roughness of
the surface of the tip is, the calmer the burning of
the el. arc is as well as the greater durability of the
electrode is.
5. the amount of protective gas - it has to be adjusted
according to the type of welding or according to
the size of gas hose. after finishing the welding gas
must flow sufficiently long to protect material and
tungsten electrode against oxidation.
Typical TIG welding errors and their impact on weld
quality
the welding current is too -
Low:
unstable welding arc.
High:
tungsten electrode tip breaks lead to turbulent
arcing.
Further, mistakes may be caused by poor welding torch
guidance and poor addition of additive material.
Welding in methode MMA
switch the machine to mma mode - coated electrode.
table 5 lists the general values for the choice of
the electrode, depending on its diameter and the
thickness of the base material. these data are not ab
-
solute and are informative only. For exact selection,
follow the instructions provided by the manufacturer
of the electrodes. the current used depends on the
position of the welding and the joint type and inc
-
reases according to the thickness and dimensions of
the part.
table 5
Strength of welded
material (mm)
Diameter of the
electrode (mm)
1.5 - 3
2
3 - 5
2.5
5 - 12
3.25
> 12
4
table 6: setting the welding current for the given
electrode diameter
Diameter of the
electrode (mm)
Welding Current
(A)
1.6
30 - 60
2
40 - 75
2.5
60 - 110
3.25
95 - 140
4
140 - 190
5
190 - 240
6
220 - 330
the approximate indication of the average current
used for welding with ordinary steel electrodes is gi
-
ven by the following formula:
I = 50 x (Øe – 1)
where: i = the intensity of the welding current e = the
diameter of the electrode
example for an electrode with a diameter of 4 mm:
i = 50 x (4 - 1) = 50 x 3 = 150 a
Correct electrode holding during welding:
45°
β
45° +70°
picture 6
Preparation of basic material:
table 7 lists the material preparation values. specify
the dimensions as shown in pic. 7.
a
s
α
d
picture 7
table 7
s (mm)
a (mm)
d (mm)
α (°)
0 - 3
0
0
0
3 - 6
0
s/2 (max)
0
3 - 12
0 - 1.5
0 - 2
60
en
