30
| en
1
2
3
4
5
6
7
1-3 mm
1-3 mm
1-3 mm
8-10 mm
0 - 5 s
POST GAS
I
0
ON
IW
I
START
I
END
picture 1 - welding process at tiG la
Selection and preparation of tungsten electrodes:
table 1 shows the welding current and diameter values for tungsten
electrodes with 2 % thorium - red electrode markings.
table 1
Diameter of the Electrode (mm)
Welding Current (A)
1.0
15 - 75
1.6
60 - 150
2.4
130 - 240
prepare the tungsten electrode according to the values in table 2 and
picture 2.
picture 2
α
table 2
α (°)
Welding current (A)
30
0 - 30
60 - 90
30 - 120
90 - 120
120 - 250
Grinding of tungsten electrodes:
By proper choice of the tungsten electrode and its preparation will affect
the properties of the welding arc, weld geometry and electrode life. the
electrode must be gently grinded in the longitudinal direction as shown in
picture 3. picture 4 shows the effect of grinding the electrode on its service
life.
picture 3
picture 4
Picture 4A -
Fine and even grinding of the electrode in the longitudinal
direction - lifetime up to 17 hours
Picture 4B -
coarse and uneven grinding in the transverse direction - lifetime
about 5 hours
parameters to compare the influence of the electrode grinding method are
given using:
hF ignition el. arc, electrodes Ø 3.2 mm, welding current 150 a and welded
material - pipe.
Protective gas:
For tiG welding, it is necessary to use argon with a purity of 99.99 %. deter
-
mine the amount of flow according to table 3.
table
3
Welding
current
(A)
Diameter of
electrode
(mm)
Welding nozzle
Flow of gas
(l/min)
n (°)
Ø (mm)
6 - 70
1.0
4/5
6/8,0
5 - 6
60 - 140
1.6
4/5/6
6.5/8.0/9.5
6 - 7
120 - 240
2.4
6/7
9.5/11.0
7 - 8
a b
Holding the welding torch during welding:
90°
45°
position W (pa)
position h (pB)
10 – 30°
15 – 40°
position s (pF)
10
- 30°
20 - 30°
position s (pF)
Preparation of basic material:
table 4 lists the material preparation values. dimensions are determined
according to pic. 5.
picture 5
a
s
α
d
table 4
s (mm)
a (mm)
d (mm)
α (°)
0 - 3
0
0
0
3
0
0.5 (max)
0
4 - 6
1 - 1.5
1 - 2
60
Basic rules during welding by TIG method:
1.
purity - grease, oil and other impurities must be removed from the weld
during welding. it is also necessary to mind purity of additional material
and clean gloves of the welder during welding.
2.
leading additional material - oxidation must be prevented. to do so,
flashing end of additional material must be always under the protection
of gas flowing from the hose.
3.
type and diameter of tungsten electrodes - it is necessary to choose them
according to the values 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 ge
-
neral values for the choice of the electrode, depending on its diameter and
the thickness of the base material. these data are not absolute and are in
-
formative 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 increases according to the thickness
and dimensions of the part.
