LORCH Handy 200 BasicPlus Manuel D'utilisation page 42

18 Basics of welding
18 .1 Stick electrode welding
Coated stick electrodes are used for the
well-known manual metal arc welding pro-
cess (stick electrode welding). The coating
of the electrode melts off during the welding
process together with the core wire. The
coating generates the gas shield. Additi-
onally the coating may alloy the weld pool
with some elements, which are lost during
the arc process. On top of the melted bath
a slag layer is generated, which covers and
protects the freezing bead against the air.
The coatings of the electrodes differ from
thickness and type, i.e. chemical composi-
tion. This results in different welding proper-
ties and consequently different applications
for the electrodes. Types and nomenclature
is defined in DIN EN 499 (formerly DIN
1913).
coating
Arc
18 .2 TIG welding
The TIG welding process is a universally
applicable procedure which leads to high-
quality joints.
The electrode of the TIG-process consists
of non-melting tungsten, the shielding gas is
an inert gas.
Inert gas is chemically neutral and does not
react with the weld metal. Inert gases are e.
g. Argon, Helium, and their mixtures. Usually
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Stick
electrode
Core rod
Gas/slag
Molten zone
pure Argon (99.9 %) is used. The shielding
gas shall be dry. DIN 32 526 defines the dif-
ferent types of shielding gas.
Basics on TIG welding
A non-melting tungsten electrode is posi-
tioned through a clamping sleeve into a
gas- or water cooled torch. The arc burns
between electrode tip and workpiece in
an inert shielding gas atmosphere. So the
tungsten electrode acts as an arc carrier.
The arc melts the workpiece point by point
and forms the weld pool. The shielding gas
escapes through the gas nozzle. The gas
protects the tungsten electrode, the arc, the
weld pool against the environmental air. So
an unfavourable oxidation is avoided. Con-
sequently poor welding results may occur
from trouble of shielding gas supply.
In case additional filler material is required,
filler wire is supplied either manually, like
gas flame welding, or automatically by me-
ans of a cold wire feeder. The filler wire shall
be equal to or higher alloyed than the base
material. Without filler wire, flange and cor-
ner welds may be easily manufactured.
Shielding gas
Tungsten-
electrode
Gas
nozzle
Shielding gas
Welding seam
Arc
Basics of welding
Filler wire
Power source
Workpiece
10.15