Selco Genesis 164 TLH/LIFT Instrucciones De Uso página 21

D.C.R.P. (Direct Current Reverse Polarity)
The reverse polarity is used for welding alloys covered with a
layer of refractory oxide with higher melting temperature in
comparison with metals.
High currents cannot be used, since they would cause an exces-
sive wear of the electrode.
D.C.S.P.-Pulsed (Direct Current Straight Polarity Pulsed)
(Fig. 8)
The use of pulsed direct current allows the welding bath to be
better controlled in particular operating conditions.
The welding bath is formed by the peak pulses (Ip), while the
base current (Ib) keeps the arc ignited.
This method helps to weld thinner sheets with fewer deforma-
tions, a better form factor and consequently a lower danger of
hot cracks and gas penetration.
Increasing the frequency (MF) the arc gets thinner, more con-
centrate, more stable and the quality of welding on thin sheets
is further increased.
Steel TIG welding
The TIG procedure is very effective for welding both carbon and
alloyed steel, for first runs on pipes and for welding where good
appearance is important.
Straight polarity is required (D.C.S.P .).
Preparing the edges
An accurate cleaning and preparation of the edges are required.
Fig.7
Fig. 8
Choosing and preparing the electrode
You are advised to use thorium tungsten electrodes (2% tho-
rium-red colouring) or alternatively cerium or lanthanum elec-
trodes with the following diameters:
Ø electrode (mm)
1.0
1.6
2.4
The electrode must be pointed as indicated in Fig.9.
(°)
30
60÷90
90÷120
Filler material
The filler rods must have mechanical characteristics com-
parable to those of the base material.
Do not use straps obtained from the base material, since they
may contain working impurities that can negatively affect the
quality of the welding.
Protective gas
Practically, pure argon (99.99%) is always used.
Welding Ø Electrode
current (A) (mm)
6-70 1.0
60-140 1.6
120-240
2.4
Copper TIG welding
Since the TIG welding is a process characterized by high heat
concentration, it is particularly suitable for welding materials
with high thermal conductivity, like copper.
For TIG welding of copper, follow the same directions as for TIG
welding of steel or specific instructions.
current range (A)
15÷75
60÷150
130÷240
Fig.9
current range (A)
0÷30
30÷120
120÷250
Gas nozzle Argon flow
n° Ø (mm) (l/min)
4/5 6/8.0 5-6
4/5/6 6.5/8.0/9.5 6-7
6/7 9.5/11.0 7-8
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