voestalpine bohler welding URANOS 1800 RC Bedienungsanleitung Seite 29

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 com-
pared with metals.
High currents cannot be used, since they would cause excessive
wear on the electrode.
7.2.1 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
Careful cleaning and preparation of the edges are required.
Choosing and preparing the electrode
You are advised to use thorium tungsten electrodes (2% thorium-
red coloured) or alternatively cerium or lanthanum electrodes
with the following diameters:
Ø electrode (mm)
1.0
1.6
2.4
The electrode must be sharpened as shown in the figure.
(°)
30
60÷90
90÷120
Filler metal
The filler rods must have mechanical characteristics comparable
to those of the parent metal.
Do not use strips obtained from the parent metal, since they
may contain working impurities that can negatively affect the
quality of the welds.
Shielding gas
Tipically, pure argon (99.99%) is used.
Welding Ø Electrode
current (A) (mm)
6-70 1.0
60-140 1.6
120-240 2.4
current range (A)
15÷75
60÷150
130÷240
current range (A)
0÷30
30÷120
120÷250
Gas nozzle Argon flow
n° Ø (mm) (l/min)
5-6
4/5 6/8.0
6-7
4/5/6 6.5/8.0/9.5
7-8
6/7 9.5/11.0
7.2.2 Copper TIG welding
Since TIG welding is a process characterized by high heat con-
centration, 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 special instructions.
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