Tig Welding (Continuos Arc); Introduction; Steel Tig Welding; Copper Tig Welding - Inteco Eagle 242 Instrucciones De Uso

5 TIG WELDING (CONTINUOS ARC)

5.1 Introduction

The TIG (Tungsten lnert Gas) welding process is based on the pre-
sence of an electric arc striken between a non-consumable elec-
trode (pure or alloyed tungsten with an approximate melting
temperature of 3370°C) and the work-piece; an inert gas (argon)
atmosphere protects the weld pool.
To avoid dangerous inclusions of tungsten in the joint, the elec-
trode must never get in contact with the workpiece; for this rea-
son the spark is started through an H.F. power source, thus ensu-
ring the remote striking of the electric arc.
Another type of start is also possible, with reduced tungsten inclu-
sions: the lift start, which does not require high frequency, but only
an initial short-circuit at low current between the electrode and
the workpiece; when the electrode is lifted, the arc will be started
and the current will increase until reaching the set welding value.
To improve quality of the end of the welding bead it is important
to control carefully the slope down of the current and it is neces-
sary that the gas goes on flowing in the welding pool some sec-
onds after the arc blowout.
Under many operational conditions, it is useful to be able to use
two preset welding currents and to be able to move easily from
one to the other (BILEVEL).
Welding polarity
D.C.S.P. (Direct Current Straight Polarity)
This is the most used polarity and ensures limited wear of the
electrode (1), since 70% of the heat concentrates on the anode
(piece).
Narrow and deep weld pools are obtained, with high advance-
ment speeds and low heat supply.
Most materials, exception made for aluminium (and its alloys)
and magnesium, are welded with this polarity.
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.

5.1.1 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
An accurate cleaning and preparation of the edges are required.
18
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 shown in the figure.
α α (°)
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

5.1.2 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.

6 TECHNICAL SPECIFICATIONS

Power supply voltage (50/60 Hz)
Max. absorbed power (x=40%)
Max. absorbed current (x=40%)
Absorbed current (x=100%)
Efficiency (x=40%)
Power factor (x=40%)
Cosϕ (x=40%)
Welding current (x=40%)
(x=60%)
(x=100%)
Adjustment range
Open-circuit voltage (limited)
Protection rating
lnsulation class
Construction standards
Dimensions (lxdxh)
Weight
Data at 40°C ambient temperature
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)
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
EAGLE 242
3x400 V +10% -10%
7.97 KW
15.70 A
10.10 A
0.90
0.76
0.99
240 A
185 A
160 A
6-240 A
73.8 V
IP23S
H
EN60974-1/EN60974-10
455x350x195 mm
16,2 Kg