Tig Welding: Procedures And Technical Data - INE SKYLINE HFP3000 Manual De Instrucciones

INE SpA Via Facca, 10 - 35013 Cittadella - PADOVA - ITALIA Tel. 049/9481111 - Fax 049/9400249 - ine@ine.it - www.ine.it
When welding, the operator might accidentally bring the
electrode too close to the weld pool, thus causing a
short circuit and consequently the blowing out of the
arc. In this case, the power source momentarily
increases the welding current supplied until the short
circuit ends; this technique is called 'Arc Force'.
The techniques used to weld joints are several;
consequently, only a few indications on how to operate
can be given.
A
The figures above show two examples of a typical butt
(fig. A) and T weld (fig. B). The inclination of the
electrode varies according to the number of passes; its
movement is a traverse swinging with brief stops on the
bead sides in order to prevent weld material from
accumulating at the centre.
Welding with covered electrodes implies that the slag
shall be removed after each pass. This operation is
extremely important to achieve a uniform and smooth
weld. Slag is removed with a small hammer or with a
metal brush, if it is crumbly.
B
45°
Page 22
10 TIG welding:
technical data
TIG welding is carried out by means of an electric arc
sustained by a infusible electrode, of pure or alloy
tungsten. Unlike other welding procedures (MMA and
MIG) the electrode does not bring filler metal to the
weld. Filler metal is generally fed by the operator by
means of sticks made of the same material as the
workpiece. An inert gas shield (either Argon or Helium)
protects the arc. The electrode must not get in contact
with the workpiece, therefore the power source should
be equipped with an HF starter which causes the arc to
strike by means of a high voltage discharge (thus
avoiding any contact with the workpiece). But the arc
can also be started without HF. This type of arc start is
called "lift arc" and can only be used if the power source
is able to provide a very low initial short-circuit current
(few amps) which prevents the electrode from
consuming. This feature is a characteristic of inverters.
A TIG welding set is made up by:
- a dc or ac power source
- a torch with an infusible electrode
- an inert gas cylinder with a pressure reducer and flow
meter
TORCH WITH
FLOW METER
INFUSIBLE
ELECTRODE
FILLER
MATERIAL
TIG welding methods are several, and vary according
to the type of material and heat requested. The main
ones are illustrated below.
Direct current, direct polarity
By this procedure the torch is connected to the positive
socket of the power source and the work return lead to
the positive one. Most of the heat (about 70%) is
absorbed and given out by the workpiece, thus giving
deep penetration. This polarity is suited to all metals
except aluminium, magnesium and the relevant alloys,
but it does not offer any cleaning action.
procedures and
PRESSURE
REDUCER
POWER SOURCE