Weldmatic 215 Operators Manual
10 Model No. CP111-0, Iss A 02/05
Quality, Reliability, Performance
7 Basic Welding Information
Choice of Shielding Gas
The choice of shielding gas is largely
determined by the consumable wire to be used.
Many proprietary shielding gas mixtures are
available.
The recommended shielding gases for use with
the Weldmatic 215 are:
• Mild Steel Argon +
5 to 25% Carbon Dioxide;
100% CO
2
• Aluminium Argon;
• Stainless Steel Argon + 1 to 2% Oxygen.
Consult your gas supplier if more specific
information is required.
Shielding Gas Flow Rate
In G.M.A. welding, one function of the
shielding gas is to protect the molten weld pool
from the effects of oxygen in the atmosphere.
Without this protection the weld deposit
becomes ‘honeycombed’ in appearance, an
effect which is described as weld porosity.
In draft-free conditions the gas flow rate
required to give adequate protection is
typically 10-12 litres/min. In situations where
drafts cannot be avoided, it may be necessary
to increase this rate up to 20 litres/min, and/or
to provide screening of the work area.
Weld porosity can also be caused by air
entering the gas stream through a damaged
hose, loose gas connection, or from restriction
in the nozzle, such as from excess build-up of
spatter.
When welding aluminium, particular care
must be taken with all aspects of shielding gas
delivery and workpiece preparation in order to
avoid weld porosity.
Establishing a Weld Setting
Once the consumable wire type, wire size
and shielding gas have been chosen, the two
variables that are adjusted in order to obtain a
the desired weld setting are;
• Wirefeed speed,
• Welding arc voltage.
The wirefeed speed determines the welding
current; increasing the speed increases the
current, and decreasing it decreases current.
The selected wirefeed speed must be matched
with sufficient arc voltage; a speed increase
requires an increase of arc voltage.
6 Normal Welding Sequence
Weld Start
Closing the welding gun switch initiates this
sequence of events:
• The gas valve is energised and gas flow
commences;
• The power source contactor function
is initiated. Welding voltage is applied
between the work piece and the
consumable wire.
• The wire drive motor is energised.
• The wire touches the work piece, and the
arc is established.
Weld End
Releasing the gun switch initiates this sequence
of events:
• The wire drive motor is de-energised, and is
dynamically braked to a stop;
• After a short pre-set period, known as
the ‘burn-back’ time, the Power-source
contactor function is released. This period
ensures that the consumable wire does not
‘freeze’ in the weld pool.
• The gas valve is de-energised and the flow
of shielding gas ceases.
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