Weldmatic 180 | Operator Manual | Model No CP141-1
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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 180 are:
– Mild Steel :
Argon + 18% Oxygen;
Argon + 2%
5% Carbon dioxide;
– Aluminium: Argon;
– Stainless Steel: Argon + 1 to 2%
Oxygen.
Consult your gas supplier if more specific
information is required.
Shielding Gas Flow Rate
In GMAW, one function of the shielding gas
is to protect the moulten 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.
6 NORMAL WELDING SEQUENCE
Weld Start
The wire feed has an in built “creep” function.
When the trigger is pressed the wire will
slowly feed out, until the wire touches the
work piece, then the arc will start, wire
speed will change to set speed.
Closing the welding gun switch initiates this
sequence of events:
– The gas valve is energised and gas flow
commences;
– Welding voltage is applied between the
work piece and the consumable wire.
– The wire drive motor is energised.
– The wire creeps out.
– The wire touches the work piece,
and the arc is established.
– Wire speeds up to selected speed
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;
– The welding current stops.
– The gas valve is de-energised and the
flow of shielding gas ceases.
The quality of the consumable wire
greatly affects how reliably a gas
metal arc welder will operate. For
best results when welding mild
steel, we recommend quality WIA
AUSTMIG ES6. Dirty, rusty or kinked
wire will not feed smoothly through
the gun cable and will cause erratic
welding. Deposits from the wire will
clog the gun cable liner requiring it
to be replaced prematurely.
