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WIRE WELDING

Preparation for Welding As for other arc welding processes the GMAW and FCAW processes require that the welder and welder’s assistant use correct protective equipment and face shields with correct shade filter glass. The guidelines given in the chapter on safety should always be followed. Preparing the equipment Before welding starts make sure that correct shielding gas in sufficient quantity is available, if shielding gas is to be used. Check that the equipment is set for correct polarity according to the wire, normally positive pole (+) to torch if solid wires are used, and negative pole (-) to torch for some flux cored wires.

Spatter must be removed to avoid disturbance in shielding gas flow.

Ensure that the return clamp is properly fastened to the workpiece, with good electrical contact. Poor return connection will influence on the equipment’s ability to provide the correct arc.

Mounting the wire spool • Check, and if necessary clean the wire feed rolls and the wire liner in the torch cable. Ensure that the rolls and liner are of correct size and quality for the wire to be used. Teflon liners are often an advantage for aluminium and stainless steel wires.

• Check that the torch contact tip and nozzle are free from spatter, and that the contact tip is of correct size for the wire to be used. Worn contact tips or liners should be replaced. When aluminium wire is used the contact tip should have a slightly larger inner diameter than with other alloys, to allow for the heat expansion in aluminium.

Use correct size contact tip.

4.03

A worn contact tip will give insufficient electrical contact.

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