15 Starting
the Weld The method used to start
the weld in a particular application will depend on such factors as the time
required for starting relative to the total setup and
welding time, the number of pieces to be welded, and the importance
of starting the weld on a particular place on the workpiece. The several methods
that are available are described below.
Note that in the descriptions, the actual controls and
switches that are operated to “start welding” are not
always named since these controls will differ depending
on the equipment being used. The instructions furnished
with the equipment will indicate what controls are used to close the contactor,
start the travel carriage, etc.
a. Pointed-Wire Start
With a pair of bolt cutters, cut the welding wire end
to a point and “inch” the wire down until the end just
contacts the workpiece. Apply the submerged arc flux
and start the weld. b.
Scratch Start “Inch” the
welding wire down until it is in light contact with the work, apply the submerged
arc flux, start the carriage, and then
apply the welding current. Because of the motion of the carriage, the welding
wire will not fuse to the workpiece, and
the weld will start. Scratch starts are
used when the starting position is not important, and when frequent starts must
be made, such as making girth welds on
small tanks or pipe. For such work, “flying” scratch starts can be made
by normally feeding the wire down to the
rotating workpiece through the layer of granulated submerged arc flux,
provided that fairly high current density is used.
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