17 d.
Molten Material Start Whenever there is
a molten puddle of submerged arc welding flux, a weld may be started by simply
inserting the electrode into the puddle and applying the
welding current. When two or more welding
wires are separately fed into one weld puddle, as is sometimes the case in
multiple electrode welding, it is only necessary to start
one wire by some other method to establish the puddle.
The other wires will then start when they are fed into this molten puddle.
e. Wire Retract Start
Retract starting is possible only when the welding equipment
is specifically adapted to this procedure. It is used
when frequent starts have to be made over a short total welding time and when
the starting position is particularly important.
Normal practice is to inch the welding wire down until
it just contacts the workpiece, making sure that good electrical
conductivity is established. Then the end of the wire is covered with submerged
are flux and the welding current is turned
on. As soon as the welding contactor closes, the wire retract starting device
embodied in the equipment momentarily reverses the feed
motor, preventing the welding wire from fusing to the
workpiece. If the workpiece is light gage,
the starting conditions become critical. The wire must make only the lightest
possible contact consistent with good electrical conductivity.
The welding head must be rigidly mounted. The end
of the wire must be clean. And the wire size must be chosen to permit operation
at high current densities since the higher
the current density, the easier the start. Continued
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