Arc Length; Rate Of Travel; Making Welded Joints - Ryobi MMA-140 Owner's Operating Manual

STICK (MMAW) BASIC WELDING TECHNIQUE

ARC LENGTH

The securing of an arc length necessary to produce
a neat weld soon becomes almost automatic. You
will find that a long arc produces more heat. A very
long arc produces a crackling or spluttering noise
and the weld metal comes across in large, irregular
blobs. The weld bead is flattened and spatter
increases. A short arc is essential if a high quality
weld is to be obtained although if it is too short
there is the danger of it being blanketed by slag
and the electrode tip being solidified in. If this
should happen, give the electrode a quick twist
back over the weld to detach it. Contact or "touch-
weld" electrodes do not stick in this way, and make
welding much easier.

RATE OF TRAVEL

After the arc is struck, your next concern is to
maintain it, and this requires moving the electrode
tip towards the molten pool at the same rate as it is
melting away. At the same time, the electrode has
to move along the plate to form a bead. The
electrode is directed at the weld pool at about 20º
from the vertical. The rate of travel has to be
adjusted so that a well-formed bead is produced. If
the travel is too fast, the bead will be narrow and
strung out and may even be broken up into
individual globules. If the travel is too slow, the
weld metal piles up and the bead will be too large.

MAKING WELDED JOINTS

Having attained some skill in the handling of an
electrode, you will be ready to go on to make up
welded joints.
When welding material up to 7mm in thickness
place the pieces 2-3mm apart, run the welding
bead along the join. A second bead can go along
the underside for extra strength (Fig.9).
When welding material from 7mm to 30mm thick
prepare the material as shown in Fig.10 filling up
the space with several layers of weld.
When welding together material over 30mm in
thickness prepare the material as shown in Fig.11
filling up the space with several layers of weld,
welding each side in turn with each welding pass.
Disconnect the Welding Power Supply from the
mains supply before changing or removing
electrodes. Use pliers to remove used electrodes
from the electrode holder or to move the welded
pieces.
THE MANUAL METAL ARC PROCESS
When an arc is struck between the metal rod
(electrode) and the workpiece, both the rod and
workpiece surface melt to form a weld pool.
Simultaneous melting of the flux coating on the rod
will form gas and slag which protects the weld pool
from the surrounding atmosphere. The slag will
solidify and cool and must be chipped off the weld
bead once the weld run is complete (or before the
next weld pass is deposited). The process allows
only short lengths of weld to be produced before a
new electrode needs to be inserted in the holder.
18
7mm
2-3mm
Fig. 9
60º
>30mm
2-3mm
6
5
4
3
2
1
Fig. 10
60º
>30mm
2-3mm
Fig. 11