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Component Identification and Explanation
Explanation of MIG and TIG Operation
more than 5 degrees lean in either side to side direction.
Holding the wire too far off from the metal will result in rough starting and
too long of wire stick out.
Once the arc has been established, the gun can then either be pushed or
pulled in the direction of the weld. In either case, the gun nozzle should
be positioned directly over the weld without angling the wire to one side or
the other of the weld as already mentioned. The gun should have no more
than 15 degrees lean pointed into (push) or pointed away from (pull) the
direction of travel. In most cases a push motion is desired. However, a lot
of texts offer conflicting information on whether to push or to pull the gun.
In reality, both are correct if used correctly and with each having particular
strength and weakness. Either one done with too much gun angle will
result in undesirable results. Most learning minded people who are well
versed in MIG quickly develop a sense of when to push and when to pull
the gun. Even for novices, a sense of when to push and pull the gun
comes quickly with a little practice. Pushing can result in shallower pene-
tration but the molten puddle is easier to see and the arc sits easily on the
leading edge. It will usually leave a aesthetically pleasing bead. However,
be careful to prevent the gun from leaning toward or away from the direc-
tion of travel too much as spatter will increase and shielding gas flow may
become turbulent, creating porosity in the weld. Pulling will result in
deeper penetration, but can result in a narrow bead without much side
fusion. It also can leave an undesirable humped appearance if not done
correctly or if travel is too slow. Whenever MIG welding with Aluminum,
whether with the standard MIG gun or the Spool gun ALWAYS push the
gun. If using Flux Cored wire, a dragging motion is almost always recom-
mended.
Weaving in Welding. Weaving (oscillating the torch or electrode from side
to side in one pattern or the other), particularly in MIG, is a topic of con-
troversy as much as whether to push or pull the MIG gun. Stringer beads
are often best for novice welders. Stringers are simply straight beads that
move forward with little or no side to side travel or oscillation. These will
offer the soundest welds for a beginner in MIG or Stick. Stringer welds
leave little or no room for contaminates to enter the weld and are the fast-
est to produce without creating an opportunity for cold lap. Moving too
quickly however with a stringer can create undercut which will weaken the
weld. The best policy is to move a slow steady speed, making sure the
sides of the weld are filled. If undercut is present, it is either from too
much voltage or moving before the wire has time to fill the area the arc has
melted.
Think of weaving as a method of "sewing" the metal together. If weaving
is of interest to you, start with the basic weave pattern. Simple weaves
using one variation or the other of a cursive "e" motion are best to begin
with. Other weave patterns can be used of course. C's, V'S, U's , Trian-
gles and many more weave patterns can be used depending upon the
application. Weaves are employed for a number of reasons. Weaves are
often considered to have a more pleasing appearance and can help bridge
gaps where fit up is a problem. A weave is also frequently used to man-
age heat build up. For example: when welding vertically weaves are al-
most always used to prevent the molten metal from sagging due to the
force of gravity. The major drawback of weaving is that it introduces a
greater possibility of getting inclusions and other forms of contamination
in the weld. Properly done weaving is a valuable tool, but it must be prac-
ticed before employing it in any structural or critical application.
Metal Pre-Cleaning.
MIG and TIG welding requires a well prepped surface to obtain a sound
weld. The removal of paint, rust mill scale, or other contaminate such as
grease should be done before welding. Stick welding is more forgiving of
rust and mill scale, but when MIG welding, contaminates will result in
porosity and inclusions in the weld, weakening it. In TIG welding it can be
disastrous. TIG requires the most cleaning effort. A grinder will usually
prep the metal sufficiently to remove oxidation and paint. However, to
remove grease a degreaser such as acetone should be used. Do not use
any degreaser such a brake cleaner with chlorinated solvents or death or
serious injury may occur!
MIG and TIG filler wires such as ER70S-6 or ER70S-2 include a sufficient
level of deoxidizers such as silicone and copper that are formulated to
allow it to handle minor to moderate amounts of rust and mill scale. These
deoxidizers will float out most moderate amounts of contaminates out of
the weld and will appear in the usual form of glassy like deposits on top of
the cooled metal. They are easily brushed off before starting the next
pass. They should not be welded over. Any pinholes that appear are a
result of trapped gas in the weld and should be ground out before the next
pass. It should be noted that some MIG wires such as ER70S-3 have low
levels of deoxidizers and must be thoroughly cleaned and ground before
welding. MIG and TIG ER70S-2 and ER70S6 are the same except that TIG
wire is cut to lengths and MIG wire is continuous. When welding fine
gauge materials in TIG, you can substitute sections of thinner MIG wire.
Multiple Pass Welds.
One of the common misunderstandings that people have when beginning
to weld is that if the welder has the power, then a single heavy pass should
be used to weld it up. This is wrong. This technique is a good way to
induce cold-lap and inclusions into the weld. Single pass welds should
not exceed 1/4" even with the heaviest wire the welder is capable of han-
dling. A thick pass may also begin to cool before contaminates and gas
pockets have the time to float out to the surface. It's far better to make
multiple smaller passes to complete a plate weld for a higher quality result.
For best results, this requires that most joints 1/4" and over be prepared
with a grinder to accept multiple weld passes. The weldment edges
should be ground to form a V, U or J shaped groove to create a recess
where the welds can be welded one on top of another. For welding
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