32
Component Identification and Explanation
well versed in MIG quickl 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 lled. If undercut is present, it is either from too
much voltage or moving before the wire has time to ll 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 t 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 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 sufciently 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 ller wires such as ER70S-6 or ER70S-2 include a sufcient
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 ne
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
with .035” wire and under, create a bead no thicker than 3/16” in a single
pass, no more than 1/8” with .030” wire, and with .025”wire and smaller
no more than 3/32 for best results. This will help maintain proper fluidity
of the weld and prevent gas from being trapped in the weld and give time
for any minor contaminates to float out of the weld. It will also help to
maintain reasonable forward travel speeds. Too slow of travel speeds will
create excess build up and can tend to create cold lap at the weld toes
NOTICE:
This unit features a slow run-in when turned on. This means the wire will feed
slowly until the arc is started. It is used to improve arc initiation and reduce weld
porosity which results in poor fusion during the arc starting process. Once the arc
is sensed, the wire speed will ramp up and weld at the selected wire speed.
Explanation of MIG Functions and Terms
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