The
increase in popularity of gas metal arc welding in recent years has caused a surge of welders
to take advantage of this versatile labor saving process.
Dr. Billy Harrell, Chair of the Division of Agricultural Sciences and Vocational Education
at Sam Houston State University, who has over 30 years of welding experience and 20 years
of instructional experience, will discuss the safety and setup of the gas metal arc
welder. Dr. Harrell also will perform and discuss 12 different gas metal arc welds.
We're going to take a few minutes to look at a MIG or GMA welding machine. You'll notice
that I'll use MIG sometime and GMA sometime. MIG is an older term that was used to describe
this process. This process uses a small diameter continuous electrode or wire. This particular
wire that we're running in this machine today is 35 thousandths of an inch in diameter.
If you wonder how much 35 thousandths is, it's rather small. It's about seven or eight
sheets of notebook paper stacked on top of each other. It's about the diameter that you
are, the gap that you would set a spark plug on an old tractor engine. So it's a rather
small wire. This wire is mild steel wire. It is copper clad. It has a coating of copper
on it that's electronically placed on the wire. The reason for the copper clad is to
give it shelf life. If we just had mild steel wire without the copper coating on it, we'd
put it in our shops, we'd put it on our machines, and it would develop an oxidation or rust
coat on it. And this oxidation as it fed through the machine, through the cable in the machine,
would cause a restriction to the movement of the wire and we could not use the process.
So most of the wire is copper clad. And this is 35 thousandths of an inch mild steel wire.
The wire that we're using today is type 28 wire. This wire comes in spools. And we'll
see a spool out of a box in a few minutes, but you should not open a box of wire until
you're ready to use it. When you open it, you take the protection off of it and you
reduce the storage life of it. So this is a sealed box. It has the information on the
front of it. It's 70 X wire. It has 70 thousand pounds plus tensile strength per square inch.
It is type 28 wire. Type 28 wire is a wire that is specially formulated for CO2 welding.
For welding of materials where it may have surface rusting and a lot of the things that
we weld in agricultural construction repairs are not that clean. It's primarily for new
metal where you do just have surface rust, but it's not that clean. So we use type 28
wire. There's also type 18 wire, type 25 wire, and other types of wire. But type 28 is a
specially formulated CO2 wire that is adapted to the welding conditions that we will use
it in. And we'll look more at an open spool in a few minutes. There are many references
that are available that will help you to understand the welding process. This particular reference
right here is called metal inert gas welding or MIG welding. And when I first started talking
to you a few minutes ago, I told you that sometime I might slip and say MIG. This reference
says MIG. But a better term is GMA or gas metal arc, meaning metal inert gas for MIG
or gas metal arc for GMA. There are six naturally occurring inert gases. The two that are used
in welding most frequently are argon and helium. In order to make this a competitive process
where it could compete with the stick electrode and it is now becoming the industry standard,
they developed how to develop a shield gas that would provide an economical weld. So
in the search, they developed the CO2 welding process. At welding temperatures, CO2 is not
an inert gas. That's the reason for the change in the term from MIG to GMA. At welding temperatures,
your CO2 gas will allow you to weld medium and high carbon steels, which if we were welding
with a stick electrode, we'd have to use a 70-18 electrode to weld. So it's very good
for mild steel. It will also allow us to weld medium and high carbon steels with the same
filler rod, the type 28 filler rod that we would use if we were welding mild steel. Let's
look at the equipment a little. This is the power supply. With GMA welding, you have a
power supply. Normally, this power supply is a DC power supply. Most GMA welding is
done with reverse polarity DC current. This particular machine is a three-phase machine.
In your lab, you may have a smaller machine that is a single-phase machine. This machine
adjusts by voltage. You may have a machine that adjusts by plugging your leads into different
voltage settings or amp settings on the front. You may have a machine that has a graduated
scale on it that you adjust by metal thickness. But in all, you're doing basically the same
thing. This is a constant voltage machine. As we change our arc length, voltage remains
near constant. So we do not have to pay as much attention to the arc length. It needs
to be somewhere around a quarter to three-eighths of an inch. We don't want to get it too long
because the electrode will tend to flex as it goes down. We don't want to tend to get
it too short because it will melt back up into our contact tube. But we do have some
variation in arc length that we're allowed in running this machine. It is a constant
voltage machine. On this machine, the first thing that we're going to do is adjust shield
gas. In order to adjust shield gas, the machine must be on. Shield gas is, the flow of shield
gas is measured in standard cubic feet an hour. This is done by either a fixed pressure
regulator or a flow meter. This machine is equipped with a flow meter. With a fixed pressure
regulator, we'd have to go inside and change an orifice in the bottom in order to change
flow. With a flow meter, we can change flow by noting the location of a float ball in
the side glass. And we can adjust and center that float ball on the cubic feet that we
want the flow an hour. So with the machine on, I will open the cylinder and I don't want
to stand right here. This is not as high a pressure as oxygen, but still it is high enough
pressure that something could happen. So I'm going to walk around and I'm behind. This
is the same type of valve that you would have on an oxygen cylinder. So we open it slowly
and then we seat it open. It is a double seating valve, so we seat it open. Then we look at
this gauge right here and this will tell us how much pressure that we have in our cylinder.
This is cylinder pressure. Then with the machine on and running, we look at the side glass
and we adjust the float ball until we get it to what we want. This being 20 cubic feet
an hour. Now references like this one will give you an indication of where to adjust
your shield gas flow. In our lab, we found that if we keep cross draft out, if that 20
cubic feet an hour has been successful for most of what we've tried to do. If you're
welding, you begin to get porosity in your weld, then you do not have enough shield gas
flow or your shield gas is being blown out of your weld zone by a cross draft. This process
cannot be accomplished where you have a lot of air movement. It has to be done where the
shield gas will stay in and exclude the oxygen and nitrogen from the weld zone that are present
in the atmosphere. The shield gas replaces those and allows us to produce the weld that
we want to. Now with shield gas adjusted, it's very important that we adjust shield
gas, that we get the correct flow and cubic feet per hour and we set this at 20. That's
a good starting place. The next adjustment that we make, we go to the machine and this
is a power supply. This is going to produce the welding current. We go to the machine
and we look over here on the left of the machine and we see a band, a red band on a graduated
scale here and these indicate voltages, but all they're going to do is indicate voltage.
We're going to set this at 21 volts and depending on the metal that you're welding and we're
talking about the thickness of the metal that you're welding, normally voltage will be somewhere
between 16 and 28 or 29 volts. In our lab, most of the time if we're welding say 12 gauge,
we'll set the voltage somewhere around 19 volts. If we're welding say quarter inch or
three sixteenths or thicker, we'll set the voltage around 21 or 22 volts, but these are
relative things. They're things that can change. So I'm going to take the crank on a hand wheel
and I'm going to crank this up to about 21 volts, which is somewhere right in there.
Here's 20, here's 21 or 22 rather, so somewhere right in here would be 21 volts. That is not
accurate. I can't use that. In order to get the voltage right, we'll run a machine and
we'll set the voltage where we read 21 volts on the voltmeter. Now while I'm doing this,
if you'll pay attention to the amp meter, you'll see as the voltmeter moves, the amp
meter is also going to move, but this is an automatic move because the amp curve is wired
into the volt curve. On this machine, we do not adjust amperage. We adjust amperage by
one, the voltage it's set on, and by two, the arc length that we're running would cause
amperage to vary. So with the machine running, we will adjust voltage. We're low. I turn
the wheel the right way and I don't know whether you can hear it or not, but you could tell
a difference in the way it was running. We set in and we set where we're holding a constant
21 volts. Now if we look back here, see we're up over 22 volts on this estimated volt scale,
but if we look over here, we're holding a constant 21. If we look right here, we're
running a little over 100 amps. And as we change this, this will automatically change.
That concludes the adjustments that we make at the power supply. This power supply could
have built into it a wire feeder, and many do have the wire feeder attached. Or in most
industrial applications for mobility, the wire feeder is attached to by cables and can
be up to 200 feet from. The wire feeder that we're fixing to go to that we use in our lab
has 50 foot of cable. We're limited in where we can put this machine. We're limited in
how far we can be from our wire feeder, but we can move our wire feeder in where we want
it to. So I'm going to move now from the power supply, it's on, the voltage adjustment is
made, the shield gas flow adjustment is made, so we're going to move now over to the wire
feeder that's over by the welding area. Now moving over to the wire feeder. As we said
just a few minutes ago, this wire feeder may be built into your machine. But in a lot of
industrial applications and a lot of applications in our lab, we need the wire feeder remote
from the machine so that we can get close to the work that we're doing. We're limited
in how far we can be from the wire feeder. Normally the longest cables are somewhere
in the neighborhood of 11 to 12 feet. Because this has, when we're pushing wire, this has
a spring steel cable in it, a lot like a control cable on your lawnmower or speedometer cable
that the wire pushes through. And it needs to be straight, it needs to not have kinks
in it, if you bend it it's going to give problems, it must be clean. So we're limited in how
far we can be from the wire feeder. The wire feeder can be located up to 200 feet from
the power supply. If we look at the wire feeder, we have a control box. On this control box
you can have different options. This particular one has an on off switch and has your wire
feed adjustment in inches per minute. It could have others. For what we do, these are the
two basics and these are the two that we need. This is the gun. If we turn it around, allow
me to move, if we turn it around and we look at the side of it, we can see more parts of
the wire feeder. Now it's just on a caddy that we built that has a storage for the cable,
has a storage for the ground that allows us to move it around. This could be on a boom
overhead, could be any configuration you can think of. This is the spool of wire. We said
a while ago that these spools are normally 25 to 30 pounds, in fact the one we looked
at I think weighed 33 pounds. But it has an adjustment on it. The adjustment on it is
the tension control on that spool. As this wire feeds off, it should feed off smoothly
so that we'll have an equal distribution of wire going to the feed rolls. These are the
feed rolls. This is a four feed roll machine. It has two prior and two after. This allows
for smoother feed of the wire. The tension on the feed rolls is important. We don't want
to get the tension so tight that we tend to crimp the wire. If we tend to flatten the
wire, it makes it where it's more difficult to feed through. And it has to feed through
without resistance. If we get resistance to feed through, we're going to get uneven feed
of wire and we're going to get a weld that is not the quality that we wanted. So the
tension is important. It must be tight enough to hold and not allow it to slip. So some
manufacturer will tell you to pull through by hand, pull the wire through by hand until
you get resistance to pull through and that's tight enough. If you start getting slipped,
then you'd have to tighten a little more. This is a mechanism that's put on here. It's
a little felt pad that's put on here to remove some of the contaminants get on the wire during
as it's being used. You may or may not use specific lubricants on your wire. If you use
a lubricant on the wire, be sure it is specified by the manufacturer for use in their machine.
A lot of, some manufacturers will say no lubricants, but there are some specially designed lubricants
that can be used to clean the wire and make it feed through more smoothly. The wire, if
it gets, if it gets, you get a coat of oxidation on the outside of it, you may have to peel
off at least one layer of wire. It's wound on here tight and a lot of times if it's been
in storage awhile, the outside of it will become contaminated. We put a cover over this.
When this is not in use, we'll lay a cover over to minimize the oxidation, to minimize
the dust contamination that we get on this wire. The only maintenance primarily is to
keep the tube clean and you keep the tube clean by blowing the tube out with compressed
air. Each time you change a spool of wire, you blow the tube out with compressed air.
Let's go back to the front of it. Okay, if we look at the gun, look at the MIG gun, it
has a control switch on it here that turns it on and when you get ready to weld, you
pull this, there are contactors in the machine that when you pull this trigger, you turn
the welding current on, you turn your shield gas on, and you turn your wire feed on. So
when you get ready to weld, you put the gun where you want it, you pull the trigger and
all of this begins. When you get ready to stop a weld, you get to where you want to
stop the weld, you release the trigger and all of this stops. In order to use this, you
really need a pair of dikes and the dikes are only used to keep your wire trimmed. Trim
off extra wire so that when you start, you won't have a whisker, you won't have extra
wire sticking up, it makes it easier to start. You need something to keep the spatter from
forming on the tip, so we use a spatter guard. And you can just dip your tip in the spatter
guard, this is a gel type, just dip your tip in the spatter guard. When it's cold, you'll
get an excess on there and you may have to wipe some of it off, but as you use it, this
is going to be warm so you dip it in there and you're just going to get a thin coat of
spatter guard on. This may be in an aerosol farm, may be in gel farm, we really prefer
the gel farm. But you do need to use a spatter guard unless it's specifically stated that
you should not use a spatter guard with this equipment. And some manufacturers may still
say that no spatter guard will be used, but you have to keep it clean. One of the reasons
that you have to keep it clean is because right here around the tip, we have holes and
this is where the shield gas flows out. The shield gas flows out through your cone here
and if this becomes plugged, shield gas is not going to flow, or it's not going to flow
evenly. So you need a little piece of wood, something soft, that you go around here and
you keep that clean with. You shouldn't do this with something hard, you know, that will
cause scratching, whatever, but a stick out of an ice cream bar or something like that
works real well. But you need something to keep that spatter out. Now when it's clean
and you keep spatter guard on it, that's going to be very easy to do. The last thing that
the wire goes through is this contact tube or contact tip. Some references are called
a contact tip, others will call it a contact tube. But this is the last thing the wire
goes through. This also conducts the current to the wire. So the contact tip needs to be
in good shape. These come in sizes for the size of wire that you're running. What we
have here is a 35 thousandths contact tip. It screws into the end of the torch, or the
gun. And you may need a pair of wire pliers to do it, you may not. It should be screwed
up tight. The new tip, you fit it over, be sure that you cut the wire so you don't have
a big rough place on the wire to score the tip as you put it in. And then you screw it
in and you screw it up tight. Then the cone is also replaceable. It will also wear out.
Over time it will erode, it may get damaged physically, you may bend it, whatever. So
it's also replaceable. This is a good cone. I'm not going to put this new one on, but
here is a new one. And another thing that you have to watch pretty close on these are
your insulators. This is a plastic material and they go on in different ways, but this
particular one screws on and it does have a top and it does have a bottom, but it screws
onto your gun and you want to put it on the right way and be sure that it's all there
because this is what keeps your cup from touching your contact tip. If this gets broke, your
cup will be loose on the end. The cup can come over and touch the contact tip. If it
touches the contact tip, you're going to have arcing there or if it gets loose enough and
it comes over and touches your tip here, you can actually damage the tip. So we do have
insulators that are replaceable, contact tips we need to keep in supply and cups we need
to keep in supply. And those are the main things that you do. When you push it on, the
amount of stick out or lack of stick out will depend on the type of welding that you're
going to do. I'm going to push it on and I'm going to get it to where it's just almost,
the contact tip is just almost flush with the cup. Okay, so we have the torch or the
gun in adjustment. Now, I clicked it a time or two by accident. When we touch this, we
will turn it on. Now, the next thing that we're going to do is set our wire feed control.
So in order to set wire feed control, the machine must be running. It's like when we
set voltage a while ago. We had an indicator of where voltage would be. We have an indicator
of where wire feed will be, but this is not accurate. When we set wire feed control, the
machine must be operating. The operator must maintain pretty well a uniform arc length
as the machine is operating. And then we adjust this by sound. If you have an engine, you're
going to adjust the carburetor on it. You may listen to it and get it where it runs
smoothly and say the carburetor is in adjustment. On this GMA machine, we're going to have it
running. We're going to adjust this. We have a wrist stat on the front. We're going to
adjust this until it sounds right. I do not have to look at it. His assistant runs it.
He will notice the difference. I will hear the difference. And he could tell me when
it's about right if he wanted to, or I could tell him when it's about right if I want to.
So if you'd step forward, take it and run it, I will make the adjustment. I hope that
you can hear it running. I'm moving a wrist stat. Now we don't move this wrist stat much.
A little bit of difference can make a lot of difference. But we move this wrist stat
until we get a very even sound at the gun. And when we get a very even sound at the gun,
we have wire feed adjustment. I'm certainly not going to say that this machine is trouble
free because it's not. Frequently, you'll have to make minor repair and adjustment to
it. The only really routine maintenance that you need to do this machine is keep the wire
feed cable clean. And in order to do that, at least each time you change a spool of wire,
you should take compressed air and blow that cable out. To do that, we'll take the cable,
we'll pull the tip off of the gun, we'll take the contact tip out, and then we'll take compressed
air, shop air. And if we get this pretty straight, it's better. We'll take compressed air and
we'll blow through that liner. And when we blow through that liner, what we're going
to do is remove the dust that has been drawn into that liner by the wire. And we're also
going to move the little flakes of copper that have been deposited in there as the wire
has been through. Of course, we said earlier the copper is necessary because without the
copper, we'd have oxidation of wire. So each time that we change a spool of wire, and if
we have trouble in between running a spool of wire, we should clean the liner. And you
clean the liner by removing the contact tip, taking compressed air, and blowing the particles
back out of it. Remember, when we put the contact image in, it should be tight. I mean,
we may want to take a pair of pliers and snug it, but it should be tight. Be sure that it's
screwed all the way in. If we operate it without it, current flows through it. If we operate
it without it, we'll have a high resistance area there. Now, to continue with feeding
the wire, a new spool of wire into the gun, we put the wire onto the gun. And then we
take the wire and we start feeding it through the feed rolls. We feed it through the guide
tubes. Now, this wire should be as smooth cut on the end as you possibly can get it.
We should not take a pair of dikes and just cut wire like that. If we take a pair of dikes
and just cut wire like that, rub your finger over it. It's going to have sharp edges on
it. As this goes through your guide tube, well, it will scratch your guide tube. So
the best thing to do as much as possible, take your dikes and try to cut that wire where
it is as smooth as possible on the end. Now, it will not be perfectly smooth, but as smooth
as possible. Then if you're using something to keep your wire clean, go ahead and install
that on your wire like we're using this felt pad to remove some of the dust, some of the
flakes that could get into the cable. Go ahead and install it. Try to keep your wire from
coming loose on your spool. Feed it through your guide tube. Pick up, we have it loose,
so we pick up the back, we feed it into the center guide tube, and then we can slip the
spring and adjusting screw on, we feed it on through to the front guide tube. Now, the
front guide tube as far as adjustment is the most critical. The front guide tube should
just almost touch the feed row, almost touch. So we get it into the front guide tube, okay?
Now we go ahead and put the feed rows back down, put slight pressure on them. We don't
need too much pressure on them. We said earlier if we put too much pressure on them, we'll
tend to flatten the wire. We want to feed the wire. We don't want the wire to slip,
but we certainly don't want to flatten the wire. Okay, now with it in this position,
we have the wire. We've cleaned the tube. We have the wire in. We have it through the
rear guide, center guide. We're into the front guide. It's going in, into the tube. Then
if one of my assistants will come forward and take the gun and hold it out straight,
we want the cable as straight as we can get it. So we'll pull it out straight. And now
we'll finish feeding by turning the gun on. So we see the wire start feeding. We see the
spool turning. We see the feed rows turning, and we're feeding wire through the gun. If
we didn't have the tube straight, if we had our hose kinks in it, it tend to hang as it
goes through. So you want to get it just as straight as you can because we have the end
of this wire feeding through there, and it can tend to hang up. It seems like it takes
a while. It does take a while. We're feeding about 10 foot of wire through here right now.
But in a second, it'll start coming out the end of the gun. There it is, okay? Just turn
it up. Now, to check adjustments, to see if adjustment is about right, one thing we can
do, we can see how much pressure it takes to pull that through. And we have resistance
to pull. We might even loosen them up a little. Remember, we don't want them too tight, but
we don't want them to slip. We want it where something happens out here at the contact
tip that we don't get a bird nest here. We want it to slip if it has extreme resistance
to move, but as long as it doesn't have extreme resistance to move, we want it to feed through
the gun. Okay, then after we've done that, we simply take the dikes, trim the wire off.
If this is a new setup that hasn't been used, we take our spatter guard, we put a coat of
spatter guard on it. We should look and be sure that our contact tube or contact tip
is about the center. We should make sure that our insulators are keeping the cup away from
the contact tube, and this should be clean so shield gas would blow out. So the machine
is ready to run. What we're going to do next is take this machine and perform the commonly
made welds with it. Not all of them, but part of them. We'll start off with just we'll run
an arc, and then we'll do welds like butt welds, lap welds, T welds, verticals up, verticals
down, horizontals, and if you will continue to do that, you can develop a skill in operating
this machine. I've now changed clothes and moved into the welding area. The first thing
let's look at is safety. We need to understand the operation of the machine. We need to understand
how to adjust the machine, but we need to understand how to operate it safely also.
One of the basic things is proper dress for welding. I have on a long sleeve cotton shirt,
I have on cotton pants, and the legs are long enough to go well down over high top boots,
and I have on steel toe boots. In addition, I have on industrial quality class B safety
or eye protection, and I'll wear dry leather gloves. These dry leather gloves will insulate
well enough as long as I handle this equipment by the parts that are intended to be handled.
Any time that I am working with the cup or with the contact tube or with the wire, the
machine should be off, and the machine is off at this time. So another thing, this machine,
this welder should be properly grounded. It should be installed by a competent electrician.
As with any other welding, we want to be sure we don't have any flammable combustible
materials around when we're welding. We need to avoid welding in damp areas. We need not
to be grounded to the material that we're welding on, and we need to follow the good
basic rules with any arc welding process. Now, let's turn the machine on. We adjusted
the machine earlier. We adjusted the shield gas flow. We adjusted the voltage on the machine.
We adjusted the wire feed on the machine. I put on my gloves, and let's look at striking
an arc or starting an arc. With the MIG welder or GMA welder, we need a pair of dikes in
our pocket. We can use the dikes to trim the wire. We want about a quarter inch or so of
stick out when we get ready to run the machine. When you get ready to start a MIG, position
the torch where you want to begin the weld. When you pull the trigger, wire feed starts,
current flow starts, and shield gas flow starts. And we'll continue until you reach the end
of the bead, and then you release the trigger, and you stop the bead. So to run a bead, we
position the gun where we want to begin. We pull the trigger. We run the bead through
until we want to stop the bead. We let the trigger off, and then the bead stops. Let's
now run a bead.
We're now welding with a GMA welder. Gas, metal, arc. We're using a 35,000-mile steel
wire. We're using carbon dioxide, CO2, for shield gas. We run it through a constant voltage
machine using DC reverse polarity current. In order to operate it, we set the shield
gas, use a flow meter to control it. We're showing the flowing shield gas at about 20
cubic feet an hour. The side of the wire, the thickness of the metal. The type of shield
gas would cause us to vary. If we were getting penetration or frost in the weld, we'd know
we needed to change the shield gas. I'm not using any motion. I'm just going back and
forth, just using a little wrist movement. Just having side to side. So we set the shield
gas, and then we set the voltage. We're welding on this quarter-inch angle iron, three to
three by quarter. It'll be quite a bit of metal here. We'll run about 22 volts. Then
we set the wire feed to the voltage. Arc length is not critical. If it gets too short, we'll
get the burn back up into the contact cube. If it gets too long, the wire will flex and
not run even. When everything is set right, this machine should run, sound a lot like
a good running engine. Even, smooth. We run a second pass. We're still running in the
flat position. Learn to control. Learn to maintain the arc, which is easy. All we have to do
is keep the contactor closed, switch on the handle. We're doing about like we did with
the stick rod. We run about a third lap. Run right up to center. First pass in the metal.
About a third on, about a third off, about a third in the center. We're at what's called
trailing. The wire is behind the gun. You get deeper penetration when you're trailing
than you do when you're leading, but it can be run lead. It's harder to see where you're
going in the trailing position. That's one of the disadvantages, because you do have
a lot of metal in the way. If you've got a very tight crack to follow, sometimes it's
hard to see or break, and it's harder to see in the trailing position. We're now going
back, and this time we are running in the leading position. Can be run this away. Sounds
a little bit different. It will not be quite as deep a penetration as if you run in the
trailing position, but it can be run this away. Advantage of this is it's a lot easier
to see where you're going. In the trailing position, sometimes you have to merely guess
where you're going. Mid can be run in any position. We're now running vertical down,
which will give us more penetration, a better well than vertical down run with a stick electrode.
Very easy to do. Push down the side a little bit more than we do in the middle, and stay
ahead of the trailing. Lace up. Stay on the side more than we do in the middle.
Stay on the side a little bit more than we do in the middle.
We're going to look at some of the wells that we did in the 3 by 3 by quarter inch angle
iron. In the process of doing them, we've covered some of them up, but we'll look and
see what we did. First thing we did was run the bead down the middle when we were doing
the discussion about what the machine was and what we were doing, but we ran the bead
down the middle. Then we came back and ran the bead on each side of the one. So this
is the one on one side that we see right here. We ran the one on the other side that we see
right here. So these were run in the flat position, running this away. We were trailing
with the wire, and I'm using a piece of big wire as a pointer here. This is what it was
actually welded with. We were trailing with the wire. The maximum trail should be 25 degrees.
If we lead with the wire, that is if the wire had been this way, we can do that, but penetration
will not be as great as if we trail with the wire. So these were both in the flat position.
Then we came back and we ran a vertical down, and this is the vertical down coming right
here. And we just went from side to side, got a sting ahead of the crater, and we came
down through here and ran that vertical down. There's no slag. There's very little cleanup.
There's very little buckshot. On good clean metal, you know it's almost ready to paint
when you get through. Then we came back and we ran a vertical up. We called it a lace
up or a vertical up, and this was where we ran the vertical up right here. Side, side,
side, side. Then we ran it up here. So several of the beads that we ran, and you can use
a piece of angle iron like this to develop a lot of skill and big welding because you
can change the angle, you can change the type of weld that you're running, and you can actually
continue to use this until you've built it out to here.
This is a 12 gauge butt. It's a little bit crooked. It's kind of hard to run straight
sometimes because when you're welding this, you get more penetration if you're trailing,
but then your cup covers up, so it's kind of hard to tell where you're going. So it's
a little bit crooked, and I apologize for that, but it shows. It's a continuous run,
and you watch and review how we ran it, and you can see we were moving on when we came
across here. Even though this is a very small wire, the deposition rate is very fast on
it. We're running a T-well on a 12 gauge plate. All we're really doing, other than carrying
it forward, is just a little bit of wrist motion back to back.
This is a T-well on 12 gauge. Again, the MIG makes welding easy. You have very little undercut.
You don't have to worry about as much as you do with a stick. Basically, all you do is
start your arc, just move it forward, and flex your wrist from side to side. If you
look at it when we ran it, you see that the electrode is just moving side to side, moving
forward, and it's going to be rather fast. Again, if you're used to stick welding, when
you get to MIG welding, deposition rate is a lot quicker, even though we're using this
little 35,000 square.
On the left, on 12 gauge plate, just a little action of the wrist. The thing that you have
to realize to do differently is it runs a lot faster.
This is a lap weld on 12 gauge. Again, with a MIG welder, you can run it straight. We
do not have to put any motion in a MIG welder. We can run it straight, or you can take your
wrist and just flex your wrist and just move the rod from side to side. It's a little bit
more comfortable than me if I have a little bit of movement, so I usually just flex the
rod from side to side. But basically, all you're doing is forward movement. You're not doing
any weaving. You're not doing any lacing. You're just coming straight across with a
MIG. Again, deposition rate is fast, so you're going to come across here pretty quick. It's
going to be quicker than you're used to coming across with a stick welder, a lot quicker
than you're used to coming across with a stick welder.
We're now running a butt weld on 316ths plate. All I'm really doing is working my wrist a
little bit as I go across the plate, trailing. Maximum penetration is trailing 25 degrees.
We've now progressed to 316ths inch plate, and if you remember when we welded, we increased
the voltage on the machine. Of course, when we increased the voltage, we also increased
the amperage. Again, this is a butt weld, and again, it's easy to make. We just use
just the wrist movement to move side to side, progress forward, and the deposition rate
is going to be very fast as you come across.
We're forming a T-wheel, 316ths plate. It's a pellet-type weld. Basically, all I'm doing
in order to perform this weld, other than going forward, is just wrist action back and
forward. We ought to have as much weld on the top as we do on the bottom. We have a
good penetration top and bottom, and not undercut the top.
This is a T-well on 316ths plate. Again, pellet-type weld made very easy. Bring the electrode
in. We trail about 25 degrees, and we just move the wrist action from side to side, forward
speed, no weave, just side to side, just forward travel. Deposition rate is pretty quick, so
you're moving on as you come across, but it makes pellet welds very easy to do.
Now doing a lap weld on 316ths plate. Maybe stay at the bottom just a little bit more
than the top, or the top will melt off. We're heating on the edge. The bottom we're heating
out in the masses of metal. But basically, all I'm doing is just wrist action as I go
across.
This is the lap weld, again on 316ths. The GMA makes pellet-type welds very easy. This
is a lap weld. Basically, all you do is bring the wire in and just work the wrist from side
to side, and you've got forward progress. So if your wrist side to side action is pretty
uniform, your forward progress is pretty uniform, you'll come up with a very uniform bead.
MIG works well in any position. We're now running a vertical down, pellet-type on 316ths
plate. Basically, all I'm doing is just wrist action side to side. Rod straight in just
a little bit. There's no slag to interfere with your arc.
This is the vertical down, and really, all we did was just move down, just moving the
wrist from side to side, letting the wire do the work. You just move the wrist from
side to side. You just follow down and just watch your craters just following along and
come on down, just moving the wrist from side to side.
Now running a vertical up, 316ths plate, 21 volts, wire feed adjusted to this. All I'm
actually doing is just flexing my wrist side to side.
This is the vertical up. Again, with this MIG welder, it's not that difficult to run.
We start at the bottom, and we just use wrist action side to side, side to side, as we go
up, dress up the weld. Deposition rate will be pretty quick. You're going to go up here
pretty fast. And if you review back to rerunning, when we ran it, you'll see that we went up
pretty quickly as we came up the weld joint.
Now running about a pellet-type vertical up, very comparable to a lace. We're down here
with a stick electrode. Stay on the side. Be sure we get a good penetration, a good
feel of any uncut on the side. Come across the middle. Move up each time you come across.
Feel like your laces move up your shoes. Again, there's no slag floating around in there.
So basically, it's an easy weld around.
We're actually showing two wells here. This well could be a vertical down the way it's
laying there. It could be a T-well. But the one we're looking at now is this one right
here. This one right here is a lace vertical up that has been run with a GMA welder. You
have to do a lot of things similar that you do when you run it with a stick welder. You
stay at the side until you see a swirl, and then you move to the other side. You stay
at the side until you see a swirl, and then move to the other side. By doing this, though,
you almost eliminate the sag in the weld due to gravity forces on your molten metal, and
you eliminate undercutting. If you look up the sides of this, you see no undercutting
on either side. And the undercutting is eliminated when you see the swirl at the end of the rod.
In summary, the GMA gas metal arc welding process is very popular in the fabricating
industry. Even though the initial investment in equipment is higher than for the conventional
stick electrode equipment, the process is extensively used because it can be performed
at a lower cost, and the finished product is good. Welding may be accomplished in any
position, flat, horizontal, vertical, or overhead. The process results in a smooth weld surface
that has a good appearance and requires less preparation for painting because there is
no slag or oily residue which is left by the flux on a stick electrode. The deposition
rate of electrode is much higher than for stick electrodes. And operator efficiency
is improved due to the continuous wire used, and the time lost in changing electrodes is
saved. Weld penetration is good, and distortion is less due to the high current density in
a narrow area and faster travel speeds. And it is easier to bridge gaps due to misalignments
and poor fit up without burn through. To perform GMA welds, you must have a complete understanding
of the equipment, its adjustment, and safe operating practices. Be sure you have adequate
protection from the arc rays. The arc is intense, and there is little or no smoke screen to
filter the rays. Be sure your welding hood and filter lens are correct and in good repair.
Even a small leak can cause painful eye burn. Also, be sure you have adequate ventilation.
Skills will develop as you practice. First develop the ability to run stringer beads,
and then progress through the other welds demonstrated. Personal and equipment safety
have been emphasized throughout this educational videotape. However, it is not intended for
this program to be used as a substitute for personal instruction and supervision, which
is to be provided by a qualified teacher.
Finally, the