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Shielded
Metal Arc Welding, also known as stick welding, melts and joins metals
by
using an electric current to melt the tip of an electrode, which is
also called the stick.
This melted electrode mixes with the melting metals in the work piece
in order to form a weld. It is a more forgiving
welding process than other types of welding since it works on a wide
variety of surfaces and is very portable. Over the years, stick welding
has been one of the most popular
forms of welding in home garages, construction sites, and maintenance
work.
The electrode’s core provides the
filling material for the weld, while the outer layer of the electrode,
the flux, helps create an arc and provides a shielding gas and
protective layer of slag—which keeps contaminants out of the weld and
can later be chipped away. Since stick welding has so many applications
and is quite affordable, it remains an important process for welders to
master for a wide variety of applications.
Preparing for Stick Welding
With
stick welding, you can weld parts that are not necessarily clean,
whether
they have paint or rust on the weld joint. Most weld joints will be
stronger if they are cleaned properly, and therefore it's always better
to clean a joint if it's part of a building's support. However, unlike
other methods such as MIG welding that require a completely clean
surface, stick welders can save time by skipping extensive joint
preparation and getting right to work on the weld.
The Correct Power Settings for Stick Welding
DC
power is preferable to AC power for stick welding since DC power is
easier to start, causes less splatter, results in less arc outages and
sticking, produces better looking welds,
permits welding in different positions, penetrates 10% more (in a DC
reverse polarity over any amp in AC), and strikes a smoother arc.
However, AC power makes it possible to stick weld
magnetized parts. It's often recommended to pick up a welder that
offers both AC and DC power options since both can prove quite useful
depending on the project.
The Right Metal for Stick Welding
Stick welding is limited to welding metals that are no thinner than 18
gauge. The most common metals welded in this way are iron and a variety
of steels, including stainless steel. However, aluminum, nickel and
copper alloys can also be joined with a stick welder. It is rarely used
on aluminum.
The Right Stick Welding Electrode
Stick welding requires frequent electrode rod changes and splatters
more than other
methods since it creates a layer of flux on the metal to protect the
weld. When the weld is completed, the flux must be chipped away.
Choosing the right electrode for the job will help lessen the splatter
and achieve the best weld for the job. The most commonly used
electrodes are 6010, 6011, 6013, 7018 and 7024. 6010 and 6011 are the
most popular all-purpose electrodes, but there are particular
applications, such as vertical welding, where a 7018 becomes the
electrode of choice.
Choose the Right Stick Welder
When
purchasing a stick welder, an excellent all-purpose welder is
a 225
to 300-amp machine. Most stick welding procedures only require 200
amps, but
having just a little more power offers flexibility for completing
bigger
jobs if needed. If faced with a job that would require more than
300 amps, such as metals over 3/8" thick, make several weld
passes. Smaller welders (115-volt) can only handle a metal thickness
of 1/8", while larger welders (220 volt) can weld a 3/8" thickness in
one pass.
Select the Best Duty Cycle for Stick Welding
A welder can only work as long as its duty cycle. A duty cycle is the
number of minutes out of a 10-minute cycle that a welder
can operate, which makes all of the difference when it comes to
efficiency and time on task. For example, a welder that creates a 200
amp DC
output at 20 percent duty cycle can weld continuously at 200 amps
for two minutes, and then must cool for eight minutes to prevent
overheating.
Maintain the Correct Arc Length
Be sure to maintain the proper arc length while welding. Arc length
varies with each electrode and
application. The best rule of thumb is to use an arc length that is
the same distance from the metal as the thickness (diameter of metal
portion/core) of the electrode used for the project. Be careful not to
hold the electrode
too close, as this produces erratic arc and high crown bead due to the
decreased welding voltage. If the arc is too far from the metal, this
will produce,
significantly more splatter and low deposition rates.
Diversify Your Stick Welding Positions
Practice welding in different positions in order to be sure you can
handle any job that comes your way. For example, construction and
maintenance work may require vertical welding. Vertical welding
requires welding uphill in a slow, side to side motion that builds the
weld upon itself without creating too large of a weld puddle. If the
area is wide, it's much easier to make multiple passes or
"stringer beads."
The Scratch Start Technique for Stick Welding
In order to strike an arc for stick welding, drag
the electrode across the metal workpiece as if striking a match. After
making contact, lift the electrode
slightly so that the arc is formed between the electrode and the piece.
If the arc goes out, that means the electrode was raised too
high from the metal. If the electrode sticks to the workpiece, use a
quick twist to free it and regrind the tip with a file.
Move at the Correct Travel Speed
The goal of every welder is to produce a smooth weld bead with a
uniform shape. If the weld has ridges like fish scales, then the travel
speed was too fast. Slow down the weld by pausing briefly on each side
while moving back and forth. Keep the arc toward the front of the weld
pool, ensuring that the weld pool doesn't run ahead and become too
large. If the weld pool becomes too large, then the travel speed is too
slow and the weld will have poor penetration. Naturally moving too fast
will also provide poor penetration and create a weak weld with a
narrow, uneven weld.
One welding instructor suggests practicing with travel speed by moving
the electrode to one side, counting to three, making another pass,
counting to three, and so forth. There are different opinions about the
most effective way to perfect one's welding speed, but using this
method or a modified version of it is a good place to start. Keep
moving the electrode across the center without stopping, as the center
will fill up if you maintain a steady side-to-side movement that pauses
on each edge of the weld joint.
The Angle of Travel for Stick Welding
Most welding is done in the flat position. For stick
welding in the flat, horizontal and overhead positions, use a "drag" or
"backhand" welding technique. The rod should be perpendicular to the
weld joint. The electrode's tip should be tilted at 5 to 15 degrees in
the direction it's traveling. Vertical welding that moves upward uses a
"push" or
"forehand" technique. The rod is tilted away from the travel direction
at 15 degrees.
Avoid Cracking When Stick Welding
Cracking often becomes a concern for multiple pass or stick welds. The
first weld bead must be a sufficiently large size and have a convex
shape that bulges outward. If the bead is too small, move at a slower
travel speed and use a short arc technique.
Resources and Sources
Written exclusively for BakersGas.com by Ed Cyzewski.
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