804 Agricultural Mechanics and Technology Systems
Copyright Goodheart-Willcox Co., Inc.
Welding Beads on Flat Plate
Welding a series of beads on small rectangular fl at
plate, called a coupon, is the starting point for most
beginning welders. See Figure 29-47. This procedure,
typically called welding a practice pad, emulates a
welding process used to build up worn parts with fi ller
metal. See Figure 29-48. It is crucial that each successive
weld completely blend into the last, leaving no holes
or voids in the fi nished surface. Sometimes a harder
or more durable surface than the original base metal
is created.
Plates for practice pads should generally be
3/16″ to 3/8″ thick, rectangular, with no dimension
longer than about 6″ or shorter than 3″. A typical size
would be 1/4″ thick and 3″ wide by 4″ long. Working
with thin materials teaches beginning welders to
be conscious of controlling the heat input. The thin
materials also allow for the use of smaller-diameter
electrodes that are less expensive and produce less
wear on the equipment. Welders who develop skills on
thin materials can easily transition to thicker materials.
A correctly welded practice pad should have
uniform beads that exhibit a relatively fl at surface
on top. There should be a minimum of high or
low spots—each bead should smoothly transition
into the next. The plate itself should display the
development of a warped curve toward the welded
surface, Figure 29-49. This distortion, or defl ection, is
evidence of adequate penetration and results from the
contracting of the layer of beads as the metal cools.
Welding a Practice Pad
The following is a procedure for creating a practice
pad. See Figure 29-50.
1. Obtain a steel coupon from your instructor or cut
one with a cutting torch.
2. Using a scrap piece of steel, set up the machine
according to manufacturer’s specifi cations and
run a test bead. Make adjustments to fi ne-tune
the settings. Remember that each machine is a
little different.
3. Strike the arc with a tapping motion.
Safety Note
Before striking the arc, call out the word cover to alert anyone nearby to avoid looking at
the arc without adequate eye protection.
Garsya/Shutterstock.com
Figure 29-47. The surface of a correctly welded
practice pad should be uniform and relatively flat.
Goodheart-Willcox Publisher
Figure 29-48. The surface of this chisel plow point
has been built up with welds and finished with hard-
surfacing electrodes to improve wear resistance.