790 Agricultural Mechanics and Technology Systems
Copyright Goodheart-Willcox Co., Inc.
penetration. When parts are accessible
for welding from both sides, weld a bead
from the back side (backing bead). Then,
penetrate and re-fuse the weld from the
front with the next bead. Setting a gap of
up to 1/8″ may be enough in many cases.
With parts that are 5/16″ or thicker, some
beveling may be required on one or both
parts, Figure 29-19. Beveling removes part
of a square edge to create a sloping edge.
The maximum weld width for butt,
fi llet, and multipass welds should be
slightly wider than the depth of the weld.
A width-to-depth ratio of 1.25:1 to 1.5:1 is
recommended for these welds to reduce the possibility of cracking due to
internal stress in the bead.
Oxyfuel or plasma cutting can be used for beveling edges, Figure 29-20.
All loose scale and dross resulting from cutting must be removed by chipping
or grinding prior to assembly and welding. It is not necessary to remove the
thin oxide layer formed on cooling. This oxide is allowed to remain on the edges
to help prevent rusting if the parts are to be stored for
some time before welding. Although grinding may be
used for beveling, in most instances it is ineffi cient.
Controlling Welding
Parameters
The key to creating a good weld is to maintain
control of the welding process. Parameters are limits
for how something should be done. Welders control
welding parameters that include current, electrode
selection, arc length, electrode angle, electrode motion,
and travel speed.
Goodheart-Willcox Publisher
Figure 29-18. Use a handheld or powered wire brush to clean steel before and after
welding beads.
37.5°
.0625" gap
.0625"
root face
Goodheart-Willcox Publisher
Figure 29-19. Bevels and a slight gap at the weld joint increase
the surface area of the bond and help to ensure penetration
through the base metal.
Bogdan VASILESCU/Shutterstock.com
Figure 29-20. A torch can be used to cut a bevel.