796 Agricultural Mechanics and Technology Systems
Copyright Goodheart-Willcox Co., Inc.
creates internal stresses that pull against
the sides of the weld, resulting in weak
spots. Welds that lack adequate size may
not stand up to stresses encountered
during service. Oversize welds produce
stress concentrations and contribute to
the likelihood of distortion in welded
components.
Weld Terms
It is important to understand the
terminology used to describe welded joints
in order to effectively communicate about
the quality of welds. The crown of a bead
is its visible upper surface. The root of the
bead is the lower or innermost portion.
Root penetration is essential to the bonding
quality of a welded bead. The legs of a
bead are the extensions of the bead past the
center of the joint, and the toes are where
the edges of the bead end. The toes should
blend smoothly into the base metal. See
Figure 29-32.
Discontinuities
A key to success in welding is consistency. Discontinuities are breaks in
the consistency of a welded bead. Some are visible, while others are inside
the metal. Some discontinuities are severe enough to be considered a fault,
while others are just inconsistencies.
When discontinuities are of an unacceptable size or in an unacceptable
location, they are called welding defects. Defects reduce strength or produce
stress concentrations within the welded bond. AWS welding codes and
standards are used to determine the number of acceptable and unacceptable
weld discontinuities for welding that is to be commercially inspected. Many
times in agricultural settings, there are no prescribed codes to follow. It
is important for welders to understand the basics of inspecting welds for
quality and to be able to evaluate welds on equipment and structures before
putting them into service.
Inspect welds for these common discontinuities:
• Porosity is a cavity-type discontinuity formed by gas trapped in
the molten weld. The gas may form bubbles or pockets as the weld
solidifies. The main causes of porosity are dirty base material, moisture fi
contamination, or incorrect welding techniques. To control porosity,
use clean base materials, properly store welding consumables, maintain
welding equipment, use recommended procedures, and weld in
suitable environmental conditions. See Figure 29-33.
Crown
height
Weld
crown
Weld
toe
Root
penetration
Root penetration
Leg length
Leg length
Weld throat
Weld crown
Weld toe
Goodheart-Willcox Publisher
Figure 29-32. Weld terminology.