814 Agricultural Mechanics and Technology Systems
Copyright Goodheart-Willcox Co., Inc.
CHAPTER
29
Review and Assessment
Summary
• In the SMAW process, a consumable electrode coated in a fl ux is used to form the
welded bead.
• All machines for SMAW are constant-current machines that provide an even supply of
amperage to the electrode.
• Welding machines are classifi ed by their maximum amperage output and their duty cycle.
A duty cycle is a rating that indicates how long a welding machine can be used at a given
output current without damaging it.
• Electrodes are classifi ed by size and by type. The size of an electrode is determined by its
diameter measured at the wire core. Electrode types are classifi ed by the makeup of their
fl ux covering.
• Four broad categories of electrodes are fast-fi ll, fi ll-freeze, fast-freeze, and low-hydrogen.
• Welded joints can be classifi ed as butt, T-, corner, edge, or lap joints. Each requires
different welding techniques and application of heat.
• The American Welding Society designates welding positions with numbers and letters.
The numbers represent the positions—1 for fl at, 2 for horizontal, 3 for vertical, and 4 for
overhead. Fillet and groove welds are represented by the letters F and G.
• Welding variables controlled by the welder include current, arc length, electrode angle,
electrode manipulation, travel speed, type of surface preparation, and selection of electrodes.
• The electrode type must be matched to the base metal composition to ensure a strong weld.
• Common discontinuities in welds include porosity, incomplete fusion, incomplete joint
penetration, undercut, overlap, and cracks.
• Weld quality is determined using many different methods. These include visual
inspection, destructive testing methods, nondestructive methods such as liquid penetrant
dye and magnetic particle inspection, radiographic testing, and ultrasonic testing.
• Arc welding safety involves planning procedures, safely arranging the work environment,
and always wearing the appropriate clothing and personal protective equipment (PPE).
• To form strong, uniform beads, the arc must be held at a consistent distance from the base
metal to form the molten pool. The arc is moved along at a pace that allows the pool to
penetrate the base metal as it accepts the addition of fi ller metal from the melting electrode.
• The amount and distribution of heat input strongly infl uences the amount of distortion
produced by a weld.
• Cast iron contains much more carbon and silicon than steel, making it less ductile and
more challenging to weld.
• Welding certifi cation is written documentation that a welder has produced welds
according to prescribed standards.