INTRODUCTION TO WELDING
In the Navy as well as private industry, welding is
widely used by metalworkers in the fabrication, main-
tenance, and repair of parts and structures. While there
are many methods for joining metals, welding is one of
the most convenient and rapid methods available. The
term welding refers to the process of joining metals by
heating them to their melting temperature and causing
the molten metal to flow together. These range from
simple steel brackets to nuclear reactors.
Welding, like any skilled trade, is broad in scope and
you cannot become a welder simply by reading a book.
You need practice and experience as well as patience;
however, much can be gained through study. For in-
stance, by learning the correct method or procedure for
accomplishing a job from a book, you may eliminate
many mistakes that otherwise would occur through trial
This chapter is designed to equip you with a back-
ground of basic information applicable to welding in
general. If you take time to study this material carefully,
it will provide you with the foundation needed to be-
come a skilled welder.
Welding is not new. The earliest known form of
welding, called forge welding, dates back to the year
2000 B.C. Forge welding is a primitive process of
joining metals by heating and hammering until the met-
als are fused (mixed) together. Although forge welding
still exists, it is mainly limited to the blacksmith trade.
Today, there are many welding processes available.
Figure 3-1 provides a list of processes used in modern
metal fabrication and repair. This list, published by the
American Welding Society (AWS), shows the official
abbreviations for each process. For example, RSW
stands for resistance spot welding. Shielded metal arc
welding (SMAW) is an arc-welding process that fuses
(melts) metal by heating it with an electric arc created
between a covered metal electrode and the metals being
joined. Of the welding processes listed in figure 3-1,
shielded metal arc welding, called stick welding, is the
most common welding process. The primary differ-
ences between the various welding processes are the
methods by which heat is generated to melt the metal.
Once you understand the theory of welding, you can
apply it to most welding processes.
The most common types of welding are oxyfuel gas
welding (OFW), arc welding (AW), and resistance
welding (RW). As a Steelworker, your primary concern
is gas and arc welding. The primary difference between
these two processes is the method used to generate the
One of the most popular welding methods uses a gas
flame as a source of heat. In the oxyfuel gas welding
process (fig. 3-2), heat is produced by burning a com-
bustible gas, such as MAPP (methylacetylene-propadi-
ene) or acetylene, mixed with oxygen. Gas welding is
widely used in maintenance and repair work because of
the ease in transporting oxygen and fuel cylinders. Once
you learn the basics of gas welding, you will find the
oxyfuel process adaptable to brazing, cutting, and heat
treating all types of metals. You will learn more about
gas welding in chapter 5.
Arc welding is a process that uses an electric arc to
join the metals being welded. A distinct advantage of arc
welding over gas welding is the concentration of heat.
In gas welding the flame spreads over a large area,
sometimes causing heat distortion. The concentration of
heat, characteristic of arc welding, is an advantage be-
cause less heat spread reduces buckling and warping.
This heat concentration also increases the depth of pene-
tration and speeds up the welding operation; therefore,
you will find that arc welding is often more practical and
economical than gas welding.
All arc-welding processes have three things in com-
mon: a heat source, filler metal, and shielding. The
source of heat in arc welding is produced by the arcing
of an electrical current between two contacts. The power