©
COPYRIGHT 1998 THE ESAB GROUP, INC. LESSON
II Other functions
of the coating are to provide arc
stability and control bead shape. More information
on coating functions will be covered
in subsequent lessons. *
Shielded Metal Arc Welding (SMAW) is
the terminology
approved by the American Welding
Society. 2.2.1
Equipment
& Operation
- One reason
for the wide acceptance of the SMAW process
is the simplicity of the necessary equipment. The
equipment consists of the following items. (See Figure
2) 1.
Welding power source
2. Electrode
holder 3.
Ground clamp 4.
Welding cables and connectors
5. Accessory
equipment (chipping hammer,
wire brush) 6.
Protective equipment (helmet, gloves,
etc.) 2.2.2
Welding
Power Sources
- Shielded metal arc welding may utilize either
alternating current (AC) or direct
current (DC), but in either case, the power source selected
must be of the constant current type.
This type of power source will deliver a relatively constant
amperage or welding current regardless
of arc length variations by the operator (See Lesson I, Section
1.9). The amperage determines the amount of heat at the arc and since it
will remain relatively
constant, the weld beads produced will be uniform in size and shape.
2.2.2.1 Whether
to use an AC, DC, or AC/DC power source depends on the type of welding
to be done and the electrodes used.
The following factors should be considered: 1. Electrode
Selection - Using a DC
power source allows the use of a greater range of
electrode types. While most of the electrodes are designed to be used on
AC or DC, some
will work properly only on DC. 2. Metal
Thickness - DC power
sources may be used for welding both heavy sections
and light gauge work. Sheet metal is more easily welded with DC
because it is easier to strike and
maintain the DC arc at low currents. FIGURE
1 COATING
CORE
ROD SHIELDING
GASES SOLIDIFIED
SLAG
WELD METAL WORK
PIECE MOLTEN
POOL
SHIELDED METAL ARC WELDING
AC OR DC POWER
SOURCE ELECTRODE
CABLE
ELECTRODE HOLDER
ELECTRODE GROUND
CABLE
WORK
SHIELDED METAL ARC WELDING CIRCUIT
FIGURE 2
