Tweco FP-235DC - Manual (Page 20)

Exposure to a Welding arc is extremely harmful to the eyes and skin.
Prolonged exposure can cause blindness and burns. NEVER strike an arc or begin
welding until you are adequately protected. Wear flameproof welding gloves, a heavy
long-sleeved shirt, cuffless trousers, high-topped shoes and a welding helmet.
To prevent ELECTRIC SHOCK, DO NOT perform any welding while
standing, kneeling or lying directly on the grounded work.
TYPES OF COMMONLY USED WELD BEADS
The following paragraphs discuss the most commonly used arc welding beads.
STRINGER BEAD
A string bead (see Figure 8) is formed by laying down a con-
tinuous strip of new metal in one steady, forward pass.
To lay a stringer bead:
1. Strike a short 1/8 inch (3.22 mm) arc and hold it at the start-
ing point.
2. When a puddle is formed and the base of the bead begins to build, move the arc along the work without
weaving or oscillating.
3. Hold the electrode so that the holder is always slightly ahead of the arc.
4. The action will pile the molten metal just behind the arc. If the electrode motion is smooth and even, the
bead will be of consistent height and width with a uniform, closely spaced ripple.
WEAVE BEAD
The weave bead will deposit metal in a wider space than would
normally be possible with the string bead (see Figure 9).
The weave bead is accomplished by:
a. Weaving from one edge of the space to be filled in to the other
edge.
b. Continue this motion as well as the forward speed of travel.
Hesitate momentarily at each edge of the weave. This will provide the same heat at the edge of the weave as
in the middle.
FINISHING THE BEAD
As the coating on the outside of the electrode burns off, it forms an envelope of protective gasses around the
weld. This prevents air from reaching the molten metal and creating an undesirable chemical reaction.
The burning coating, however, forms slag. Slag formation appears as an accumulation of dirty metal scale on
the finished weld. The slag should be removed with a welding hammer or chisel, after it is cooled.
Peening the slag from a weld joint causes small chips of metal to fly
through the air. Metallic chips flying through the air can cause eye injury or injury to
other parts of the head, hands or exposed portions of the body. Wear eye glasses
with side shields and protect the hands and other exposed parts of the body with
protective garments or if possible work with a shield between the body and the
workpiece.
16
Figure 9: Weave Bead
Figure 8: Stringer Bead