Lincoln Electric LTW2 LEARNING TO STICK WELD - Manual (Page 4)

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LEARNING TO STICK WELD
LEARNING TO STICK WELD
No one can learn to weld simply by reading about it. Skill
comes only with practice. The following pages will help the
inexperienced welder to understand welding and develop
his skill. For more detailed information, order a copy of
“New Lessons in Arc Welding”, available from the James F.
Lincoln Foundation.
the aRc-weLDing ciRcuit
The operator’s knowledge of arc welding must go beyond the arc
itself. If you want to get the most out of your welding practice, your
knowledge of welding must go beyond the arc. You also need to
understand how to control the arc, and this requires knowledge of the
welding circuit and the equipment that provides the electric current
used in the arc. Figure 1 is a diagram of the welding circuit. The
circuit begins where the electrode cable is attached to the welding
machine and ends where the work cable is attached to the welding
machine. Current flows through the electrode cable to the electrode
holder, through the holder to the electrode and across the arc. On the
work side of the arc, the current flows through base metal to the work
cable and back to the welding machine. The circuit must be complete
for the current to flow. To weld, the work clamp must be tightly
connected to clean base metal. Remove paint, rust, etc. as necessary
to get a good connection. Connect the work clamp as close as
possible to the area you wish to weld. Avoid allowing the welding
circuit to pass through hinges, bearings, electronic components or
similar devices that can be damaged.
This arc-welding circuit has a voltage output of up to 79 volts, which
is enough to shock.
The electric arc is made between the work and the tip end of a small
metal wire - the electrode - which is clamped in a holder. The holder
is held by the welder.
ELECTRIC SHOCK CAN KILL.
CAREFULLY REVIEW THE ARC WELDING
SAFETY PRECAUTIONS AT THE BEGINNING
OF YOUR OPERATOR’S MANUAL.
A gap is made in the welding circuit (see figure 1) by holding the tip of
the electrode 1/16-1/8” away from the work or base metal being
welded. The electric arc is established in this gap and is held and
moved along the joint to be welded, melting the metal as it is moved
Arc welding is a manual skill requiring a steady hand, good physical
condition, and good eyesight. The operator controls the welding arc
and, therefore, the quality of the weld made .
What Happens in the Arc?
Figure 2 illustrates the action that takes place in the electric arc. It
closely resembles what is actually seen during welding.
The “arc stream’’ is seen in the middle of the picture. This is the
electric arc created by the electric current flowing through the space
between the end of the electrode and the work. The temperature of
this arc is about 6000°F. (3315°C.), which is more than enough to
melt metal. The arc is both very bright and very hot. If you look at the
arc with your naked eye, you risk several hours’ or days’ worth of
pain and poor, blurry vision. A welding helmet with a very dark lens,
specifically designed for arc welding, must be used whenever viewing
the arc.
Have you ever watched water flow from a garden hose onto soft soil
or earth? Eventually, the water will build up enough to displace and
dig into the soil beneath it. It may even form a small crater that then
fills with water. The arc works the same way, melting the base metal
and actually digging into it as it moves across the surface of the base
metal. The molten metal forms a molten pool or crater and tends to
flow away from the arc. As it moves away from the arc, it cools and
solidifies. A slag forms on top of the weld to protect it during cooling.
ARC RAYS CAN BURN
EYES AND SKIN.
when uSing an open aRc pRoceSS, it iS
neceSSaRy to uSe coRRect eye, heaD anD
boDy pRotection.
PROTECT YOURSELF AND OTHERS, READ
“ARC RAYS CAN BURN” AT THE FRONT OF THE
OPERATOR’S MANUAL SUPPLIED WITH THE
WELDER.
WARNING
To electrical
(earth) ground.
FIGURE 1—The welding circuit for Shielded Metal
Arc Welding(SMAW)
FIGURE 2—The welding arc