Clarke Arc/Tig135, Инструкция по эксплуатации и обслуживанию

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4
PRINCIPLES OF OPERATION
The ARC/TIG welder, as its name suggests, is designed to be used for both Metal ARC, AND TIG
welding. To accomplish this, two sets of welding leads are required, one for each method
employed.
ARC WELDING
Shielded Metal Arc welding is by far the most widely used of the various arc welding processes.
It employs the heat of the arc to melt the base metal and the tip of a consumable flux covered
electrode.
The electrode and the workpiece are part of an electric circuit. This circuit begins with the
electric power source and includes the welding cables, an electrode holder, a workpiece
connection, the workpiece, and an arc welding electrode. One of the two cables from the power
source is attached to the work. The other is attached to the electrode holder.
Welding commences when an electric arc is struck between the tip of the electrode and the work.
The intense heat of the arc melts the tip of the electrode and the surface of the work close to the
arc. Tiny globules of molten metal rapidly form on the tip of the electrode, then transfer through
the arc stream into the molten weld pool. In this manner, filler metal is deposited as the electrode
is progressively consumed.
The arc is moved over the work at an appropriate arc length and travel speed, melting and fusing
a portion of the base metal and continuously adding filler metal. Since the arc is one of the
hottest of the commercial sources of heat (temperatures above 9000
0
F (5000
0
C) have been
measured at its centre), melting of the base metal takes place almost instantaneously upon arc
initiation.
If welds are made in either the flat or the horizontal position, metal transfer is induced by the
force of gravity, gas expansion, electric and electromagnetic forces, and surface tension. For
welds in other positions, gravity works against the other forces.
The process requires sufficient electric current to melt both the electrode and a proper amount of
base metal. It also requires an appropriate gap between the tip of the electrode and the base
metal or the molten weld pool. These requirements are necessary to set the stage for
coalescence.
The sizes and types of electrodes for shielded metal arc welding define the arc voltage
requirements within the overall range and the current requirements within the overall range. The
current may be either alternating or direct, depending upon the electrode being used, but the
power source must be able to control the level of current within a reasonable range in order to
respond to the complex variables of the welding process itself.