Lincoln Electric LN-15 - Manual (Page 2)

How
STT ® works
A BACKGROUND CURRENT
between 50 and 100 amps
maintains the arc and
contributes to base metal
heating. After the electrode
initially shorts to the weld
pool, the current is quickly
reduced to ensure a solid
short. PINCH CURRENT is
then applied to squeeze
molten metal down into the
pool while monitoring the
necking of the liquid bridge
from electrical signals. When
the liquid bridge is about to
break, the power source
reacts by reducing the current
to about 45-50 amps.
Immediately following the arc
re-establishment, a PEAK
CURRENT is applied to
produce plasma force pushing
down the weld pool to prevent
accidental short and to heat
the puddle and the joint.
Finally, exponential TAIL-OUT
is adjusted to regulate overall
heat input. BACKGROUND
CURRENT serves as a fine
heat control.
THE STT PROCESS
The TAIL-OUT
CONTROL adjusts
the rate that the
current is changed
from PEAK to
BACKGROUND.
Basically, the TAIL-
OUT is a coarse
heat control.
A B C D E A
B. When the “ball” shorts to
the puddle, the current is
reduced to a low level
allowing the molten ball to
wet into the puddle. A. STT ® produces a
uniform molten ball and
maintains it until the “ball”
shorts to the puddle.
C. Automatically, a precision
PINCH CURRENT waveform
is applied to the short. During
this time, special circuitry
determines that the short is
about to break and reduces
the current to avoid the
spatter producing “explosion”. E. STT ® circuitry senses that
the arc is re-established, and
automatically applies PEAK
CURRENT, which sets the
proper arc length. Following
PEAK CURRENT, internal
circuitry automat-ically
switches to the
BACKGROUND
CURRENT, which serves as
a fine heat control.
D. STT ® circuitry re-
establishes the welding arc
at a low current level.
BACKGROUND
CURRENT
PINCH
CURRENT
PEAK TIME
PEAK
CURRENT
TAIL-OUT
SPEED
Surface Tension Transfer ® (STT ® )
W A V E F O R M C O N T R O L T E C H N O L O G Y ® ™
PROCESS
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