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24
9 Welding Process
9.2
Gap Stud Welding
– The solenoid, which is integrated into the welding gun, lifts the welding element
from the workpiece (see figure,
position 1
) to the adjusted value ”lift” above the
workpiece and tensions a pressure spring (see figure,
position 2
).
– As soon as the welding piston has reached the upper stop, the current to the
solenoid is cut. Simultaneously, the welding thyristor is triggered and releases the
current flow to the welding element.
– The capacitors of the stud welding unit are discharged. Because of the high
discharge current, the ignition tip evaporates explosion-like. The air gap between
welding element and workpiece is ionized (see figure,
position 3
). An arc is pro-
duced.
– The light arc melts the face of the welding element together with an area of the
workpiece of about the same dimension (see figure, position 4).
– The welding element is moved by the pressure spring to the workpiece with a
speed of 0.5 to 1.5 m/s. The adjusted spring force and the preset lift distance
controls the plunging speed of the welding element.
– Higher plunging speed leads to shortened arc time and consequently to lower
welding energy with identical voltage setting.
– The arc is cut as soon as the welding element touches the workpiece.
– Now the capacitors are short-circuited and the rest of the energy drains off (see
figure,
position 5
).
– The pressure spring continues to push the welding element into the weld pool.
–
The weld pool solidifies and the welding element is physically connected to the
workpiece.
–
The time period between ignition of the arc and solidification of the weld pool is
about 1 to 2 ms.
Summary of Contents for 92-10-1504B
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