the arc is impelled along the peripheral edges of the tubes while heating up the faying surfaces to the point of solidus
(red hot condition). Finally, the I3 current of about 1100 A during
the upsetting of the two tubes whose faying surfaces are in red hot
condition. A high current in stage III (also referred to as expulsion
current) is expected to play an important role in the cleaning action
by expelling the impurities when forging action is employed. These
specifications of current are applicable only for welding T11 tubes
of 47.6 mm diameter with 6.6 mm thickness.
MIAB welding process is divided into four stages based on the
time as specified by the manufacturer. T1 (0.5–1 s) is the time during
which the tubes, initially with a gap between them are shorted. T2
(4–6 s) is the time period in which the shorted tubes are retracted
followed by the arc striking between the tubes. Further, in this stage
of time, the arc starts to slowly rotate along the peripheral edges of
the tube ends. During this stage of time, I1 current of (280–300 A)
is employed. In stage T3 (20–30 s), arc accelerates and rotates with
a high speed of about 250 m/s (linear) along the peripheral edges
of the tubes while heating up the faying surfaces to the point of
solidus (red hot condition). A current of 200–220 A (I2 current) and
is provided during the T3 stage. Finally, upsetting action takes place
in T4 (0.3 s) by supplying a current of 1100 A (as per I3 stage).