Combined with the formation of welding joints at
various average currents, as shown in Fig. 8, the weld
pool dimension at an average current of 90 A is the best
when the maximum temperature of the weld pool is
almost 200 °C which is higher than its melting point. The
defects occur at other average currents, caused by either
excessive or insufficient heat input. When the average
current maintains at 80 A, the welding joint is
deteriorated and discontinued because of its poor arc
stiffness. In addition, the formation of joint between the
web and flange is poor with incomplete fusion defects.
At the average current of 100 A, the highest temperature
of the weld pool is almost 350 °C which is higher than
the melting point, which leads to some collapse. The
microstructures of welds are greatly affected by the
average currents. Generally, the kinetic energy for
growing microstructures increases with increasing the
applied current, as shown in Fig. 9. To ensure that the
weld fusion case is acceptable, the welding current must
be reduced as much as possible.
In conclusion, the optimum average current is 90 A
with good formation of T-joint and uniform
microstructure
Combined with the formation of welding joints atvarious average currents, as shown in Fig. 8, the weldpool dimension at an average current of 90 A is the bestwhen the maximum temperature of the weld pool isalmost 200 °C which is higher than its melting point. Thedefects occur at other average currents, caused by eitherexcessive or insufficient heat input. When the averagecurrent maintains at 80 A, the welding joint isdeteriorated and discontinued because of its poor arcstiffness. In addition, the formation of joint between theweb and flange is poor with incomplete fusion defects.At the average current of 100 A, the highest temperatureof the weld pool is almost 350 °C which is higher thanthe melting point, which leads to some collapse. Themicrostructures of welds are greatly affected by theaverage currents. Generally, the kinetic energy forgrowing microstructures increases with increasing theapplied current, as shown in Fig. 9. To ensure that theweld fusion case is acceptable, the welding current mustbe reduced as much as possible.In conclusion, the optimum average current is 90 Awith good formation of T-joint and uniformmicrostructure
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