Two aluminium alloy plates each $$10$$ $$mm$$ thick and $$1$$ $$m$$ long are welded without crowning by multipass tungsten inert gas butt welding. The joint configuration is $$V$$-type with $${60^ \circ }$$ angle and root gap is maintained at $$5$$ $$mm.$$ If electrode of $$5$$ $$mm$$ diameter with $$500$$ $$mm$$ length is used for welding, then the number of electrodes required is

In an arc welding operation carried out with a power source maintained at $$40$$ volts and $$400$$ amperes, the consumable electrode melts and just fills the gap between the metal plates to be butt-welded. The heat transfer efficiency for the process is $$0.8,$$ melting efficiency is $$0.3$$ and the heat required to melt the electrode is $$20$$ $$J/m{m^3}$$. If the travel speed of the electrode is $$4$$ $$mm/s$$, the cross-sectional area, in $$m{m^2}$$, of the weld joint is ________________.

In a $$DC$$ $$arc$$ welding operating, the length characteristic was obtained as $${V_{arc}} = 20 + 5l$$ where the $$arc$$ length $$l$$ was varied between $$5mm$$ and $$7mm.$$ Here $${V_{arc}}$$ denotes the arc voltage in volts. The $$arc$$ current was varied from $$400A$$ to $$500A.$$ Assuming linear power source characteristic, the open circuit voltage and the short circuit current for the welding operation are

During a steady gas metal arc welding with direct current electrode positive polarity, the welding current, voltage and weld speed are $$150A,$$ $$30V$$ and $$6m/min$$ respectively. A metallic wire electrode of diameter $$1.2mm$$ is being fed at a constant rate of $$12m/min.$$ The density, specific heat and melting temp of the wire electrode are $$7000$$ $$kg/{m^3},$$ $$500$$ $$J/kg$$ and $${1530^ \circ }C$$ respectively. Assume the ambient temp to be $${30^ \circ }C$$ and neglect the latent heat of melting. Further consider that $$2/{3^{rd}}$$ of the total electrical power is available for melting of the wire electrode. The melting efficiency (in percentage) of the wire electrode is