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# GATE Mechanical 1989 Question

An arc welding $DC$ power source has a linear power source characteristic with open circuit voltage ${V_O} = \,\,80$ volts and short circuit current ${{\rm I}_S} = 1000amps.$ The voltage-length characteristic of the arc is given by $V=20+4L$ volts where $L$ is the arc length in $mm,$ calculate the optimum length of arc for obtaining maximum arc power at welding. What voltage and current setting should be done on the power source for maximum arc power.

# GATE Mechanical 1990 Question

Manual metal arc welding is to be used for welding two plates each measuring $800 \times 200 \times 19mm.$ Given that
Length of weld $\,\,\,\,\,\,\,\,\,\,$$\,\,\,\,\,\,\,\,\,\,\,$$:180mm$
Length of electrode$\,\,\,\,\,\,\,\,\,\,\,$ $:450mm$
Stub length$\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,$$\,\,\,\,\,\,\,\,\,\,\, :50mm Diameter of electrode \,\,\,\,\, :3mm Weld reinforcement area :10\% Spatter and other losses :15\% Root gap = land = 2mm Angle of groove\,\,\,\,\,\,\,\,\,\,\,$$\,\,\,\,\,\,\,\,\,$ $:{60^ \circ }$
Estimate the required number of electrodes for the weld.

# GATE Mechanical 1992 Question

A low carbon steel is to be welded by the manual metal arc welding process using a linear $V$-$I$ characteristic $DC$ power source.

The following data is available.
$O.C$ voltage of the power source $=62V,$
$S.C$ current for the setting used $=130A,$
ARC length $=4mm,$
Traverse speed of welding $=15cm/min$
Efficiency of heat input $= 85\%$
The relation between the arc length $L$ in $mm$
and arc voltage $V$ is $V=20+1.5L$
Calculate the heat input into the work piece.