1
GATE PI 2010
+2
-0.6
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
A
$$39.58$$
B
$$45.25$$
C
$$49.38$$
D
$$54.98$$
2
GATE PI 2009
+2
-0.6
Autogeneous gas tungsten arc welding of a steel plate is carried out with welding current of $$500A,$$ voltage of $$20V,$$ and weld speed of $$20mm/min.$$ Consider the heat transfer efficiency from the arc to the weld pool as $$90\%$$. The heat input per unit length (in $$kJ/mm$$) is
A
$$27$$
B
$$35$$
C
$$45$$
D
$$55$$
3
GATE PI 2008
+2
-0.6
Two pipes of inner diameter $$100mm$$ and outer diameter $$110mm$$ each are joined by flash butt welding using $$30V$$ power supply. At the interface, $$1mm$$ of material melts from each pipe which has a resistance of $$42$$ Ohms.If the unit melt energy is $$64.4$$ $$MJ/{m^3}$$, then time required for welding (in $$S$$) is
A
$$1$$
B
$$5$$
C
$$10$$
D
$$20$$
4
GATE PI 2008
+2
-0.6
Aluminium strips of $$2mm$$ thickness are joined together by resistance spot welding process by applying an electric current $$6000$$$$A$$ for $$0.15sec$$. The heat required for melting aluminium is $$2.9J/m{m^3}.$$ The diameter and thickness of the weld nugget are found to be $$5$$ $$mm$$ and $$2.5mm$$ respectively. Assuming the electrical resistance to be $$75$$ micro-ohms, the percentage of total energy utilized in forming the weld nugget is
A
$$28$$
B
$$35$$
C
$$65$$
D
$$72$$
GATE PI Subjects
Engineering Mechanics
Theory of Machines
Machine Design
Fluid Mechanics
Thermodynamics
Casting
Joining of Materials
Metal Forming
Machine Tools and Machining
Metrology
Industrial Engineering
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