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

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

Which of the following powders should be fed for effective oxy-fuel cutting of stainless steel

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