Two metallic sheets, each of 2.0 mm thickness are welded in lap joint configuration by resistance spot welding at a welding current of 10 KA and welding time of 10 milliseconds. A spherical fusion zone extending up to the full thickness of each sheet is formed. The properties of the metallic sheets are given below:
Ambient temp = 293 K
Melting point temp = 1793 K
Density = 7000 kg/m3
Latent heat of fusion = 300 kJ/kg
Specific heat = 800 J/kgK
Assume:
(i) Contact resistance along sheet – sheet interface is 500 micro-ohm and along electrode – sheet interface is zero.;
(ii) No conductive heat loss through the bulk sheet material; and
(iii) The complete weld fusion zone is at the melting temperature
the melting efficiency (in%) of the process is...........
(a) 50.37(b) 60.37
(c) 70.37 (d) 80.37