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During a steady gas metal arc welding with direct current electrode positive polarity, the welding current, voltage and weld speed are 150 A, 30 V and 6 m/min respectively. A metallic wire electrode of diameter 1.2 mm is being fed at a constant rate of 12 m/min. The density, specific heat and melting temp of the wire electrode are 7000 kg/m3, 500 J/kg and 1530°C respectively. Assume the ambient temp to be 30°C and neglect the latent heat of melting. Further consider that 2/3rd of the total electrical power is available for melting of the wire electrode. The melting efficiency (in percentage) of the wire electrode is
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- 39.58
- 45.25
- 49.38
- 54.98
Correct Option: A
I = 150 A, V = 30 V
Speed V = 6m/min.
dw = 1.2 mm Fr = 12 m/min
ρelectrode = 7000 kg/m³
C = 500 kJ/kg
Tm = 1530°C TA = 30°C
Heat Required for welding
| = | d²w × δelectrode × C∆T | |
| 4 |
| = | (1.2 × 10-3)² × | × 7000 × 500 × [1530 - 30] | ||
| 4 | 60 |
= 1187.52 Joules
Power developed = P = VI = 30 × 150 = 4500 J
Heat Available for melting = 2/3 × 4500 = 3000j
| Melting efficiency = | = 34.58% | |
| 3000 |
