Question
Two mild steel plates of similar thickness, in butt-joint configuration, are welded by gas tungsten arc welding process using the following welding parameters.
| Welding valtage | 20 V |
| Welding current | 150 A |
| Welding speed | 5 mm/s |
A filler wire of the same mild steel material having 3 mm diameter is used in this welding process. The filler wire feed rate is selected such that the final weld bead is composed of 60% volume of filler and 40% volume of plate material. The heat required to melt the mild steel material is 10 J/mm3. The heat transfer factor is 0.7 and melting factor is 0.6. The feed rate of the filler wire is __________ mm/s (round off to one decimal place).
Answer :
Correct answer is : 10.695
ηh = 0.7, ηm = 0.6, Hm = 10 J/mm3
V = 20V, I = 150 A, velocity = v = 5 mm/s
feed rate of filler material in joint f = 60% = 0.6
fe = feed rate of electrode, diameter of electrode, de = 3 mm
Area of bead, A = 25.2 mm2
by balancing the volume flow:
volume of metal from electrode per unit time = volume of metal deposited in joint per unit time
Ae × fe = A × f × v
π/ 4 (3)2 × fe = 25.2 × 0.6 × 5
fe = 10.695 mm/sec
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