Oxidizing flame requires flux except for welding which of the following metals:
Stainless steel
Cast iron
Brass
Zinc, lead
Which of the following flame is the hottest?
Reducing flame
Neutral flame
Oxidizing flame
All have same temperature
An acetylene/oxygen flame burns at ___ °C.
2,250
2,526
3,073
3,773
In oxygen/acetylene welding for the complete combustion of C2H2:
1/5th proportion of the O2 comes from the cylinder
2/5th proportion of the O2 comes from the cylinder
3/5th proportion of the O2 comes from the cylinder
5/5th proportion of the O2 comes from the cylinder
With the decrease of electrode extension:
Electrical resistance decreases
Bead width increases
More forceful arc
All three options (a, b, and c) are correct
Effect of welding speed (w) on melting efficiency?
With increase of w, melting efficiency increase
With decrease of w, melting efficiency increase
W has no effect on melting efficiency
All of these
Increase in welding current tends to cause:
More distortion
Less distortion
More reinforcement
Both (a) and (c)
In a DC arc welding operation, the voltage-arc length characteristic was obtained as Varc = 20 + 5*l, where the arc length l was varied between 5 mm and 7 mm. Here Varc denotes the arc voltage in Volts. The arc current was varied from 400 A to 500 A. Assuming linear power source characteristic, the open circuit voltage and the short circuit current for the welding operation are:
45 V, 450 A
75 V, 750 A
95 V, 950 A
150 V, 1500 A
In case of arc welding of steel with a potential of 20 V and current of 200 A, the travel speed is 5 mm/s and the cross-sectional area of the joint is 20 mm^2. The heat required for melting steel may be taken as 10 J/mm^3 and heat transfer efficiency as 0.85. The melting efficiency will be nearly:
18 %
29 %
36 %
42 %
A direct current welding machine with a linear power source characteristic provides open circuit voltage of 80 V and short circuit current of 800 A. During welding the machine, the measured arc current is 500 A corresponding to an arc length of 5.0 mm and the measured arc current is 460 A corresponding to an arc length of 7.0 mm. the linear voltage (E)-arc length (L) characteristic of the welding arc can be given as (where E is in volt and L is in mm)?
E = 80 + 8L
E = 80 + 2L
E = 20 + 8L
E = 20 + 2L