## 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