CWI Welding Process Principles 3

Question 1

What is the purpose of using a 'backing bar' in a groove weld?

Accepted Answer

To support the molten weld pool and ensure complete root fusion

Answer

A backing bar (or backing strip) is placed behind the root of the joint to support the molten pool, prevent burn-through, and help achieve complete joint penetration.

Question 2

Which transfer mode in GMAW is generally associated with the highest heat input and is used for thick materials in the flat position?

Accepted Answer

Spray transfer

Answer

Spray transfer operates at high voltage and current, producing a steady stream of fine droplets with high heat input, making it suitable for thick materials in the flat or horizontal position.

Question 3

In GTAW, what is the effect of using pure argon shielding gas on an aluminum weld?

Accepted Answer

It provides cathodic cleaning action that removes the oxide layer

Answer

When welding aluminum with GTAW using AC, the electrode-positive half-cycle provides a cathodic cleaning action that breaks up and removes the refractory aluminum oxide layer.

Question 4

What is 'arc blow' in SMAW, and when is it most commonly encountered?

Accepted Answer

Magnetic deflection of the arc; most common with DC on ferromagnetic materials near the end of a joint

Answer

Arc blow is caused by unbalanced magnetic fields in the workpiece deflecting the arc, and it most frequently occurs with DC welding on ferromagnetic steel, particularly near joint ends or heavy fixturing.

Question 5

Which welding process deposits filler metal using the resistance heating of a wire electrode fed into a molten slag pool?

Accepted Answer

Electroslag welding (ESW)

Answer

Electroslag welding uses the electrical resistance of a molten slag pool to generate heat, melting both the consumable electrode and base metal as the weld progresses vertically.

CWI Practice Test

CWI Practice Test

CWI Welding Process Principles 3