CWI Welding Process Fundamentals 3

Question 1

What is 'porosity' in a weld and what commonly causes it?

Accepted Answer

Gas pockets trapped in the solidifying weld metal, often from contamination or moisture

Answer

Porosity results from gases (hydrogen, oxygen, nitrogen) becoming trapped as the weld pool solidifies, commonly caused by moisture, contamination, or inadequate shielding.

Question 2

Which electrode designation is a low-hydrogen SMAW electrode?

Accepted Answer

E7018

Answer

E7018 has a low-hydrogen iron powder coating (indicated by the '8' suffix), requiring storage in a rod oven to prevent moisture absorption.

Question 3

What does 'undercutting' refer to in welding inspection?

Accepted Answer

A groove melted into the base metal at the weld toe that is not filled by weld metal

Answer

Undercut is a groove or channel burned into the base metal along the weld toes or root that weakens the joint by reducing cross-sectional area.

Question 4

In plasma arc welding (PAW), what distinguishes the 'keyhole' technique from conventional welding?

Accepted Answer

A focused plasma jet penetrates completely through the base metal, creating a hole that is filled as the torch progresses

Answer

The keyhole technique in PAW uses a constricted, high-energy plasma column to pierce through the workpiece; the molten metal flows around and behind, producing full-penetration welds in one pass.

Question 5

What is the significance of the 'interpass temperature' in multi-pass welding?

Accepted Answer

It is the maximum temperature of the weld area between passes, controlled to prevent metallurgical damage

Answer

Interpass temperature is the maximum allowed temperature of the weld zone before depositing the next pass, preventing excessive heat input that can degrade toughness and mechanical properties.

CWI Practice Test

CWI Practice Test

CWI Welding Process Fundamentals 3