456A Weld Quality Control

Question 1

What is the difference between a weld discontinuity and a weld defect?

Accepted Answer

A discontinuity is any interruption in the normal weld structure; it becomes a defect only when it exceeds the acceptance criteria specified by the applicable code or standard

Answer

They are the same thing

Answer

A discontinuity is always acceptable; a defect is always rejectable

Answer

A discontinuity is visible; a defect is hidden

Question 2

What is visual inspection (VT) and why is it the most important NDE method?

Accepted Answer

A systematic examination of welds before, during, and after welding using the unaided eye or visual aids; important because it is the first line of quality control and can prevent defects rather than just finding them

Answer

Using a magnifying glass to examine welds after completion only

Answer

Using cameras to photograph welds

Answer

A pass/fail test based only on weld appearance

Question 3

What does radiographic testing (RT) detect in welds?

Accepted Answer

Subsurface (internal) discontinuities such as porosity, slag inclusions, lack of fusion, incomplete penetration, and cracks by passing X-rays or gamma rays through the weld

Answer

Only surface cracks

Answer

Only weld surface profile defects

Answer

Hardness variations in the weld

Question 4

What is a Welding Procedure Specification (WPS) and why is it required?

Accepted Answer

A written document specifying all essential variables for a specific weld (process, filler metal, preheat, interpass temperature, technique, etc.) — required to ensure consistent, code-compliant welds

Answer

A description of the welder's qualifications

Answer

A list of approved welding equipment

Answer

A purchase order for welding consumables

Question 5

What is the purpose of preheat in welding and when is it required?

Accepted Answer

To slow the cooling rate of the weld and HAZ, reducing the risk of hydrogen-induced cracking, reducing residual stresses, and improving fusion in thick or high-carbon/alloy steels

Answer

To make the metal easier to cut

Answer

To increase welding speed

Answer

To dry moisture from the electrode

Question 6

What is the purpose of a bend test in weld qualification?

Accepted Answer

To evaluate weld ductility, fusion, and soundness by bending a specimen to a specified radius and examining the outer surface for cracks or discontinuities exceeding the acceptance criteria

Answer

To test if the weld can be straightened

Answer

To test the hardness of the weld

Answer

To determine the weld's tensile strength