CWI Metallurgy and Weld Discontinuities Questions and Answers

Question 1

In the heat-affected zone (HAZ) of a single-pass carbon steel weld, which region is characterized by the largest grain size and is typically located immediately adjacent to the fusion boundary?

Accepted Answer

Grain-coarsened region (GCHAZ)

Answer

Grain-refined region (FGHAZ)

Answer

Partially transformed region

Answer

Tempered region

Question 2

A welder completes a groove weld on a thick section of high-strength, low-alloy (HSLA) steel using an SMAW electrode that was not stored in a proper rod oven. An inspection performed 48 hours later reveals a crack in the heat-affected zone. What is the most likely type and cause of this discontinuity?

Accepted Answer

Hydrogen-induced crack caused by moisture in the electrode.

Answer

Solidification crack caused by high sulfur content.

Answer

Lamellar tear caused by through-thickness strain.

Answer

Crater crack caused by improper weld termination.

Question 3

During fabrication, a T-joint is made by welding a plate perpendicularly onto the surface of another, thicker plate. After welding, a crack is found in the base material of the thicker plate, running parallel to the plate surface and having a step-like appearance. This discontinuity is best described as:

Accepted Answer

A lamellar tear.

Answer

A fatigue crack.

Answer

A hot crack.

Answer

A lack of fusion discontinuity.

Question 4

A welding procedure for a thick-walled chrome-moly pressure vessel requires post-weld heat treatment (PWHT). What is the primary metallurgical reason for performing this step?

Accepted Answer

To temper brittle microstructures and reduce residual stresses.

Answer

To increase the ultimate tensile strength of the weld.

Answer

To refine the as-welded grain structure of the weld metal.

Answer

To remove entrapped slag from within the weld deposit.

Question 5

Solidification cracking, also known as hot cracking, is most likely to occur in a weld metal that has:

Accepted Answer

A wide solidification temperature range and high levels of impurities like sulfur and phosphorus.

Answer

A high concentration of deoxidizers like silicon and manganese.

Answer

A very low carbon equivalent and slow cooling rate.

Answer

A fully austenitic microstructure with low residual stress.

Question 6

Which of the following is the LEAST likely cause of porosity in a Gas Metal Arc Welding (GMAW) weld?

Accepted Answer

Low travel speed with appropriate heat input.

Answer

Inadequate shielding gas flow rate.

Answer

Contaminants such as oil or moisture on the base material.

Answer

An excessively long electrode extension (stickout).