CWI Weld Discontinuities and Defects 5

Question 1

What is 'reheat cracking' and in which type of steel is it most commonly encountered?

Accepted Answer

HAZ cracking that occurs during post-weld heat treatment (PWHT) in low-alloy Cr-Mo steels

Answer

Reheat cracking occurs in the coarse-grained HAZ of low-alloy Cr-Mo steels during PWHT or elevated temperature service when creep relaxation cannot occur without intergranular fracture.

Question 2

A weld inspector measures a fillet weld and finds the convexity exceeds the code limit. Which repair action is typically required?

Accepted Answer

Grinding to reduce the convexity to within acceptable limits

Answer

Excessive convexity is corrected by mechanically grinding the weld face to reduce the profile to within code-specified limits.

Question 3

Which discontinuity is described as 'wagon tracks' on a radiograph and what does it represent?

Accepted Answer

A pair of parallel dark lines indicating incomplete fusion at the root of a double-V groove weld

Answer

Wagon tracks on a radiograph appear as two parallel dark lines representing incomplete fusion along both faces of the root pass in a double-V or CJP groove weld.

Question 4

When a weld shows evidence of 'crater cracks,' what is the primary corrective preventive measure during welding?

Accepted Answer

Backstepping the weld and properly filling the crater before breaking the arc

Answer

Crater cracks are prevented by pausing at the end of each weld pass to properly fill the crater to a flat or slightly convex profile before extinguishing the arc.

Question 5

Linear porosity aligned along the weld axis MOST likely indicates:

Accepted Answer

Gas entrapment from a contamination source localized along the joint

Answer

Linear porosity aligned along the weld axis typically indicates a consistent contamination source along the joint, such as oil, moisture, or rust on the joint faces.

CWI Practice Test

CWI Practice Test

CWI Weld Discontinuities and Defects 5