CWI Weld Discontinuities and Defects 4

Question 1

Which non-destructive testing method is BEST suited for detecting subsurface planar discontinuities parallel to the weld surface in a thick plate?

Accepted Answer

Ultrasonic testing (UT)

Answer

Ultrasonic testing is most effective for detecting internal planar discontinuities such as laminations and cracks, especially those parallel to the surface in thick sections.

Question 2

What is the primary difference between a 'discontinuity' and a 'defect' in welding inspection terminology?

Accepted Answer

A defect is a discontinuity that exceeds the acceptance criteria of the applicable code

Answer

A discontinuity is any interruption in the material's typical structure, while a defect is a discontinuity that fails to meet the acceptance criteria of the applicable welding code.

Question 3

Arc strikes outside the weld zone are considered defects primarily because they:

Accepted Answer

Create hard, brittle zones that can initiate cracking in the base metal

Answer

Arc strikes cause rapid localized heating and quenching of base metal, creating hardened zones with potential cracking that can initiate fatigue failure.

Question 4

A weld cross-section shows a narrow, incomplete fusion line between the weld metal and base metal on one side of the groove. This is BEST described as:

Accepted Answer

Lack of fusion (LOF) / incomplete fusion

Answer

Lack of fusion (incomplete fusion) occurs when the weld metal fails to fuse completely with the base metal or adjacent weld passes at the fusion interface.

Question 5

Which factor MOST influences the formation of hot cracks in austenitic stainless steel welds?

Accepted Answer

High sulfur and phosphorus content promoting low-melting boundary films

Answer

Hot cracking in austenitic stainless steels is primarily caused by sulfur and phosphorus segregating to grain boundaries and forming low-melting-point films that crack during solidification.

CWI Practice Test

CWI Practice Test

CWI Weld Discontinuities and Defects 4