Metallurgy & Weld Quality Inspection Flashcards

What is the primary cause of hydrogen-induced cracking (HIC) in SAW welds?

Answer: Diffusible hydrogen from moisture in flux

Moisture absorbed in SAW flux decomposes in the arc and introduces diffusible hydrogen into the weld metal, which can cause HIC in susceptible microstructures.

Which non-destructive testing method is most effective for detecting subsurface lack-of-fusion defects in a SAW weld?

Answer: Ultrasonic testing

Ultrasonic testing can detect internal volumetric and planar defects such as lack of fusion that are inaccessible to surface methods.

In the heat-affected zone (HAZ), the region immediately adjacent to the fusion line is called:

Answer: Coarse-grained HAZ

The coarse-grained HAZ (CGHAZ) is closest to the fusion line, where peak temperatures cause significant austenite grain growth.

A SAW weld bead shows excessive convexity. What is the most likely consequence?

Answer: Stress concentration at the weld toes

Excessive convexity creates a sharp angle at the weld toes, acting as a stress riser that reduces fatigue resistance.

Carbon equivalent (CE) formulas are used to predict:

Answer: Susceptibility of steel to hydrogen cracking

Carbon equivalent quantifies a steel's hardenability and its tendency to form brittle martensite, indicating risk of hydrogen-induced cracking.

Which type of weld discontinuity is classified as a planar defect and is most detrimental to structural integrity?

Answer: Crack

Cracks are planar defects with essentially zero radius of curvature at their tips, making them far more damaging than volumetric discontinuities under loading.

What does a Charpy V-notch test primarily measure in weld metal evaluation?

Answer: Notch toughness and transition temperature

The Charpy V-notch test measures absorbed impact energy, used to determine notch toughness and ductile-to-brittle transition temperature of weld metal.