AWS Welding Metallurgy & Heat Treatment 2

Question 1

What is the primary purpose of preheating before welding high-carbon steel?

Accepted Answer

Reduce the risk of hydrogen-induced cracking

Answer

Preheating slows the cooling rate, allowing hydrogen to diffuse out and reducing the risk of hydrogen-induced (cold) cracking in the heat-affected zone.

Question 2

Which microstructural phase in steel is hardest and most brittle, often forming in rapidly cooled welds?

Accepted Answer

Martensite

Answer

Martensite forms when austenite is rapidly quenched, trapping carbon in a distorted body-centered tetragonal lattice, resulting in high hardness and brittleness.

Question 3

What does the term 'carbon equivalent' (CE) indicate in welding?

Accepted Answer

Weldability based on carbon and alloying element content

Answer

Carbon equivalent (CE) is a formula that quantifies a steel's weldability by accounting for the combined effect of carbon and other alloying elements on hardenability.

Question 4

Post-weld heat treatment (PWHT) of carbon steel welds is primarily performed to:

Accepted Answer

Refine grain size and relieve residual stresses

Answer

PWHT (stress relief) reduces residual stresses, tempers hard microstructures, and improves ductility and toughness in the weld and HAZ.

Question 5

Which region of the heat-affected zone experiences the highest peak temperature during welding?

Accepted Answer

Coarse-grained HAZ

Answer

The coarse-grained HAZ is nearest the fusion line and experiences temperatures well above the upper critical temperature, causing significant austenite grain growth.

AWS Practice Test

AWS Practice Test

AWS Welding Metallurgy & Heat Treatment 2