AWS AWS Weld Metallurgy & Heat Treatment 4

Question 1

What is the primary purpose of post-weld heat treatment (PWHT) on carbon steel weldments?

Accepted Answer

Relieve residual stresses and temper the HAZ

Answer

PWHT relieves residual stresses induced during welding and tempers hard microstructures in the heat-affected zone to improve toughness.

Question 2

Which microstructure is most commonly associated with hydrogen-induced cracking (HIC) in the HAZ of high-strength steels?

Accepted Answer

Martensite

Answer

Martensite is a hard, brittle microstructure susceptible to hydrogen-induced cracking because it traps hydrogen at grain boundaries and defects.

Question 3

What does the carbon equivalent (CE) formula help predict in welding?

Accepted Answer

Preheat requirements and crack susceptibility

Answer

The carbon equivalent formula combines carbon and alloying element percentages to estimate a steel's hardenability and required preheat to prevent cracking.

Question 4

When welding austenitic stainless steel, sensitization occurs primarily in which temperature range?

Accepted Answer

800–1500°F (427–816°C)

Answer

Sensitization in austenitic stainless steel occurs between approximately 800–1500°F as chromium carbides precipitate at grain boundaries, depleting chromium.

Question 5

In welding metallurgy, what does 'HAZ softening' refer to in precipitation-hardened aluminum alloys?

Accepted Answer

Loss of strength in the heat-affected zone due to overaging or dissolution of strengthening precipitates

Answer

HAZ softening in precipitation-hardened aluminum alloys results from the welding heat overaging or dissolving the strengthening precipitates, reducing strength.

AWS Practice Test

AWS Practice Test

AWS AWS Weld Metallurgy & Heat Treatment 4