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AWS Weld Metallurgy & Heat Treatment Flashcards

7 cards from real AWS practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

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

    Answer: Relieve residual stresses and temper the HAZ

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

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

    Answer: Martensite

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

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

    Answer: Preheat requirements and crack susceptibility

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

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

    Answer: 800–1500°F (427–816°C)

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

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

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

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

  6. What is the function of preheat when welding high-carbon or alloy steels?

    Answer: Slow the cooling rate to reduce hardness and minimize cracking

    Preheat slows the cooling rate through the critical temperature range, reducing the formation of hard martensite and lowering the risk of cold cracking.

  7. What is 'liquation cracking' (hot cracking) in the partially melted zone (PMZ)?

    Answer: Cracking caused by low-melting-point constituents forming liquid films at grain boundaries during cooling

    Liquation cracking occurs when low-melting-point phases form liquid films at grain boundaries in the PMZ, which rupture under tensile stress as the weld cools.