Welding 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.
Read the first 7 Welding Metallurgy & Heat Treatment flashcards as text
What is the primary purpose of preheating before welding high-carbon steel?
Answer: Reduce the risk of hydrogen-induced cracking
Preheating slows the cooling rate, allowing hydrogen to diffuse out and reducing the risk of hydrogen-induced (cold) cracking in the heat-affected zone.
Which microstructural phase in steel is hardest and most brittle, often forming in rapidly cooled welds?
Answer: Martensite
Martensite forms when austenite is rapidly quenched, trapping carbon in a distorted body-centered tetragonal lattice, resulting in high hardness and brittleness.
What does the term 'carbon equivalent' (CE) indicate in welding?
Answer: Weldability based on carbon and alloying element content
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.
Post-weld heat treatment (PWHT) of carbon steel welds is primarily performed to:
Answer: Refine grain size and relieve residual stresses
PWHT (stress relief) reduces residual stresses, tempers hard microstructures, and improves ductility and toughness in the weld and HAZ.
Which region of the heat-affected zone experiences the highest peak temperature during welding?
Answer: Coarse-grained HAZ
The coarse-grained HAZ is nearest the fusion line and experiences temperatures well above the upper critical temperature, causing significant austenite grain growth.
Hot cracking in austenitic stainless steel welds is most commonly associated with:
Answer: Low-melting-point segregates at grain boundaries
Hot cracking (solidification cracking) occurs when low-melting-point impurities (sulfur, phosphorus) segregate to grain boundaries and remain liquid as the weld contracts.
Which heat treatment process involves heating steel above its upper critical temperature and then cooling in still air to refine grain structure?
Answer: Normalizing
Normalizing heats steel above the upper critical (Ac3) temperature and cools it in air, producing a uniform, refined grain structure with improved mechanical properties.