Metallurgy & Material Science Flashcards
7 cards from real WCL practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Metallurgy & Material Science flashcards as text
What is the significance of the 'carbon equivalent' (CE) formula in welding?
Answer: It estimates hardenability and cold cracking susceptibility of the base metal
The CE formula combines carbon and alloying element percentages to estimate how hardenable a steel is and thus how susceptible it is to hydrogen-induced cold cracking.
Interpass temperature control during multi-pass welding primarily prevents which metallurgical problem?
Answer: Excessive grain growth and reduced toughness in the HAZ
Allowing interpass temperature to become too high causes prolonged exposure to elevated temperatures, promoting coarse grain growth and degrading HAZ toughness.
Which type of stainless steel is NOT hardenable by heat treatment?
Answer: Austenitic stainless steel
Austenitic stainless steels cannot be hardened by heat treatment because they do not undergo a martensitic transformation; they can only be work-hardened.
What is 'hot cracking' (solidification cracking) in welds, and what promotes it?
Answer: Cracking in the fusion zone during solidification due to low-melting-point segregates
Hot cracking occurs when low-melting-point compounds (e.g., iron sulfides) segregate to grain boundaries during solidification, forming liquid films that tear under shrinkage stresses.
In welding metallurgy, what is the 'heat-affected zone' (HAZ)?
Answer: The base metal region heated enough to alter its microstructure without melting
The HAZ is the portion of the base metal adjacent to the fusion zone that is heated sufficiently to cause microstructural changes but does not reach the melting point.
What purpose does post-weld heat treatment (PWHT) serve in pressure vessel welding?
Answer: It relieves residual stresses and tempers hard HAZ microstructures
PWHT tempers martensite, reduces residual welding stresses, and improves toughness and ductility in the HAZ, meeting code requirements for pressure-containing welds.
Which copper alloy is considered most weldable and commonly joined by GTAW?
Answer: Deoxidized copper (phosphorus-deoxidized)
Phosphorus-deoxidized copper contains minimal oxygen, preventing porosity during welding and making it the most readily weldable copper alloy.