Welding Metallurgy & Materials Flashcards
7 cards from real Architecting on AWS Certification 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 & Materials flashcards as text
What is the 'nil ductility transition temperature' (NDT) and why is it important in welded structural design?
Answer: The temperature below which fracture mode transitions from ductile to brittle, determining the minimum safe operating temperature for welded structures
The NDT is the temperature below which a material fractures without plastic deformation; structural components must not operate below this temperature to avoid catastrophic brittle fracture.
Which alloying element in nickel-base superalloy filler metals is primarily responsible for their high-temperature strength and oxidation resistance?
Answer: Chromium
Chromium forms a protective Cr2O3 oxide scale that provides oxidation resistance and also solid-solution strengthens the nickel matrix at elevated temperatures.
What is 'solidification cracking' and during which phase of the welding thermal cycle does it occur?
Answer: A crack that forms in the weld metal during the final stages of solidification when liquid films are present between dendrites
Solidification cracking (hot cracking) occurs when low-melting liquid films persist between dendrites near the solidus temperature and cannot withstand the tensile stresses from thermal contraction.
In FCAW and SMAW, what is the primary function of the slag that forms on top of the weld bead?
Answer: To protect the hot weld metal from atmospheric contamination and control cooling rate
Slag shields the solidifying weld metal from oxygen and nitrogen, and its thermal insulation slows cooling, reducing susceptibility to martensite formation and improving mechanical properties.
What is 'stress corrosion cracking' (SCC) in welded structures, and which combination of conditions is required for it to occur?
Answer: Simultaneous presence of a susceptible material, a corrosive environment, and tensile stress (residual or applied)
SCC requires the simultaneous combination of a susceptible material, a specific corrosive medium, and sufficient tensile stress; removing any one factor prevents cracking.
What is the significance of the 'T8/5' cooling parameter in weld metallurgy?
Answer: The time in seconds for the weld pool to cool from 800°C to 500°C, which controls HAZ microstructure in steels
T8/5 is the cooling time through the critical 800–500°C range where austenite transforms; fast T8/5 promotes martensite/bainite, while slow T8/5 promotes ferrite/pearlite in the HAZ.
Which non-destructive testing (NDT) method is most effective for detecting planar, surface-breaking cracks at weld toes in ferritic steel?
Answer: Magnetic particle testing (MT)
Magnetic particle testing creates a leakage field at surface or near-surface discontinuities in ferromagnetic materials, making it highly sensitive to planar cracks at weld toes.