Material Selection & Properties 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 Material Selection & Properties flashcards as text
What is the effect of phosphorus on the weldability of carbon steel?
Answer: Increases susceptibility to cold cracking and reduces notch toughness
Phosphorus segregates to grain boundaries and solidification fronts, causing cold cracking and severely reducing impact toughness in weld metal.
Which nickel alloy is designated as Inconel 625 and known for its outstanding weldability?
Answer: Ni-Cr-Mo alloy (61% Ni, 22% Cr, 9% Mo)
Inconel 625 is a nickel-chromium-molybdenum alloy with approximately 61% Ni, 22% Cr, and 9% Mo, prized for both weldability and corrosion resistance.
What is the primary reason for specifying low-hydrogen (H4 or H8) electrodes when welding high-strength steels?
Answer: To prevent hydrogen-induced cold cracking in the HAZ
Hydrogen diffuses into the HAZ during welding and causes delayed cold cracking; low-hydrogen electrodes minimize diffusible hydrogen to prevent this failure mode.
Which property is most important when selecting a filler metal to weld a pressure vessel operating at cryogenic temperatures?
Answer: Excellent Charpy impact toughness at service temperature
Cryogenic service requires weld metal with high notch toughness at low temperatures, typically achieved with austenitic stainless or nickel-alloy filler metals.
What is 'precipitation hardening' (PH) in stainless steel grades like 17-4 PH?
Answer: Strengthening by heat treatment that causes fine precipitates to form within the matrix
Precipitation hardening strengthens stainless steel by controlled aging heat treatment that causes fine intermetallic precipitates to form, blocking dislocation movement.
What does the designation 'ER70S-6' indicate about a solid wire electrode?
Answer: It produces welds with 70 ksi tensile strength and contains silicon and manganese deoxidizers
ER70S-6 indicates an electrode-rod for GMAW with minimum 70 ksi tensile strength, solid wire, and the '-6' suffix denotes high silicon and manganese for deoxidation.
What characteristic makes martensitic stainless steel (e.g., 410) more difficult to weld than austenitic grades?
Answer: Transformation to hard, brittle martensite upon cooling, requiring preheat and PWHT
Martensitic stainless steels undergo a hardening transformation upon cooling, creating a hard, crack-susceptible HAZ that requires preheat and post-weld heat treatment.