AWS AWS Metallurgy & Materials 1 — Questions and Answers
Question 1: Which iron-carbon phase forms when austenite is rapidly quenched and is known for its high hardness?
- Ferrite
- Pearlite
- Martensite (Correct answer)
- Bainite
Correct answer: Martensite
Martensite forms during rapid quenching of austenite and is the hardest iron-carbon microstructure.
Question 2: What is the carbon content range (by weight) that defines low-carbon (mild) steel?
- 0.05%–0.15%
- 0.15%–0.30% (Correct answer)
- 0.30%–0.60%
- 0.60%–1.00%
Correct answer: 0.15%–0.30%
Low-carbon or mild steel contains approximately 0.15%–0.30% carbon by weight.
Question 3: The heat-affected zone (HAZ) in a weldment is the region that:
- Has been melted and resolidified
- Was heated but did not melt, yet had its microstructure altered (Correct answer)
- Remains completely unaffected by welding heat
- Contains the weld metal deposit only
Correct answer: Was heated but did not melt, yet had its microstructure altered
The HAZ is the base metal region adjacent to the weld that was heated enough to alter its microstructure without melting.
Question 4: Which alloying element in steel primarily improves hardenability by slowing the austenite-to-pearlite transformation?
- Sulfur
- Phosphorus
- Chromium (Correct answer)
- Nitrogen
Correct answer: Chromium
Chromium is a strong carbide former that significantly improves hardenability in steel.
Question 5: What does the term 'weldability' primarily describe?
- The ability of a metal to be cut by plasma
- The ease with which a metal can be welded to produce a sound joint (Correct answer)
- The tensile strength of a completed weld
- The melting point of a base metal
Correct answer: The ease with which a metal can be welded to produce a sound joint
Weldability refers to how readily a material can be welded to form a defect-free, serviceable joint.
Question 6: Preheating before welding high-carbon steel primarily serves to:
- Increase travel speed
- Reduce the risk of hydrogen-induced cracking (Correct answer)
- Eliminate post-weld heat treatment
- Increase weld bead convexity
Correct answer: Reduce the risk of hydrogen-induced cracking
Preheat slows the cooling rate of the HAZ, reducing hydrogen-induced (cold) cracking susceptibility.
AWS AWS Metallurgy & Materials 1
Which iron-carbon phase forms when austenite is rapidly quenched and is known for its high hardness?