CWS CWS Metallurgy & Material Properties 1 — Questions and Answers
Question 1: Which alloying element in steel has the greatest effect on hardenability and is the primary contributor to the carbon equivalent (CE) formula?
- Manganese
- Carbon (Correct answer)
- Silicon
- Chromium
Correct answer: Carbon
Carbon has the greatest individual effect on hardenability and is the primary element in the carbon equivalent formula used to assess weldability.
Question 2: What microstructural transformation occurs in steel when it is heated above the upper critical temperature (Ac3) and then rapidly quenched?
- Pearlite formation
- Ferrite formation
- Martensite formation (Correct answer)
- Austenite formation
Correct answer: Martensite formation
Rapid quenching from above Ac3 traps carbon in the iron lattice, forming hard, brittle martensite — a body-centered tetragonal structure.
Question 3: A CWS supervisor is welding ASTM A514 (T-1) high-strength steel. What is the primary welding concern with this material?
- Hot cracking due to sulfur content
- Hydrogen-induced cold cracking (Correct answer)
- Sigma phase embrittlement
- Liquation cracking in HAZ
Correct answer: Hydrogen-induced cold cracking
A514 high-strength, low-alloy quenched and tempered steel has high hardenability and is highly susceptible to hydrogen-induced cold cracking (HICC) in the HAZ.
Question 4: What does the term 'sensitization' refer to in austenitic stainless steel?
- Increased corrosion resistance after welding
- Chromium carbide precipitation at grain boundaries causing intergranular corrosion (Correct answer)
- Stress relief of weld residual stresses
- Work hardening of the weld surface
Correct answer: Chromium carbide precipitation at grain boundaries causing intergranular corrosion
Sensitization occurs when austenitic stainless steel is heated between 800–1500°F, causing chromium carbides to form at grain boundaries and depleting chromium from adjacent zones.
Question 5: Which heat treatment process is used to refine grain size and relieve internal stresses in carbon steel after welding?
- Solution annealing
- Normalizing (Correct answer)
- Martempering
- Austempering
Correct answer: Normalizing
Normalizing heats steel above Ac3, holds it, then air-cools to refine grain structure and relieve stresses induced by welding or forming.
Question 6: What is the heat-affected zone (HAZ) in a weld?
- The portion of the base metal that melted during welding
- The weld metal deposited by the filler material
- The base metal region that did not melt but had its microstructure altered by welding heat (Correct answer)
- The zone protected by flux or shielding gas
Correct answer: The base metal region that did not melt but had its microstructure altered by welding heat
The HAZ is the region of base metal adjacent to the weld that did not melt but experienced temperatures high enough to alter its grain structure and mechanical properties.
CWS CWS Metallurgy & Material Properties 1
Which alloying element in steel has the greatest effect on hardenability and is the primary contributor to the carbon equivalent (CE) formula?