WCL Metallurgy & Material Science 2

Question 1

What is the primary reason carbon content is limited in structural steel used for welding applications?

Accepted Answer

Higher carbon increases brittleness and cold cracking risk

Answer

Elevated carbon content raises hardenability and increases susceptibility to hydrogen-induced cold cracking in the heat-affected zone.

Question 2

Which phase transformation occurs when austenite is rapidly quenched and results in a hard, brittle microstructure?

Accepted Answer

Martensite formation

Answer

Rapid quenching traps carbon in a body-centered tetragonal lattice, forming martensite—the hardest and most brittle steel microstructure.

Question 3

What does the term 'preheat' accomplish metallurgically in high-carbon steel welding?

Accepted Answer

It slows the cooling rate to reduce martensite formation

Answer

Preheat raises the base metal temperature, slowing post-weld cooling and reducing the likelihood of martensite formation in the HAZ.

Question 4

Which alloying element in stainless steel is primarily responsible for corrosion resistance?

Accepted Answer

Chromium

Answer

Chromium (minimum ~10.5%) forms a passive chromium oxide film on the surface that protects stainless steel from oxidation and corrosion.

Question 5

What is 'sensitization' in austenitic stainless steel and when does it occur?

Accepted Answer

Chromium carbide precipitation at grain boundaries between 800°F–1500°F

Answer

Sensitization occurs when chromium carbides precipitate at grain boundaries, depleting adjacent zones of chromium and making them susceptible to intergranular corrosion.

(WCL) Welding Certification Los Angeles Practice Test

(WCL) Welding Certification Los Angeles Practice Test

WCL Metallurgy & Material Science 2