CMS Industrial Materials & Metallurgy 3

Question 1

What is the purpose of the martensite transformation in steel hardening?

Accepted Answer

To produce a hard, body-centered tetragonal microstructure by rapid quenching

Answer

Rapid quenching traps carbon in the iron lattice, distorting it into a body-centered tetragonal structure called martensite, which is extremely hard and brittle.

Question 2

Which alloying element is added to steel to improve its machinability by forming soft inclusions that act as chip breakers?

Accepted Answer

Sulfur

Answer

Sulfur forms manganese sulfide (MnS) inclusions in steel that act as internal lubricants and chip breakers, significantly improving machinability.

Question 3

What is work hardening (strain hardening) in metals?

Accepted Answer

Increase in hardness and strength due to plastic deformation at room temperature

Answer

Work hardening is the increase in a metal's hardness and yield strength resulting from plastic deformation, which increases dislocation density and impedes further dislocation movement.

Question 4

In the iron-carbon phase diagram, what is the maximum carbon content that defines the boundary between steel and cast iron?

Accepted Answer

2.14% C

Answer

The boundary between steel and cast iron occurs at 2.14% carbon, which represents the maximum solubility of carbon in austenite at the eutectic temperature.

Question 5

Which surface hardening process introduces nitrogen into the surface layer of steel to increase hardness without quenching?

Accepted Answer

Nitriding

Answer

Nitriding diffuses nitrogen into the steel surface at temperatures below the critical temperature, forming hard nitride compounds without requiring subsequent quenching.

(CMS) Certified Manufacturing Specialist Practice Test

(CMS) Certified Manufacturing Specialist Practice Test

CMS Industrial Materials & Metallurgy 3