Heat Treatment

Question 1

How does heat treatment affect steel?

Answer 1

Affects the mechanical and physical properties by changing the internal structure of a sample

Question 2

What 2 reasons permits the microstructure of steel to be altered?

Answer 2

1) Since iron is allotropic it can goes through a crystal change while maintaining it’s solid state
2) Carbon moves and diffuses out of the material thus changing material properties.

Question 3

What is the crystal structure of Iron below 910 degrees Celcius?

Answer 3

Body-centered cubic

Question 4

What is the crystal structure of Iron above 910 degrees Celcius?

Answer 4

Face-centered cubic

Question 5

What affects the critical temperature of steel?

Answer 5

The amount of Carbon present in the sample

Question 6

What is an Euectoid?

Answer 6

The lowest temperature at which steel changes from FCC to BCC crystal structure

Question 7

Full anneal heat treatment provides the __________, most ________ condition for steel. It results in a __________ grain structure.

Answer 7

Softest, ductile, course

Question 8

How are full anneal treatment samples cooled?

Answer 8

Slow cooled in a furnace dropping 10-40 degrees Celcius every hour

Question 9

Normalizing produces __________ and ____________ steel. It has a ___________ and ______________ grain structure compared to annealing.

Answer 9

hard, strong, uniform, fine

Question 10

How are normalized treatment samples cooled?

Answer 10

Still air

Question 11

Quenching provides steel of maximum _________ by forming __________. This happens because quenching does not allow time for Carbon to diffuse out.

Answer 11

Hardness, martensite

Question 12

What is the purpose of tempering heat treatment?

Answer 12

A critical process carried out following quenching to restore ductility and toughness in the material by letting Carbon diffuse out of the sample.

Question 13

How do you know how much heat is required for tempering heat treatment?

Answer 13

The samples are heated below their Lower Transformation Temperature. This allows for Carbon to diffuse out of the sample forming tempered martensite.

Note: this decreases hardness and strength

Question 14

What is the purpose of case hardening?

Answer 14

Case hardening improves surface hardness of low carbon steel. Carburizing process adds Carbon to the surface while the material maintains a ductile core.