Structure and Properties of Construction Steel

Question 1

What are three type of construction steels?

Answer 1

Low carbon .2 % C I beams

High strength low alloy steel .2% C (Mn, Cr, Ni alloys)

Heat treated construction alloy steel .2% (Cr, C, Mo alloys)

Question 2

What are strengthening mechanisms in metals?

Answer 2

• Solid solution strengthening
• Grain refinement
• Phase hardening
• Precipitation hardening
• Dispersion hardening
• Work hardening

Question 3

Explain solid solution hardening (3).

Answer 3

Addition of one or more metals can increase the strength of metals
Distortion of lattice and clustering of like atoms also impede dislocation movement. (this is introducing basketball in nest of golf balls must be 15% or higher difference)
Roughening of slip planes

Question 4

What is grain refinement?

Answer 4

Grain boundaries are barriers to dislocation motion
Grain boundaries stop dislocation movement and hence strengthen the metals.
Fine grain size is desirable, and hence metals are produced with finer grains

Question 5

What is precipitation hardening?

Answer 5

Precipitates hinder dislocation motion

Question 6

What is dispersion strengthening?

Answer 6

Same as precipitation strengthening but T independent

Question 7

Why are different alloying elements added to construction steels

Answer 7

Differing in radius size. This allows for greater inability to move.