SS and Wrought Alloys

Question 1

What is wrought alloys?

Answer 1

• manipulated/ shaped by cold working
• use for orthodontic wires
• partial denture clasps

Question 2

Steel

Answer 2

Composition
- 98% iron
- 2% carbon

if above 2% normally cast iron, pig iron

Other constituents
- chromium 1% to improve tarnish
- manganese as sulphur scavenger
- molybdenum, silicon, nickel, cobalt

Question 2

Uses of steel

Answer 2

• cutting instruments
• forceps

Question 3

Iron

Answer 3

Allotropic
- undergoes 2 solid state phase changes with temperature

1. Temp > 1400 c
   - body centred cubic crystallined structure 0.05%
2. 900 c < Temp < 1400 c
   - face centred cubic structure
   - higher carbon solubility 2%
3. Temp < 900c

Question 4

Alloy

Answer 4

• two metals that form a common lattice structure
• soluble in one another
• form a solid solution

Question 5

SS composition

Answer 5

• 74% iron
• 18% chromium
• 8% nickel
• 0.1% carbon

Question 6

Cold working

Answer 6

• work done on metal/ alloy at low temp
• below recrytallisation temp
• bending, rolling, swaging
• causes SLIP- dislocations collect at grain boundaries
• stronger, harder material
• work at strain hardening

Question 7

Elastic module

Answer 7

• ability of a material to undergo large deflections (to form arc) without permanent deformation
• returns to its original shape