Chapter 2, lesson 2

Question 1

Explain what plain carbon steel is?

Answer 1

A plain carbon steel is when an alloy adds into a pure metal.

The alloy added may be: (intentionally added ones)
1. Carbon
2. Silicon
3. Manganese

The harmful impurities added may be: (added in un-intentionally)
1. Sulphur
2. Phosphorus

Question 2

What is a liquid solution?

Answer 2

One or more substances dissolves in another substance

The liquid produce is called a homogeneous liquid mixture

Question 3

What is a solid solution?

Answer 3

When an alloy atom replaces the host atom without changing the lattice structure

Question 4

What is a phase?

Answer 4

A phase is any substance which has a homogenous substance

Question 5

What is allotropism?

Answer 5

It is the ability to exist in more 1 physical form for example IRON.

Different forms affect the mechanical property, UTS and %E

Question 6

Describe the key features of pure iron phase diagrams:

Answer 6

1. At Solidification BCC iron forms
2. At 1400°C BCC iron changes to FCC iron
3. At 910°C FCC iron changes to BCC iron
4. At 768°C , iron goes from paramagnetic to ferromagnetic

Question 7

Describe the key features in a FE-C diagram

Answer 7

1. Before UPPER critical temperature, phase is Austenite
2. In between UPPER critical temperature and LOWER critical temperature, phase is Austenite + Ferrite
3. Below LOWER critical temperature,
   (Hypoeuctecoid steel): phase is ferrite + Pearlite
   (hypereuctecoid steel): phase is cementite + pearlite

Question 8

Describe the properties of Austenite

Answer 8

• Gamma iron
• It is the solid solution of Carbon in FCC iron
• properties: very soft, very ductile, non-magnetic

Question 9

Describe ferrite and it’s properties

Answer 9

• Alpha iron
• Solid solution of Carbon in BCC form
•Properties: Very soft, very ductile, magnetic

Question 10

Describe Cementite and it’s properties

Answer 10

• A compound, Iron Carbide
• It’s crystal structure is Orthorhombic
• Properties: Very hard and Brittle

Question 11

Describe Pearlite and it’s properties

Answer 11

• Mechanical mixture of ferrite and Cementite
• Alternate layering
• Properties: high UTS, the lamellar structure creates a strong composite material

Question 12

Summarise the difference between Ferrite, Pearlite and Cementite

Answer 12

FERRITE:
- high UTS
- high %E = ductile
- low hardness

PEARLITE:
- High UTS
- low %E
- low Hardness

CEMENTITE:
- low UTS
- high hardness

Question 13

Compare the 3 different types of Eutectoid steel

Answer 13

1. Normal Eutectoid Steel: carbon is 0.8% added
2. Hypo Eutectoid Steel:
   <0.8% of Carbon added
3. Hyper Eutectoid Steel:
   > 0.8% of Carbon added

Question 14

What is the relationship between the carbon % added and the mechanical properties

Answer 14

Increase in Carbon added: higher UTS (only to 0.8%), increase in hardness but drop in ductility.

Question 15

Describe the 5 different plain Carbon Steel

Answer 15

1. Dead mIld Steel
2. mild steel
3. Medium carbon steel
4. High carbon steel
5. Carbon tool steel

Question 16

Describe the %Carbon, property and applications for Dead Mild Steel

Answer 16

1. 0.05%-0.15% carbon
2. It’s soft and ductile
3. Used for car bodies, tubes and chains

Question 17

Describe the % Carbon, property and applications of Mild Steel

Answer 17

1. 0.15%-0.30%
2. Soft and ductile
3. Used for ship plates, steel sections for constructions

Question 18

Describe the % Carbon, property and applications of Medium carbon steel

Answer 18

1. 0.30%-0.60%
2. Best combination of strength and toughness
3. Used for gears, crankshafts

Question 19

Describe the Carbon%, property and applications of High carbon steel

Answer 19

1. 0.60%-0.80%
2. High strength
3. Used for screw drivers

Question 20

Describe Carbon%, property and applications of Carbon tool Steel

Answer 20

1. 0.80%-1.40%
2. High hardness and wear resistance
3. Used for Files, axes