Materials Technology, level 3, September 2011

Question 1
1.1 Name any four mechanical properties of metals.               (4)

1.2 What is elasticity of a metal?                         (2)

1.3 What is meant by the plasticity of a metal?                    (2) 

1.4 State two physical properties of metals.                   (2)

1.5 Steel is categorised in four categories, name the four.               (4)

1.6 Name two characteristics of copper: not the use of copper.       (2)

1.7 The numbering available for brass, in accordance with the SABS are CuZN39Pb2.
What does ZN39, Pb2 cu stand for?                                   (3)

1.8 The copper pipe 460/0 is graded to be used where?              (1)
                                                                                                                                     (20)

Question 2

2.1 Name two properties and two uses of glass reinforced plastics.          (2)

2.2 Name two types of plastics.                                          (2)

2.3 State three uses of asbestos.                                                                                (3)

2.4 What is an atom?                                                     (1)

2.5 Name three properties of styrene Butadiene rubber (natural rubber).           (3)

2.6 Epoxy resin have some good characteristics and uses!
Name two uses and two characteristics                                  (4)

2.7 Name three uses for polyester resins.                                          (3)
                                                                                                                         (17)

Question 3

3.1 Please explain the vapour transport stage when quenching the material (cooling).        (7)

3.2 The charge in a cupola furnace composed of various materials: name them.               (5)

3.3 Identify the mark parts, 1 to 5 of the Bessemer converter in Figure 1.                        (4)

                                                                                    Figure 1


3.4 Name one advantage of a blast furnace.                                                          (1)

3.5 Name one advantage of a Bessemer converter.                                                (1)

3.6 What is the function of the Tuyéres nozzle?                                                       (1)
                                                                                                                     (20)


Question 4

4.1 Iron has two distinct and different atomic structures; name the difference.                (2)

4.2 Explain the meaning of soaking the steel.                                                             (1)

4.3 Quenching oils must have certain characteristics; name two of them.                       (2)

4.4 Case hardening is a two part process. Explain the two parts.                                 (2)

4.5 What is nitrading?                                                                                          (1)

4.6 A cold chisel must be temper to harden the tip, what is the tempering colour?           (1)

4.7 Why is the steel annealed?                                                                                (4)

4.8 Explain the term air hardening.                                                                           (3)

4.9 Describe the annealing of copper.                                                                      (2)

4.10 What is the function of a ladle?                                                                         (1)

4.11 What is the function of Limestone?                                                                   (1)                                                                                                                                                 (20)
Question 5

5.1 What is the purpose of torsional testing?  Name the properties of the test.                 (5)

5.2 Draw the load extension graph for mild steel and explain the steps A & F                (6)

5.3 Figure 2, shows a Brinell hardness tester.  Name the various parts, 1 to 9.                 (9)
                                                                                                                         (20)

                                                                             Figure 2

                                                                                                 TOTAL  MARKS: 100

Memorandum

Question 1

1.1 Hardness, toughness, brittleness, ductility, malleability, tensile strength or 

tenacity; elasticity; stress; strain; compressive strength and plasticity.               ANY 4 (4)

1.2 This is the ability of a metal to return to its original shape after a load has 

been removed from it.                                                                                         (2)

1.3 This is the ability of a material to flows to new shapes under pressure and to retain 

its new form.                                                                                                      (2)

1.4 Colours Thermal conductivity

Density Expansion

Boiling point Electrical conductivity

Melting Specific heat                                                                               ANY 2 (2)

1.5 Low carbon steel High carbon steel Medium carbon steel Alloy steel                   (4)

1.6 High electrical conductivity

Resistance to corrosion high thermal conductivity

Copper is a ductile material

Copper is a good base for many alloying agent

If copper is cold-worked, its strength and brittleness increase. ANY 2                   (2)

1.7 ZINK 39%; Lead 2% and 59% copper                                                       (3)

1.8 This pipe can only be used above ground.                                                       (1)

                                                                                                                                (20)

Question 2

2.1 PROPERTIES USES

High strength to weight ratio Boats

Resistance to corrosion Trailers

Dimensional stability Aircraft

Ease of fabrication Household appliance

High tensile strength Water & fuel tanks

High compressive strength Surfboards / vehicle components (4)

2.2 Thermoplastics                                                                                           (1)

Thermosetting plastics                                                                                        (1)

2.3 Clutch linings roofing sheets   Brake shoes heater panels   Insulating materials  
fire resistant materials                                                                                     ANY 3 (3)

2.4 The atom is the smallest particle of any substance.                          (1)

2.5 Low tensile strength

Good abrasion resistance

High heat build-up when subjected to dynamic stressing

Temperature resistance up to 110⁰C

High insulation properties

Good weather and ozone resistance                                                          ANY 3 (3)

2.6 Characteristics

Excellent adhesion to metals, glass, stone, etc.

Great mechanical strength and toughness

Chemical resistance

Dielectric strength

Low shrinkage on setting

Absence of volatiles on setting

Available as adhesives, moulding powers and coating                               ANY 2        (2)

Uses

Bonding of metals, glass, ceramics and plastics in buildings, boats and furniture.

Encapsulating electrical and electronic equipment

Moulds and dies for plastic forming, jigs, anti corrosive linings.             ANY 2          (2)

2.7 Car bodies, boat hulls, luggage trunk, computer components, fishing rods, etc ANY 3 (3)

                                                                                                                         (20)

Question 3

3.1 The next stage occurs when the temperature of the hot surface area drops and the 

Vapour blanket cannot be maintained.  This is the stage of fastest cooling, during which 

The natural surface comes into contact with the coolant.  As the coolant boils, vapour 

Forms into the main body of the coolant.                                                                 (7)

3.2. Pig iron

Grey cast iron scrap

Steel scrap

Coke fuel

Limestone flux                                                                                                (5)

3.3 Bressemer parts Identification (Figure 1)                                                        (4)

3.4 Disadvantages

Can only produce pig iron requiring further refining.

Takes a long time to start producing from cold.                                               (1)

3.5 Remove impurities in a short length of time.                                                (1)

3.6 Tuyéres nozzles are used to blow hot air into the furnace .                          (1)

                                                                                                            (20)

Question 4

4.1 Different atomic structure – one existing at room temperature.                   (1)

One above the transformation temperature.  

The steel must be held in the furnace at the correct temperature for a certain time.      (1)

4.3 Correct viscosity

High flash point to reduce fire risk

Low volatility to reduce the duration of the vapour blanket stage

Resistance to oxidation, carbonization and sludging                                   ANY 2 (2)

4.4 Carburising in which the carbon content of the surface is increased.                 (1)

Heat treatment in which the core is refined and the case hardened.                 (1)

4.5 It is a gas method of case hardening.                                                        (1)

4.6 Red brown nearly purple                                                                        (1)

4.7 Annealing softens the steel and remove internal stresses caused, for example, by 

welding or cold working.  This process also refines the grain structure and reduces 

brittleness.                                                                                                   (3)

4.8 Some steels are best harden after reaching the correct temperature by jets of air. (3)

4.9 Evenly heat the copper work piece to a dull red and immediately quench in water. (2)

4.10 The Ladle’s function is to transport the molten liquid metal.                         (1)

4.11 A type of white or grey stone containing calcium carbonate, used as flux in blast 

and cupola furnaces.                                                                                    (1)

                                                                                                                           (20)

Question 5

5.1 a) Moduled of elasticity in shear

b) Yield shear strength

c) Ultimate shear strength

d) Modulus of rupture in shear

e) Ductility                                                                                             (5)

5.2 Extension graph                                                                                  (6)

                                                  (9)

5.3. Brinell Hardness tester:  Figure 2

                                                                                                  (20)