IV. Comprehension

Ex.12. Agree or disagree with the following statements:

1. Copper is a reddish – brown tough metal.

2. Non-ferrous metals are very cheap.

3. An addition of alluminium makes brasses stronger.

4. All – ferrous castings will take a high polish and will not rust so easily as the ferrous metals.

5. The metal most frequently used to make non-ferrous metal castings is copper.

6. Usually where aluminium alloys are made the aluminium predominates.

7. Aluminium is a strong, yellow metal.

Ex.13. Answer the following questions:

1. What are the main characteristics of non – ferrous metals?

2. What are the properties of copper and what is it used for?

3. What purposes is aluminium used for?

4. What metals are used for producing non – ferrous castings?

5. What do you know about brasses?

6. What do you know about bronzes?

7. What are the main properties of non – ferrous castings?

8. Why are attempts made to replace non – ferrous metals by ferrous ones?

Ex. 14. Complete the table. Use the information from the text A

Non – ferrous metals

	Copper	Aluminium	Bronze	Aluminium alloys
Appearance	Reddish brown tough metal
Qualities	High electric conductivity
Used for	Wires, pipes, telephone cables

V. Oral Practice

Ex. 15. Speak on the topic “Non-ferrous metals” using the table of ex.14

Ex. 16. Prove that non ferrous metals are very important.

VI. Reading and comprehension

Ex.17. Read the text without a dictionary for 5 minutes and define the quality of the aluminum and the processes which improve its quality.

Aluminium

Aluminium, lightweight, strong, and readily formable. Aluminium and its alloys, numbering in the hundreds, are available in all common commercial forms. Because of their high thermal conductivity, many aluminium alloys are used as electrical conductors.

Commercially pure aluminium has a tensile strength of about 13, 000 psi. Cold-working the metal approximately doubles its strength. For greater strength aluminium is alloyed with other elements such as manganese, silicon, copper, magnesium or zinc. Some alloys are further strengthened and hardened by heat treatments. Most aluminium alloys lose strength at elevated temperatures, although some retain significant strength to 500 ⁰F.

Aluminium is produced by electrolytic means from bauxide, an aluminium hydroxide, and makes a good clean casting with a fairly coarse grain structure. It is a fair substitute for cast iron except that it is a bit more ductile. On the other hand, it can be rolled or drawn into sheets, rods, and tubes that can be bent due to their ductility whereas cast iron cannot.

The aluminium alloys with copper, manganese, silicon and nickel are pretty numerous and are selected either for their corrosion resistance, high electrical conductivity, ductility and /or higher strength.