UNIT V. BUILDING MATERIALS (II)

6) In general, metals are good conductors of electricity.

These characteristics are possessed by all metals but the metals themselves differ from one another. Steel and cast iron are.referred to the group of ferrous metals. Cast iron is the cheapest of the ferrous metals It is chiefly used in building for compressed members of construction, as the supporting members.

When an engineer designs a steelwork he must carefully consider that the steel frame and every part of it should safely carry all the loads imposed upon it. The steel framework must be carefully hidden in walls, floors and partitions. It is steel and metal that is employed as reinforcement in modern ferroconcrete structures. In the curriculum of the Institute there is a special course on metal structures.

Steel. There are different kinds of steel. Alloyed steel (or special steel) is corrosion-resistant steel. This kind of steel is widely used in building. Stainless steel is also corrosion-resistant steel. It is used for cutlery, furnace parts, chemical plant equipment, valves, ball-­bearings, etc.

Non-Ferrous Metals. Non-ferrous metals have the following characteristics: high electric and heat conductivity, high corrosion resistance, non-magnetic qualities, light weight.

Aluminium. This is the oldest and best known light metal. It is used in aircraft, automobile, chemical and some other industries.

Copper. Copper is the best conductor of electricity. There are different alloys with copper. An alloy of copper and tin is called bronze. This metal is often used for making various ornaments.

Exercise. Answer the following questions:

1. What do ferrous metals include? 2. Is iron the main component of non-ferrous metals? 3. What properties do metals possess? 4. Do the metals themselves differ from one another? 5. Is cast iron the cheapest of the ferrous metals? 6. What must an engineer carefully consider when he designs a steelwork? 7. Where must the steel framework be carefully hidden? 8. Is alloyed steel corrosion-resistant steel? 9. What is it used for? 10. Is aluminium the oldest and best known light metal? 11. Do you know

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that the best conductor of electricity is copper? 12. An alloy of copper and tin is called bronze, isn't it?

TEXT 5B. ALUMINIUM IN STRUCTURES

Read the text and then render it in Russian:

Aluminium is not a new material. Probably the first example of large-scale structural use of aluminium was in 1933 when the floor steelwork of a large road bridge in Pittsburg, Pennsylvania, was replaced with aluminium and the resulting saving in dead weight • about 1 ton/ft run - enabled the bridge to carry with greater safety the increased loads of modern traffic. Apart from the construction of aircraft, aluminium has thus a structural history of about only half a century. Extensive use of aluminium in buildings such as aircraft hangers did not occur until about 30 years ago.

In many ways aluminium has been slow in making progress, mainly because of its cost; it is produced by electrolytic means which requires cheap hydro-electric power. About 10 units of electricity are required to make 1 1b. New reduction plants of large capacity have been coming into service in many parts of the world and these provide increased production with improved efficiency. The use of aluminium in structures may well expand in corresponding manner as simultaneous advances are being made with the development of improved aluminium materials and products.

The principal virtues of aluminium are lightness combined with strength and freedom from corrosion. The extent to which the latter two properties are developed depends on the alloy concerned.

The advantage of lightness - one-third the density of mild steel with nearly the same strength - is particularly of value where weight saving is of importance - in lift bridges, long span roofs, dome roofs, crane jibs and in a wide range of moving and portable structures.

Exercises

I. Translate into Russian (in written form).

1. Aluminium alloys can possess the strength of steel, though only a third the weight. 2. Cows give more milk when there are cool, heatreflecting aluminium roofs on their dairy barns. 3. Aluminium offers a bright hope

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