FROM THE HISTORY OF METALS
Metals began to be widely used as construction materials not so long iigo. Before the beginning of the nineteenth century metals played little structural role in the process of building. Mostly they served for joining parts of buildings. The ancient Greeks and Romans are known to use bronze for joining slabs of stone.
It was only in the eighteenth century when the first all-metal structure was built in Europe. It was a cast-iron bridge across the river Severn in England. The strength of the bridge turned out to be so great that now, more than two centuries after its construction, it still carries heavy modern traffic across the Severn.
In the first half of the nineteenth century cast iron and wrought iron were introduced and used for industrial construction in Europe and North America. Steel was not widely used, being considered a rare and expensive building material. Inexpensive steel first began to be produced and used only with the invention of the Bessemer process, in the 1850s. From that period on, metal started to be used as rather popular and useful building material. The famous Eiffel Tower of Paris was constructed of wrought iron in 1889. By that period several steel frame skyscrapers had already been built in the United States. That was the beginning of the new era; a new highly useful and popular construction material had been born and introduced into building industry.
1. For what purposes were metals mostly used before the beginning of the nineteenth century?
2. What did ancient Greeks and Romans use bronze for?
3. When and where was the first all-metal structure built? What can you say about its present-day condition?
4. What kinds of iron were introduced in the first half of the nineteenth century?
5. Why was steel as a building material unpopular for a long period?
6. What is the essence of the Bessemer process?
7. What was the global result of its invention?
8. What material is the famous Eiffel Tower constructed of?
9. In what country were the first skyscrapers built?
10. Are they good to live in? Would you like to live in a skyscraper?
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The Empire State Building was built in 1931 in the United States of America. Its construction took about two years. The exterior of the skyscraper is supported by a framework produced of steel. It should be noted that 60,000 tons of steel were used for its production. The Empire State Building is considered to be one of the tallest and spacious construction of the world. It can be attended by 80,000 people simultaneously.
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What is steel as a construction material? Steel may be classified as iron with the controlled amount of carbon. The amount of carbon in steel is generally less than 1.7 per cent. Ordinary structural steel should contain less than three tenth of one per cent carbon. This kind of steel also contains small amounts of phosphorus, sulfur, oxygen, nitrogen and silicon. Like iron and its alloys, steel belongs to ferrous metals. It is a hard substance. Accordingly, it can be pulled, forged, and melted. Generally, steel, this strong metal, like other metals, is a good conductor of electricity. Alloyed steel and stainless steel are corrosion-resistant kinds of steel. Corrosion-resistant materials are known lo be widely used for plant equipment, furnaces, valves, etc.
It should be noted that steel frames as a whole and their separate parts should be carefully designed: their function is to be able to carry the loads imposed on them and supported by them.
1. What group of metals does steel belong to?
2. What substances can steel contain?
3. What amount of carbon does steel generally contain?
4. What materials can be used for producing plant equipment?
5. What is the construction purpose of steel frames? For what reason must they be carefully designed?
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