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Activity

I. A group of students are on an excursion at the Steel works. Take them around and explain what they see starting from the value of alloys and finishing with making different types of steel.

II. You are a team of engineers who design various things.

a) Consider the advantages and disadvantages of various steels care­fully.

Class of Steel

Advantages

Disadvantages

carbon steels

tool steels

stainless steels

corrosion resistant

b) Decide which steels you will use for making the objects named below. Give your reasons.

Knives, nails, hammers, cables, automobile bodies, ships, con­tainers, machine tools, aircraft undercarriages, bank vaults.

Writing

I. A) Complete the table with the data you have obtained.

Class of Steel

Composition

Properties

Use

carbon steels

Fe, С

tool steels

Fe, C, Co, Ni, W, Mo, V, Cr

stainless steels

Fe, C, Ni, Mo, Ті, Al, Nb, Cu, N, S, P, Se, Cr

does not rust

b) Choose one type of steel and write its description.

II. Translate the passage into Ukrainian.Use the dictionary if necessary.

Owing to the valuable properties of stainless steel its application may vary from spoons to bank vaults. This steel does not rust because of the interaction between its alloying elements and the environ­ment. Stainless steel contains iron, chromium, manganese, silicon, carbon and significant amounts of nickel and molybdenum. These elements react with oxygen from water and air and produce a very thin stable film of metal oxides and hydroxides, which may prevent additional corrosion because it limits the access of oxygen and water to the metal layers below. This film may not be seen without a power­ful microscope that is why steel seems stainless when it is in fact cor­roded at the atomic level.

In summary, stainless steel does not rust because it may form a corrosion product layer for the protection against further attacks of oxygen.

Further Reading

I. Learn the following words and word-combinations to comprehend the text.

average

high-alloy steel

undercarriage

composition

tungsten

addition

carbon steel

tiny

low-alloy steel

wear-resistant

overheat­ing

performance

II. Read the text attentively to learn more about various kinds of steel. Classes of Steel

Steels vary greatly but the major classes are carbon steels, low-alloy steels (up to 8% alloying elements, i.e. tool steels), and high-alloy steels (more than 8% alloying elements, i.e. stainless steels).

In carbon steels the carbon content may range from 0.015% to 2%. The steel that was used for the Golden Gate Bridge, for instance, is car­bon steel with the following average chemical composition: C: 0.81% (0.85), Mn: 0.66%, P: 0.026% (0.04), S: 0.028% (0.04), Si: 0.24%. The addition of this tiny amount of carbon made the steel much stronger and harder. Carbon steels account for about 90% of the world's steel production. They may be used for automobile bodies, appliances, machinery, ships, containers, and the structures of buildings.

Tool steels are special steels that are engineered to particular service requirements. These expensive alloys are exceptionally strong, hard, wear-resistant, tough, nonreactive to local overheat­ing. They contain tungsten, molybdenum, vanadium, and chromium in different combinations, and often cobalt or nickel for better high-temperature performance. They are used for machine tools, aircraft undercarriages, in buildings and bridges.

Stainless steels comprise any alloy steel that contains 10-30% chromium. The presence of chromium, together with the low carbon content, gives a remarkable resistance to corrosion and heat. Other elements, such as nickel, molybdenum, titanium, aluminum, niobi­um, copper, nitrogen, sulphur, phosphorus, and selenium, may be added for obtaining better corrosion resistance and other valuable properties.

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