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Ferrous metals and steels

Ferrous metals consist of iron combined with carbon, silicon and other elements.

But carbon is the most important element in ferrous alloys.

Ferrous metals are used in industry in two forms: steel and cast iron? Which differ in the quantity of carbon content?

Alloys consist of a simple metal combined with some other element.

Steel is a ferrous material having some carbon content. There are two kinds of steel: carbon steel and alloy steels.

Carbon steel should contain only iron and carbon without any other alloying element.

Alloy steels are those in which in addition to carbon an alloying element is present. These alloying elements have an effect on the properties of steel. They increase its strength and hardness, for example, high percentage of chromium makes steel rust-resistant, and we call it ‘stainless steel’.

Strength, ductility and machinability are the most important industrial and commercial properties of steel. Such prosperities as resistance to wear, electrical conductivity, magnetic properties are important in special uses of metals.

According to their chemical and mechanical properties steel may be used in different branches of industry, for example, in machine building, rocket engineering, automobile industry, ect.

Вопросы к тексту:

1. What elements do ferrous metals consist of?
2. What are alloy steels?
3. In what branches of industry are steels used?

IRON AND OTHER METALS

Thousands of miles of railway track form an intricate network of steel over the world, helping to carry daily billions of freight for different industries. Bridges, motorcars, lorries, ships, locomotives, cutlery, and razor blades are but a few of the many products turned out by the steel industry. But where does all this steel come from? How is it made?

The extraction of iron

Steel is the finished product in an industry which first makes pig iron from iron ores. These ores are abundant, and therefore iron is cheap to produce.

Iron is extracted in a blast-furnace. Iron ore, coke and limestone are fed continuously into the top of the blast-furnace the raw materials fall into the top of the tall cylindrical furnace, which may be over 100 feet high. The outer shell of the furnace is of iron plates riveted together, and inside this casing is a lining of firebrick about eighteen inches thick, which is capable of withstanding high temperatures. The furnace is approximately twenty feet wide at its maximum width, and only eight feet wide at the narrowest part, i.e., at the bottom, where molten iron and slag fall through into a well, from which the two materials are runoff at intervals. About six feet from the base of the furnace, six narrow cylindrical water-cooled devices, called tuyeres, force a blast of air at about 800ºC into the furnace. The hot gases leaving the top of the furnace are used to heat the air passing through the tuyeres.

Вопросы к тексту:

1.        What is steel?

2.        How iron is produced?

3.        Describe the blast-furnace.

GOLD

Gold, silver, and six metals of the platinum group – platinum, palladium, osmium, iridium, rhodium, and ruthenium belong to precious metals.

Gold is a dense, lustrous, yellow precious metal. It has several qualities which have made it valuable throughout history. Gold is attractive in colour and brightness. It is highly malleable, durable to the point of virtual indestructibility, and usually found in nature in a pure form. It is one of the heaviest of all metals. Gold is a good conductor of heat and electricity. It is also soft and the most malleable and ductile of metals.

Gold was one of the first metals attracting human attention. It is visually pleasing and workable and does not tarnish or corrode. So gold is universally accepted in exchange for goods and services in form of coins or bullion. It played a major role as a high-denomination currency, although silver has been standard medium of payments.

Gold occur mostly in the native state and combine with tellurium, selenium, and possibly bismuth.

It often occurs with copper and lead deposits. There are two types of deposits containing gold hydrothermal veins (with quartz and pyrite); and placer deposits.

The origin of enriched veins is not fully known, but it is believed that the gold was carried up from great depths with other minerals.

Вопросы к тексту:

1. What is gold?
2. What are the main properties of gold?
3. Where does gold occur?

GENERAL INFORMATION ON MINING

As has been said, mining refers to actual ore extraction. Broadly speaking, mining is the industrial process of removing a mineral-bearing substance from the place of its natural occurrence in the Earth's crust. The term "mining" includes the recovery of oil and gas from wells; metal, non-metallic minerals, coal, peat, and other hydrocarbons from the earth. In other words, the work done to extract mineral, or to prepare for its extraction is called mining.

The tendency in mining has been toward the increased use of mining machinery so that modern mines are characterized by tremendous capacities. This has contributed to improving working conditions and raising labour productivity.

Mining can be done either as a surface operation (quarries or open-pits) or it can be done by an underground method. The problem of depth also affects the mining method.

Working the deposit means the extraction of mineral. With this point in view a number of underground workings is driven in barren (waste) rock and in mineral. Mine workings vary in shape, location and function.

Depending on their function mine workings are exploratory (разведочные), if they        are        driven        with        a        view        to finding mineral,        and        as        productive  (эксплуатационные) if they are used for the immediate extraction of useful mineral. The rock surfaces at the sides of workings are called the sides or the ribs. The surface above the workings is the roof in coal mining. The surface below is called the floor.

The factors such as function, direct access to the surface, driving in mineral or in barren rock can be used for classifying mine workings.

1. Underground workings:

1. Long or deep may be: 1) vertical; 2) sloping (наклонные); 3) horizontal.
2. Production faces, whose dimensions (размеры) depend on the

thickness of the deposit being worked, and on the method of mining it.

2. Opencasts.

Вопросы к тексту:

1. What is mining?
2. What factors influence the choice of the mining method?
3. Are exploratory workings driven with a view to finding and proving mineral or are they driven for immediate extraction of mineral?

ATMOSPHERIC PRESSURE

The air surrounding the earth is a mixture of gases: nitrogen, oxygen and small quantities of other gases. For measuring the atmospheric pressure barometer is used. Today there are two kinds of barometers - the mercury barometer and the aneroid barometer. The Italian physicist Torricelli invented the mercury barometer some 300 years ago. The atmosphere is the most dense at sea level and the height of the mercury column is about 30 inches. French scientist Pascal showed that at the top of a mountain the height of the mercury column drops. It drops because there is less air above that point and hence a lesser downward pressure on the mercury surface. The other type of barometer is aneroid barometer. It consists of a thin metal box from which the air has been removed. When the barometric pressure begins to fall, it is a sign of changing weather and rain usually follows. As the storm passes, the barometer rises again. So, watching the changes of barometric pressure we can forecast the weather for that place.

Вопросы к тексту:

1.        Is the air a mixture of gases?

2.        What kinds of barometers do you know?

3.        Who invented mercury barometer?