METALS IN PERSPECTIVE

Man has always tried to improve his standard of living by changing his surroundings and by making tools to simplify the everyday tasks necessary for his existence. At first, the only materials he could use were those he could see around him - stone, wood and so on. He survived in competition with other animals because of his abilities with his hands and their co-ordination with his brain. Because he did not have the strength and speed of some animals, his survival depended on his skilful use of tools to get food and to keep him warm and safe.

Since the Stone Age, man has found many more materials that he can work with to his advantage. His ingenuity has led him to discover the potential of many natural products. However, the materials that helped him most to develop were the metals. Their characteristics of strength coupled with the ease with which they can be shaped made metals of vital importance in the technology of the past. The exploitation of other properties, such as electrical and thermal conductivity, made it possible to develop high technologies appropriate to the fields of space travel, communications and nuclear engineering.

The first metals which man discovered were copper and gold, because they occur naturally in the pure state. They were used because they could be shaped easily, gold being especially soft. The discovery that copper could be obtained in sufficient quantities for beating into vessels and weapons was an important step in the use of metals, but the discovery that copper ore would produce copper was probably accidental. Perhaps a block of ore was used in a pottery kiln, and the metal was found after the fire had cooled.

Copper had been smelted and used for two thousand years before the potential of iron became evident. In the course of smelting activities, no doubt iron ores and the substance resulting from smelting them were encountered.

When it was found that hammering the smelted iron ore, while still hot, could produce a workable metal there was still no great use for it because it was no improvement on bronze. Eventually it was discovered that repeated hammering and heating in a fire improved the properties of iron, although it was not realised that the process increased the carbon content. Plunging the hot metal into cold water then produced a hard material superior to any other available.

Heating the metal and then allowing it to cool slowly produced a tougher and less brittle metal, although it was not as hard as the ‘quenched’ iron. Iron is still the most widely used metal today and heat treatment is still an important process for modifying its properties for its many uses.

By approximately 1200 BC all the basic metallurgical arts had been discovered. Of these, the most important are concerned with: (1) the extraction of the pure metal from the ore, (2) the mixing of metals and the addition of impurities to produce different properties, and (3) the heat treatment required to modify the mechanical properties.

2.Find in the text English equivalents to the following words and word combinations:

покращувати, існування, використання, здатність, винахідливість, приводити до, електро- та теплопровідність, з’являтися, відкриття, кування, достатня кількість, вміст вуглецю, зброя, домішки.

3.Make up word combinations from the following words and translate them into Ukrainian:

standard, thermal, everyday, travel, tasks, mechanical, use, natural, conductivity, space, important, nuclear, products, metallurgical, engineering, pure, of living, state, step, ore, arts, properties, iron, skilful.

4.Write the adjectives in brackets either in the Comparative or Superlative Degree.

1. The (simple) material in ancient times was wool.

2. Metal became (important) than wool.

3. Gold is (good) electrical conductor than aluminum.

4. Steel is (hard) than copper.

5. Iron is still the (important) metal today.

6. The (large) use of metal started during the Second World War.

5.Answer the following questions:

1. What material has helped man most?

2. What metals did man discover first? Why?

3. What was an important step in the use of metals?

4. When was copper firs used?

5. What metal is the most widely used?

6. What process can be used to modify the properties of iron?

7. How many basic metallurgical arts are there?

Section 4

1.Read and translate the following text:

ALLOYS

There are many applications of non-ferrous metals in the unalloyed state, but in most cases, some alloying element is added. The solids obtained when two or more metals are mixed in the molten condition and allowed to solidify are called alloys. Each constituent of an alloy is called a component. Alloys may be binary (two-component), ternary (three-component), etc. The ability of various metals to form alloys differs greatly.

Alloys are usually prepared, simply by melting two or more metals together and then this liquid mixture is allowed to cool and solidify. If no chemical reaction occurs between or among the constituents, the resulting alloy is a simple mixture. In some cases there is a definite reaction and the resulting alloy is a chemical compound. In a third type the degree of combination of the metals is such that the product can be described best by calling it a solid solution. The enormous importance of alloys lies in the fact that by combining metals in this fashion almost any desired set of properties can be obtained.

The non-ferrous metals may be mixed in various proportions to form many alloys, chief among them being brasses, bronzes, and aluminium alloys. The alloying of copper with other elements increases the strength of the metal in some cases and improves the anti-corrosive and anti-friction properties in others. There is a wide range of use for non-ferrous alloys. Their nature differs greatly from that of the ferrous metals. By varying the proportions of non-ferrous metals, alloys that are hard or soft, weak or strong, can be produced. When alloying, the metal with the highest melting point should be melted first, then the one with the next highest melting point, and so on until all of the metals that are to make up the alloy are melted together. For example, to make a red-brass alloy, the copper is melted first, then the zinc, then the lead, and at last the tin. As soon as the mixture is hot enough to run the castings, it should be taken out of the furnace, otherwise the zinc, tin and lead may burn away.

Alloys of copper with a number of elements including tin, aluminium, manganese, iron and beryllium are called bronzes. It is an alloy containing primarily copper and tin, but other elements may be added to the alloy to increase its properties such as hardness and resistance to wear.

The most common bronzes are known as straight bronze, phosphor bronze, and manganese bronze. Straight bronze is usually a mixture of copper and tin, but there are many bronzes that contain zinc and lead, especially the cheap mixtures. Phosphor bronze may be made by adding a little phosphorus to the mixture. If phosphor tin is used and alloyed with the copper, better result will be obtained than if the phosphorus is mixed with the copper. Manganese bronze alloys are usually made by using both copper that contains from 5 to 15 per cent of manganese and copper that contains no manganese.

Alloys of copper and zinc are called brasses. Brasses are yellowish or reddish alloys of copper and zinc in different proportions. We observe some brasses contain about 60% copper and 40% zinc, but some brasses contain as high as 90% copper with only 10 per cent zinc. An addition of tin makes brasses stronger. Scientists suggest brasses to be treated without heating them as they are very ductile. They are corrosion-resistant and are used for making musical instruments, bearings, etc.

Aluminium is used extensively for castings that are to be light in weight, light in colour, or that must not rust. Since aluminium is too soft for making castings, it is necessary to mix some other metals with it. The metals that alloy freely with aluminium are copper, tin, and iron. Usually, where aluminium alloys are made, the aluminium predominates. Alloys of copper and aluminium which contain from 5 to 10 per cent of the latter are called aluminium bronzes. They have a fine yellow colour resembling gold and are used in making imitation jewellery and statuary.

All non-ferrous castings will take a high polish and will not rust as easily as the ferrous metals, a characteristic that makes them especially useful in wet or damp places. Non-ferrous metals are rather expensive and therefore nowadays scientists try to replace them by some ferrous alloys of lower coat possessing the same properties.

2.Find in the text English equivalents to the following words and word combinations:

затвердіти, сплав, можливість, плавлення, складові, антикорозійні властивості, антифрикційний, лиття, піч, ржавіти, оброблятися, олово.

3.Make up word combinations from the following words and translate them into Ukrainian:

4.Write the following pronouns in the Nominative case:

him, us, her, them, you, me.

5.Pick out the pronouns in the following sentences and say what person each one is.

1. They are usually prepared by melting two or more metals.

2. It may be binary and ternary.

3. We can prepare alloys by melting two or more metals together.

4. You know that the nature of non-ferrous alloys differs greatly from that of the ferrous metals.

5. I always mix non-ferrous metals in various proportions to form alloys.

6. She tried to make a red-brass alloy by melting copper, zinc, lead and tin.

7. He suggests brasses to be treated without heating them as they are very ductile.

6.Write out these sentences again using pronouns instead of the words in the brackets.

1. (The solids) are obtained when two or more metals are mixed.

2. (Alloys) may be binary or ternary.

3. (Aluminum) is used extensively for casting.

4. Now scientists try to replace (non-ferrous metals) by some ferrous alloys.

5. (D. Mendeleyev) created the Periodic Table of Elements.

6. (The students of our group) have successfully passed all exams.

7. A lot of new important discoveries were made by (scientists) last century.

8. The best report was prepared by (my friend).

9. The laboratory workers usually helps (the students) to use the equipment of the laboratory properly.

7.Answer the following questions:

1. What solids are called alloys?

2. What is the procedure of preparing alloys?

3. What is called the bronze?

4. What is called the brass?

5. What is called aluminum bronze?

6. Why do scientists try to replace non-ferrous metals with ferrous ones?

Section 5

1. Read and translate the following text:

Date: 2015-01-02; view: 1667