1. General understanding:

1. What is steel?

2. What are the main properties of steel?

3. What are the drawbacks of steel?

4. What kinds of steel do you know? Where are they used?

5. What gives the addition of manganese, silicon and chromium to steel?

6. What can be made of mild steels (medium-carbon steels, high-carbon steels)?

7. What kind of steels can be forged and welded?

8. How can we get rust-proof (stainless) steel?

9. What is used to form a hard surface on steel?

10. What are high-speed steels alloyed with?

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

1. сплав железа и углерода

2. прочный и жесткий

3. легко коррозирует

4. нержавеющая сталь

5. низкое содержание углерода

6. ковкость

7. листовое железо, проволока, трубы

8. конструкционные стали

9. пригодны для ковки и сварки

10. твердый и хрупкий

11. режущие инструменты

12. хирургические инструменты

13. инструментальная сталь

14. упрочнять

15. добавление марганца (кремния, хрома, вольфрама, молибдена, ванадия)

Text 4. Methods of steel heat treatment

Quenching is a heat treatment when metal at a high temperature is rapidly cooled by immersion in water or oil. Quenching makes steel harder and more brittle, with small grains structure.

Tempering is a heat treatment applied to steel and certain alloys. Hardened steel after quenching from a high temperature is too hard and brittle for many applications and is also brittle. Tempering, that is re-heating to an intermediate temperature and cooling slowly, reduces this hardness and brittleness. Tempering temperatures depend on the composition of the steel but are frequently between 100 and 650 °C. Higher temperatures usually give a softer, tougher product. The colour of the oxide film produced on the surface of the heated metal often serves as the indicator of its temperature.

Annealing is a heat treatment in which a material at high temperature is cooled slowly. After cooling the metal again becomes malleable and ductile (capable of being bent many times without cracking).

All these methods of steel heat treatment are used to obtain steels with certain mechanical properties for certain needs.

1. General understanding:

1. What can be done to obtain harder steel?

2. What makes steel more soft and tough?

3. What makes steel more malleable and ductile?

4. What can serve as the indicator of metal temperature while heating it?

5. What temperature range is used for tempering?

6. What are the methods of steel heat treatment used for?

2. Translate into English the following words and word combinations:

температура нормализации

мелкозернистая структура

быстрое охлаждение

закалённая сталь

состав стали

окисная плёнка

индикатор температуры

медленное охлаждение

Text 5. Ferrous metals

In studying engineering processes an engineer who is to build a machine must select suitable materials for each machine member. One must know the characteristics of engineering materials. These are as follows: strength, stiffness, ductility, toughness, elasticity, fatigue resistance, shock resistance, corrosion resistance, wear resistance, hardness resistance, frictional qualities, machinability, casting and forging properties. They depend upon the chemical composition and the physical structure of the material.

From the point of tonnage produced and used, iron is the world's most common metal, followed in turn by copper, zinc, lead and aluminium.

Cast iron is a general term applied to iron-carbon alloys containing more than 1.7 per cent of carbon. Cast iron without the addition of alloying elements is weak in tension and shear, strong in compression and has low resistance to impact. It is obtained from the cupola furnace where pig iron is re-melted in contact with coke. Grey cast iron has the carbon present in the free or graphite state and is soft, easily machined, and only moderately brittle. White.cast iron has most of the carbon in the combined state and is therefore hard and brittle. Malleable cast iron is made by heating white iron castings for a period of several days in ! airtight pots filled with an oxide of iron.

Steel is a ferrous material with a carbon content from 0.1% to 1.0%. Semisteel is a name to a metal made by melting 20 to 40% of steel scrap with cast iron in the cupola. Steel castings are more expensive but stronger and tougher.

Wrought iron is quite ductile and can be easily rolled, drawn, forged and welded. It has high resistance to corrosion. The carbon content is generally less than 0.1% and the material must contain not-less than 1% of slag.

Cast steel normally contains about 0.5% of carbon, and is used to replace cast iron when castings of considerable strength are required. Forged steel is steel that Has been hammered, drawn, pressed or rolled in the process of manufacturing of a particular part.