Unit 8 text 8. Steel

The most important metal in industry is iron and its alloy – steel. Steel is an alloy of iron and carbon. It is strong and stiff, but corrodes easily through rusting,

although stainless and other special steels resist corrosion. The amount of carbon in steel influences its properties considerably. Steels of low carbon content (mild steels) are quite ductile and are used in the manufacture of sheet iron, wire, and pipes. Medium-carbon steels containing from 0.2 to 0.4 per cent carbon are tougher and stronger and are used as structural steels. Both mild and medium-carbon steels are suitable for forging and welding. High-carbon steels contain from 0.4 to 1.5 per cent carbon, are hard and brittle and are used in cutting tools, surgical instruments, razor blades and springs. Tool steel, also called silver steel, contains about 1 per cent carbon and is strengthened and toughened by quenching and tempering.

The inclusion of other elements affects the properties of the steel. Manganese gives extra strength and toughness. Steel containing 4 per cent silicon is used for transformer cores or electromagnets because it has large grains acting like small magnets. The addition of chromium gives extra strength and corrosion resistance, so we can get rust-proof steels. Heating in the presence of carbon or nitrogen-rich materials is used to form a hard surface on steel (case-hardening). High-speed steels, which are extremely important in machine-tools, contain chromium and tungsten plus smaller amounts of vana­dium, molybdenum and other metals.

Vocabulary:

alloy ['ӕloi] – сплав

carbon – углерод

stiff – жесткий

to corrode [kә'raud] – разъедать, ржаветь

rusty – ржавый

stainless – нержавеющий

to resist [ri'zist] – сопротивляться

tough [tAf] – крепкий, жесткий, прочный, выносливый

forging – ковка

welding ['weldiŋ] – сварка

brittle ['britl] – хрупкий, ломкий

cutting tools – режущие инструменты

surgical instruments – хирургические инструменты

blade [bleid] – лезвие

spring [spriŋ] – пружина

inclusion [in'kluʒn] – включение

to affect [әfekt] – влиять

manganese – марганец

silicon ['silikәn] – кремний

rust-proof – нержавеющий

nitrogen – азот

tungsten – вольфрам

Exercise 1

Answer the questions for 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?

Exercise 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. инструментальная сталь