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II. Famous Scientists. Dmitry Ivanovlch Mendeleyev




UNIT 1

METALS

I. Text A: Metals, Text B: Steel, Text C: Methods of steel heat treatment

II. Famous Scientists. Dmitry Ivanovlch Mendeleyev.

Text A: METALS

Metals are materials most widely used in industry because of their properties. The study of the production and properties of metals is known as metallurgy.

The separation between the atoms in metals is small, so most metals are dense. The atoms are arranged regularly and can slide over each other. That is why metals are malleable (can be deformed and bent without fracture) and ductile (can be drawn into wire). Metals vary greatly in their properties. For example, lead is soft and can be bent by hand, while iron can only be worked by hammering at red heat.

The regular arrangement of atoms in metals gives them a crystalline structure. Irregular crystals are called grains. The properties of the metals depend on the size, shape, orientation, and composition of these grains. In general, a metal with small grains will be harder and stronger than one with coarse grains.

Heat treatment such as quenching, tempering, or annealing controls the nature of the grains and their size in the metal. Small amounts of other metals (less than 1 per cent) are often added to a pure metal. This is called alloying () and it changes the grain structure and properties of metals.

All metals can be formed by drawing, rolling, hammering and extrusion, but some require hot-working. Metals are subject to metal fatigue and to creep (the slow increase in length under stress) causing deformation and failure. Both effects are taken into account by engineers when designing, for example, airplanes, gas-turbines, and pressure vessels for high-temperature chemical processes. Metals can be worked using machine-tools such as lathe, milling machine, shaper and grinder.

The ways of working a metal depend on its properties. Many metals can be melted and cast in moulds, but special conditions are required for metals that react with air.

Vocabulary:


property

metallurgy

separation ,

dense

arrangement

regularly ,

to slide

malleable , ,

bent pp of bend

to fracture

ductile ,

to draw ,

wire

lead

iron ,

grain

to depend

size ,

shape ,

composition

coarse ,

treatment

quenching

tempering ,

annealing ,

rolling

to hammer (. )

extrusion

metal fatigue

creep

stress ,

failure ,

vessel , ,

lathe

milling machine

shaper

grinder

to melt ,

to cast ,

mould ( )


General understanding:


1. What are metals and what do we call metallurgy?

2. Why are most metals dense?

3. Why are metals malleable?

4. What is malleability?

5. What are grains?

6. What is alloying?

7. What is crystalline structure?

8. What do the properties of metals depend on?

9. What changes the size of grains in metals?

10. What are the main processes of metal forming?

11. How are metals worked?

12. What is creeping?


Exercise 1.1. Find the following words and word combinations in the text:


1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

11.

12.

13.

14.

15.

16.

17.

18.

19.


Exercise 1.2. Complete the following sentences:


1. Metals are...

2. Metallurgy is...

3. Most metals are...

4. The regular arrangement of atoms in metals...

5. Irregular crystals...

6. The properties of the metals depend...

7. Metals with small grains will be...

8....controls the nature of the grains in the metal.

9. Alloying is...

10. All metals can be formed by...

11. Creep is...

12. Metals can be worked using...


Exercise 1.3. Explain in English the meaning of the following words:


1. malleability

2. crystalline structure

3. grains

4. heat treatment

5. alloying

6. creep


Exercise 1.4. Translate into English:

1. , .

2. - .

3. , .

4. .

5. .

6. - .

Text : 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 a 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

carbon

stiff

to corrode ,

rusty

stainless

to resist

considerably ,

tough , , ,

forging

welding

brittle ,

cutting tools

surgical instruments

blade

spring

inclusion

to affect

manganese

silicon

rust-proof

nitrogen

tungsten


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


1.

2.

3.

4.

5.

6.

7. , ,

8.

9.

10.

11.

12.

13.

14.


15. (, , , , )

Text : 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 color of the oxide film produced on the surface of the heated metal often serves as the indicator of its temperature.

Annealing isa 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 withoutcracking).

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

Vocabulary:


to immerse

to apply

intermediate

oxide film

annealing ,

cracking


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?

Exercise 1.6. Translate into English the following words and word combinations:


1.

2.

3.

4.

5.

6.

7.

8.


FAMOUS PEOPLE OF SCIENCE





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