Text 2. Iron and Steels

Iron is an incredibly useful substance. It's less brittle than stone yet, compared to wood or copper, extremely strong. If properly heated, iron is also relatively easy to shape into various forms, as well as refine, using simple tools. There certainly aren't any iron shortages to worry about. The Earth's crust is 5 percent iron, and in some areas, the element concentrates in ores that contain as much as 70 percent iron.

Very pure iron is prepared by reducing ferric oxide with hydrogen at 1,000 degrees C or by vacuum melting of a product obtained by electrolysis of ferrous ammonium sulphate solution. Chemically pure iron is produced by thermal decomposition of iron pentacarbonyl at 200 to 250 degree C, when iron is deposited as a fine powder.

Physical Properties of Iron. Pure iron is a grayish-white soft metal. Its melting point and boiling point are 1,538 degree C and 2,735 degree C respectively. Pure iron is malleable and ductile and does not harden on quenching. It is more magnetic than any other metal, and its magnetic properties remain unaffected even at a very high temperature. Iron is a good conductor of heat and electricity.

Pure iron exists in three allotropic forms, depending on temperature. These are distinguished as α-, γ- and δ-iron respectively. These differ in their thermal stability, crystal structure, hardness, magnetic properties and in their ability to dissolve carbon.

Chemical Properties of Iron. Pure iron is unaffected by dry air and pure water at ordinary temperature, but commercial iron rusts in moist air and water. Pure iron gives off hydrogen, nitrogen and carbon monoxide on heating. The metal burns brilliantly when heated in oxygen and also undergoes combustion in burning sulfur. It decomposes steam at red heat, which is utilized in the manufacture of hydrogen.

Steel is the most important form of commercial iron. Steel is manufactured by blending carbon and iron in a specified ratio, where the normal percentage of carbon ranging from 0.2 to 2.14 per cent of the total weight. Apart from carbon, the other alloying materials used in the production of steel include manganese, chromium, tungsten and vanadium which impart desired properties to the steel. This metal has a wide range of properties.

The properties of steel are related to the carbon content and heat treatment. The carbon content usually ranges from 0.25 to 2 percent. As the percentage of carbon is increased, the tensile strength of the steel also enhances, but the ductility drops. Steel with 2 percent carbon resembles "cast iron" in being hard and brittle. On the other hand, steel containing a small proportion of carbon is soft and ductile like "wrought iron," and is called "mild steel."

The melting point of steel varies from 1,298.89 to 1,500 degree C. If steel is heated to redness and quenched in cold water, it gets very hard and brittle, and the product is known as "quenched steel." If this is again heated in between 200 to 300 degree C and allowed to cool slowly, the steel recovers its elasticity to some extent. This process is known as "tempering." By adjusting the temperature of tempering, steel of any desired degree of hardness can be produced. The surface color of steel changes according to temperature due to the presence of a thin oxide film during tempering. For instance, heating it to 230 degree C produces a pale yellow color, while an intense blue color is formed by heating to 300 degree C.

Special and Alloy Steels. Silicon, titanium, vanadium, molybdenum, chromium, manganese, tungsten, nickel and cobalt are used in the production of special steels with desired physical and mechanical properties. Sometimes, more than one of these elements is used. They are generally added to the melt steel in an electric furnace. For example:

• Silicon steel containing about 3.5 percent silicon and very little carbon is employed for making electromagnets and transformers.

• The presence of 2 percent of chromium in steel makes it very tough, suitable for ball-bearings and armor plates.

• Stainless steel contains about 12 to 15 percent chromium, and is resistant to the action of organic acids.

Application. Steel is extensively employed for structural purposes, for making tools, machineries, railroads and domestic articles. It is also used for making bar magnets, magnetic needles, armor plates, razors, knives, swords, watches and springs.

http://metallics.org.uk/how-iron-and-steel-work/

Vocabulary:

Substance – вещество To heat- нагревать Shortage – нехватка, недостаток Earth's crust – земная кора ferric oxide – оксид железа (III) melt – плавить ferrous ammonium sulphate solution – раствор сернокислой закиси железа и амония decomposition – разложение, распад iron pentacarbonyl – пентакарбонил железа soft – мягкий melting point – точка (температура) плавления boiling point – точка кипения quenching – закалка allotropic form – аллотропическая модификация to dissolve – растворять To rust- ржаветь moist air – влажный воздух combustion – горение, сжигание Steel – сталь specified ratio – установленное соотношение

manganese – марганец tungsten – вольфрам to impart – передавать heat treatment – термообработка tensile strength – прочность на растяжение to enhance – усиливать, увеличивать cast iron – чугун wrought iron – ковкий чугун mild steel – малоуглеродистая сталь quenched steel – закаленная сталь elasticity - упругость to some extent – до некоторой степени tempering – нормализация oxide film – оксидная пленка Silicon – кремний electric furnace – электрическая печь Tough – вязкий, прочный ball-bearing – шариковый подшипник armor plates – броневая плита Stainless steel – нержавеющая сталь organic acid – органическая кислота

Exercise 11. Connect the two matching parts of the sentences. Use the text 2.

Pure iron is	is produced by heating steel to redness and then cooling in cold water
Iron	is enhanced as the percentage of carbon is increased.
Tensile strength	a grayish- white soft metal
Quenched steel	imports the desired properties to steel.
Alloying element	decomposes steam at red heat
Commercial iron	contains 12 -15 % of chromium and withstands the action of organic acids.
Stainless steel	usually rusts in moist air and water

Exercise 12. Speak about the basic steel properties using the following facts:

1. Steel is made by melting iron and carbon;

2. Alloying elements (Mn, Cr, W, Mo, V) are added to obtain desired properties of steel;

3. To improve steel properties some methods of heat treatment are used;

4. Special steels are used according to their properties.

Exercise 13. Translate the sentences and state the function of the Infinitive.

1. Three blast furnaces are used to make molten iron from iron ore. 2. In order to transport the molten iron special insulated rail cars are used. 3. Steel can also be tempered to give it greater hardness. 4. To anneal is to provide formability to steel. 5. One way we save energy is to capture gases from blast furnace. 6. Iron ore to be melted needs purification and refinery. 7. It is not possible to discover mineral deposits in the mantle using present thechnology.8. Engineers consider metals to be the only materials worth for constructing a mechanism or a structure. 9. A metal structure must have high efficiency. 10. To produce stainless steel small amount of vanadium are added to the iron-carbon alloy.

Exercise 14. Fill in the gaps using the collocations rather than, as well as, in order to. Underline sentences where the Infinitive is used.

1. The program should help students find the right solution … … give them answer. 2. … … reading everything we made a list of preferable publications. 3. There are advantages … … … disadvantages of recycling the metal structures. 4. It is necessary to live slowly … … … live long. 5. Choose healthy way of life … … visiting doctors. 6. We use the ammeter … … measure the current. 7. The process may have differences … … … similarities. 8. … … … translate the text read the related literature in Russian. 9. Steel is used to make cars, house ware … … … in food industry for packaging. 10. … … … save energy the exhaust gases are captured from the furnace and then used for heating … … pollute the atmosphere.

Exercise 15. Watch the video “How to make steel” www.youtube.com/watch?v=fPO1hRloJy8 , answer the questions.

1. What is the main topic of the lecture?

2. Can you remember the name of the lecturer?

3. Name the basic components of steel.

4. What kind of elements are called trace?

5. What trace elements are added to iron and carbon for?

6. Can you remember the average temperature to make steel?

7. Is it possible to make steel at home?

8. Where is it possible to meet stainless steel products?

Exercise 16. Fill in the Work sheet 1.