Iron and its properties

Iron (Fe) is a relatively dense metal with a silvery white appearance and distinctive magnetic properties. The metal is the fourth most abundant element on earth after oxygen, silicon, and aluminium. It melts at a temperature of 1538ºC.

Iron is allotropic, i.e. it exists in different forms. Its crystal structure is either body-centered cubic or face-centered cubic depending on the temperature. At room temperature, pure iron has a bcc structure referred to as alpha ferrite. This persists until the temperature is raised to 912ºC when it transforms into an fcc arrangement known as austenite. With further heating, austenite remains until the temperature reaches 1394ºC, the point at which the bcc reappears. This form of iron, called delta ferrite, remains until the melting point is reached.

Iron is the cheapest and the strongest of the heavy metals. The pure metal is malleable and can be easily shaped by hammering but apart from some electrical applications it is rarely used without adding other elements to improve its properties.

1. What is iron like?

2. Iron is the most widespread metal on earth, isnt’it?

3. What is the melting point of iron?

4. What does iron crystal structure depend on?

5. What temperature range is characteristic of austenite?

6. What form of iron follows austenite?

7. Why does not pure iron find many applications?

4.3. Reading comprehension. Read the text below and for questions 1­–5 choose the best answers from a–d.

1. Which statement is true according to passage 1?

a) Iron doesn’t exist free in nature.

b) Deposits with more than 70% iron are commercially attractive.

c) Nothing affects an ore’s quality.

d) Hematite, magnetite, limonite and siderite are forms of pure iron.

2. Slag is

a) charged into the furnace at the beginning of making iron.

b) a solid waste.

c) formed when the carbon monoxide reacts with the hot iron ore.

d) a liquid substance formed at the stage when the hot carbon dioxide rises in the furnace.

3. Which statement is not true according to passage 3?

a) As the hot carbon dioxide rises in the furnace, it turns into carbon monoxide.

b) In the furnace, carbon monoxide forms iron and carbon dioxide as a result of reacting hot iron ore with carbon monoxide.

c) The iron ore doesn’t contain impurities.

d) Slag is formed in the furnace.

4. The molten iron and liquid slag

a) drain to the top of the furnace.

b) form a layer in the furnace.

c) pass out of the furnace.

d) have the same density.

5. The best title to the text is

a) Iron and Its Properties.

b) Iron Ores and Ironmaking.

c) Pig Iron.

d) Iron and Iron Ores.

Vocabulary

hematite n	—	красный железняк, гематит
magnetite n	—	магнитный железняк, магнетит
limonite n	—	бурый железняк, лимонит
siderite n	—	шпатовый железняк, сидерит
influence v, n	—	влиять, воздействовать; влияние, воздействие
deposit n	—	месторождение
proceed n	—	протекать
charge v, n	—	загружать, шихта
flux n	—	флюс
blast v	—	дуть, продувать
tuyere n	—	фурма
impurity n	—	примесь
melt v	—	выплавлять, расплавлять
slag n	—	шлак
casting n	—	литье
right angle	—	прямой угол
a number of	—	ряд, несколько

1. Iron seldom occurs free in nature but it is usually found in the form of ores: hematite, magnetite, limonite, and siderite. Deposits with less than 30% iron are commercially unattractive. An ore’s quality is also influenced by its other constituents.

2. Making iron from ore proceeds in a blast furnace. It is a tall unit with a strong blast of air blowing through it from bottom to top. At the beginning of the process the furnace is charged with coke, iron ore and flux in the proper proportions. Then hot air is blasted at high pressure through tuyeres [twi:´jeәz]. At this stage the coke burns to form carbon dioxide (CO₂).

3. As the hot carbon dioxide rises in the furnace, it meets more hot coke and is reduced to carbon monoxide (CO). The carbon monoxide then reacts with the hot iron ore, forming iron and carbon dioxide. At the same time, the flux absorbs impurities from the ore, forming a liquid known as slag.

4. The molten iron and liquid slag drain to the bottom of the furnace, where they form two layers – the slag floats on top of the denser molten iron. The iron and slag leave the furnace at different levels.

5. The product of the blast furnace became known as pig iron from the method of casting. It involved running the liquid iron into a main channel connected at right angles to a number of shorter channels. The whole arrangement resembled a sow suckling her litter, so the lengths from the shorter channels were known as pigs.

Notes

drain to the bottom – стекать вниз two layers – две несмешивающиеся жидкие фазы

sow n – свинья (свиноматка) suckle v – вскармливать litter n – выводок