M. Ibbotson - Professional english in use engineering (794233), страница 8
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metal.3Aluminium (AI) is a common ................................ .4 Steel (Fe + C) is a widely used ................................ metal.5 Although it is used in steel, carbon is ................................ .6 Aluminium is relatively lightweight for a ................................ material.11.2Decide whether the sentences below are true or false, and correct the false sentences. Look atB opposite to help you.1 The elements that make up a compound are chemically bound.2 Alloys are chemical compounds that are frequently used in engineering.3Alloys can contain both metallic and non-metallic constituents.4 In an alloy, an alloying metal is the biggest constituent, by percentage.511.3Steel is a metallic element.Complete the extract about concrete and steel, using suitable forms of the word reinforcefrom C opposite. Sometimes there is more than one possible answer.(1) ................................
concrete is one of the most widely used construction materials, and one wetake for granted. However, using steel bars to (2) ................................ concrete structures locatedoutdoors is only possible thanks to a fortunate coincidence: concrete and steel have practically thesame coefficient of thermal expansion - in other words, as atmospheric temperature varies, theconcrete and the steel (3) ................................ expand and contract at the same rate, allowing uniformmovement.
Using a (4) ................................ material with a different coefficient of expansion would notbe feasible. For example, (5) aluminium-................................concrete would quickly disintegrate.11.4Read the text below and find two elements, two compounds, an alloy and a composite.Look at A, B and C opposite to help you.Generally, the steel used in reinforced concrete will have previously been exposed to waterand to the oxygen in the air.
As a result, it will usually be partly corroded, being coveredwith a layer of iron oxide (rust). However, once the steel is inside the hardened concrete,it will be protected from air and water, which prevents further rusting. Additionally, thecement in concrete does not react aggressively with the iron in steel.Ove-r ..f-o tjouThink of some of the materials used to make products or str uct ures you know about. Saywhether the materials are elements, compounds, mixtures, al loys or composites.
If they arecomposites, wh<1t materials are used (a) as the matrix, and (b) as re inforcement?Professional English in Use Engineering29W-SteelCarbon steelsThis extract from an article in an engineering journal is about different types of steel.Steel is the most widely used engineering material.Technically, though, this well-known alloy of ironand carbon is not as simple as one might think. Steelcomes in a huge range of different grades, each withdifferent characteristics. For the inexperienced, it canbe difficult to know where to begin.A good place to start is with the two main types of steel.The first, carbon steels, consist of iron and carbon, andcontain no significant quantities of other metals.
Carbonsteels can be divided into three main grades:• Mild steel - the most widely used grade - is a low carbon steel which contains upto approximately 0.3% carbon.• Medium carbon steel contains between approximately 0.3% and 0.6% carbon.• High carbon steel contains between approximately 0.6% and 1.4% carbon.Note: The chemical symbo l for iron = Fe, and carbon = C.- - Alloy steelsThe article goes on to look at alloy steels.The second main category of steel is alloy steels, which consist of iron, carbon andone or more alloying metals.
Specific grades of alloy steel include:• low alloy steels, which contain 90% or more iron, and up to approximately 10% ofalloying metals such as chromium, nickel, manganese, molybdenum and vanadium• high strength low alloy steels (HSLA), which contain smaller quantities of theabove metals (typically less than 2%)• stainless steels, which contain chromium as well as other metals - such as nickel and which do not rust.• tool steels, which are extremely hard, and are used in cutting tools.
They containtungsten and/or cobalt. A widely used grade of tool steel is high-speed steel,which is used in cutting tools that operate at high temperatures, such as drill bits.Notes : The terms carbon steel and alloy steel can cause confusion, as carbon steels are also alloys,and alloy steels also contain carbon.The chemica l symbo l for chromium = Cr, cobalt= Co, nicke l = Ni, manganese= Mn,molybdenum = Mo, tungsten = W, and vanadium = V.-CorrosionOne weakness of mild steel is that it corrodes - its surface progressivelydeteriorates due to a chemical reaction.
This reaction takes place betweenthe iron in the steel and the oxygen (0 2 ) in the air, to form iron oxide. Wheniron corrodes, we say that it rusts. In some metals, such as aluminiwn (Al),the presence of corrosion is not a problem, as the layer of oxide around themetal remains hard, which prevents it from oxidizing any further. However,when mild steel goes rusty, the rust on the surface comes off continuously,and a new rusty layer forms, progressively 'eating into' the metal.30Professional English in Use Engineering12.1Decide whether the sentences below are true or false, and correct the false sentences.
Look atA and B opposite to help you.Steel is an alloy of iron and carbon.Mild steel is a high carbon steel.Alloy steels contain carbon.Chromium and nickel are used as alloying metals in steel.Low alloy steels contain more chromium than iron.Stainless steel is an alloy steel.7 Tungsten is added to steel to make it softer.8 High-speed steel is suitable for making cutting tools that get very hot.2345612.2Complete the table with words related to corrode, oxide and rust. Then use the words tocomplete the sentences below. There is more than one possible answer. Look at C opposite tohelp you.VerbAdjectiveNouncorrodedoxidizedI go rusty1 When steel is exposed to air and water, it ................................................ .2 A br own/red material on the surface of steel is called ................................................
.3 The strength of steel is reduced if it is ................................................ .12.3Complete the article about a special type of steel, using words from A, B and C opposite.eathering steelThe perennial problem with mild (1) ................................ is that it(2) ................................ when exposed to air and water. Generally,the only solution is either to apply a protective coating, or touse another (3) ................................ of steel that is resistant to the(4) ................................
process- the most well-known being{5) ................................ steel, which contains significant quantitiesof (6) ................................ and, often, nickel.There is, however, an alternative solution. So-calledweathering steel is a special alloy suitable for outdoor use.But rather than being completely protected from corrosion,the surface of the steel is allowed to go (7) ................................ .Once a layer of (8) ................................
has formed on the surface, itstabilizes and forms a hard protective layer This layer differsfrom ordinary (9) ................................ oxide, as it does not continueto eat into the metal. While not everyone may like the 'rustylook', weathering steel has been widely used in architecturalapplications and outdoor sculptures.Ove..r ..f-o tjou~Think about some items you're familiar with that are made of steel, but which are notprotected (for example, by paint) . How serious is the potential problem of corrosion? How isit prevented or limited- for example, by using a specific grade of steel?Professional English in Use Engineering31Non-ferrous metals-Common non-ferrous engineering metalsThese website extracts look at the engineering applications of some non-ferrous metals -thatis, metals that do not contain iron.Aluminium is widely used, often in alloy forms .
An example is duralumin, an alloyused in aircraft manufacturing, which also contains copper ( 4.4%) and magnesium(1.5%). Aluminium can also be alloyed with titanium to produce very strong,lightweight metals.Copper is an excellent electrical conductor, which makes it ideal for use in electric wires.Good ductility also makes it suitable for pipes. Copper is widely used in alloys, notablybrass (copper and zinc) and bronze (copper and tin, and sometimes lead) .Silver is a precious metal - a reference to its high cost. It is a better electricalconductor than any other material, so it is often used for electronic connections. Anotherprecious metal - gold - is also an excellent conductor, and is highly corrosion-resistant.Notes: For more on metals and alloys, see Unit 11. For more on ductility, see Unit 18.The chemical symbol for aluminium =AI, copper= Cu, magnesium = Mg, titanium = Ti,zinc = Zn, tin = Sn, lead = Pb, silver = Ag and gold = Au.- - Plating with non-ferrous metalsNon-ferrous metals can be used to protect steel from corrosion by plating it- that is,covering it with a thin layer of metal.
An example is galvanizing (zinc plating).Steel can be hot-dip galvanized, by placing it in molten (liquid) zinc. It can also be electrogalvanized, which is a type of electroplating. With this technique, the steel component isplaced in a liquid (often an acid)- called the electrolyte- and connected to the negativeterminal (-) of an electrical supply, to become the cathode (the negative side). A piece of zincis also placed in the electrolyte, and is connected to the positive terminal (+) of the supply.This then becomes the anode (the positive side). An electric current then flows between thepieces of metal, through the electrolyte.
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