Metals - tecnologiafuentenueva - home... 5 4.3 Electrolysis .....6 5 Ferrous products .....7 5.1...

I.E.S. Cristo del Socorro Luanco Technology

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MetalsMetalsMetalsMetals

1 History ..............................................................................................................................................2 2 General properties of metals. .......................................................................................................3 3 Classification of metals..................................................................................................................3

3.1 According to their composition: ............................................................................................3 3.2 According to their iron content: ............................................................................................3 3.3 According to their density:.....................................................................................................4

4 The process of obtaining metals ..................................................................................................4 4.1 Mining .......................................................................................................................................4 4.2 Siderurgy..................................................................................................................................5 4.3 Electrolysis ..............................................................................................................................6

5 Ferrous products ............................................................................................................................7 5.1 Soft iron....................................................................................................................................7 5.2 Cast iron...................................................................................................................................7 5.3 Steels........................................................................................................................................8

6 Non ferrous metals.........................................................................................................................9 6.1 Copper......................................................................................................................................9 6.2 Aluminium ..............................................................................................................................10 6.3 Tin ...........................................................................................................................................11 6.4 Zinc .........................................................................................................................................12 6.5 Other metals..........................................................................................................................12

7 Metalworking .................................................................................................................................13 7.1 Casting ...................................................................................................................................13 7.2 Plastic deformation...............................................................................................................14 7.3 Machining ..............................................................................................................................15 7.4 Joining metals .......................................................................................................................15 7.5 Heat treatments ....................................................................................................................16 7.6 Hand Tools ............................................................................................................................16


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1111 HistoryHistoryHistoryHistory

In the metal ages there were three distinct periods, each of which is named for the materials that, because of their importance at these times, represented each period:

- The Copper Age (3000-5000 years ago): owing to its low resistance, it was only used in decorative utensils.

- The Bronze Age (3000-5000 years ago): a mix of copper and tin which had better properties than either of the two metals separately.

- The Iron Age (2000 years ago): much more resistant than bronze. The Hittites were the first to master iron.

The first metal object made by Humans was invented around 7000 years ago. The first metal they used was copper. However, it wasn’t very strong so they found out that when they added tin to the copper, the mixture was stronger and it was called bronze.

Later, iron has been discovered and new objects become possible, such as

weapons, the wheel or the plow. The wheel was very important in transport as it was used in carts pulled by bullocks. The plow allowed humans to work faster and in greater areas.

Human beings realized that raw materials were very important for making new tools. The search for these new metals and raw materials was the beginning of trade.


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2222 GGGGeneraleneraleneraleneral properties of metals. properties of metals. properties of metals. properties of metals.

Generally, the pure metals are very difficult to obtain and also have not interesting mechanical properties. That’s why, in most cases, are found with some impurities which give them more mechanical resistance.

• Tenacity: The ability to support impacts without breaking. Metals are tenacious.

• Ductility: The ability to form threads.

• Malleability: The ability to form sheets.

• Hardness: Scratch resistance. Metals are relatively hard materials.

• Density: the quotient of the mass and volume of a form.

• Electrical and thermal conductivity: Metals conduct heat and electricity well.

• Metallic shine: Metals characteristically shine after being recently cut (before oxidation).

• Except mercury all metals are solid at room temperature.

3333 Classification of metals.Classification of metals.Classification of metals.Classification of metals.

3.13.13.13.1 According to their compositionAccording to their compositionAccording to their compositionAccording to their composition::::

- Pure metalsPure metalsPure metalsPure metals: Metals composed of only one metallic element. For example: gold, silver, iron, copper etc.

- Metal alloysMetal alloysMetal alloysMetal alloys: An alloy is an homogeneous combination of two or more metals. For example: bronze, brass, steel, etc

3.23.23.23.2 According to their iron content:According to their iron content:According to their iron content:According to their iron content:

- FFFFerrouserrouserrouserrous: These are iron (the pure metal) or alloys that contain iron (steels and cast iron).


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- Non ferrousNon ferrousNon ferrousNon ferrous: These are pure metals which aren't iron (e.g. copper) or metal alloys that don't contain iron e.g. bronze, copper, aluminium, lead, zinc, tin, brass, titanium, chrome, silver, gold.

3.33.33.33.3 According to their density:According to their density:According to their density:According to their density:

- UltralightUltralightUltralightUltralight: Density less than 2 g/cm3. For example, magnesium.

- LightLightLightLight: Density between 2 and 5 g/cm3. Aluminium and titanium are light.

- HeavyHeavyHeavyHeavy: Density superior to g/cm3. All the other metals are heavy: steel, copper, gold, zinc, tin.

4444 The process of obtaining metals The process of obtaining metals The process of obtaining metals The process of obtaining metals

1.- Obtaining the minerals from mines and pits etc.

2.- Separation of the mineral into ore and gangue. The oreoreoreore is the mineral that contains the metal we are interested in (for example, cuprite is the ore of copper). The ganguegangueganguegangue (impurities) is of no interest.

3.- Obtaining the pure metal from the mineral.

4.- Final treatment: They improve the properties and/or change the physical form of the metals.

4.14.14.14.1 MiningMiningMiningMining


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Mining is an industrial activity that consists in extracting elements, compounds and minerals, which are of some economic interest, from the earth. These extractions take place in mines, pits or quarries.

There are two types of mines:

- Open air mines

- Undergroud mines

4.24.24.24.2 SiderurgySiderurgySiderurgySiderurgy

Siderurgy is the term used for the industry dedicated to obtain iron. The iron industry has its own name because of the enormity of the use of iron in society today. From iron we obtain steel, which is one of the most important materials we have.

Usually, we use the term iron when the most appropriate is steel.

The siderurgic process takes place in installations called 'blast furnaces''blast furnaces''blast furnaces''blast furnaces'. The raw materials used are:

- Iron oresIron oresIron oresIron ores, mainly magnetite, hematite and siderite.

- LimestoneLimestoneLimestoneLimestone. The limestone reacts with the impurities and produces slag.

- Coke coalCoke coalCoke coalCoke coal. It burns and produces the heat to melt the ore.

Siderurgic process:

1. The raw materials are put into the top of the blast furnace and hot air is introduced into the lower part.

2. When the materials descend a chemical reaction takes place. The iron separates from the elements which were contained in the original mineral.

3. The waste materials –slagslagslagslag- stay at the top, floating on the molten metal, and the molten metal comes out of the bottom (iron + carbon + impurities).


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4. The molten iron is also called pig ironpig ironpig ironpig iron, the immediate product of the blast furnace. Pig iron has impurities and a very high carbon content, typically 3-5%, which makes it very brittle and not useful directly as a material. This molten metal is directed towards the steel industry.

5. To become steel, it must be melted and reprocessed to reduce the carbon to the correct amount, at which point other elements can be added to improve the properties. This operation is done in a special container called converterconverterconverterconverter.

Scheme of the iron and steel production

4.34.34.34.3 Electrolysis Electrolysis Electrolysis Electrolysis

This is a process mainly used to obtain and/or purify non-ferrous metals. The purification or refining consists in eliminating all the impurities still left in the metal after obtained from the


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mineral. It is used to obtain copper, aluminium, magnesium, zinc and titanium, among others.

The term comes from the words electro - electricity and lysis - break i.e. breaking because electricity is passed through.

For example, bauxite is used as a starting raw material to obtain aluminium. Using the electrolytic process we can get aluminium which is 99.9 % pure.

5555 Ferrous productsFerrous productsFerrous productsFerrous products

The ferrous products obtained after the operations realised in the blast furnace and the steelworks are classified according to their carbon content (raw material in the blast furnace). That is:

5.15.15.15.1 Soft ironSoft ironSoft ironSoft iron

The percentage of carbon is less than 0.1 %. It's a brittle material with many bad mechanical properties. It has good magnetic qualities. It is used to create electromagnets, transformers and electrical applications.

5.25.25.25.2 CCCCaaaast ironst ironst ironst iron

The percentage of carbon is between 2% and 5%. It is less ductile than steel but harder because carbon makes the metal harder but, at the same time, more fragile. It can be melted and moulded easily. They are used in engines and machines (they absorb vibrations well), manhole covers, etc.


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5.35.35.35.3 SteelsSteelsSteelsSteels

The carbon percentage is between 0.1% and 2%. There are different kinds of steels depending on the carbon content and the presence of another metals mixed with iron. The steel production started in the XIX century. The more important types of steel are:

- Mild Steel: Mild Steel: Mild Steel: Mild Steel: the carbon content is very low. It is ductile, malleable and tough, but not very hard. It is the metallic material more used for general purpose applications, it is used for screws, car bodies, structures for construction (tubes, sheets, profiles, bars), etc.

- Hard Steel:Hard Steel:Hard Steel:Hard Steel: the carbon content is higher than the mild steel, therefore is harder and less ductile and malleable. It is used for gears, mechanisms, pieces of machines or engines and also for some tools.

- Stainless steel:Stainless steel:Stainless steel:Stainless steel: it is an alloy of steel with chrome and nickel, these additives prevents the progressive oxidation of iron. Thus, the material doesn’t oxidize and can be used outdoor or to make objects exposed to water, as well as the fabrication of containers, pipes, tanks and other instruments for the alimentary industry.


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o Special steels:Special steels:Special steels:Special steels: such as tool steel and high speed steel. Are alloys with chrome, vanadium, molybdenum, tungsten, etc. depending on the desired properties and applications. Are used for high quality tools, drills, knifes, orthopaedics, etc.

6666 NoNoNoNonnnn ferrous metals. ferrous metals. ferrous metals. ferrous metals.

6.16.16.16.1 CopperCopperCopperCopper

Copper was the first metal used by the man because it can be found directly in nature (it is a native metal). Nevertheless, actually the copper is obtained from the ores cuprite and chalcopyrite.

Main properties:

- It has a very characteristic reddish colour.


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- It is very ductile and malleable.

- The main property is the high electrical conductivity.

Main applications:

- Electric wires or cables.

- Pipes for fluid transportation (heating systems, etc.)

- Making alloys such as bronze (copper and tin) and brass (copper and zinc).

6.26.26.26.2 AluminiumAluminiumAluminiumAluminium

Although aluminium is the most abundant metal in the earth’crust, it is very difficult to obtain because its chemical bonds are very stable.

The main ore is the bauxite; from bauxite is obtained the alumina and the aluminium is obtained from alumina (aluminium oxide) through the process of electrolysis, with a high energetic cost.

The main properties are the following:

- Bright white colour

- Light

- Oxidation resistant.

Due to these properties, the main applications are:

- Pieces and elements in vehicles, specially in aircrafts, due to the low weight.

- Window frames, due to the resistance to oxidation.

- High tension cables.


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The recycling of aluminium is extremely important, since it takes a lot of energy to extract this metal from nature, and its recycling process is simple and cheap.

6.36.36.36.3 TinTinTinTin

The tin is a silvery-white metal, ductile and malleable.

The main properties are:

- Very low melting point (321 ºC).

- Resistant to oxidation and, generally, to chemical attack.

The tin is seldom used as a pure metal. The main applications are in combination with other metals, forming alloys:

- To make bronze. BronzeBronzeBronzeBronze is a metal alloy consisting of copper and tin, but sometimes with other elements. It is a material resistant to corrosion and with low-friction properties. It is used for pieces of machines, ship propellers, sculptures, coins, musical instruments, bells, etc.

- To make a material which is also called tintintintin plate plate plate plate or simply tin . It consists in a steel plate covered by a thin layer of tin in order to avoid the steel oxidation. It is used to make cans for the alimentary industry.

- Combined with lead, it is used to solder wires, due to its low melting point (around 200 ºC)


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6.46.46.46.4 Zinc Zinc Zinc Zinc

It a grey colour material usually used in alloys. The main properties are:

- Very corrosion and oxidation resistant.

- Poor mechanical properties.

Applications:

- To produce galvanized steel. Galvanized steelGalvanized steelGalvanized steelGalvanized steel is a material composed by steel covered by a thin layer of zinc. This material has the good mechanical properties of the steel and it is resistant to oxidation due to the zinc cover. It is used for open-air structures such as high-voltage towers.

- Ducts and pipes for rainwater.

- To produce brass. BrassBrassBrassBrass is an alloy composed by copper and zinc, similar to bronze. It is used for musical instruments, decoration (due to the gold-like appearance), pieces of machines, etc.

6.56.56.56.5 Other metalsOther metalsOther metalsOther metals

- LeadLeadLeadLead is a dense metal, highly malleable and very soft and easy to handle. That’s why it was used to make tubes, these tubes or pipes can be easily shaped. Nevertheless, it is no suitable for drinking water lead because it is


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poisonous. It is also resistant to chemical attack and absorbs radiations. It is used for batteries and for protection against radioactivity.

- Titanium Titanium Titanium Titanium is a metal with low density and good corrosion resistant. It is used to make some alloys, mainly for aerospace applications and also for surgical instruments and implants.

- NickelNickelNickelNickel is a metal resistant to corrosion, it is used to make alloys, the main application is the elaboration of stainless steel.

- Tungsten Tungsten Tungsten Tungsten is a metal with high density and very high melting point. It is used to make very hard steels for high quality tools and also for filaments for incandescent lamps.

7777 MetalworkingMetalworkingMetalworkingMetalworking

Once produced the material, there are different methods of shaping and developing different products for different applications.

The main methods of working with metal are described as follows.

7.17.17.17.1 Casting Casting Casting Casting

Casting is a process consisting in:


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- Making a model of the desired form or the piece or object.

- With this model, a mould should be made. Usually, the mold is made of wet sand or ceramics.

- The mould is filled with the molten metal where it is allowed to solidify.

- The metal solidified, with the shape of the mould is the final product, which is expelled or broken out of the mould.

Casting is most often used for making complex shapes that would be difficult or uneconomical to make by other methods.

Motor blocks, streetlights and bells are examples of objects made following this procedure.

7.27.27.27.2 Plastic deformationPlastic deformationPlastic deformationPlastic deformation

Plastic deformation is a procedure used with malleable material. It involves using heat and pressure to make a piece.

There are different types:

- RollingRollingRollingRolling is a fabricating process in which the metal is passed through a pair (or pairs) of rolls. The thickness of the metal is reduced due to the effect of the rolls; meanwhile, the shape can be modelled.

- Forging Forging Forging Forging consists on applying compressive force or stress to the metal. Historically, this has been done by blacksmiths, using hammers, though today the process has been industrialized.


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- ExtrusionExtrusionExtrusionExtrusion is a process used with relatively soft materials, typically with aluminium, but also with plastics. The material is pushed or drawn through a hole of the desired cross-section. Aluminium profiles are produced by this method.

7.37.37.37.3 MachiningMachiningMachiningMachining

This consists of giving form to the metal by cutting out a piece from a larger piece. Much of modern day machining is controlled by computers.

Different procedures of machining are:

- DrillingDrillingDrillingDrilling, used to make holes, with a rotating cutter called drill.

- TurningTurningTurningTurning: the piece is rotating and a cutting tool is applied to give the desired shape.

- MillingMillingMillingMilling:::: the workpiece is held stationary and a rotating cutter is used for the shaping of metal.

7.47.47.47.4 Joining metalsJoining metalsJoining metalsJoining metals

Metals can form the following types of unions:


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- PermanentPermanentPermanentPermanent: destroying the union means destroying the materials that form the union. The main technique is weldingweldingweldingwelding, this is often done by melting the work pieces and adding a filler material.

- DetachableDetachableDetachableDetachable: it is possible to end the union and recuperate the starting materials intact. It is made using screwsscrewsscrewsscrews, rivetsrivetsrivetsrivets, etc.

7.57.57.57.5 Heat treatmentsHeat treatmentsHeat treatmentsHeat treatments

Heat treatment is a group of techniques used to alter the properties of a material, usually to improve the hardness and mechanical properties of the metals.

The main important heat treatments applied to metals are:

- TemperingTemperingTemperingTempering or hardening or hardening or hardening or hardening refers to heating steel above a critical temperature, then cooling it rapidly. Steel becomes harder and with a higher mechanical resistance. It is used typically for cutting tools. Traditionally, the blacksmiths performed the tempering entering the hot metal piece into water.

- AnnealingAnnealingAnnealingAnnealing is done by heating the steel, maintaining it at a suitable temperature, and then cooling very slowly. It relaxes internal stresses and the material gets softer.

7.67.67.67.6 Hand Hand Hand Hand ToolsToolsToolsTools

Some of the most common hand tools are:

RulRulRulRulersersersers. They can be made of metal or wood. It is used to measure things. In England rulers normally measure in inches, which is the same as 2.54 centimetres.


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HammersHammersHammersHammers are used to hit nails in, shape things or deform them. It is made of a handle (normally made of wood) and a head (of iron)

The benchbenchbenchbench clampclampclampclamp is used to hold pieces (of metal or of other materials) so that we can work with them more easily. It holds the material firmly and we must be careful because the 'mouth' of the clamp can leave a mark on the piece if it is soft.

FilesFilesFilesFiles are used to remove small bits of metal or wood and create smoother surfaces. There are many types of files

depending on the shape and what the grooves are like.

There are many types of screwdriverscrewdriverscrewdriverscrewdriverssss, some are longer than others, some are designed for use with certain screws and others for use with other screws but all are used as screwdrivers

SawsSawsSawsSaws: There are saws for wood and saws for metal, it depends on the teeth (some are larger than others). Wood saw tend to have an open arc and metal saws tend to have a closed arc.

Metals - tecnologiafuentenueva - home... 5 4.3 Electrolysis .....6 5 Ferrous products .....7 5.1...

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