METALS 1. METALS: they are substances from minerals which contanin one or more metallic elements, and somethimes non-metalic substances such a carbon. 1.1 USES OF METALS: Metals have many uses and are a key element in

transport, telecomunications, agricultur, construction and manufacturins among other sectors.

2. HOW METALS ARE OBTAINED: There is a process from the mining of minerals (raw materials) to using metals to make different objects:

• Metals come from minerals which are part of rocs (aluminium is taken from bauxite)

bauxite high voltaje power lines

• Mining is carried out in surfaces mines or underground mines. • The useful minerals (ore) and the useless minerals (gangue) must be

separated. • The ore is taken to an ironworks to obtain the metal after complex

processes.

Metallurgy is the group of industries involved in mining and transforming metallic minerals.

Metallurgy

3. PROPERTIES OF METALS. Metals are hard, non-adhesive, cold and very smooth if they have been polished or treated. Some characteristics are:

• They are good electricals, termal and acoustic conductor. • They are ductile and malleable. • They are tough. • They melt at high temperaturas so the can be used for welding. • They expand when the temperatura rises and contract when it cools. • Some are magnetic and are attracted to magnets. • Most of them rust when they come into contact with air and oxygen. • They can be recycled and reused. • Some of them such as lead or mercury are toxic for the environment.

4. CLASSIFIYING METALS. Metals can be classified as ferrous and non-ferreous.

• Ferrous metals: Theis main component is iron. They include: Pure iron, cast iron and steel.

• Non ferrous metals: Their component is not iron- or they contain very little of it. This group includes: cooper, bronze, aluminium, tin and zinc.

5. FERROUS METALS. Iron minerals from the Earth´s surface undergo different processes to obtain pure iron and its alloys: Steel and cast iron. Depending on the percentage of carbon, they are classified as:

• Pure Iron: The concentration of carbon is between 0,008% and 0,03%.

Properties: Greyish White color and good magnetic properties. Disadvantages: It melts at high temperatura, difficult to machine, fragile and brittle.

Uses: Rarely used. Used in electronics and electricals components. • Cast iron: The concentration of carbon is between 0,03% and 1,76%

Properties: Very hard and resistant. Uses: Machine parts, casing for engines, stand or machines, pistons, Street lamps, drain covers…

• Steel: The concentration of carbon is between 1,76% and 6,67% Properties: Very hard and resistant. Very resistant to traction, easy to weld, alloys with chrome and nikel to make stainless Steel. Uses: Structures in construction, car chassis, boats, trains, machinery, tools, screws, domestic appliances, kitchen utensils, taps…

6. THE STEEL MAKING PROCESS It includes the following stages:

• Iron mineral is washed to eliminate any impurities. • It is crushed and sieved to separate the gangue fron the ore. • The ore ir mixed with coke and limestone and then put into a blast

furnace with temperatues of over 1500º.

• Slag is obtained, this by-product is made up of carbon and impurities. • The pig iron is taken to a converter to:

- Reduce the percentage of carbon. - Eliminate impurities. - Adjust the composition of the Steel with other metals.

• Steel undergoes different termal processes to improve mechanicals

properties: - Quenching, which is cooling the metal very quickly when it is red

hot. - Tempering, where the hot metal is cooled very slowly.

7. NON-FERROUS METALS They are classified, according to their density, into the following categories: ultra-light, light and heavy. 7.1 Ultra-l ight metals Magnesium from magnesite, dolomite, carnalite, epsomite and olivine. Properties: Shiny, silvery White, very light, soft and maleable, but not very ductile, reacts very strongly with oxygen. 7.2 Light metals Aluminium from bauxite. Properties: Silvery White, higly resistant to corrosion, very soft, low density, high malleability and ductility, good at conducting electricity and heat. Uses: High voltaje power lines, planes, cars, bycicles, light metalwork, roofing, decoration, kitchen tools and drinks cans. Titanium: from rutile and ilmenite. Properties: Reddish, very shiny, soft, good electrical and thermal conductor, very malleable ans ductile, rust easily. Uses: Electrical wiring, telephones lines, pipes, radiators, decoration, architecture, jewellery and handicraft. Brass: from copper and zinc (alloy) Properties: Very resistant to corrosion. Uses: Handicraft, jewellery, plumbing, capacitors and turbines. Bronze: from copper and tin (alloy) Properties: Resistant to general wear and corrosión. Uses: Boat propellers, filters, church bells, sculptures, nuts, bearings and cogs. Zinc: from sphalerite and hemimorphite. Properties: Bluish grey, fragile, not very hard. Uses: Roofing, plumbing and car industry. A layer is used to stop corrosión. Tin: from cassiterite. Properties: Shiny White, very soft and maleable, does not oxidise. Lead: from galena. Properties: silvery grey, soft and maleable, lead fumes are toxic. Uses: Batteries, protective measures against nuclear radiation. As additive in glass to increase its hardness and add weight.

8. Shaping techniques To make pieces for sale or industry, the metal goes through a series od shaping processe, depending on the type of metal and what we want to make. Roll ing: The metal is passed through a series of rollers that compress it, reduce its thickness and increase its lenght. Uses: Sheets, plates, bars.

Extrusion: The heated metal is pushed through a hole by a piston, using compression.

Forging: The metal piece is shaped by repeated and continuos compression forces using hammers, tongs and anvils. Uses: Railings, bed headboards, horseshoes, keys, tools…

Punching: This is a cold forging process, a sheet of metal is hit with a punch to make shape in a mould. Uses: Holllow pieces, such as washers, bearings…

Bending: A metal sheet is subjected to force to make a curved shape in specific curve radius. Uses: Curved pieces, car body parts, sinks…

Wire drawing (trefilado): A wire is pulled through a hole that has the required dimensions. The wire increase its lenght while reducting its diameter. Uses: Metal strings and wires.

Casting: Molten metal is poured into container with a hollow space inside, which is the shape of the object we want to make. The mould can be made from sand, Steel os cast iron. Casting process: 1. The metal is heated in a furnace. 2. The liquid metal is poured into the mould. 3. It is left to cool down. 4. The piece is removed from the mould. Uses: Engine blocks, fire hydrants, sculptures, ornaments, jewellery…

1. Look for the meaning of the words in red of the text. and write them with its translation on your notebook: 2.Draw in your notebook the pictures of the steel making process and all the pictures of the diferent shapings techniques with the names of each part and its translation such as you see un the pictures. 1. Debes buscar el significado de las palabras en rojo del texto y copiarlas con su traducción en tu cuaderno. 2. Dibujar en tu cuaderno el dibujo del proceso de fabricación del acero y los dibujos de cada una de las técnicas de conformación con los nombres de cada una de las partes en inglés y su traducción.