It is not easy to find in nature Metals in their pure form. They are usually alloyed with other metals.
The metals group has some common properties:
Mechanical properties
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They are hard, tough and can be malleable and ductile.
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Thermal properties
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They are conductors of heat; depending on the temperature, they expand or contract and can be soldered easily.
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Electrical and magnetic properties
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They are good conductors of electricity; some are magnetic, for example iron and cobalt.
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other
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They rust easily, conduct sound and are solid at room temperature.
They can be recycled and reused. Some of them, such as lead or mercury are toxic for the enviroment. |
According to their composition, metals can be classified as:
- Ferrous: if they contain mainly iron.
- Non ferrous: they don’t contain iron.
Ferrous metals: are formed by iron and its alloys with carbon. dependding on the percentage of carbon alloys of iron are classedas:
Pure Iron
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It contains less than 0.03% of carbon. It’s brittle and doesn’t have many applications.
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Steel
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It`s Made mainly with iron and 0.03% to 1.76% of carbon. It’s tough and easy to work with. It’s widely used.
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Cast Iron
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It's made from iron and 2% to 6.67% carbon. It’s very hard but it is not tough as steel.
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There are many non ferrous metals. In this unit we have studied:
Copper
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It’s a very good conductor of electricity. It’s very ductile and malleable and can be shaped easily.
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Tin
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It’s easy to work with and melt. It’s used as a filler metal to soft soldering. When it is allowed with cooper it is called bronze.
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Aluminium
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It’s very light, highly resistant to corrosion, non toxic and easy to shape. It has many applications.
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Zinc
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It is malleable, ductile and very resistant to corrosion. It is mainly used to protect others metals from rust. When it is allowed with cooper is called brass.
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Before working with metals, we must know which tools to use.
Measurements and layout
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Ruler, set square, steel tipped compass, centre punch.
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Holding and bending
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Gloves, jack, vice, pliers.
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Cutting
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Pliers, tinsnips.
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Perforating
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Punch and hammer, drill.
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Filling
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File.
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Joints
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Rivets, glue, soldering, nuts and bolts, pins.
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Treatments
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Rust-inhibiting paint, chrome.
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