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Engineering and materials

WeldingWhat kinds of metals and plastics do engineers use? And what is the difference between them?

One of the most important parts of product design is choosing the right material for the job. You wouldn’t build a bridge out of plastic, after all! Below are the most common materials engineers use along with an explanation of the properties of each one.

Ferrous metals

These are metals which contain iron, usually as a major part. Iron is hardly ever used pure because it is very soft. This means that machines made of iron tend to tear and break easily. By adding small amounts of substances such as graphite, iron becomes much stronger and easier to work with. Stainless steel and cast iron are examples of ferrous metals.

Non-ferrous metals

These are metals which contain no iron, or only a tiny amount of iron. Many of these metals, such as copper and lead, are used in their pure forms by engineers because they have very useful properties.

Copper, for instance, is good at conducting heat, and so is very useful in pipes. Tin does not corrode very easily, so it is useful as a covering for other metals such as steel.


All plastic materials are made up of polymer chains. These are chains of atoms joined up together. Thermoplastics are ones which, when heated, allow more movement in the polymer chains. With thermoplastics you can do this again and again to mould and remould the product.

Thermoplastics are used to make things such as plastic bottles, tarpaulins and sometimes even clothes.

Thermosetting plastics

These are composed in a similar way to thermoplastics– with polymer chains made up predominantly of hydrogen and carbon atoms. However, the difference is that thermosetting plastics ‘set’ once they have been melted and moulded, meaning that the process can only happen once.

Formica is an example of a thermosetting plastic. It is used to make kitchen work surfaces, electrical fittings and even toilet seats.

Natural materials

This is a broad category, and it includes any other material that comes from natural sources. Things such as wood, rubber, glass, oil, textiles and ceramics all fall into this category.

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