Recycled metals – What do we use them for?

Posted September 26th 2017

In the society of today, recycling is more prevalent than ever. We are encouraged to recycle whenever we can, but what happens to the things we do recycle? Where do they end up?

Metal is one of the major materials that can be recycled. Aluminum, iron, steel, copper and brass can all be recycled and reused, more than once, to make new products. Not only is it easy to use the scrap metal to make new products but it also reduces the need for new mining. It makes economical sense to recycle and reuse materials where possible and by doing this we can cut CO2 emissions, air and water pollution. When you bear in mind that the average household uses over 600 food tins and 380 drinks cans per year, it isn’t difficult to see how this energy can be saved.

How scrap metal is used differs depending on the metal. Some of the most commonly recycled metals are aluminum and steel, which can be recycled over and over again without losing their quality. The benefit of this is that the recycled metals can be used to make the same items. They are commonly used to make new food packaging – often the packaging will carry a mark to let you know that it has been recycled, and it can take as little as 8 weeks for a tin to be bought at the supermarket, used, recycled and make its way back to the supermarket. Most food tins contain at least a percentage of scrap metal if they are not made from 100% recycled metal. Recycled aluminum is also commonly used in the construction industry, alongside scrap iron, particularly in the building of bridges and roads. Other uses include the manufacture of aircraft, cars and even home furnishings.

recycled metals

The History of Metal in Sheffield

Posted September 15th 2017

The city of Sheffield is well known for steel manufacturing and metallurgy. From the 18th century onwards it was quickly established as one of the main industrial cities in the UK, although it was recognised for the manufacture of knives as early as the 14th century with a notable mention from Chaucuer in The Reeve’s Tale.

Ay by his belt he baar a long panade,

And of a swerd ful trenchant was the blade.

A joly poppere baar he in his pouche;

Ther was no man, for peril, dorste hym touche.

A Sheffeld thwitel baar he in his hose.

Round was his face, and camus was his nose;

The location of the city, situated amongst a multitude of rivers and streams, made it ideal for water powered industries to flourish and in the 1600s, Sheffield became the hub of cutlery production in England, outside London. In the 1740s, Benjamin Huntsman, who lived just outside Sheffield in the town of Handsworth, invented a version of crucible steel process that would produce better quality steel than had previously been possible. His method involved a coke-fired furnace that could be heated to a staggering 1,600 degrees °C. Clay crucibles would first be heated, before adding an alloy of carbon and iron known as blister steel. After 3 hours in the furnace the pots were removed, and impurities skimmed off, before the molten steel was cast and cooled. Also notable at this time was the invention of Sheffield plate by Thomas Boulsover, a combination of layers of copper and silver that is very strong and was used to produce a multitude of household goods. Because there was a large amount of copper, covered with a thin coating of silver, items were able to be produced at a far lower cost than if they were made only of silver.

In 1912, Harry Brearly discovered stainless steel in his research laboratory based in Sheffield. The metal was marketed as Staybrite in England by Firth Vickers and was used in the new entrance to the Savoy Hotel in London in 1929. Although when he applied for a US patent Brearly found that someone in the US had already registered one, he was able to join forces with Elwood Haynes to create the American Stainless Steel Corporation.

As steel began to be mass-produced the population of the city grew exponentially from the 18th to the 20th century, going from 60,995 in 1801 to 577, 050 in 1951. Although the industry has since declined Sheffield is still recognised as a key contributor to the metal industry and continues to manufacture specialist steel today.

sheffield metal history


Casting Metals

Posted September 7th 2017

‘Casting’ is a process used in metalworking where a metal in liquid form is poured into a mould and allowed to cool in the cavity to form a specific shape. It is a commonly used process for making complex shapes as the use of the mould allows for great detail and it is more economical than other processes might be. Once the metal has solidified it is removed from the mould and is known as a casting. Items commonly produced by casting include pieces of jewellery, sculptures, tools and some weapons.

The process of casting has been used for thousands of years, but it has been steadily refined and modern casting can now be broken down into two distinct sub-categories – expendable and non-expendable casting. In the expandable casting process, a temporary mould is used that cannot be reused, whereas in non-expendable casting the mould can be reused. This is then further differentiated by which material and which pouring method is used.

There are a variety of materials that can be used for casting, including non-metals such as sand and plaster. If using metal, the most common ones are iron, aluminium, steel, copper and zinc. When casting metals, a non-expendable method of casting is commonly used. For example, permanent mould casting uses a reusable mould, usually also made of metal, to cast metals such as iron, zinc, tin, aluminium and copper, amongst others. Usually, gravity is used to fill the mould, but vacuum or gas pressure can also be used. Another popular method is die casting which pushes molten metal into a mould using high pressure. Die casting usually uses non-ferrous metals such as zinc, copper and aluminium alloys, but it is also possible to use ferrous metals, although they are less common.

It is possible for defects to occur during the cooling period, also known as the solidification process, such as gas porosity and solidification shrinkage. Because of the nature of the casting process, it is difficult to do anything to prevent these from occurring so proper steps should be taken throughout the process to combat these. Shrinkage, for example, usually happens when the metal cooling in the mould is less dense in its liquid form, meaning as it cools to a solid the density decreases. In order to prevent this a suitable metal should be used.

casting metal