David Havel
The Enduring Value of Metal Recycling
Metals are one of the oldest recycled materials. Historically, metals were costly and hard to obtain. Modern mining and recycling have made metals abundant in today’s world. One of the main reasons for high rates of metal recycling was not always good environmental stewardship, but the high value of metals. All through history, as metals have evolved, they have changed industry and even warfare. The side with the most advanced metals often had an advantage historically.
Metals have always been difficult to obtain and require large amounts of energy and inputs of other materials to mine and refine, making them a costly material. Recycling metals allows for considerable savings when compared to mining the raw materials and refining virgin metal. Virgin metal is considered metal that has been processed from iron ore and other raw materials without the use of recycled content.
Foundries: A Century-Old Recycling Industry
The foundry industry is one specific example of an old-time recycler of metals. Castings are used in automotive, medical and heavy industry, just to name a few. If you pay close attention, you will find that often you are never more than a few feet from some sort of casting. Municipal castings are often overlooked as we walk over them, but they are everywhere.
Columbia Steel is a provider of heavy industry castings and has been for over 100 years. Throughout its casting operations, vast amounts of metal have been recycled. The majority of the castings that Columbia Steel works with are for various types of crushers, most often rock crushers. When installed in a rock crusher, these liners apply the crushing forces to the rock and prevent wear to the frame components of the crusher.
A typical cone crusher liner set
How Recycled Metal Becomes New Castings
When manufacturing items such as crusher liners, a mold is made from sand, with the cavity in the mold shaped to the desired casting. Metal is then melted and once its elemental analysis falls within specification, it is then typically transferred to a pouring ladle. Then the liquid metal from this ladle is poured into the mold. Metals have high melting temperatures and care must be taken when working with them to avoid injuries.
“One of the main reasons for high rates of metal recycling was not always good environmental stewardship, but the high value of metals.”
A large ladle can be seen pouring a typical sand mold.
The charge that melts into the molten metal is made from many items. In a foundry, it is common to use a fairly large amount of recycled metal. This recycled metal will come from many sources. The first source will be risers and gates which are items that are needed to make the casting in the mold but are later cut from the casting before it is ready for use. Additionally, most foundries use steel scrap leftovers from other industrial users as part of the molten metal make up. This material can be remnants from machine shops or steel fabricators. In many cases, worn castings are purchased back and incorporated into the molten metal charge.
Additional materials include a carbon source, ferroalloys that are mined and processed and some fluxing materials to help purify the metal. When these items are all melted together, they produce the desired metal composition for the final casting.
Chopped up steel remnants to be used in molten production are seen above left. Above right shows foundry gates and risers ready to be reused. Below worn castings have been broken into pieces and are ready to be added to a metal charge.
Besides being a lower cost source of metal, recycling prevents large amounts of used items from building up in disposal yards. As can be seen below above used automobiles would pile up into mountains if they were not recycled.
