The need for recycling scrap metal is undeniable: natural resources are not infinite with a constant demand for metal products by humans. Also, the cash for cars oshawa is pretty good. Mining and further processing of ore is detrimental to the environment, as it is accompanied by harmful emissions into the atmosphere. Recycling scrap metal, on the other hand, reduces the cost of producing metal and metal products and is not as harmful to the ecosystem.
The metal obtained from recycled scrap is almost as good as the metal extracted from ore. Therefore, there are virtually no restrictions on the use of recycled scrap metal in manufacturing.
Ways to recycle
Recycling is not simply transferring scrap metal to a recycling company. Melting or compacting, which completes the recycling, is preceded by stages.
The methods of recycling scrap metal are applied according to its:
type (ferrous, non-ferrous, precious);
Category (according to the quality of the scrap);
The percentage of contamination.
The melted metal at the plant is turned into rolled metal (rebar, sheets, etc.) or into ingots, convenient for transportation, from which the buyer (industrial enterprise) makes metal products, focusing on the demand. However, before this happens, scrap must be prepared in the best ways for it.
Types of scrap metal and ways of its processing
Scrap is divided into ferrous (iron, steel, iron), nonferrous (copper, brass, aluminum, lead, etc.), and precious (silver, gold, platinum). The recycling methods for each type of scrap are specific.
The process of recycling scrap non-ferrous and precious metals, or recycling, is more complex than that of ferrous metals, since specific technologies are used for each metal. Non-ferrous metal scrap is obtained from large household or automobile appliances, and the recycling points set a minimum batch of any scrap (usually from 100 kg).
Much more often and in larger batches, ferrous scrap is processed. When processing ferrous scrap, particular importance is attached to its dimensions: scrap metal of optimal dimensions for placing in the melting furnace is more convenient for recycling. The requirements to the dimensions of black scrap of each class and group are also specified in the regulatory documents. The methods of processing black scrap depend directly on its type, quality and dimensions.
Recycling of black scrap metal
The process of recycling black scrap includes sorting, shredding, cleaning followed by pressing or casting. All these stages are mandatory: omitting even one of them leads to a deterioration in the properties of the final product.
Grading is required to separate ferrous and nonferrous scrap and sort it into groups according to metal quality, dimensions and percentage of impurities in accordance with GOST requirements. Pre-sorting is carried out manually by people who deliver scrap metal to the collection points and by the staff of these points. But to exclude human factor and get quality metal from secondary raw material today more often special equipment for automatic sorting of black scrap is used. And only with the help of special equipment black scrap is sorted by its chemical composition in terms of the percentage of carbon and impurities it contains.
Modern steelworks are increasingly sorting scrap themselves using special equipment. But the option of sorting the scrap metal directly at the recipient site is still popular due to its cost-effectiveness.
Black scrap is milled with regard to its dimensions. The separation of scrap into fractions is done by:
Cutting into pieces of the required size – using gas, plasma equipment or scissors (gantry, alligator);
Bundling – with the help of baling equipment scrap metal is converted into convenient for transportation briquettes;
Explosive crushing: metal is crushed (or metal structures are dismantled) by means of an explosive wave in a specially prepared area;
mechanical crushing – by means of shredders and specialized mills (rolls, hammers, etc.).
The process of scrap shredding affects not only the convenience of its remelting, but also on the transport of metal waste from the site to the enterprise: large-sized pieces of scrap, as well as recyclables, compacted into bars or briquettes, takes less space in transport than unshredded scrap of non-standard size, and, therefore, at one time is transported in larger quantities.
Scrap metal is usually covered with dust, dirt, traces of paint, oil, varnish, and mixed with garbage. The contamination is removed in order to get quality metal. At small collection points, they are limited to assessing the quality of the scrap and cleaning it manually. But larger companies, which collect scrap, use professional cleaning methods, based on separation, that is separation of the metal fraction from the non-metal. The separation is carried out by an air flow, which sweeps away nonmetallic particles, leaving the scrap, or by a magnetic separator (flat, drum), which attracts iron and steel, but has no effect on the nonmetallic inclusions.
Scrap metal companies carry out their activities under license. This means that they are responsible for the quality of the scrap which they deliver to the steelworks. Therefore, no collection point will accept scrap whose contamination is dangerous for further processing. It is forbidden to accept:
pressurized metal containers;
Metal containers filled with paint, glue or oil;
scrap covered with a layer of oil (scrap with individual oil stains may be accepted);
components and subassemblies of units that contain machine oil;
Containers with explosives;
Any scrap metal arriving at the scrap dealer is subject to mandatory radioactive monitoring with special equipment (dosimeters, search instruments), which is repeated before it is transported to the metallurgical plant.
Nor will scrap metal that has been corroded be accepted for cleaning and subsequent recycling. Some spots of rust on it are quite acceptable, but if the impact with a hammer separates the rust, this scrap is considered unsuitable for processing.
This stage of the recycling process takes place directly at the company or mini-mill. It is exposed to thermal treatment in an electric or plasma furnace. In parallel with the remelting of scrap, the properties of the metal are changed, if necessary. For example, to improve its quality, special additives are used to reduce its phosphorus and sulfur content: the latter significantly worsen the quality of the produced steel, making it brittle. By adding alloying elements (chromium, nickel, and vanadium), smelters obtain steel with desired mechanical, physical, and chemical characteristics.
In addition to the melting itself, companies are also involved in metal rolling, which results in the production of finished metal sheets, strips, fittings, and ingots.