Currently, steel melting or cast iron production is impossible without ferroalloys. These materials belong to the basic elements used in these manufacturing processes. This page deals with ferroniobium description: classification, applications, grades, types of products.
Main information
A ferroalloy is an iron alloy with various elements of Mendeleyev’s Periodical Table. Currently there 100 elementary and complex industrial ferroalloys that combine about 25 chemical elements.
Ferroalloys allow producing materials with improved and special properties - structural, corrosive-stable (stainless), heatproof, heat-resistant, precision and electric steel, special foundry iron and other alloys.
Discovery
The ferroalloy was made in the 60s of the 19th century in France. This happened due to the development of technology of reduction smelting in crucible furnaces (later - in blast furnaces). However, these technologies were suitable for melting ferroalloys with a low content of the main element only and did not allow producing high-percentage alloys and refractory metal alloys as they could not provide the process temperature that would be high enough. Russian scientist V. V. Petrov was the first to apply an electric arc (electrothermal method) for reducing metal oxides with carbon (C). This allowed solving a problem with the temperature that was not high enough. In 1907 F. M. Beket developed the electrothermal method of producing low-carbon ferroalloys applying silicon (Si) as a reducing reagent. Another Russian scientist N. N. Beketov developed the aluminothermic process that allows producing low-carbon materials.
Classification
Industrial ferroalloys are classified by production volume. There are “large” and “small” alloys.
The grade can be divided into a few parts. The first one contains Fe and means “ferroalloy”. The second part contains the main element. It is the basis of the ferroalloy and determines its name and properties. W - tungsten, Мо - molybdenum, Nb - niobium, V - vanadium are the most common ones. The third part contains a number that determines the weight per cent of the main element. Also the grade can contain letters and numbers that mean the presence of additional elements in the chemical composition. Thus, e.g., letter, (а) in ferrotungsten grade means that it contains a few percent of aluminum.
Examples of ferroalloy grades
FeMo60 - ferromolybdenum with at least 60% of Mo;
FeNiб58 - ferroniobium with 50-65% of Nb;
FeW80(а) - ferrotungsten with at least 80% of W and at least 3% of Al;
FeV40У0,5 - ferrovanadium, V weight per cent - 35-48%, С weight per cent - 0,5%.
Advantages / drawbacks
Advantages:
a lower cost if compared with pure metals;
presence of iron in the chemical composition reduces the melting temperature of the main element. This allows melting steel alloyed with refractory metals under lower temperatures.
Drawbacks:
most ferroalloys contain sulphur, phosphorus, carbon, manganese and other admixtures that can be transited to the product;
the alloying agent content in the ferroalloy is much lower than in pure alloys.
Ferroalloy application
Steel, cast iron and alloy production is the main application. Ferroalloys are used for alloying and deoxidation of melted materials. The first process allows significantly improving the steel properties by adding such elements as tungsten, molybdenum or nickel. The second process is intended for removing oxygen from the material as it is an adverse admixture and can significantly deteriorate the mechanical properties.
Besides metallurgy, ferroalloys serve as sources of chemical elements in applying protective metal coatings. Also, they are used for receiving high-(chemically) purity substances, for reduction in metallothermic processes, for mineral dressing.
Ferroalloy products
The list of ferroalloys is rather small if compared with ferrous or non-ferrous metals. It includes slugs and ground screened particles. This is determined by their main application as alloying agents or scavengers melted together with the produced steel or cast iron. There is no need to produce sheets, rods or wire for this.