Understanding Ferroalloys: Definition and Types
Ferroalloys are iron-based alloys that contain significant amounts of elements other than carbon, such as chromium, manganese, or aluminum. These alloys are crucial to the steel industry because they enhance various properties of steel and stainless steel, including corrosion resistance, wear resistance, and mechanical strength. Additionally, ferroalloys play a vital role in reducing the negative effects of sulfur during steel production.
Ferroalloys are primarily produced in blast furnaces or electric arc furnaces, though they can also be created through carbothermic reactions, direct reduction, or by adding elements to molten iron.
Common Types of Ferroalloys
Since each ferroalloy serves a different purpose, many types exist. These are the most common.
Ferrochrome: Enhancing Corrosion Resistance
Ferrochrome, also known as ferrochromium, typically consists of 50 to 70% chromium by weight. It is an alloy of chromium and iron, primarily used in the production of steel, accounting for approximately 80% of global consumption.
Ferrochrome is generally produced in an electric arc furnace through a carbothermic reaction, carried out at extreme temperatures close to 2800°C. Reaching these high temperatures requires a significant amount of electricity, making production expensive in countries with high energy costs. The leading producers of ferrochrome are China, South Africa, and Kazakhstan. In steel production, adding ferrochrome increases the alloy’s resistance to corrosion and high temperatures, making it an essential alloying element for stainless steel applications.
BORINOX® Process: A Perfect Match for Ferrochrome Alloys
Bortec’s BORINOX® process is highly effective for hardening stainless steel containing chromium, offering increased wear resistance without sacrificing corrosion protection. This gas-based diffusion treatment strengthens the surface of chromium alloys, making them ideal for industries where both wear and corrosion resistance are critical, such as aerospace and industrial machinery.
Ferromanganese: A Crucial Addition for Strength
Ferromanganese is known for its high manganese content and can be produced in a blast furnace or, more commonly, in a submerged arc furnace, a type of electric arc furnace. Production occurs through carbothermic reduction by heating a mixture of manganese oxide, iron oxide, and carbon.
High-carbon ferromanganese is the most widely consumed ferroalloy globally in terms of quantity and is widely used in steelmaking. Its addition enhances the strength and flexibility of steel, making it suitable for ferrous alloys used in construction and structural applications. China is the main manufacturer of this ferroalloy.
Ferromolybdenum: Boosting Durability and Corrosion Resistance
Ferromolybdenum combines molybdenum and iron, containing between 60% to 75% molybdenum. During production, molybdenum oxide is mixed with iron oxide and aluminum, followed by an aluminothermy reaction. Electro-beam melting is applied to purify the end product, resulting in a ferroalloy that improves corrosion resistance, wear resistance, and weldability in ferrous alloys.
Ferromolybdenum is used widely in producing machine tools, military hardware, vehicles, and ships, as well as in high-speed tool steels and superalloys. Leading producers of ferromolybdenum include China, Chile, and the US.
Ferronickel: Essential for Stainless Steel Production
Ferronickel, containing about 35% nickel, is produced via a carbothermic reaction and is often applied in producing austenitic stainless steels and nickel alloy steels. In 2008, the steelmaking industry accounted for up to 98% of ferronickel consumption in the US. Ferronickel also has applications in electronics and battery manufacturing. Japan, New Caledonia, and Colombia are primary producers.
The nickel content in ferronickel improves corrosion resistance and toughness in alloys of iron, making it a valuable alloying element for producing ferrous alloys designed to withstand extreme environments.
NICKELCOAT®: Advanced Corrosion Protection for Nickel-Based Alloys
Bortec offers NICKELCOAT®, a high-phosphorus nickel coating that provides superior corrosion resistance, especially in highly acidic environments like those found in the oil and gas industry. NICKELCOAT® is frequently used in CO₂ injection wells and other applications that demand exceptional protection against corrosive gases, extending the lifespan of components in these challenging environments.
Ferrosilicon: Improving Steel Strength and Deoxidation
Ferrosilicon is a ferroalloy containing between 15% to 90% silicon by weight, with a particularly high proportion of iron silicides. It is manufactured by reducing silica with coke or iron, making it a critical deoxidizer in steel production.
Ferrosilicon helps to deoxidize steel and ferrous metals, significantly improving hardness, strength, and corrosion resistance. China is the primary producer of ferrosilicon, heavily relied upon in the steel industry to ensure quality control of the final product.
Ferrotitanium: Superior Strength and Corrosion Resistance
Ferrotitanium consists of 45% to 75% titanium, with iron and sometimes small amounts of carbon added. It is produced using an induction furnace where titanium, steel, and iron are melted together. Known for its corrosion resistance, high strength, and low density, ferrotitanium is widely used in steel production for deoxidizing and desulfurization.
Ferrotitanium’s characteristics make it ideal for applications that require low weight and high durability, especially in ferrous alloys used in the aerospace and automotive industries. Main producers include Brazil, China, and India.
Ferrotungsten: High-Temperature Performance for Aerospace
Ferrotungsten is an alloy combining iron and tungsten and is categorized into grade A (75% to 82% W) and grade B (70% to 75% W). Production involves converting tungsten to tungsten oxide, then heating it with hydrogen or carbon. The resulting powder is mixed with iron to create the alloy, with wolframite, scheelite, and ferberite as raw material sources.
Ferrotungsten is often used in high-temperature applications, such as aerospace, due to its ability to raise an alloy’s melting temperature. The main manufacturers of ferrotungsten are China, Bolivia, and Russia.
Ferrovanadium: Toughness and Impact Resistance
Ferrovanadium, consisting of 35% to 85% vanadium, is used primarily to deoxidize steel. It enhances steel’s hardness, toughness, and impact resistance, improving its corrosion resistance. Production occurs via silicon or aluminum reduction, with China, Russia, and South Africa as primary producers.
How Bortec’s Treatments Enhance Ferroalloy Performance
In addition to the natural benefits of ferroalloys, Bortec Group offers advanced surface treatments that further enhance their properties. The BORINOX® process provides superior wear resistance and surface hardening for stainless steel and other chromium-based alloys without compromising corrosion resistance. Similarly, BOROCOAT® enhances the wear resistance of various steel types, including ferromanganese and ferrotitanium alloys, by creating a hard diffusion layer that protects against abrasion and adhesion.
For nickel-based alloys, NICKELCOAT® offers unparalleled corrosion protection, making it the perfect complement to ferronickel applications in highly corrosive environments like oil and gas operations.
