What is A Ferrous Metal?
A metal with the descriptor “ferrous” means that it has iron in its composition. When the term ferrous metal is used, it also usually implies that iron is a large percentage of the elemental composition.
If it’s not the most abundant element, it would probably be the second or third most prolific. If a metal only contains trace amounts of iron, as many metals do, then that small amount is not considered enough to declare the metal ferrous.
Ferrous metals are magnetic and have high strength and hardness due to their iron content, which makes them ideal for architectural and structural uses such as the tallest skyscrapers, as well as bridges, railways, and more.
Ferrous metals also have magnetic properties, which is why you can use magnets to pin things to your refrigerator door, although their high carbon content means that many ferrous metals are prone to rusting. The exceptions to this are stainless steel, which doesn’t rust because of the chromium, and wrought iron which doesn’t rust due to the high pure iron content.
Some common ferrous metals include alloy steel, carbon steel, cast iron, and wrought iron. Ferrous metals are known and used for their strength.
What is Ferrous?
In chemistry, the adjective Ferrous indicates a compound that contains iron (II), meaning iron in its +2-oxidation state, possibly as the divalent cation Fe2+. It is opposed to “ferric” or iron (III), meaning iron in its +3-oxidation state, such as the trivalent cation Fe3+.
This usage has been largely replaced by the IUPAC nomenclature, which calls for the oxidation state is indicated by Roman numerals in parentheses, such as iron (II) oxide for ferrous oxide (FeO), iron (III) oxide for ferric oxide (Fe2O3), and iron (II, III) oxide for the oxide Fe3O4 that contains both forms of iron.
Outside chemistry, “ferrous” means generally “containing iron”. The word is derived from the Latin word Ferrum (“iron”). Ferrous metals include steel and pig iron (with a carbon content of a few percent) and alloys of iron with other metals (such as stainless steel). “Non-ferrous” is used to describe metals and alloys that do not contain an appreciable amount of iron.
The term “ferrous” is usually applied only to metals and alloys. The adjective ferruginous is used instead to refer to non-metallic substances that contain iron, such as “ferruginous water”; or to an orangish-brown color resembling that of rust.
Properties of Ferrous Metals
Ferrous metals share some basic properties, including being prone to rust and being magnetic. The list of common ferrous metal properties includes:
- Good tensile strength
- Good electrical conductivity
- Low corrosion resistance
- Silver in color
- Usually, magnetic
Ferrous metals can include a wide range of different alloying elements, including chromium, nickel, manganese, molybdenum, and vanadium, manganese. These alloying elements give ferrous materials different properties that allow them to be used in a variety of engineering and other applications including tools, pipelines, containers, cutlery, and larger fabrications like skyscrapers.
Examples of Ferrous Metals
Some common ferrous metals include alloy steel, carbon steel, cast iron, and wrought iron, let’s discuss each of them one by one.
Steel is made by adding iron to carbon which hardens the iron. Alloy steel becomes even tougher as other elements like chromium and nickel are introduced. Steel is made by heating and melting iron ore in furnaces. The steel can is tapped from the furnaces and poured into molds to form steel bars. Steel is widely used in the construction and manufacturing industries.
2. Carbon Steel
Carbon steel has higher carbon content in comparison to other types of steel making it exceptionally hard. It is commonly used in the manufacturing of machine tools, drills, blades, taps, and springs. It can keep a sharp cutting edge.
3. Alloy Steel
Alloy steels incorporate elements such as chromium, nickel, and titanium to impart greater strength and durability without increasing weight. Stainless steel is important alloy steel made using chromium. Alloy steels are used in construction, machine tools, and electrical components.
4. Stainless Steel
Stainless steel is another group of ferrous metals that are commonly used. In general, stainless steels have a high amount of chromium that helps them to resist corrosion better than carbon steels. Stainless steels can be further broken down into subgroups.
Austenitic stainless steels have the most corrosion resistance, with high amounts of nickel and chromium. There are also ferritic, martensitic, and duplex stainless steels. Each has their own advantages and disadvantages depending on the application.
Common applications of stainless steels include appliances, pharmaceutical and medical equipment, food-grade equipment, and knives.
5. Cast Iron
Cast iron is an alloy made from iron, carbon, and silicon. Cast iron is brittle and hard and resistant to wear. It’s used in water pipes, machine tools, automobile engines, and stoves.
Cast iron is produced when a carbon content of 1.5-4% is alloyed with iron. Other elements including silicon, manganese, Sulphur, and phosphorus will be present, but only in small quantities. Cast iron is brittle but has a good wear resistance due to its hardness. It is also easy to cast, relatively cheap, has high compressive strength, and has a low melting point.
6. Wrought Iron
Wrought iron is an alloy with so little carbon content it’s almost pure iron. During the manufacturing process, some slag is added which gives wrought iron excellent resistance to corrosion and oxidation, however, it is low in hardness and fatigue strength.
Wrought iron is used for fencing and railings, agricultural implements, nails, barbed wire, chains, and various ornaments.
Alloy Steels and the Alloying Elements
Alloy steels make up another subgroup of ferrous metals, with each alloying element having its own effect on the material properties. These alloying elements include chrome, copper, nickel, silicon, and titanium, but can be combined to provide a range of properties. Here are the properties of the most common of these alloying elements:
Chromium is used to make stainless steel, with chromium levels of over 11% making metals corrosion-resistant. An oxidized chromium layer on top of the metal will prevent the underlying metal from coming into contact with oxygen, thereby greatly reducing the chance of corrosion. Chromium also increases the hardness, tensile strength, toughness, and wear resistance of a metal.
Manganese can be used as an alloying element to prevent iron sulfides from forming, as well as increasing strength at high temperatures, improving ductility and wear resistance. Manganese can also improve hardenability through quenching, reducing the danger of defect formation and making the metal more stable.
Nickel, when used with other elements, can increase ductility and corrosion resistance. For example, a mix of 18% chromium and 8% nickel creates extremely durable stainless steel.
Silicon can be used to increase the magnetic properties of metal as well as improve strength and provide elasticity for applications like springs.
Vanadium carbides also limit the grain size of a metal, increasing the ductility of the alloyed material. Vanadium also improves the strength, hardness, wear and shock impact resistance. However, if used in quantities that are too high it can have a negative impact on material properties.
Molybdenum offers a good effect on steel alloys operating at high temperatures. It not only improves mechanical properties, but also provides higher resistance to rust and corrosion, and amplifies the effects of other alloying elements.
Applications of Ferrous Metals
Ferrous metals are used in a variety of applications. Listed below are its major uses:
- Sturdy crushing machinery.
- Nuts, bolts girders, and plates.
- Car cylinder blocks and gear wheels.
- Machine tool parts, machine handles, and engine parts.
- Vices, brake drums, and plumbing fittings.
- Gears and shafts.
- Cutting equipment for lathes.
- Kitchen draining boards and cutlery.
- Aircraft and pipes.
- Chisels, files, and lathe tools.
- Garden tools, hammers, drills, dies, and taps.
- Metal ropes, springs, and wire.