14 Types of Steel

John Spacey, January 15, 2021

Steel is an alloy of iron and carbon that has been produced since antiquity. Modern variations of steel are an extremely common metal used in buildings, infrastructure, tools, ships, vehicles, machines and consumer products. The following are common types of steel.

Stainless Steel

Stainless steel contains a minimum of 11% chromium. This improves the corrosion and heat resistance of the metal. The following are common types of stainless steel.

Type	Description
304	Contains chromium between 18% and 20% and nickel between 8% and 10.5%. A very common stainless steel that is used in consumer goods such as cookware.
18/8	Type 304 Stainless steel that is 18% chromium and 8% nickel
18/10	Type 304 Stainless steel that is 18% chromium and 10% nickel
18/0	Stainless steel that is 18% chromium and 0% nickel
316	Adds 2.2% molybdenum with 17.5% chromium and 11.5% nickel. Generally higher grade than 304 or 18/0. Provides greater corrosion resistance to acids and chloride ion.

Traditionally, nickel is a slightly more expensive metal than chromium such that a high nickel content is viewed as the premium metal. Actual prices vary on the market with time.

Alloy Steel

A steel that is alloyed with other elements. Strictly speaking all steels are alloys, because they contain carbon. However, the term alloy steel is only used for mixes with other elements such as manganese, nickel, chromium, molybdenum, silicon, vanadium, aluminum and tungsten. This is done to improve the machinability of the metal or the quality of end-products.

High Alloy Steel

An alloy steel with a high content of non-iron elements. This is defined as either 4% or 8%. It is possible for high alloy steel to be up to 50% non-iron. Stainless is a high alloy steel.

Low Alloy Steel

An alloy steel with a low content of non-iron elements below 4% or 8% depending on the standard. Most alloy steels are low alloy.

Structural Steel

Steel that conforms to national quality standards and grades such that it has the well defined properties required for buildings and infrastructure.

Hardened Steel

Steel that is harder than regular steel due to treatments that change its structure. This often involves heating the steel with a process known as tempering.

Electrical Steel

Steel designed to have specific magnetic and electrical properties. Often an alloy steel that contains silicon.

Low-background Steel

Stocks of steel manufactured before the first nuclear tests in the 1940s. Steel is produced with air such that radioactive impurities in the atmosphere contaminate the metal. Low-background steel is used for specialized low-radiation applications such as Geiger counters.

Galvanized Steel

Steel that has been coated in zinc to prevent corrosion. Used for inexpensive items that require corrosion resistance such as nails and metal signs.

Tinplate

Steel coated with a thin layer of tin. Used to make tin cans. Historically used to make low quality corrosion resistant items such as cheap pots and pans.

Cast Iron

Cast iron is an alloy of iron and carbon with greater than 2% carbon. This makes the metal more brittle. Cast iron is not considered steel. It has a lower melting point than steel and is easy to cast and machine. This is the origin of its name. Cast iron takes on colors such as white, grey and green depending on its impurities and microstructure.

Wrought Iron

A iron alloy with less than 0.08% carbon and slag inclusions that give it a wood-like grain. Production of wrought iron peaked in the 1860s as higher grade steel became cheaper to manufacture. Wrought iron now has a historical feel to it and is considered largely obsolete. It is almost pure iron and has around 250,000 inclusions per square inch.

Damascus Steel

Steel was produced as early as 1800 BC. It was common for ancient steel to be higher quality than wrought iron. Steel was historically used to produce premium items such as swords. For example, a high carbon steel known as Wootz steel was produced in India from around 500 BC. This was imported to the Middle East and sold to Europe where it was known as Damascus steel. Steel was historically expensive. For example, King Porus once rewarded Alexander the Great with 30 pounds of steel.

Above: Wootz and Damascus steel have a characteristic wavy pattern in the metal.

Tamahagane

Japan has several types of steel such as Tamahagane that are still manufactured with traditional methods that generally date back to the 16th century. This is gives the metal a premium price due to its labor intensive production and association with traditions such as samurai swords. These vary in carbon content from about 0.5% to 1.5% and some contain chromium making them similar to stainless steel. As with Damascus steel, the quality of these steels is surrounded in much folklore. However, unlike Damascus steel, the methods of production of traditional Japanese steels have been preserved and sustained over time.