What are the Four Main Types of Steel?

You will see a steel product lying somewhere around you no matter where you look. Be it kitchen appliances, medical equipment, or tools, steel products have become an integral part of our day-to-day lives. However, not all these products contain the same type of steel. Even though every steel alloy is made of iron and carbon, there are more than 3,500 different steel grades available in the market. Some steel alloys are heavy and sturdy, while others are more pliable and heat-resistant. 

There are four main types of steel, each possessing a unique chemical structure and physical properties that make them well-suited for specific purposes. Depending on the amount of carbon, additional alloying elements, and the processing method, the properties of different steel types can vary. According to the properties suitable for their application, different types of steel are produced. 

To help you find the best steel for your needs, we have explained the four main types of steel and the various purposes they serve below. 

Carbon Steel

The name for carbon steel comes from the fact that it contains only trace amounts of alloying elements. Though all kinds of steel are made of carbon, carbon steel is distinctive for the absence of other alloying metals in its makeup. 

Carbon steel is often confused with cast iron; however, both are different alloys. Carbon steel contains up to 2% carbon, while the carbon percentage in cast iron can range from 2% to 3.5%. Due to this high percentage of carbon, cast iron has a more brittle nature and rough texture. 

Even though carbon steel is an alloy made of both iron and carbon, it is often defined in more than one way in the manufacturing industry. The following definitions apply to carbon steel in the metals market. 

  • Steel that contains up to 2% carbon.
  • Steel that is not classified as alloy steel, i.e., lacks any standard amount of elements, such as cobalt tungsten, zirconium, chromium, nickel, etc.
  • Steel with less than 0.4% copper.

Carbon steel does not possess alloy classification because of the absence of other alloying elements in its composition. Due to this simplicity, carbon steel is popular in the manufacturing industry and accounts for over 90% of all steel production. 

Despite the low carbon percentage in its composition, carbon steel is strong and durable, making it ideal for numerous purposes. Due to the elemental nature of carbon, it is remarkably strong, making it the top-rated choice of raw material for things like automotive parts, knives, high-tension wires, and other similar items. It has a dull and matte appearance and is vulnerable to corrosion. 

Depending on the carbon content in the alloy, carbon steel can be divided into three subgroups. Below the 2% carbon threshold, each steel type possesses the same inherent strength of carbon; however, their core properties and functionality change according to the carbon content. 

Low Carbon Steel

Low carbon steel, also known as plain carbon steel and mild carbon steel, is the most common type of carbon steel in the metals market. It typically contains up to 0.30% of carbon. There are numerous reasons for its popularity in the manufacturing industry. For starters, it is the least expensive type of steel, and thanks to its low carbon content, it is easier to manufacture than medium and high carbon steel. 

You can also easily add other alloying metals – such as magnesium – to enhance its properties. Its high ductility and low hardness make it an ideal choice of material for machinery, pipes, automobile components, medical equipment, surgical instruments, structural components, etc. Some core properties of low carbon steel are low cost, mild strength, high weldability, low hardness, and high machinability. All these properties also make it an ideal choice for carburizing. 

Medium Carbon Steel

Medium carbon steel refers to steels that contain between 0.3% to 0.60% of carbon. Its chemical makeup also includes 0.31% to 1.60% magnesium. A high carbon content gives this variety high strength and makes it much stronger than low carbon steel. However, this strength comes with some downsides. Medium carbon steel is more laborious to manufacture and weld due to its low ductility and toughness. Some core properties of medium carbon steel are medium toughness, low hardenability, and medium weldability. Due to these core properties, it is a suitable raw material for making gears, cranks, pressure structures, machinery parts, railway tracks, etc.

High Carbon Steel

High carbon steel refers to steels that contain more than 0.60% and up to 1.50% of carbon. Magnesium is also a part of its chemical composition, its content varying from 0.31-0.90%. Such a high carbon content makes it the strongest of all the varieties of carbon steel. It is the choice of every manufacturer whenever a project requires hardness and toughness. However, high carbon steel does not come without its drawbacks. It can be hard to form, cut, or weld carbon steel due to its high toughness. Some core properties of high carbon steel are high toughness, low machinability, high strength, and low weldability. Due to these properties, it is the top choice to produce spring steel, brick nails, railway tracks, trencher blades, etc. 

Stainless Steel

Stainless steel is characterized by the presence of chromium as the principal alloying element. It typically contains between 10% to 15% chromium. Like all other steel varieties, stainless steel also contains carbon and iron. However, it is the presence of chromium that sets stainless steel apart and gives it unique properties. 

Chromium is oxidation-resistant, so it protects the steel from rusting and increases its longevity. One key selling point of stainless steel is that it is highly resistant to corrosion and does not degrade for a long, long time – it is about two hundred times more corrosion-resistant than low carbon steel. This high corrosion-resisting nature of stainless steel makes it highly prized in the construction industry. 

Stainless steel also has distinctive sheen and luster, a property lent by chromium. The gloss of the steel is directly proportional to its chromium content. So the higher the chromium content, the higher the sheen, and the higher the cosmetic value of the steel.

Stainless steel variants make the archetypal choice for storage functions for hazardous construction materials thanks to their strength and ability to withstand high temperatures. In addition to that, stainless is very easy to mold into different shapes, making it an extremely versatile material. Due to such high versatility, stainless steel plays a role in manufacturing a wide range of products, such as medical equipment, home appliances, silverware, and automotive appliances. 

Stainless steel is also grouped into different subcategories, each possessing unique properties and serving distinct purposes. 

Austenitic Alloys

Austenitic alloys are the most common types of stainless steel in the global steel market. They contain a higher percentage of chromium and nickel, which increases their corrosion resistance and makes them non-magnetic. They are also durable and non-heat-treatable, which is why this variety is known for its role in manufacturing commercial kitchen equipment and food processing appliances. 

Ferritic Alloys

These make the least expensive stainless steel variety due to their low nickel and carbon content. They typically contain 12-17% of chromium and trace amounts of carbon and nickel. Ferritic alloys are magnetic and can not be hardened by heat treatment. Their chromium-induced strength and gloss make them the top choice of raw material for the manufacture of automotive applications. 

Martensitic Alloys

Martensitic alloys form the lowest proportion of the global stainless steel market. They contain 11-17% of chromium, up to 1.2% of carbon, and trace amounts of nickel. Hardness and toughness are the hallmarks of martensitic alloys, but they have poor oxidation properties and are highly vulnerable to corrosion. Their magnetic and heat-treatable properties make them ideal choices for the manufacture of surgical equipment, as well as cutlery and cutting tools. 

Alloy Steel

Alloy Steel

Alloy steel makes the most diverse and wide range of steel alloys with an equally diverse range of properties. They are made by fusing iron with various alloying elements, such as copper, chromium, aluminum, silicon, cobalt, nickel, and tungsten. Each of the metals contributes its unique properties to the end product. By varying their proportions, the properties of the steel – such as its corrosion resistance, strength, and weldability – can be manipulated and customized for different purposes. 

Due to the variety of alloy elements available in the market, you can get steels with almost any desired attribute. They can serve a plethora of purposes according to their properties. For instance, aluminum alloy steel is lightweight, heat-resistant, and pliable, making it an ideal choice for power generators and hot exhaust systems. Copper alloys make corrosion-resistant steel commonly used in electrical wiring and commercial heat exchangers. Vanadium alloy steels are shock-absorbent and vibration-resistant, which are often found in springs and other automotive parts. 

This versatility makes alloy steel highly valued in the construction industry. Moreover, since most steel alloys are cheap, they are a common occurrence in many building projects.

Tool Steel

The last main group of steel is tooling steel. The name arises from the fact that these steels are commonly used to make manufacturing machinery and tools. They typically contain hard metals known for their impact resistance and cutting abilities, such as tungsten, vanadium, molybdenum, and cobalt. 

The combination of these ultra-hard metals increases the heat resistance and durability of the alloys. This variety is known for being hard, strong, abrasive, and both heat and scrape resistant. Such features make them ideal for cutting and drilling equipment, especially in high-impact environments. 

The Takeaway

With more than 3000 different steel grades, there are endless possibilities for its usage. We hope that this guide can help you choose the type of steel best suited to the goal you are seeking to accomplish.