Mild Steel – All You Need to Know

Due to its excellent properties, mild steel has become an in-demand material in steel fabrication. It has unparalleled weldability and machinability, which has led to an exponential increase in its usage.

In this article, we will discuss the importance of mild steel, its uses and how it’s made.

What Is Mild Steel?

Mild steel is a type of carbon steel with a low amount of carbon, thus, the terms low-carbon steel and mild steel are generally used interchangeably. Carbon steels are metals that contain a small percentage of carbon (max 2.1%), which enhances the properties of pure iron. The carbon content varies depending on the requirements for the steel. Low-carbon steels contain carbon in the range of 0.05 to 0.25%.

There are different grades of mild steel. But they all have carbon content within the above-mentioned limits. Other elements are added to improve useful properties like corrosion resistance, wear resistance and tensile strength.

How Is Low Carbon Steel Made?

Carbon content is uniformly increased by heat treating steel. As carbon content increases, steel develops hardness but loses ductility. This means that the metal becomes brittle and may fracture instead of bending when applying an excess load.

The manufacturing processes for mild steel are similar to other carbon steels. Higher carbon steels just contain more carbon, resulting in different properties like high strength and hardness values compared to mild steel.

These processes have developed over time and are now much more cost-effective than before. In modern manufacturing, three steps are involved in manufacturing mild steel out of pure iron.

Primary Steelmaking

In this leg of the steelmaking process, the iron ore is mixed with coal and lime and heated in a blast furnace having a 100 to 400-ton capacity. Lime acts as a flux and forms a protective layer on top of the hot molten metal.

Modern primary steelmaking uses Basic Oxygen Furnace (BOS) or Electric Arc Furnace (EAF) processes. These are both based on the original Bessemer process for steelmaking.

In the basic oxygen furnace process, oxygen is blown through the molten iron while scrap steel is added to the converter. This reduces the carbon content to a maximum of 1.5%.

In developed countries, the electric arc furnace is used to feed scrap steel through extremely high-powered electric arcs. This results in impressive quality steel.

Secondary Steelmaking

The second step in the process of making mild steel includes further reducing its carbon content and adding alloying elements.

Manipulating the furnace conditions (temperature, cooling rate, etc.) also aids this process. Ultimately, the type of steel desired will decide the secondary steelmaking process. One may choose from the following processes:

• CAS-OB
• Degassing
• Ladle furnace
• Ladle injection
• Stirring

Casting and Primary Forming

Once the steel has reached the desired carbon content and alloy composition, it is ready for casting. Modern steel production primarily uses continuous casting, where the molten steel is poured into a water-cooled mould and gradually solidified as it is continuously withdrawn. This process shapes the steel into semi-finished forms such as slabs, blooms, or billets.

These semi-finished products may exhibit surface imperfections or internal stresses. To improve their surface quality and mechanical consistency, hot rolling is commonly applied as the first forming process. Hot rolled steel is typically categorised into flat products, long products, custom shapes, and seamless tubes.

Secondary Forming

While the steel is technically complete after hot rolling, secondary forming processes are often employed to refine its final shape and mechanical properties to meet application-specific requirements.

• These processes include:
• Cold rolling for dimensional precision and surface finish
• Machining for complex or tight-tolerance components
• Coating and tempering to enhance durability
• Surface treatments to improve corrosion resistance or appearance

Chemical Properties of Mild Steel

Mild steel is a type of low-carbon steel, typically containing up to 0.25% carbon. In some classifications, carbon content up to 0.45% may still fall under the definition of mild steel, depending on its intended use.

The low carbon content makes mild steel highly machinable and weldable, allowing it to be cut, shaped, and joined with minimal internal stress.

Various alloying elements can be added to enhance its chemical and mechanical properties:

• Chromium (Cr) – improves hardness and corrosion resistance by forming a stable oxide layer.
• Copper (Cu) – provides additional protection against atmospheric corrosion.
• Manganese (Mn), Phosphorus (P), Sulphur (S), and Cobalt (Co) – contribute to machinability, toughness, and formability.

Other elements may be introduced to enhance wear resistance, ultimate tensile strength, and heat resistance, depending on the application. While untreated mild steel is prone to rust, galvanising or coating processes are commonly applied to increase durability and environmental resistance.

Physical Properties of Mild Steel

Mild steel possesses a set of physical characteristics that make it suitable for a broad range of industrial applications. Key properties include:

• High tensile and impact strength – withstands mechanical loads and shocks
• Good ductility and weldability – easy to work with in fabrication
• Magnetic metal – due to its ferrite content
• Excellent malleability – allows for cold-forming into complex shapes
• Suitable for various heat treatment options – enables tuning of mechanical properties to meet specific performance needs

These attributes, along with its affordability and availability, explain the widespread use of mild steel across construction, manufacturing, and engineering sectors.

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Applications and Use-Cases

It would not be an exaggeration to say that if you looked out your window, you would see something made from mild steel. It is the most common type of metal used around us.

From buildings to massive sea-going vessels, there is mild steel involved. Some of the applications are as follows.

Construction

In construction, there is a need for materials that can be joined easily and are able to withstand changing loads. Mild steel, therefore, is the perfect material for extensive use. Some grades of mild steel are actually called structural steels for that reason.

It also meets strict seismic and wind requirements, cannot be damaged by insects and is resistant to rot and fire.

The fact that it is relatively cheaper compared to other steels doesn’t hurt either. Mild steel is therefore used in structures big or small, from bridges to buildings.

Machinery Applications

Mild steel is widely used in machinery and automobile manufacturing. It is cheap, suitable for different cutting and coating methods and has good weldability while providing good enough physical properties. These attributes make it useful for producing frames, panels, etc.

Pipelines and Poles

The excellent ductility of mild steel has made it the perfect contender for the manufacturing of pipelines and poles that need to withstand extreme environments.

While mild steel pipes can be easily welded to each other, they also retain a certain degree of flexibility. As the pipelines may shrink in cold weather or expand on hot days, this is a necessary feature for the metal.

Cutlery and Cookware

While previously the exclusive domain of stainless steel, modern-day chefs are coming to love mild steel cookware more and more because of some of the advantages it offers.

The cutting equipment stays sharp for a longer time, has a higher temperature limit, and can be modified to become a non-sticking material.

Seasoning the metal helps to overcome the factor of corrosive wear.

Fencing

Mild steel can be shaped into incredibly specific shapes, which makes it perfect to be used in fencing. It is also visually appealing, so it looks beautiful besides being functional.

Mild steel may also be galvanised or coated with the right paint to make it long-lasting and rustproof.

Common Grades

The following are some of the widespread mild steel grades. A common denominator for all of them and other similar metals is their universal nature. Their properties make them a popular choice for a wide range of applications.

EN 1.0301

Equivalent grades: AISI 1008; C10; DC01

EN 1.0301 carbon steel contains 0.1% carbon, 0.4% manganese and 0.4% silicon. It also contains small amounts of copper (Cu), nickel (Ni), chromium (Cr), aluminium (Al), and molybdenum (Mo).

This grade has excellent weldability and is commonly used for extruded, forged, cold headed, and cold-pressed parts and forms. It is primarily used in automotive equipment, furniture, and appliances.

EN 1.1121

Equivalent grades: AISI 1010

EN 1.1121 carbon steel contains carbon in the range of 0.08% to 0.13%. Manganese is present in the range of 0.3% to 0.6%. It is used in the manufacturing of cold headed fasteners and bolts.

This mild steel grade also has good formability and ductility and can be formed using traditional methods. It also supports joining by practically all the welding techniques. Its strength may be improved by heat treatment, such as quenching and tempering, but the cost of carrying out these processes is rather high.

It is a general-purpose steel largely present in various structures and the automotive industry.

EN 1.0402

Equivalent grades: AISI 1020; C22

This grade of steel has excellent weldability. EN 1.0402 is especially suitable for carburised parts. It also has a good balance between ductility, strength and toughness.

It has a carbon content from 0.18% to 0.23% with a manganese content range of 0.3% to 0.6%. Compared to EN 1.1121, it is not used as commonly but it does have great machinability in its as-forged condition.

This grade finds use in machinery in the form of hydraulic parts and camshafts.

Fractory offers metal fabrication services, such as laser cutting, sheet metal bending and CNC machining, for a wide range of low-carbon steels. If you don’t find the material grade you need on our platform, please contact your account manager, since they are most likely still able to accommodate your needs.