Low Carbon Steel: Properties, Advantages, Types and Uses

What is Low Carbon Steel?

Low carbon steel, also known as mild steel or plain carbon steel, is an alloy of iron and carbon which contains a small amount of carbon, usually between 0.04 and 0.25% by weight. Low carbon steel may also include other elements such as manganese, silicon, sulfur, and phosphorus. These other elements are added to improve specific properties like strength or hardness.

Because of the small amount of carbon used, low carbon steel is more malleable, ductile, and weldable. These qualities make low carbon steel versatile, cost-effective, and easy to work with. That is why low carbon steel is the most widely used steel across industries such as construction, automotive, manufacturing, and piping and tubing.

 

Low Carbon Steel Chemical Composition

Low carbon steel is an alloy of iron and carbon. But it can contain small amounts of other elements to improve its properties. The following are other elements that can be present in low carbon steel and their roles:

• Iron (Fe): covers over 98% of the composition. Iron is the primary component that forms the basic structure of steel. In its pure form, iron is soft, weak, and ductile. But when alloyed with carbon, it provides strength and durability.
• Carbon (C): between 0.04 and 0.25%. The purpose of carbon is to increase the strength and hardness of the steel. Low carbon content gives steel good ductility and malleability.
• Manganese (Mn): between 0.25 and 1.65%. Its primary purpose is to neutralize impurities such as oxygen and sulfur. Manganese also increases strength and hardness.
• Silicon (Si): between 0.1 and 0.6%. It acts as a deoxidizer and improves strength. Silicon also enhances the fluidity of molten steel, making liquid flow better during casting. This helps manufacturers fill molds completely, even complex shapes.
• Sulfur (S): up to 0.05%. We can describe sulfur as a necessary evil. This is because sulfur is a harmful impurity, but it improves machinability.
• Phosphorus (P): up to 0.04%. It improves strength and hardness, but too much phosphorus can make steel brittle.

 

Properties of Low Carbon Steel

Low carbon steel has both mechanical and physical properties that make it suitable for many applications.

 

Mechanical properties of Low Carbon Steel

Mechanical properties of low carbon steel describe how it behaves under forces or loads. These properties tell us about low carbon steel strength, durability, and how it can be shaped and worked with.

• Tensile strength (300-500 MPa): tells us how much pulling force low carbon steel can handle before breaking. 300 – 500 MPa is enough for many structural uses such as building beams and columns, automotive frames and chassis and pipes and tubing.
• Yield strength (200-350 MPa) is the stress at which low carbon steel starts to deform permanently. This means that if you bend a low carbon steel rod above 350 MPa, it won’t return to its original shape. For low carbon steel, the yield strength is lower compared to medium or high-carbon steels.
• Elongation (20-35%) is how much low carbon steel can stretch before it breaks. 20-35% elongation means that a 1 meter steel wire can stretch 20-35 cm before breaking. Because low carbon steel is ductile, its elongation is high compared to other steels. Because of high elongation, low carbon steel is easier to draw into wires or roll into sheets.
• Hardness ( 80-150 HB) measures low carbon steel resistance to scratching, indentation, or wear. Low carbon steel is soft compared to medium or high-carbon steels. This less hardness makes low carbon steel highly ductile and malleable.

 

Physical properties of Low Carbon Steel

Physical properties are characteristics of a material that can be observed or measured without changing what the material is. Those properties include weight, heat behavior, and size changes with temperature. Physical properties of low carbon steel include the following:

• Density (approximately 7.85 g/cm³): It tells us how heavy steel is for a given volume. For low carbon steel, 7.85 g/cm³ means that 1 cubic cm of steel weighs 7.85grams. Knowing density, engineers can easily predict the weight of beams, rods, or machine parts made from low carbon steel.
• Melting point (1450-1530 °C). This is the temperature at which steel becomes liquid, allowing it to be cast into shapes such as pipes, rods, or structural components.
• Thermal conductivity (50 to 65 W/m·K): Measures how easily heat passes through low carbon steel. Low carbon steel’s good thermal conductivity makes it suitable for engines, appliances, and machinery.
• Coefficient of thermal expansion (11.5–13 × 10⁻⁶ /°C): It measures how much low carbon steel changes in response to a change in temperature. Knowing CTE helps engineers design safe products and structures that can handle heat or cold without damage.

 

Advantages of Low Carbon Steel

Low carbon steel has several advantages that make it a popular choice in many industries:

• Excellent ductility. Low carbon steel can be easily bent, rolled, pressed, drawn, or stamped into complex shapes without breaking.
• Superior weldability. Low carbon content allows low carbon steel to be joined to itself or to other metals using various welding methods without cracking.
• Cheap price. Low carbon steel is cost-effective. This makes it ideal for large-volume production and construction projects.
• Good machinability. Low carbon steel has lower hardness. This makes it easy to cut, drill, turn, and mill using standard tools without tool wear or difficulty in shaping.
• Easy recycling. Low carbon steel is 100% recyclable, helping reduce environmental i

 

Disadvantages of Low Carbon Steel

Low carbon steel has the following disadvantages:

• Poor corrosion resistance. Low carbon steel rusts easily when exposed to moisture, air, or harsh chemicals. Low carbon steel needs protective coatings or treatments for outside or wet uses.
• Lower strength. Low carbon steel has less tensile strength and hardness compared to medium or high carbon steels. Hence, it is not ideal for cutting tools, blades, or structures that need very high strength.
• Limited high-temperature performance: Low carbon steel loses strength at high temperatures. It is not suitable for furnace parts, engine components, or any other applications that must withstand extreme heat.

 

Types of Low Carbon Steel

The following are the common types of low carbon steel. These types differ in their composition, the way of processing, and the properties they gain after processing.

1. .Mild Steel
   Mild steel is the most common type of low carbon steel. It has excellent machinability and weldability because of its low carbon content. This makes it easy to cut, shape, and join to itself or other materials. Mild steel is widely used in automotive parts and in construction elements such as beams, columns, and pipelines.
2. Hot-Rolled Steel
   Hot-rolled steel is made by processing steel at very high temperatures (above 1,700°F or 927°C). This steel is malleable and easier to form. Due to high-temperature processing, hot-rolled steel has a rough surface and less precise dimensions. But compared to other steels, hot-rolled steel is strong and affordable. Hot-rolled steel is used in automotive components, structural beams, and railroad tracks.
3. Cold-Rolled Steel
   Cold-rolled steel is steel that has been processed at room temperature after hot rolling. This gives it a smoother surface and higher strength than hot-rolled steel. Cold-rolled steel is used for home appliances such as refrigerators, washing machines, automotive parts, and metal furniture like cabinets and lockers.
4. Deep-Drawing Steel (DDS)
   Deep-Drawing Steel (DDS) is a special type of low-carbon steel designed for the deep drawing process. Deep-drawing steel is known for exceptional ductility and formability. It is used for making automotive body panels, cookware, and containers.
5. High-Strength Low-Alloy (HSLA) Steel
   HSLA steel contains small amounts of alloying elements, such as manganese or vanadium, to increase its strength and toughness without adding much weight. It is commonly used in automotive frames, bridges, offshore platforms, and heavy machinery.

 

Common Grades of Low Carbon Steel

Low carbon steel is divided into the following grades based on its chemical composition and mechanical properties. Each grade has unique strengths and uses.

• ASTM A36 is one of the most widely used grades. It has good weldability and formability. These properties make it popular in construction for beams, columns, and structural parts.
• SAE 1008 is known for its high ductility, meaning it can stretch and form easily. It is often used in products that need bending or shaping, such as wires and deep-drawn parts.
• AISI 1020 offers a good balance of strength and ductility. Because of this, it is commonly used in mechanical parts and automotive components.
• AISI 1018 is valued for its excellent machinability and weldability. It is often chosen for precision parts that need accurate cutting, drilling, or shaping.

 

How is Low Carbon Steel Made?

Low carbon steel is made through the following steps:

1. Melting raw materials: Iron ore and other raw materials are melted in a primary furnace, such as a blast furnace, to form molten iron.
2. Transferring to a secondary furnace: The molten iron is moved to a steelmaking furnace, like a Basic Oxygen Furnace (BOF).
3. Reducing carbon: In the BOF, the excess carbon is lowered to the desired low level for low carbon steel.
4. Adding other elements: Alloying elements can be added to improve strength, ductility, or other properties.
5. Shaping the steel: The liquid steel is poured into molds to solidify into slabs or ingots, which are then rolled, forged, or otherwise processed into the final forms.

 

What is Low Carbon Steel Used for?

Low carbon steel is used in many industries due to its strength, ductility, and versatility. The following are the areas where low carbon steel is commonly used:

• Construction: Low carbon steel is used to make structural parts like beams, columns, and reinforcement bars. Low carbon steel is used because it is strong, easy to shape, weld, and install. With these qualities, construction becomes faster and cost-effective.
• Automotive: Low carbon steel is used to make car parts such as chassis, body panels, and frames. Being lightweight and ductile, low carbon steel is safe and easy to form into complex shapes.
• Manufacturing: Low carbon steel has good machinability and weldability. It is used to produce machinery frames, supports, and equipment parts such as gears and casings.
• Appliances: Low carbon steel is used to make household appliances such as refrigerators, washing machines, and ovens. Protective coatings are used to prevent rust.

 

Is Low Carbon Steel Eco-friendly?

Yes. Low carbon steel is eco-friendly because it uses sustainable manufacturing processes that reduce greenhouse gas emissions. Low carbon steel is highly durable, and it is 100% recyclable, allowing scrap steel to be reused without using quality.

 

FAQ

Is low carbon steel magnetic?

Yes. Low carbon steel is magnetic because its main component, iron, is a ferromagnetic material. Besides, the lower the carbon content, the stronger the steel’s magnetism becomes.

 

Where on a motor vehicle would low carbon steel be used?

Low carbon steel is used to make car body panels, the frame (chassis), suspension parts, fuel tanks, and bolts or fasteners. It is used because it costs less, is flexible, and easy to shape into complex parts. These qualities make it suitable for making many vehicle components.

 

Does low carbon steel rust?

Yes. All forms of carbon steel, which are iron-based alloys, are liable to rust, including low-carbon steel. To prevent rust, protective coatings such as paint, oil, or galvanization are applied.

 

What’s the most ductile steel?

Low carbon steel is the most ductile type of steel. Its low carbon content allows it to stretch, bend, and form into shapes easily without breaking. For steel, the lower the carbon, the more ductile the steel. This high ductility of low carbon steel makes it ideal for parts that need flexibility.