Apr. 29, 2024
Minerals & Metallurgy
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.
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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 this 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 contents 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:
Casting and Primary Forming
Once the steel has the specified carbon content and other elements that enhance its performance, the molten steel is poured into a mould. This is the casting process. Here, the steel is shaped and allowed to solidify. Afterwards, the solidified metal is cut into desired shapes like slabs, blooms and billets.
At this stage, the raw material slabs might be affected by casting defects. To improve surface quality, hot rolling is often used as the primary forming process. Hot rolled steel products are usually categorised into flat products, custom products, long products, and seamless tubes.
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Secondary Forming
Although we have completed mild steel production by the end of the abovementioned process, it is usually formed one more time to improve its mechanical properties in line with application requirements.
Secondary forming gives it the final shape and properties. The forming methods include:
Chemical Properties of Mild Steel
As mentioned above, mild steel has lower carbon content than medium and high carbon steels. The carbon content is up to 0.25% in mild steel but some schools of thought consider carbon steel as mild steel up to a carbon content of 0.45%.
The low carbon content makes this steel a highly machinable metal. It can be cut, machined and formed into intricate shapes without adding proportional stresses to the workpiece. It also facilitates better weldability.
A host of alloying elements can improve the chemical properties. These elements will affect the physical/chemical properties favourably and make the final product suitable for the application. The elements that may be added include chromium (Cr), cobalt (Co), phosphorus (P), sulphur (S), and manganese (Mn), among others.
For instance, chromium imparts corrosion resistance and increases mild steel’s hardness. In its pure form, mild steel will rust easily due to oxidation. Unlike iron oxide, chromium metal on exposure to the atmosphere forms a dense layer of chromium oxide that does not fall off and ultimately protects the metal underneath from further corrosion attacks.
Copper in limited quantities also works like chromium oxide. Mild steel pipes may be galvanised for better protection from the atmosphere.
Other elements may be added to improve wear resistance, ultimate tensile strength, and heat resistance.
Physical Properties of Mild Steel
Its impressive properties are responsible for growing use in a variety of industries. Some mild steel’s physical properties are as follows:
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 weather extreme atmospheres.
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 also is 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
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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 our sales engineers since they are most likely still able to accommodate your needs.
Steel is the most used material in construction, manufacturing and industry. Two of the most used types of steel are mild steel and carbon steel.
While both are used for similar purposes, there are several key differences between the two that make them better suited for different applications.
In this article, we will take a closer look at mild steel and carbon steel and examine the differences between them, including their carbon content, mechanical properties, and manufacturing and finishing processes.
Whether you are a metal fabricator, engineer or just looking to better understand mild steel and carbon steel, we will provide you with all the information you need to make an informed decision.
Mild steel is a type of carbon steel with a low amount of carbon (typically 0.05% to 0.25%); these are also known as “low carbon steels.” Low carbon steel is considered a relatively inexpensive and versatile material that is commonly used in various construction and manufacturing applications.
The low carbon content makes mild steel more ductile and easier to shape, form and weld than other types of steel. Mild steel has good machinability and can be easily drilled, cut, and fabricated into various shapes and sizes.
In addition, low carbon steel has a relatively high tensile strength, making it suitable for use in high-stress applications such as beams, columns and machinery components. It’s versatility and affordability make it a popular choice for a wide range of applications.
Read more about mild steel here.
Carbon steel is a type of steel that contains carbon as the main alloying element, with other elements present in smaller amounts. This metal is commonly used in the manufacturing of many products and structures due to its high strength and low cost.
Carbon steel can be further classified into various grades based on its chemical composition and mechanical properties, such as low carbon steel (mild steel), medium carbon steel, high carbon steel and ultra high carbon steel. Each grade has its own specific uses and applications, depending on the desired properties of the final product.
Medium to high carbon steel is commonly used to make machinery components, such as gears, crankshafts and shafts. Its high strength, and particularly high hardness make it an ideal choice for a wide range of tooling applications.
There are several types of carbon steel, each with unique properties and applications. These types include:
Also known as “mild steel,” this type of steel is more ductile and easier to shape, form and weld compared to other carbon steel types. This makes mild steel a popular choice over higher-carbon steels when it comes to construction and manufacturing applications.
Contains 0.3% to 0.6% carbon content, making it stronger and harder than low-carbon steel but also more brittle. It is often used in applications that require both strength and ductility, such as machinery components, automotive parts and building frames.
High carbon steel contains 0.6% to 1.5% carbon content and is known for its high strength and hardness, but high carbon steel is even more brittle than medium-carbon steel. High carbon steel is used in applications that require high strength such as knife blades, hand tools and springs.
Comparison Mild Steel Carbon Steel Carbon Content Low Medium to Ultra-High Mechanical Strength Moderate High Ductility High Moderate – Low Corrosion resistance Poor Poor Weldability Good Generally not suitable Cost Inexpensive Slightly higher per weight
The manufacturing process for mild steel and carbon steel varies depending on the type of steel and the intended qualities for the final product. The manufacturing process is often divided into three stages:
Steel can be created entirely from recycled material or from a mix of recycled and virgin steel using the BOF process.
Mild and carbon steel are commonly produced using the basic oxygen furnace (BOF) method, which involves the transformation of raw materials such as iron ore and coke into liquid steel.
The liquid steel is poured into molds to produce slabs or ingots. Pure oxygen is pushed through the liquid steel to oxidize the extra carbon, resulting in a finished product with a carbon content of up to 0.5%.
Market needs for higher-quality steel products with more consistent characteristics fueled the development of secondary steelmaking processes. This allows manufacturers to alter the carbon content to produce the resulting low carbon steel, medium carbon steel, high carbon steel or ultra-high carbon steel.
In an electric arc furnace, steel composition is changed by adding or removing specific components or by manipulating the temperature. EAF processes involve:
The elimination of oxygen is a vital step in secondary steelmaking. As molten steel begins to solidify, the presence of oxygen causes a reaction with carbon, producing carbon monoxide gas.
Controlling deoxidation can be used to change the material properties of the final product and hence the steel’s suitability for various desired applications. Deoxidizing steel processes involve:
Traditional casting methods entail pouring molten steel into individual molds positioned on rail cars. Continuous casting of molten steel into shapes more appropriate for downstream processing is possible with casting machines.
Ingots are moved to soaking pits to be reheated for hot rolling. In a continuous casting machine, steel is produced into slabs, blooms or billets.
The finishing procedure for mild steel and carbon steel can have a significant impact on the end product’s appearance and performance. Carbon steel is finished using:
Solid cast ingots must be rolled into more usable shapes and sizes, similar to continuous casting ingots. The rolls rotate faster than the steel as it enters the machine, propelling it forward and compressing it.
To break up the as-cast microstructure, steel is heated above the recrystallization temperature. This results in a more uniform grain size and an even carbon distribution throughout the steel.
Cold forming is done at temperatures lower than the recrystallization temperature. This procedure improves the finish while increasing the strength by up to 20% through strain hardening. In a rolling mill, semi-finished materials are further processed into intermediate products. They are then ready for downstream industries to manufacture and process them.
The goal of heat-treating steel is to change the distribution of carbon in the product and the interior microstructure which modifies its mechanical properties. When the mechanical qualities of steel are changed by heat treatments, an increase in ductility leads to a decrease in hardness and strength (and vice versa).
Steel is heated to approximately 55 °C (130 °F) over its top critical temperature. The upper critical temperature is maintained until the entire product has been uniformly heated, at which point it is air-cooled. This is the most frequent type of heat treatment, and it imparts exceptional strength and hardness to steel.
Steel is heated to a solid solution temperature for one hour before cooling at a rate of 21 °C (70 °F) per hour. Internal tensions are eliminated, resulting in soft and ductile steel.
This is similar to normalizing heat treatment, except that cooling is expedited by quenching the steel in water, brine or oil. The resulting material is extremely hard but extremely brittle, leaving it prone to breaking and cracking.
As a result, for exact control of the steel’s properties, it is usually followed by a controlled cooling rate down to room temperature in a process known as tempering or stress relief.
Approximately one-third of all steel manufactured is surface coated to prevent corrosion and increase weldability and paintability.
Galvanizing is the application of a zinc surface layer to steel. The steel is heated before entering a zinc bath, where liquid zinc coats the product’s surface. Gas-knives are used to adjust the coating thickness. A small amount of aluminum is added to the zinc solution to prevent the zinc coating from breaking.
Electrolytic galvanizing is another method for putting a zinc layer on steel goods. By regulating the current in an electrolyte solution, zinc is deposited onto the surface of the steel. This approach allows for more precise control of coating thickness.
For more on metal finishing options, check out our video blog.
Steel raw materials are further processed by downstream companies into the desired finished products. Various processing procedures, such as machining and joining, which include uniformly removing surface metal with machine tools and welding, are common.
Carbon steel is predominantly made of iron, which makes it more susceptible to rust. When exposed to moist or humid conditions, carbon steel can corrode and form rust, which is a reddish-brown oxide of iron. This is because the steel reacts with oxygen in the air to produce iron oxide (rust). The same applies for mild steel.
However, the rate of corrosion for carbon steel can be influenced by several factors, including the environment in which it is used, the presence of other metals or substances that can accelerate corrosion as well as the specific type of carbon steel.
Some types of carbon steel may be more resistant to rust than others, and the use of coatings, such as paint or electroplating, can help to reduce the risk of rust formation.
Both types of carbon steel have their own unique properties and advantages that make them more suitable for some applications than others. Which one is better typically comes down to your specific requirements.
Mild steel is better used for low-stress applications due to its ease of fabrication and low cost, while carbon steel (from medium carbon steel to ultra high carbon steel) is better used for high-strength applications due to its high carbon content and strength.
Carbon steel has a significant advantage over mild steel in terms of strength. Carbon steel can be up to 20% stronger than mild steel, making it an excellent choice for high-strength applications or where high hardness is required.
One of the most significant disadvantages of carbon steel is its high cost. Because of its increased carbon content, carbon steel is often more expensive than mild steel.
Furthermore, carbon steel is more difficult to weld than mild steel, making it less appropriate for welding applications.
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 SteelWhat 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 this 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 contents 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:
Casting and Primary Forming
Once the steel has the specified carbon content and other elements that enhance its performance, the molten steel is poured into a mould. This is the casting process. Here, the steel is shaped and allowed to solidify. Afterwards, the solidified metal is cut into desired shapes like slabs, blooms and billets.
At this stage, the raw material slabs might be affected by casting defects. To improve surface quality, hot rolling is often used as the primary forming process. Hot rolled steel products are usually categorised into flat products, custom products, long products, and seamless tubes.
Scale Your Manufacturing from Prototyping to Series
Personal account manager
Quality assurance
Payment terms for companies
On-time delivery by Fractory
Secondary Forming
Although we have completed mild steel production by the end of the abovementioned process, it is usually formed one more time to improve its mechanical properties in line with application requirements.
Secondary forming gives it the final shape and properties. The forming methods include:
Chemical Properties of Mild Steel
As mentioned above, mild steel has lower carbon content than medium and high carbon steels. The carbon content is up to 0.25% in mild steel but some schools of thought consider carbon steel as mild steel up to a carbon content of 0.45%.
The low carbon content makes this steel a highly machinable metal. It can be cut, machined and formed into intricate shapes without adding proportional stresses to the workpiece. It also facilitates better weldability.
A host of alloying elements can improve the chemical properties. These elements will affect the physical/chemical properties favourably and make the final product suitable for the application. The elements that may be added include chromium (Cr), cobalt (Co), phosphorus (P), sulphur (S), and manganese (Mn), among others.
For instance, chromium imparts corrosion resistance and increases mild steel’s hardness. In its pure form, mild steel will rust easily due to oxidation. Unlike iron oxide, chromium metal on exposure to the atmosphere forms a dense layer of chromium oxide that does not fall off and ultimately protects the metal underneath from further corrosion attacks.
Copper in limited quantities also works like chromium oxide. Mild steel pipes may be galvanised for better protection from the atmosphere.
Other elements may be added to improve wear resistance, ultimate tensile strength, and heat resistance.
Physical Properties of Mild Steel
Its impressive properties are responsible for growing use in a variety of industries. Some mild steel’s physical properties are as follows:
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 weather extreme atmospheres.
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 also is 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 our sales engineers since they are most likely still able to accommodate your needs.
Steel is the most used material in construction, manufacturing and industry. Two of the most used types of steel are mild steel and carbon steel.
While both are used for similar purposes, there are several key differences between the two that make them better suited for different applications.
In this article, we will take a closer look at mild steel and carbon steel and examine the differences between them, including their carbon content, mechanical properties, and manufacturing and finishing processes.
Whether you are a metal fabricator, engineer or just looking to better understand mild steel and carbon steel, we will provide you with all the information you need to make an informed decision.
Mild steel is a type of carbon steel with a low amount of carbon (typically 0.05% to 0.25%); these are also known as “low carbon steels.” Low carbon steel is considered a relatively inexpensive and versatile material that is commonly used in various construction and manufacturing applications.
The low carbon content makes mild steel more ductile and easier to shape, form and weld than other types of steel. Mild steel has good machinability and can be easily drilled, cut, and fabricated into various shapes and sizes.
In addition, low carbon steel has a relatively high tensile strength, making it suitable for use in high-stress applications such as beams, columns and machinery components. It’s versatility and affordability make it a popular choice for a wide range of applications.
Read more about mild steel here.
Carbon steel is a type of steel that contains carbon as the main alloying element, with other elements present in smaller amounts. This metal is commonly used in the manufacturing of many products and structures due to its high strength and low cost.
Carbon steel can be further classified into various grades based on its chemical composition and mechanical properties, such as low carbon steel (mild steel), medium carbon steel, high carbon steel and ultra high carbon steel. Each grade has its own specific uses and applications, depending on the desired properties of the final product.
Medium to high carbon steel is commonly used to make machinery components, such as gears, crankshafts and shafts. Its high strength, and particularly high hardness make it an ideal choice for a wide range of tooling applications.
There are several types of carbon steel, each with unique properties and applications. These types include:
Also known as “mild steel,” this type of steel is more ductile and easier to shape, form and weld compared to other carbon steel types. This makes mild steel a popular choice over higher-carbon steels when it comes to construction and manufacturing applications.
Contains 0.3% to 0.6% carbon content, making it stronger and harder than low-carbon steel but also more brittle. It is often used in applications that require both strength and ductility, such as machinery components, automotive parts and building frames.
High carbon steel contains 0.6% to 1.5% carbon content and is known for its high strength and hardness, but high carbon steel is even more brittle than medium-carbon steel. High carbon steel is used in applications that require high strength such as knife blades, hand tools and springs.
Comparison Mild Steel Carbon Steel Carbon Content Low Medium to Ultra-High Mechanical Strength Moderate High Ductility High Moderate – Low Corrosion resistance Poor Poor Weldability Good Generally not suitable Cost Inexpensive Slightly higher per weight
The manufacturing process for mild steel and carbon steel varies depending on the type of steel and the intended qualities for the final product. The manufacturing process is often divided into three stages:
Steel can be created entirely from recycled material or from a mix of recycled and virgin steel using the BOF process.
Mild and carbon steel are commonly produced using the basic oxygen furnace (BOF) method, which involves the transformation of raw materials such as iron ore and coke into liquid steel.
The liquid steel is poured into molds to produce slabs or ingots. Pure oxygen is pushed through the liquid steel to oxidize the extra carbon, resulting in a finished product with a carbon content of up to 0.5%.
Market needs for higher-quality steel products with more consistent characteristics fueled the development of secondary steelmaking processes. This allows manufacturers to alter the carbon content to produce the resulting low carbon steel, medium carbon steel, high carbon steel or ultra-high carbon steel.
In an electric arc furnace, steel composition is changed by adding or removing specific components or by manipulating the temperature. EAF processes involve:
The elimination of oxygen is a vital step in secondary steelmaking. As molten steel begins to solidify, the presence of oxygen causes a reaction with carbon, producing carbon monoxide gas.
Controlling deoxidation can be used to change the material properties of the final product and hence the steel’s suitability for various desired applications. Deoxidizing steel processes involve:
Traditional casting methods entail pouring molten steel into individual molds positioned on rail cars. Continuous casting of molten steel into shapes more appropriate for downstream processing is possible with casting machines.
Ingots are moved to soaking pits to be reheated for hot rolling. In a continuous casting machine, steel is produced into slabs, blooms or billets.
The finishing procedure for mild steel and carbon steel can have a significant impact on the end product’s appearance and performance. Carbon steel is finished using:
Solid cast ingots must be rolled into more usable shapes and sizes, similar to continuous casting ingots. The rolls rotate faster than the steel as it enters the machine, propelling it forward and compressing it.
To break up the as-cast microstructure, steel is heated above the recrystallization temperature. This results in a more uniform grain size and an even carbon distribution throughout the steel.
Cold forming is done at temperatures lower than the recrystallization temperature. This procedure improves the finish while increasing the strength by up to 20% through strain hardening. In a rolling mill, semi-finished materials are further processed into intermediate products. They are then ready for downstream industries to manufacture and process them.
The goal of heat-treating steel is to change the distribution of carbon in the product and the interior microstructure which modifies its mechanical properties. When the mechanical qualities of steel are changed by heat treatments, an increase in ductility leads to a decrease in hardness and strength (and vice versa).
Steel is heated to approximately 55 °C (130 °F) over its top critical temperature. The upper critical temperature is maintained until the entire product has been uniformly heated, at which point it is air-cooled. This is the most frequent type of heat treatment, and it imparts exceptional strength and hardness to steel.
Steel is heated to a solid solution temperature for one hour before cooling at a rate of 21 °C (70 °F) per hour. Internal tensions are eliminated, resulting in soft and ductile steel.
This is similar to normalizing heat treatment, except that cooling is expedited by quenching the steel in water, brine or oil. The resulting material is extremely hard but extremely brittle, leaving it prone to breaking and cracking.
As a result, for exact control of the steel’s properties, it is usually followed by a controlled cooling rate down to room temperature in a process known as tempering or stress relief.
Approximately one-third of all steel manufactured is surface coated to prevent corrosion and increase weldability and paintability.
Galvanizing is the application of a zinc surface layer to steel. The steel is heated before entering a zinc bath, where liquid zinc coats the product’s surface. Gas-knives are used to adjust the coating thickness. A small amount of aluminum is added to the zinc solution to prevent the zinc coating from breaking.
Electrolytic galvanizing is another method for putting a zinc layer on steel goods. By regulating the current in an electrolyte solution, zinc is deposited onto the surface of the steel. This approach allows for more precise control of coating thickness.
For more on metal finishing options, check out our video blog.
Steel raw materials are further processed by downstream companies into the desired finished products. Various processing procedures, such as machining and joining, which include uniformly removing surface metal with machine tools and welding, are common.
Carbon steel is predominantly made of iron, which makes it more susceptible to rust. When exposed to moist or humid conditions, carbon steel can corrode and form rust, which is a reddish-brown oxide of iron. This is because the steel reacts with oxygen in the air to produce iron oxide (rust). The same applies for mild steel.
However, the rate of corrosion for carbon steel can be influenced by several factors, including the environment in which it is used, the presence of other metals or substances that can accelerate corrosion as well as the specific type of carbon steel.
Some types of carbon steel may be more resistant to rust than others, and the use of coatings, such as paint or electroplating, can help to reduce the risk of rust formation.
Both types of carbon steel have their own unique properties and advantages that make them more suitable for some applications than others. Which one is better typically comes down to your specific requirements.
Mild steel is better used for low-stress applications due to its ease of fabrication and low cost, while carbon steel (from medium carbon steel to ultra high carbon steel) is better used for high-strength applications due to its high carbon content and strength.
Carbon steel has a significant advantage over mild steel in terms of strength. Carbon steel can be up to 20% stronger than mild steel, making it an excellent choice for high-strength applications or where high hardness is required.
One of the most significant disadvantages of carbon steel is its high cost. Because of its increased carbon content, carbon steel is often more expensive than mild steel.
Furthermore, carbon steel is more difficult to weld than mild steel, making it less appropriate for welding applications.
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