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Carbon Steel Definition: What Is Carbon Steel Made Of?

Carbon Steel Definition: What Is Carbon Steel Made Of?
Carbon Steel Definition: What Is Carbon Steel Made Of?

For many industrial uses, knowing what carbon steel is made of and its properties is necessary. The goal of this blog post is to give an in-depth view of carbon steel by discussing its chemical composition, physical attributes, and application areas across various industries. This article will help readers better understand why such combinations still serve as basics for different sectors like building or automobile manufacturing, among others, with tool-making and pipeline construction being no exception. Whether one has been working in related fields before or just starting their career path here – there should be something valuable for anyone interested in learning more about this topic.

What is Carbon Steel?

What is Carbon Steel?

Definition of Carbon Steel

An iron-carbon alloy with a carbon content of up to 2.1% by weight is called carbon steel. The difference between it and other types of steel is that this material contains more carbon, which affects its hardness, strength, and ductility. Though it usually has small quantities of manganese, silicon, and incidental impurities, it does not have any appreciable amounts of alloying elements such as chromium or nickel found in stainless steel. There are three main grades for this kind of steel: low carbon (mild), medium carbon, and high carbon steel. They find their particular uses according to their mechanical properties.

Composition of Carbon Steel

Carbon steel is mainly composed of iron and carbon, where the percentage range for carbon contents usually does not exceed 2.1 percent by weight. The carbon steel also consists of other elements like silicon and manganese, as well as residual impurities such as phosphorus and sulfur, which may be found in limited quantities. These trace elements can change their strength and ductility, among other mechanical properties. Unlike stainless steels, chromium or nickel are not major alloying components in carbon steel; thus, they lack corrosion resistance properties exhibited by these metals when used singly or together with others in such proportions that give rise to stainlessness, but this does not mean that all forms or grades must contain them at any level whatsoever because there is variation depending on specific types or grades though basic formulation principles remain constant throughout applicable industry standards.

Types of Carbon Steel: Low, Medium, High

Mild Steel (Low Carbon Steel): Low carbon steel (also known as mild steel) has an average carbon content ranging from 0.05% to 0.25% by weight. It can be easily bent and twisted without breaking, so it is often used for making things that need to be joined together by welding or shaping such as buildings, cars bodies or machine parts. Although less hard than many types of metals, it can still be machined easily because of this quality.

Medium Carbon Steel: Carbon steel with a medium amount of carbon usually contains between 0.30% and 0.60%. This kind of metal gives you both strength and ductility at the same time i.e., you don’t have to choose one over another! It can be toughened through heat treatment which makes it perfect for stuff like train tracks where you want something strong enough but also workable with welding machines or other tools used in factories that make parts for machinery.

High Carbon Steel: This is one very strong steel used when tensile strength must be at its highest level possible among all materials available today; hence, people refer to them as having ‘high’ tensile strength steels too! They contain anywhere around 0.60%-1.5% carbon per mass ratio). These metals are usually brittle and cannot withstand being bent or stretched without breaking apart – they will snap if subjected to these forces repeatedly -. The reason why they are very hard is because the more amount of carbon atoms present within their atomic structure the greater will be their hardness levels achieved during heat treatment processes such as quenching followed by tempering operations that involve cooling down rapidly from high temperatures into water baths or oil baths.

How Does Carbon Content Affect Steel?

How Does Carbon Content Affect Steel?

Amount of Carbon in Steel

Steel’s hardness, strength, ductility, and weldability are all affected by the amount of carbon in it. Various steel types have different amounts of carbon. With higher carbon levels, steel becomes harder and stronger but less ductile and weldable. Low-carbon steel is highly ductile and easy to weld, while medium-carbon steel has a good balance between strength and ductility; high-carbon steel, on the other hand, is extremely hard but brittle with limited useful toughness for welding purposes.

Effects on Mechanical Properties

The more carbon there is in steel, the more it affects certain mechanical properties.

  1. Hardness: If the carbon content were higher, then the hardness of the steel would increase as well, which means that it would become more resistant to being worn away by friction or rubbing.
  2. Strength: With an increased amount of carbon present within its composition also comes a rise in tensile strength – this lets materials withstand larger amounts of pulling force before breaking occurs.
  3. Ductility: Conversely, it still follows that if one adds extra amounts of carbon into their alloy mixtures, they will find themselves with decreased ductility – metals’ ability to be stretched without tearing apart easily.
  4. Weldability should be taken into account when utilizing carbon steels for construction purposes: But if there is a lot of carbon content used during welding procedures may become harder due to higher risks associated with crack formations and other defects caused by too much penetration heat input.

These impacts must be understood so that suitable steels are chosen for different engineering and industrial applications.

Percentage of Carbon and Tensile Strength

The connection between carbon percentage and tensile strength in steel is well-studied in material science. A steel’s tensile strength changes considerably as its carbon content goes from low to high, typically ranging between 0.05% and 2.1%. Steels have low levels of tensile strength when they contain less than 0.3% carbon (usually around 400-550 MPa) but are highly ductile and weldable. Medium-carbon steels (about 0.3%-0.6%) offer a good balance between ductility and strength; they generally feature tensile strengths within the range of 550-900 MPa. High-carbon steels (above 0.6%) achieve extremely high tensile strengths – often over 900 MPa – but become very brittle after being welded because their ductility drops significantly at this point due to increased cracking susceptibility associated with higher carbon levels during solidification cooling periods while still above room temperature. Therefore, different mechanical properties can be obtained by selecting appropriate amounts of carbon for various applications where steel is used as a structural material.

What Are the Properties of Carbon Steel?

What Are the Properties of Carbon Steel?

Mechanical Properties of Carbon Steel

Depending on carbon content, carbon steel has different mechanical properties, all of which have been found useful in many applications. The following are the most important mechanical properties:

Tensile Strength:

  • Low Carbon Steel: Its tensile strength is approximately 400-550 MPa.
  • Medium Carbon Steel: Tensile strength (TS) lies between 550 – 900 MPa.
  • High Carbon Steel: TS can be greater than 900 MPa.


  • Low Carbon Steel: It has a hardness of about 120-170 BHN (Brinell Hardness Number).
  • Medium Carbon Steel: Its hardness value ranges from 170 to 210 BHN. Such levels of hardness are exhibited by some forms of steel, which are made up mostly or entirely from this type of carbon steel alloying element(s).
  • High Carbon Steel: The hardness is between 210 and 350 BHN.


  • As its carbon content increases so does brittleness; hence ductility reduces with an increase in carbon concentration. This means that low-carbon steels have high ductility with elongation at fracture typically ranging from around twenty percent up until thirty percent while medium-carbon steels offer moderate ductility but high-carbon ones only show limited amounts thereof where usually less than ten percent elongation at breakage occurs.

Impact Resistance:

  • Low Carbon Steel – High impact resistance, suitable for applications requiring high toughness.
  • Medium Carbon Steel – Moderate impact resistance.
  • High Carbon Steel – Lower impact resistance thereby making it more prone to brittle failure.

Fatigue Strength:

  • Typically, fatigue strength improves as the level of cyclic loading below which material can withstand indefinitely increases with increasing amounts of carbon atoms incorporated into its structure. However this improvement comes along with a decrease in impact toughness and ductility values.

These qualities demonstrate why different kinds of carbon steels should be used for different purposes within industries; knowledge about these features will enable one to choose right materials for optimal performance in specific applications ranging from those where the design calls for components having both high ductility and impact resistance to others such as cutting tools which demand elevated tensile strength combined with hardness.

Physical Properties and Corrosion Resistance


  • Commonly, carbon steel is about 7.85 g/cm³ in density and this really applies to mild, medium and strong carbon steels.

Thermal Conductivity:

  • Low Carbon Steel: It has a thermal conductivity of around 60 W/m·K which makes it good for the manufacture of parts requiring heat transfer ability.
  • Medium and High Carbon Steels: They usually exhibit lower thermal conductivities (about 50 W/m·K) due to more carbon being present as well as added alloying elements.

Electrical Conductivity:

  • The electrical conductivity of carbon steel decreases with increasing amounts of carbon but still remains higher than that in medium or high-carbon steel grades.

Melting Point:

  • The melting points for most types of carbon steels fall within the range of 1425°C to 1540°C; these figures may vary slightly depending on other metals that have been alloyed with iron along with their content level in relation to weight.

Corrosion Resistance:

  • On the whole, when compared against stainless steels, general-purpose carbon steel shows weak resistance towards rusting caused by exposure to moisture together with aggressive chemical environments lacking proper shielding methods.Carbonizing steel can be made more resistant by applying coatings onto its surface, galvanizing it or mixing different metals such as chromium into its compound structure.

In selecting materials for specific applications where performance is required over time, one must take into account physical properties as well as corrosion resistance levels associated with different grades/forms/finishes available under various grades/forms/finishes available under various forms/conditions of treatment.

Heat Treatment and Its Effects

Heat treatment is a crucial phase that modifies the physical and mechanical properties of carbon steel thus improving its performance for specific uses. It usually involves heating the metal to a specific temperature, soaking at that temperature for a particular period then cooling with controlled speed. Annealing, normalizing, quenching and tempering are the four main types of heat treatments.


  • This method entails heating carbon steel to below its melting point and allowing it to cool slowly. The process softens material, increases ductility by relieving internal stresses so that it becomes more workable.


  • It is similar to annealing but with higher temperatures followed by air cooling. This helps in refining grain structure thereby increasing strength as well toughness of the metal.


  • Steel is heated up above the critical range and then cooled rapidly by immersing it in water or oil. Hardness and strength go up through this process, although brittleness may occur occasionally.


  • After quenching has been done; reheating takes place at lower temperature levels before being cooled again . Brittleness reduction happens concurrently with maintenance of increased hardness and strength achieved during quenching process.

Each of these techniques affects microstructure of carbon steels leading to combinations of properties suitable for different engineering needs. It is therefore important to have knowledge about them when selecting materials for use in various applications.

How Is Carbon Steel Different from Other Steels?

How Is Carbon Steel Different from Other Steels?

Carbon Steel vs Stainless Steel


  • Carbon Steel: Carbon steel is mainly made of iron and carbon, with a carbon content between 0.05% and 2.0%. In smaller amounts, there may also be additional elements like silicon, manganese or copper.
  • Stainless Steel: This type of steel has higher chromium levels (minimum 10.5%) than other steels do; it often contains nickel as well as molybdenum or titanium among its alloys too. Chromium is key because it promotes the formation of an oxide layer on the metal surface which makes stainless steel corrosion-resistant.

Corrosion resistance

  • Carbon Steel: Generally speaking, this material does not have great resistance against corrosion when compared to stainless steels. That means if they are put in contact with moisture or aggressive environments without protection like coatings or any anti-corrosive treatment – they will rust and eventually decay over time.
  • Stainless Steel: The chromium content in stainless steel gives it excellent corrosion resistance properties that protect against rusting. Carbon steel could benefit from these protections, too. Hence stainless steels can be used even under harsh conditions such as those found in marine, chemical processing plants or medical equipment.

Mechanical properties

  • Carbon Steel: It is hard and strong due to its high level of hardness; this quality can be achieved by heat treating like quenching followed by tempering processes. However, brittle nature may occur more frequently when compared with stainless steel.
  • Stainless Steel: Provides a good compromise between strength and ductility; although generally softer than carbon steel but some grades are designed for structural applications where high tensile strength is required too.


  • Carbon Steel: Because it is cheap yet still possesses sufficient strength – many buildings use beams made out of carbon steel during construction stages while automotive industry finds countless applications for them ranging from vehicle chassis manufacturing through suspension systems all way down into various tools & machinery production including pipelines among others..
  • Stainless Steel: Commonly used in industries which demand high resistance to corrosion as well as looking good visually; kitchen appliances or medical instruments are prime examples where this metal might be employed due to its anti-rusting features such as cladding materials used for architectural purposes like railings etc.

Understanding carbon steels versus stainless steels involves knowing what they are made up of, how these elements affect their properties and what areas each type excels at.

Carbon Steel vs Low-Alloy Steel

Carbon steel and low-alloy steel have different chemical compositions that give them specific qualities.


  • Carbon Steel: It is made of iron and carbon, usually with a carbon content between 0.2% and 2.1% by weight. There may be traces of other elements, but they hardly affect anything.
  • Low-Alloy Steel: This type contains significant amounts of additional metals such as chromium, nickel, molybdenum, or vanadium – generally no more than 5% by weight; these are used together with steel to create superior materials possessing certain properties required in particular applications like higher strength or better resistance to corrosion/abrasion, etc.


  • Strength & Hardness: Low alloy steels tend to have higher tensile strengths and toughness compared to carbon steels due to the presence of alloying elements. These make them suitable for use under heavy loads where other materials would fail.
  • Corrosion Resistance: In terms of corrosion resistance alone, without taking into account any protective coatings or maintenance measures employed when working with metal products – traditional (non-stainless) carbon steels rust easily while low-alloys offer some improvement but not as much as stainless varieties do; still certain low alloy grades can withstand aggressive environments better than plain-carbon ones.
  • Costs involved: Carbon is cheaper because it has less in its composition and fabrication processes are simpler; on the other hand, these additional components necessary during production increase costs for making aluminized sheets, which should serve a longer timespan before being replaced, thus reducing frequent disassembly needs, thus lowering maintenance expenses over time.


  • Carbon Steel: Widely used in construction due to its affordability combined with the adequate mechanical properties needed for this industry. Examples include reinforcing bars used in concrete structures, automotive body parts like fenders or doors, and various structural members joining different metals together within one item.
  • Low-Alloy Steel: Frequently employed anywhere strong materials are required including aerospace engineering applications where high strength-to-weight ratio matters most; automotive components such as suspension arms subjected to heavy loads from road bumps etc.; pressure vessels used under extreme temperatures, corrosive environments or both simultaneously – military armor plates designed specifically against ballistic threats.

In simple terms, low alloy materials have more chemicals than regular carbon ones, which gives them extra qualities like a harder surface, but they still can be corroded if not taken care of properly this might cost more during the construction phase, but saves money later on through reduced maintenance frequency while still achieving satisfactory performance levels.

High Carbon Steel vs Low Carbon Steel

The main difference between high carbon steel and low carbon steel is their carbon content and the subsequent mechanical and physical properties this imparts.

  • Carbon Content: High-carbon steel usually contains between 0.6% and 1.0% of carbon, while low-carbon steel has a carbon content ranging from 0.04% to 0.3%. These different levels of carbon greatly affect what they can do.
  • Hardness and Strength: Compared to low-carbon steels, high-carbon ones have superior tensile strength and hardness because they have more percentage of carbons in them, thus making it wear resistance as well as durability for applications like cutting tools or blades which need these features most. However, such increased rigidity also means less ductility but more fragility at high-carbon steels.
  • Malleability & Ductility: Low-carbon steels are highly malleable (can be hammered thin) and ductile (can be bent without breaking). They are used in making structural beams because they can easily absorb impacts without breaking or bending too much before returning back to their original shape again, which is why many cars have parts made out of this material, including body panels, etcetera.
  • Weldability: Welding requires preheating as well as special techniques so that it does not crack during the process; thus, welding ability becomes better when there is a lower amount of carbon present within the metal being welded together. Such a case applies to low-carbon steel than high-carbon one, where we know that the latter needs more heating up than the former.
  • Cost: Low-carbon steels generally cost less than high-carbon steels mainly due easier manufacturing processes involved coupled with availability factors too since they contain smaller amounts of carbons which make them more workable.

What Are the Typical Uses of Carbon Steel?

What Are the Typical Uses of Carbon Steel?

Widely Used in the Automotive Industry

Different components are made of carbon steel, which is extensively used in the auto industry due to its versatility and performance.

  • Low Carbon Steel: Malleable and weldable, this type is used on body panels, bolts, nuts, and non-critical structural components.
  • High Carbon Steel: It is applied in making such elements like springs, cutting tools, as well as high-stress parts characterized by high strength and resistance to wear.

Automobile manufacturers achieve an appropriate balance between costs; performance as well as longevity required in vehicle construction which they can get by choosing the right types of carbon steel. High-carbon steel is among the various types of steels employed for numerous automotive uses.

Applications in Construction

The construction industry heavily relies on carbon steel because of its durability, strength, and adaptability. It is used for making important building components.

  • Beams and Columns: High-carbon steel is employed in the manufacturing process of beams and columns which are vital support structures for buildings and bridges.
  • Reinforcement Bars (Rebar): Rebars use low carbon steel since it can resist tensile forces that pull apart or compress concrete under pressure.
  • Pipes and Tubing: Low- and high-carbon steels are used to make pipes and tubing for water and gas supply, among other utilities; however, the former is preferred because it is easier to install and maintain.
  • Architectural Elements: Carbon steel has wide decorative and functional uses in architecture, such as railings, gates, and fences, due to its versatility and aesthetics.

Construction projects acquire improved structural strength plus efficiency by taking advantage of different properties exhibited by low or high-carbon steels.

Other Industrial Uses of Carbon Steel

Due to its versatile properties, carbon steel is widely used in many different industries. Below are a few common examples:

  • Machinery production: Carbon steel is often selected for use in heavy-duty manufacturing due to its strength and durability. It can be found in agricultural machinery, fabricating tools, and various other machine components.
  • Energy sector: Within the energy industry, carbon steel is employed for pipeline construction as well as storage tanks and structural parts of oil rigs or refineries because it can handle high pressure systems with ease.
  • Automotive applications: Carbon steels are used for making cars and engine parts such as gears or exhaust systems that need good wear resistance so that they last long enough under tough conditions.
  • Shipbuilding materials: Steel plays an important role throughout ship building where it may form part or whole sections like decks/hulls thanks largely to its robustness when faced by marine environments which tend being corrosive.
  • Railway components: Carbon steel has an extensive application area, too, with railroad tracks and wheels, among others, made from this material due mainly to its high stress tolerance capabilities under heavy loads commonly experienced here.

Industry can ensure performance safety and economy by using different grades of carbon steel.

Reference Sources


Carbon steel


Frequently Asked Questions (FAQs)

Q: What is the composition of carbon steel?

A: Carbon steel is mainly composed of iron and carbon, with a weight percentage ranging between 0.05% and 2.1%. Other elements can be present in small amounts, but their major constituents are iron and carbon, which are used to make different kinds of steel due to their versatility.

Q: What are some types of carbon steels?

A: The three primary classifications for this material type are low-carbon steel, medium-carbon steel, and high-carbon steel. Classification is done according to %C content, i.e., the amount or proportionality that tells us how much pure elemental C exists within such samples.

Q: What are the main properties of carbon steels?

A: Carbon steels have various main features, including hardness levels, ductility levels (ability), strength levels, and malleability aspects. These traits may vary significantly with carbon content and any heat treatments applied to them during processing into usable forms like bars or sheets, for example.

Q: How is carbon steel compared with alloyed steel?

A: Carbon Steel is an alloy made up mostly of Fe(C) in contrast with Alloyed Steel, which also has additional elements such as Cr, Ni, or V, etc., that can improve specific material properties like hardness, corrosion resistance or durability for instance while still maintaining high-strength characteristics too if needed.

Q: How do I heat treat a piece made out of CS?

A: Heat treatment refers to heating up and then cooling down slowly to produce desired changes within the workpiece made out of Carbon Steel. Heating should be done at specific temperatures before cooling through controlled means, which increases hardness levels, among other things. Typical methods involve annealing, quenching followed by tempering.

Q: What are the uses for high-carbon steel?

A: High-carbon steel is known for being hard and strong, making it ideal for applications where wear resistance is required. This includes items such as cutting tools, blades, springs, and high-strength wires.

Q: Why is carbon steel often used in construction?

A: Carbon steel is commonly used in construction due to its strength, versatility, and cost-effectiveness. It is one of the most popular materials for building bridges, buildings, and pipelines because it can withstand harsh weather conditions better than any other material available on the market.

Q: What organization sets the standards for carbon steel grades?

A: An example of an organization that sets standards for different types of carbon steels based on their grade would be The American Iron and Steel Institute (AISI). They provide guidelines regarding composition and material properties,, among other related metals.

Q: What determines the grade of steel?

A: The chemical composition, including percentages of carbon content along with other alloying elements, will determine what classification level—or grade—a given sample may fall under, but additionally, material properties like tensile strength, hardness levels, etc., play a significant role, too.

Q: How does having a lot of carbon benefit steel?

A: Having more carbons increases hardness and strength while decreasing ductility. Wherever great resilience and long-lastingness are needed, high-carbon steels could prove useful, although they might become brittle compared to their lower counterparts when subjected to certain conditions.

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Greetings, readers! I’m Liang Ting, the author of this blog. Specializing in CNC machining services for twenty years now, I am more than capable of meeting your needs when it comes to machining parts. If you need any help at all, don’t hesitate to get in touch with me. Whatever kind of solutions you’re looking for, I’m confident that we can find them together!

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