Low, medium, and high-carbon steel: everything you need to know

Link to Puhuasheng

What is low-carbon steel?

Low-carbon steel, also known as mild steel, has a comparatively low ratio of carbon to iron compared to other steel types. Typically, its carbon content is within the range of 0.05% and 0.32% by weight. This gives low-carbon steel low strength while making it more malleable and ductile compared to high-carbon steel.

One of the major benefits of low-carbon steel is its cost-effectiveness. As it requires less carbon and other alloying elements, it's normally less expensive than other types of steel. Moreover, low-carbon steels are more readily available and simpler to work with than higher-carbon steels, which makes them a popular choice for a wide range of applications.

What are the uses of low-carbon steel?

Despite its low strength compared to other steel types, low-carbon steel is still strong enough for use in structural applications. Low-carbon steels are also used for machinery parts, as they help to reduce machining costs. Low-carbon steels are easy to shape, which speeds up production times and reduces the cost of machining compared to other materials, such as aluminum. Low-carbon steels are ideal for use in automobile manufacturing, construction, and various types of equipment due to their versatility and ease of fabrication. Furthermore, low-carbon steels are often used in the production of consumer goods and appliances, highlighting their wide range of applications.

Components made of low-carbon steel

Types of low-carbon steel

There are different low-carbon steels with varying amounts of carbon. Below are examples of different types and their applications:

Type Industry Applications Low-carbon structural steel Construction Buildings, bridges Low-carbon sheet and strip steel Sheet metal work Automotive body panels, appliances and other uses that require thin, flat material Low-carbon tubing and piping steel Construction, automotive, heavy equipment, oil and gas Mechanical tubes, pipes for fluid transport, and structural tubing Low-carbon pressure vessel steel Heavy equipment, machinery manufacturing Boilers, pressure vessels and other uses where material must withstand high internal pressures Low-carbon galvanized steel Construction, HVAC, automotive Roofing, automotive body panels, ductwork High-strength low-alloy (HSLA) steel Construction Building frames, bridges, support structures

 

Grades of low-carbon steel

The three primary standards for all carbon steels in the U.S. are:

• ASTM International: Formerly known as American Society for Testing and Materials. An international standards organization that develops and publishes voluntary consensus technical standards.
• AISI: The American Iron and Steel Institute, who play a lead role in the development and application of new steels and steelmaking technology.
• SAE: Formerly the Society of Automotive Engineers, now known as SAE International.

ASTM is the most widely used. For example, one standard is ASTM A307, which covers the specification for carbon steel bolts, studs, and threaded rod with 60,000psi tensile strength.
 
Under this standard fall two grades:

1. Grade A: Intended for general applications that don&#;t require high strength or are exposed to minimal stress.
2. Grade B: Designed for applications where higher strength is needed &#; this grade is also used for flanged joints in piping systems.

Standards provide a consistent framework to ensure that materials meet the necessary performance criteria for their intended applications. Grades, on the other hand, are specific classifications within those standards.
 
Each grade has unique properties and characteristics determined by factors such as chemical composition, heat treatment and mechanical properties. For example, in the table below, you&#;ll notice the same standard &#; SAE J403 &#; with three different grades. This is due to the carbon content in each grade.
 
Some commonly used grades of low-carbon steel include:

 

Standard Grade Application ASTM A36/A36M A36 Structural steel grade used in buildings, bridges, construction equipment ASTM A513/A513M Automotive parts, machinery components ASTM A53/A53M B Structural and pressure applications, such as water and gas transmission ASTM A516/A516M 70 Boilers and pressure vessels SAE J403 Wire products and fasteners SAE J403 Sheet metal work, automotive components, and wire products SAE J403 Cold heading, automotive components, and sheet metal work ASTM A/AM 33 Sheet metal work, automotive components and construction materials

 

Properties of low-carbon steel

Each grade has slightly different properties, although the melting point of low-carbon steel is about the same. That said, we can still give a range of values to give you an idea of this material&#;s overall properties.

Property Value Density 0.103 &#; 0.292 lb/in³  Tensile Strength, Yield - psi  Fracture Toughness 30.0 &#; 105 ksi-in½  Shear Modulus &#; ksi Melting Point °F Thermal Conductivity 176 &#; 645 BTU-in/hr-ft²-°F 

 

What is medium-carbon steel?

Medium-carbon steel has a carbon content typically ranging between 0.3% and 0.6%. This category of steel offers a balance between the ductility and formability of low-carbon steel and the strength and hardness of high-carbon steel.

Medium-carbon steels are stronger and harder than low-carbon steels. This is due to their increased carbon content, but it also means they&#;re less ductile and more difficult to form and weld. They often require heat treatment, such as quenching and tempering, to achieve desired mechanical properties. This is possible with its manganese content, which ranges between 0.30% to 0.60%.

What are the uses of medium carbon steel?

Medium-carbon steels are commonly used in applications where higher strength and toughness are needed, as shown in the table below. It&#;s also used to make small components, such as concealed hinges.

Types of medium-carbon steel

Common types of medium-carbon steel and their applications include:

Type Industry Application Medium-carbon structural steel Construction, Manufacturing Buildings, bridges, heavy-duty equipment Medium-carbon sheet and strip steel Sheet metal work Machinery parts, Automotive parts Medium-carbon tubing and piping steel Construction, automotive, heavy equipment Mechanical tubes, pipes for fluid Medium-carbon pressure vessel steel Oil and gas, food and beverage, pharmaceutical Pressure vessels Medium-carbon alloy steel Automotive, Heavy machinery Gears, shafts, axles, connecting rods Medium-carbon quenched and tempered steel Automotive, Construction, Heavy machinery Gears, axles, transmissions, crane booms, excavation arms

 

Grades of medium-carbon steel

Products made from medium-carbon steel adhere to specific standards. Within those standards are grades. Commonly used grades of medium-carbon steel &#; and the standard they fall under &#; include:
 

Standard Grade Application SAE J403 Gears, shafts, machine parts SAE J404 Gears, axles, aircraft landing gears, and drilling equipment ASTM A29 Axles, bolts, studs, and other machinery parts ASTM A576 Bolts, studs, couplings, bushings, shafts and gears ASTM A29 Gears, axles, and shafts ASTM A434 Class BD (AISI/SAE ) Bolts and other fasteners, connecting rods, gears and shafts ASTM A829 Gears, axles, and drilling equipment

 

Properties of medium-carbon steel

Each grade has its own properties that distinguishes it from other medium-carbon steel grades. The table below gives you a range of values for medium-carbon-steel properties.

Property Value Density 0.280 &#; 0.285 lb/in³  Tensile Strength, Yield &#; psi  Fracture Toughness 73.7 &#; 130 ksi-in½  Shear Modulus &#; ksi Melting Point &#; °F Thermal Conductivity 152 &#; 361 BTU-in/hr-ft²-°F

 

What is high-carbon steel?

High-carbon steel contains a carbon content ranging between 0.60% &#; 1.5%. It&#;s the most corrosion resistant of the steels due to its high amount of carbon. This increased carbon significantly enhances the steel's hardness, tensile strength, and wear resistance. In turn, that makes it suitable for applications that demand high strength and wear resistance.

However, the higher carbon content also makes these steels more brittle and less ductile, which makes it more susceptible to cracking under certain conditions. High-carbon steel is also more challenging to weld than lower-carbon-content steels, due to the risk of cracking and brittleness in the heat-affected zone.

What are the uses of high-carbon steel?

High-carbon-steel uses include anything needing wear resistance and durability, as shown in the table below. High-carbon steel is often used to manufacture springs. A note about plain high-carbon steel, which is often used to mean high-carbon steel. They are different. Plain high-carbon steel consists mostly of carbon and iron, without any significant amounts of alloying elements.

Types of high-carbon steel

High carbon steel, known for its high strength and hardness, typically contains carbon content between 0.6% and 1.0%. This steel type is characterized by its excellent wear resistance and ability to hold a sharp edge, making it ideal for cutting tools, springs, and high-strength wires. While it is less ductile and more brittle than low carbon steel, the increased carbon content provides enhanced durability and toughness, making high carbon steel suitable for demanding applications. High-carbon steel types, and their applications, include:

Type Industry Application Plain high-carbon steel Manufacturing, automotive, construction Springs, knives, cutting tools, brake components High-carbon tool steel Manufacturing, metalworking, woodworking Cutting tools, punches, dies, injection molding tools, extrusion dies, router bits High-carbon bearing steel Industrial machinery, automotive, aerospace Ball and roller bearings for engines; also, transmissions, wheels, heavy machinery, gearboxes, pumps High-carbon spring steel Electronics, automotive, manufacturing Leaf springs, coil springs, machinery, springs for electronic devices

 

Grades of high-carbon steel

Grades of all carbon steels are subsets of specific standards. Some of the most commonly used grades of high-carbon steel include the following:

Standard Grade Application ASTM A29/A29M AISI/SAE Springs, gears, axles, heavy-duty machinery components ASTM A29/A29M AISI/SAE Springs, cutting tools, industrial knives and blades ASTM A29/A29M AISI/SAE Springs, automotive suspension components, agricultural machinery parts ASTM A29/A29M AISI/SAE Heavy-duty springs, automotive components, heavy machinery parts ASTM A295 AISI/SAE Bearing steel used in the manufacture of ball and roller bearings ASTM A600 AISI/SAE M2 High-speed tool steel used for cutting tools, drills, and taps ASTM A686 AISI/SAE W2 Water-hardening tool steel used for cutting tools, dies, punches, and woodworking tools

 

Properties of high-carbon steel

Because standards and grades vary between each other, there is no one value for the properties of high-carbon steel. Below is a broad range of what you can expect.

Property Value Density 0. &#; 0.298 lb/in³  Tensile Strength, Yield &#; psi Fracture Toughness 12.0 &#; 150 ksi-in½  Shear Modulus &#; ksi  Melting Point 2,800-2,900°F Thermal Conductivity &#; 361 BTU-in/hr-ft²-°F

 

The differences between low, medium and high-carbon steel

The essential difference is in the steels&#; carbon content, which gives each different characteristics.

  Low-carbon steel Medium-carbon steel High-carbon steel Carbon Content 0.05% to 0.32% 0.30% to 0.60% 0.60% to 1.5% Characteristics Ductile
Malleable
Tough
Easily joined and welded
Poor corrosion resistance Stronger
Harder
Less ductile
Less malleability
Good corrosion resistance Very strong
Very hard
Poor ductility
Poor malleability
Better corrosion resistance

 

Download free CADs and try before you buy

Free CADs are available for most solutions, which you can download. You can also request free samples to make sure you&#;ve chosen the right product for what you need. 

If you&#;re not quite sure which solution will work best for your application, our experts are always happy to advise you.

Whatever your requirements, you can depend on fast dispatch. Request your free samples or download free CADs now.

Questions?

us at or speak to one of our experts for further information on the ideal solution for your application 800-847-.

Steel in which the main interstitial alloying constituent is carbon

Carbon steel is a steel with carbon content from about 0.05 up to 2.1 percent by weight. The definition of carbon steel from the American Iron and Steel Institute (AISI) states:

• no minimum content is specified or required for chromium, cobalt, molybdenum, nickel, niobium, titanium, tungsten, vanadium, zirconium, or any other element to be added to obtain a desired alloying effect;
• the specified minimum for copper does not exceed 0.40%;
• or the specified maximum for any of the following elements does not exceed the percentages noted: manganese 1.65%; silicon 0.60%; copper 0.60%.

  [

  1

  ]

The term carbon steel may also be used in reference to steel which is not stainless steel; in this use carbon steel may include alloy steels. High carbon steel has many different uses such as milling machines, cutting tools (such as chisels) and high strength wires. These applications require a much finer microstructure, which improves the toughness.

As the carbon content percentage rises, steel has the ability to become harder and stronger through heat treating; however, it becomes less ductile. Regardless of the heat treatment, a higher carbon content reduces weldability. In carbon steels, the higher carbon content lowers the melting point.[2]

Properties

[

edit

]

Carbon steel is often divided into two main categories: low-carbon steel and high-carbon steel. It may also contain other elements, such as manganese, phosphorus, sulfur, and silicon, which can affect its properties. Carbon steel can be easily machined and welded, making it versatile for various applications. It can also be heat treated to improve its strength, hardness, and durability.

Carbon steel is susceptible to rust and corrosion, especially in environments with high moisture levels and/or salt. It can be shielded from corrosion by coating it with paint, varnish, or other protective material. Alternatively, it can be made from a stainless steel alloy that contains chromium, which provides excellent corrosion resistance. Carbon steel can be alloyed with other elements to improve its properties, such as by adding chromium and/or nickel to improve its resistance to corrosion and oxidation or adding molybdenum to improve its strength and toughness at high temperatures.

It is an environmentally friendly material, as it is easily recyclable and can be reused in various applications. It is energy-efficient to produce, as it requires less energy than other metals such as aluminium and copper.[3]

Type

[

edit

]

Mild or low-carbon steel

[

edit

]

Mild steel (iron containing a small percentage of carbon, strong and tough but not readily tempered), also known as plain-carbon steel and low-carbon steel, is now the most common form of steel because its price is relatively low while it provides material properties that are acceptable for many applications. Mild steel contains approximately 0.05&#;0.30% carbon[1] making it malleable and ductile. Mild steel has a relatively low tensile strength, but it is cheap and easy to form. Surface hardness can be increased with carburization.[4]

The density of mild steel is approximately 7.85 g/cm3 (7,850 kg/m3; 0.284 lb/cu&#;in)[5] and the Young's modulus is 200 GPa (29×10^6 psi).[6]

Low-carbon steels[7] display yield-point runout where the material has two yield points. The first yield point (or upper yield point) is higher than the second and the yield drops dramatically after the upper yield point. If a low-carbon steel is only stressed to some point between the upper and lower yield point then the surface develops Lüder bands.[8] Low-carbon steels contain less carbon than other steels and are easier to cold-form, making them easier to handle.[4] Typical applications of low carbon steel are car parts, pipes, construction, and food cans.[9]

High-tensile steel

[

edit

]

High-tensile steels are low-carbon, or steels at the lower end of the medium-carbon range,[citation needed] which have additional alloying ingredients in order to increase their strength, wear properties or specifically tensile strength. These alloying ingredients include chromium, molybdenum, silicon, manganese, nickel, and vanadium. Impurities such as phosphorus and sulfur have their maximum allowable content restricted.

Higher-carbon steels

[

For more Low-Carbon Steel T Postsinformation, please contact us. We will provide professional answers.

edit

]

Carbon steels which can successfully undergo heat-treatment have a carbon content in the range of 0.30&#;1.70% by weight. Trace impurities of various other elements can significantly affect the quality of the resulting steel. Trace amounts of sulfur in particular make the steel red-short, that is, brittle and crumbly at high working temperatures. Low-alloy carbon steel, such as A36 grade, contains about 0.05% sulfur and melt around 1,426&#;1,538 °C (2,600&#;2,800 °F).[10] Manganese is often added to improve the hardenability of low-carbon steels. These additions turn the material into a low-alloy steel by some definitions, but AISI's definition of carbon steel allows up to 1.65% manganese by weight. There are two types of higher carbon steels which are high carbon steel and the ultra high carbon steel. The reason for the limited use of high carbon steel is that it has extremely poor ductility and weldability and has a higher cost of production. The applications best suited for the high carbon steels is its use in the spring industry, farm industry, and in the production of wide range of high-strength wires.[11][12]

AISI classification

[

edit

]

The following classification method is based on the American AISI/SAE standard. Other international standards including DIN (Germany), GB (China), BS/EN (UK), AFNOR (France), UNI (Italy), SS (Sweden) , UNE (Spain), JIS (Japan), ASTM standards, and others.

Carbon steel is broken down into four classes based on carbon content:[1]

Low-carbon steel

[

edit

]

Low-carbon steel has 0.05 to 0.15% carbon (plain carbon steel) content.[1]

Medium-carbon steel

[

edit

]

Medium-carbon steel has approximately 0.3&#;0.5% carbon content.[1] It balances ductility and strength and has good wear resistance. It is used for large parts, forging and automotive components.[13][14]

High-carbon steel

[

edit

]

High-carbon steel has approximately 0.6 to 1.0% carbon content.[1] It is very strong, used for springs, edged tools, and high-strength wires.[15]

Ultra-high-carbon steel

[

edit

]

Ultra-high-carbon steel has approximately 1.25&#;2.0% carbon content.[1] Steels that can be tempered to great hardness. Used for special purposes such as (non-industrial-purpose) knives, axles, and punches. Most steels with more than 2.5% carbon content are made using powder metallurgy.

Heat treatment

[

edit

]

Iron-carbon phase diagram, showing the temperature and carbon ranges for certain types of heat treatments

The purpose of heat treating carbon steel is to change the mechanical properties of steel, usually ductility, hardness, yield strength, or impact resistance. Note that the electrical and thermal conductivity are only slightly altered. As with most strengthening techniques for steel, Young's modulus (elasticity) is unaffected. All treatments of steel trade ductility for increased strength and vice versa. Iron has a higher solubility for carbon in the austenite phase; therefore all heat treatments, except spheroidizing and process annealing, start by heating the steel to a temperature at which the austenitic phase can exist. The steel is then quenched (heat drawn out) at a moderate to low rate allowing carbon to diffuse out of the austenite forming iron-carbide (cementite) and leaving ferrite, or at a high rate, trapping the carbon within the iron thus forming martensite. The rate at which the steel is cooled through the eutectoid temperature (about 727 °C or 1,341 °F) affects the rate at which carbon diffuses out of austenite and forms cementite. Generally speaking, cooling swiftly will leave iron carbide finely dispersed and produce a fine grained pearlite and cooling slowly will give a coarser pearlite. Cooling a hypoeutectoid steel (less than 0.77 wt% C) results in a lamellar-pearlitic structure of iron carbide layers with α-ferrite (nearly pure iron) between. If it is hypereutectoid steel (more than 0.77 wt% C) then the structure is full pearlite with small grains (larger than the pearlite lamella) of cementite formed on the grain boundaries. A eutectoid steel (0.77% carbon) will have a pearlite structure throughout the grains with no cementite at the boundaries. The relative amounts of constituents are found using the lever rule. The following is a list of the types of heat treatments possible:

Spheroidizing

Spheroidite forms when carbon steel is heated to approximately 700 °C (1,300 °F) for over 30 hours. Spheroidite can form at lower temperatures but the time needed drastically increases, as this is a diffusion-controlled process. The result is a structure of rods or spheres of cementite within primary structure (ferrite or pearlite, depending on which side of the eutectoid you are on). The purpose is to soften higher carbon steels and allow more formability. This is the softest and most ductile form of steel.

[

16

]

Full annealing

Carbon steel is heated to approximately 400 °C (750 °F) for 1 hour; this ensures all the ferrite transforms into austenite (although cementite might still exist if the carbon content is greater than the eutectoid). The steel must then be cooled slowly, in the realm of 20 °C (36 °F) per hour. Usually it is just furnace cooled, where the furnace is turned off with the steel still inside. This results in a coarse pearlitic structure, which means the "bands" of pearlite are thick.

[

17

]

Fully annealed steel is soft and ductile, with no internal stresses, which is often necessary for cost-effective forming. Only spheroidized steel is softer and more ductile.

[

18

]

Process annealing

A process used to relieve stress in a cold-worked carbon steel with less than 0.3% C. The steel is usually heated to 550 to 650 °C (1,000 to 1,200 °F) for 1 hour, but sometimes temperatures as high as 700 °C (1,300 °F). The image above shows the process annealing area.

Isothermal annealing

It is a process in which hypoeutectoid steel is heated above the upper critical temperature. This temperature is maintained for a time and then reduced to below the lower critical temperature and is again maintained. It is then cooled to room temperature. This method eliminates any temperature gradient.

Normalizing

Carbon steel is heated to approximately 550 °C (1,000 °F) for 1 hour; this ensures the steel completely transforms to austenite. The steel is then air-cooled, which is a cooling rate of approximately 38 °C (100 °F) per minute. This results in a fine pearlitic structure, and a more-uniform structure. Normalized steel has a higher strength than annealed steel; it has a relatively high strength and hardness.

[

19

]

Quenching

Carbon steel with at least 0.4 wt% C is heated to normalizing temperatures and then rapidly cooled (quenched) in water, brine, or oil to the critical temperature. The critical temperature is dependent on the carbon content, but as a general rule is lower as the carbon content increases. This results in a martensitic structure; a form of steel that possesses a super-saturated carbon content in a deformed body-centered cubic (BCC) crystalline structure, properly termed body-centered tetragonal (BCT), with much internal stress. Thus quenched steel is extremely hard but brittle, usually too brittle for practical purposes. These internal stresses may cause stress cracks on the surface. Quenched steel is approximately three times harder (four with more carbon) than normalized steel.

[

20

]

Martempering (marquenching)

Martempering is not actually a tempering procedure, hence the term marquenching. It is a form of isothermal heat treatment applied after an initial quench, typically in a molten salt bath, at a temperature just above the "martensite start temperature". At this temperature, residual stresses within the material are relieved and some bainite may be formed from the retained austenite which did not have time to transform into anything else. In industry, this is a process used to control the ductility and hardness of a material. With longer marquenching, the ductility increases with a minimal loss in strength; the steel is held in this solution until the inner and outer temperatures of the part equalize. Then the steel is cooled at a moderate speed to keep the temperature gradient minimal. Not only does this process reduce internal stresses and stress cracks, but it also increases impact resistance.

[

21

]

Tempering

This is the most common heat treatment encountered because the final properties can be precisely determined by the temperature and time of the tempering. Tempering involves reheating quenched steel to a temperature below the eutectoid temperature and then cooling. The elevated temperature allows very small amounts spheroidite to form, which restores ductility but reduces hardness. Actual temperatures and times are carefully chosen for each composition.

[

22

]

Austempering

The austempering process is the same as martempering, except the quench is interrupted and the steel is held in the molten salt bath at temperatures between 205 and 540 °C (400 and 1,000 °F), and then cooled at a moderate rate. The resulting steel, called bainite, produces an acicular microstructure in the steel that has great strength (but less than martensite), greater ductility, higher impact resistance, and less distortion than martensite steel. The disadvantage of austempering is it can be used only on a few sheets of steel, and it requires a special salt bath.

[

23

]

Case hardening

[

edit

]

Case hardening processes harden only the exterior of the steel part, creating a hard, wear-resistant skin (the "case") but preserving a tough and ductile interior. Carbon steels are not very hardenable meaning they can not be hardened throughout thick sections. Alloy steels have a better hardenability, so they can be through-hardened and do not require case hardening. This property of carbon steel can be beneficial, because it gives the surface good wear characteristics but leaves the core flexible and shock-absorbing.

Forging temperature of steel

[

edit

]

[24]

See also

[

edit

]

References

[

edit

]

Bibliography

[

edit

]

• DeGarmo, E. Paul; Black, J T.; Kohser, Ronald A. (), Materials and Processes in Manufacturing (9th ed.), Wiley, ISBN 0-471--4.

• Oberg, E.; et al. (), Machinery's Handbook (25th ed.), Industrial Press Inc, ISBN 0---3.

• Smith, William F.; Hashemi, Javad (), Foundations of Materials Science and Engineering (4th ed.), McGraw-Hill, ISBN 0-07--6.

Want more information on Y Post with Teeth? Feel free to contact us.