Carbon steel is commonly used in various industries, including automotive, construction, and energy. It comes in different types like low carbon steel grades, medium carbon steel grades, and high carbon steel grades. The difference in carbon content in each grade greatly impacts their properties, whether it’s weldability, formability, or wear resistance. If you want to know more about various carbon steel grades and their potential applications, keep reading!
Low Carbon Steel Grades: Definition, Properties, and Characteristics
Low carbon steel grades also known as mild carbon steel has a very low ratio of carbon to iron ratio. It ranges anywhere from 0.05% to 0.32% by weight, which makes these steel grades low in strength and highly malleable compared to other steel types. What truly sets it apart is its low cost, which is due to the use of fewer carbon and other alloying elements. Let’s look at some of its unique properties:
Property | Value |
Tensile Strength | 20300 – 347000 psi |
Fracture Toughness | 30.0 – 105 ksi-in½ |
Melting Point | 2600°F |
Density | 0.103 – 0.292 lb/in³ |
Thermal Conductivity | 176 – 645 BTU-in/hr-ft²-°F |
Grades of Low Carbon Steel and Their Applications
Here’s an overview of the different types of low carbon steel grades, along with their unique properties and applications:
AISI 1018
AISI 1018 is a common low carbon steel grade with excellent weldability, producing a uniform case. It has 0.14 – 0.20% carbon, which makes it highly machinable and is often used in the automotive and construction industries. It undergoes various heat treatments, such as:
- Normalizing: In this process, AISI 1018 is heated to 890°C – 940°C and then cooled in air for further processing.
- Tempering: To reduce the brittleness of steel, AISI 1018 is tempered at 150°C–200°C.
- Annealing: Annealing is helpful in increasing the ductility of steel and reducing its hardness. This low carbon steel grade is annealed at 870°C – 910°C and allowed to cool in the furnace.
AISI 1020
AISI 1020 is actually a low tensile carbon steel with a Brinell hardness ranging from 119 to 235. It has a carbon content of 0.20% and is resistant to induction hardening or flame hardening. It’s typically used in the manufacturing of gears, axles, and other machine components. Other than annealing, it undergoes other heat treatments like:
- Carburizing: AISI 1020 is heated at 880°C – 920°C in a specified carburizing environment, followed by holding it for a sufficient amount of time to achieve the desired carbon content and case depth.
- Core Refining: Core refining is the process by which impure molten iron is converted into steel by reducing its carbon content and removing other impurities. To core refine AISI 1020, it’s cooled and heated at 870°C to 900 °C. Then it’s held for a specific period of time until the temperature is constant for all the sections and is quenched in oil or water.
A36
It’s the most commonly used mild and hot-rolled steel with top-notch welding properties. You can easily weld, punch, grind, and tap it without any hassle. It has high carbon content compared to AISI 1018 and 1020 low carbon steel grades, standing at around 0.25 – 0.290 %. Typical applications of A36 carbon steel include:
- Normalizing: Normalizing of A36 happens at 899°C – 954°C.
- Hardening: Hardening is carried out at 788°C – 816°C to make it stronger and resistant to wear.
- Stress Relieving: In this process, the A36 is heated below its transformation range, at 677°C – 927°C, and then cooled to relieve internal residual stresses.
Common Low Carbon Steel Standards
Now that you’ve learnt the details of different low carbon steel grades, let’s discuss the standards for assigning these grades:
- ASTM International: ASTM International was formerly known as the American Society for Testing and Materials. It’s a standards organization that develops and publishes voluntary standards for materials like steel, plastics, metals, and paints.
- AISI: The AISI, or the American Iron and Steel Institute, serves as the voice of the American Steel industry in the public arena. It’s helpful in the development of new steel and steelmaking technology, guiding industry players.
- SAE: The Society of Automotive Engineers (SAE) was founded by Henry Ford, along with other engineers and scientists, in 1905. It’s an organization that creates and promotes quality standards and technical specifications for vehicles, steel parts, and systems, addressing safety concerns.
- EN: EN Steel, or European Norm Steel, has a huge category of steel grades defined by European standards. Know that the higher the EN number, the better the properties of the steel.
- JIS: Japanese Industrial Standards (JIS) for steel is a detailed classification system that outlines the chemical composition, mechanical properties, and applications for various types of steels.
Medium Carbon Steel Grades: Definition, Properties, and Characteristics
Medium carbon steel grades, also referred to as M2, have a higher carbon content than low carbon steel grades, typically between 0.30% to 0.60%. It also has manganese in its composition, which helps remove impurities and improves the toughness of steel.
These steel grades are harder than low carbon steel grades, which also makes them difficult to weld and form. Overall, it performs well under heat and can easily withstand tough environments and wear. Here’s a glimpse into its unique properties:
Property | Value |
Yield Strength | 420 Mpa |
Magnetism | Magnetic in nature |
Density | 7.75 to 7.89 g/cm3 |
Hardness | 200 Mpa |
Grades of Medium Carbon Steel and Their Applications
Just like low carbon steel grades, medium carbon steel also comes in different versions. Let’s discuss each to understand its properties and applications:
4140 Steel
One of the medium carbon steel grades includes AISI 4140, which is actually a chromium-, molybdenum-, and manganese-containing alloy steel. The carbon content in this steel grade ranges from 0.380 to 0.430. It’s known for its incredible fatigue strength and abrasion resistance. Common applications include hydraulic cylinders, shafts, and other heavy machinery parts. Just like low carbon steel grades, 4140 steel is also heat-treated via:
- Forging: Forging is actually the compression of steel using localized forces, usually by heating it to high temperatures and then hammering or pressing it between dies. AISI 4140 is forged at 926 to 1205°C to improve its overall grain structure.
- Hot Working: In this, the steel is shaped by plastic deformation at a temperature above its recrystallization temperature. To hot work 4140 medium carbon steel grade, you need to heat it at 816 to 1038°C.
1045 Steel
The 1045 medium carbon steel grade is typically supplied in a black, hot-rolled, or normalized condition. It has a 0.45% carbon content and is particularly known for its weldability, machinability, and high strength. This steel grade is a good choice if you want to make sprockets, gears, axles, and shafts. Here are the different heat treatments for it:
- Normalizing: 870 °C – 920 °C
- Stress Relieving: 550 °C – 660 °C
- Hardening: 820 °C – 850 °C
- Annealing: 800 °C – 850°C
1060 Steel
Another one of the medium carbon steel grades includes 1060 with a carbon content of 0.55-0.660, slightly higher than 1045 and the low carbon steel grades. It has high hardness, wear resistance, and is ferromagnetic in nature. In addition, it’s relatively brittle but can be used to make hard blades and knives for machinery and other tools. Let’s look at the various heat treatments the 1060 steel grade undergoes:
- Annealing: 700-800 °C
- Quenching: 800-900 °C
- Tempering: 150-600 °C
High Carbon Steel Grades: Definition, Properties, and Characteristics
High carbon steel grades, as evident by the name, are steels with high carbon content, typically over 0.6%. However, if it’s higher than 1%, it belongs to the ultra-high carbon steel group. This steel is exceptionally strong, hard, and wear-resistant; however, it is also more brittle and less ductile. Here’s a glimpse into the properties of AISI 52100, a popular high carbon steel grade:
Property | Value |
Density | 7.81 g/cm² |
Yield Strength | 2033 MPa |
Hardness | 64 |
Magnetism | 770ºC |
Melting Point | 1424–1460ºC |
Thermal Conductivity | 46.6 W/m.K |
Machinability Rating | 50% |
Grades of High Carbon Steel and Their Applications
The following are the popular grades of high carbon steel, along with their unique properties, so you can understand why they are different from low carbon steel grades:
AISI/SAE 52100
AISI/SAE 52100 is a high-carbon, chromium-containing, low-alloy steel that exhibits high rolling fatigue strength and hardness. It’s used in the manufacturing of ball and roller bearings and heat-treated via:
- Normalizing: 872°C
- Quenching: 816°C
- Forging: 927 to 1205°C
- Hot Working: 205 to 538°C
AISI/SAE 1080
Another one of the high carbon steel grades is AISI/SAE 1080, which is a plain carbon steel containing 0.80% carbon. Its hardness and strength make it suitable for a variety of applications, including heavy-duty springs, automotive components, and heavy machinery parts. Here’s an overview of the various heat treatments for this steel grade:
- Normalizing: 830 °C
- Annealing: 790–845 °C
Conclusion
It’s important to understand the difference between low carbon steel grades, medium carbon steel grades, and high carbon steel so you can pick the right one for your applications. Wondering where you can get top-notch steel products? Look no further than Zhaojian Steel! We have a wide range of certified steel grades that can offer you great value for your money.
