Low, Medium, and High-Carbon Steel: Everything You Need to Know

by AMC

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Posted on April 18, 2024 at 03:57 PM

Welcome to our comprehensive guide on low, medium, and high-carbon steel. Each type is distinguished by its carbon content, which significantly influences its properties. Low-carbon steel, with its lower carbon content, offers excellent weldability and ductility, making it suitable for applications requiring formability and versatility. Medium-carbon steel strikes a balance between strength and flexibility, finding use in automotive parts and machinery components. On the other hand, high-carbon steel, with its increased carbon content, delivers exceptional hardness and wear resistance, making it ideal for cutting tools and springs. In this guide, explore into the unique characteristics of each type, their applications across industries, and key considerations for choosing the right steel for your specific needs.

What is low-carbon steel?

Low-carbon steel, often referred to as mild steel, has a relatively low proportion of carbon compared to other steel varieties. Typically, its carbon content ranges between 0.05% and 0.32% by weight. This characteristic gives low-carbon steel moderate strength while enhancing its malleability and ductility in comparison to high-carbon steel.

One of the key advantages of mild steel is its cost-effectiveness. Its lower requirement for carbon and additional alloying elements contributes to its affordability compared to other steel grades. Additionally, it is more readily accessible and easier to manipulate than higher-carbon steels, making it a favored option across various applications.

What are the uses of low-carbon steel?

Low-carbon steel finds utility in structural applications despite its lower strength relative to other steel types. It is also employed in machinery components, aiding in cost reduction during machining processes. Its ease of shaping facilitates faster production cycles and reduced machining expenses compared to alternative materials like aluminum.

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

Low-Carbon Steel Grades

The grades of low-carbon steel are defined by standards set by organizations like ASTM International, AISI, and SAE:

1. ASTM International: Known for developing and publishing technical standards globally.
2. AISI: Plays a significant role in advancing steel technology and standards.
3. SAE: Focuses on automotive engineering and related standards.

Among these, ASTM standards are widely used. For instance, ASTM A307 covers specifications for carbon steel bolts, studs, and threaded rods with a 60,000 psi tensile strength.

Under ASTM A307, there are two grades:

• Grade A: Suited for general applications with low-stress requirements.
• Grade B: Designed for applications needing higher strength, including flanged joints in piping systems.

Standards ensure materials meet specific performance criteria. Grades within these standards, such as those in SAE J403, vary based on factors like chemical composition, heat treatment, and mechanical properties. These distinctions result in different grades within the same standard, as seen in the table below, where carbon content dictates grade differences.

Here are some commonly used grades of low-carbon steel:

Standard	Grade	Application
ASTM A36/A36M	A36	Structural steel grade used in buildings, bridges, construction equipment
ASTM A513/A513M	1010	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	1006	Wire products and fasteners
SAE J403	1008	Sheet metal work, automotive components, and wire products
SAE J403	1010	Cold heading, automotive components, and sheet metal work
ASTM A1011/A1011M	33	Sheet metal work, automotive components and construction materials

Properties of low-carbon steel

Property	Value
Density	0.103 – 0.292 lb/in³
Tensile Strength, Yield	20300 - 347000 psi
Fracture Toughness	30.0 – 105 ksi-in½
Shear Modulus	10200 – 11600 ksi
Melting Point	2600°F
Thermal Conductivity	176 – 645 BTU-in/hr-ft²-°F

Medium Carbon Steel

What is medium-carbon steel?

Medium-carbon steel falls within the carbon content range of 0.3% to 0.6%. It strikes a balance between the ductility of low-carbon steel and the strength of high-carbon steel.

The increased carbon content in medium-carbon steel contributes to its greater strength and hardness compared to low-carbon steel. However, this also reduces its ductility and makes it less malleable, requiring more effort in forming and welding processes. Heat treatment, such as quenching and tempering, is often necessary to achieve desired mechanical properties.

Additionally, medium-carbon steel typically contains manganese, which further enhances its strength and hardenability. The manganese content in this steel ranges from 0.30% to 0.60%, contributing to its overall performance characteristics.

What are the uses of medium carbon steel?

Medium-carbon steel finds a range of applications where a balance between strength and ductility is crucial. Here are some common uses:

Types of medium-carbon steel

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

Standard	Grade	Application
SAE J403	1045	Gears, shafts, machine parts
SAE J404	4140	Gears, axles, aircraft landing gears, and drilling equipment
ASTM A29	1045	Axles, bolts, studs, and other machinery parts
ASTM A576	1045	Bolts, studs, couplings, bushings, shafts and gears
ASTM A29	4140	Gears, axles, and shafts
ASTM A434	Class BD (AISI/SAE 4140)	Bolts and other fasteners, connecting rods, gears and shafts
ASTM A829	4140	Gears, axles, and drilling equipment

Properties of medium-carbon steel

Property	Value
Density	0.280 – 0.285 lb/in³
Tensile Strength, Yield	35500 – 252000 psi
Fracture Toughness	73.7 – 130 ksi-in½
Shear Modulus	10400 – 11900 ksi
Melting Point	2597– 2800°F
Thermal Conductivity	152 – 361 BTU-in/hr-ft²-°F

Medium Carbon SteelHigh Carbon Steel

What is high-carbon steel?

High-carbon steel contains a carbon content ranging from 0.60% to 1.5%. This high carbon content contributes to its exceptional hardness, tensile strength, and wear resistance, making it ideal for applications requiring high strength and resistance to wear and abrasion.

High-carbon steel is renowned for its corrosion resistance due to the elevated carbon levels. However, its increased brittleness and reduced ductility make it more prone to cracking under certain conditions. Welding high-carbon steel poses challenges due to the risk of brittleness and cracking in the heat-affected zone, requiring specialized techniques to mitigate these issues.

What are the uses of high-carbon steel?

High-carbon steel finds extensive use in applications that demand exceptional wear resistance and durability. One of its primary applications is in the manufacturing of springs, where its ability to withstand high stress and maintain elasticity is crucial, especially in automotive suspension systems and industrial machinery. Additionally, high-carbon steel is preferred for cutting tools such as knives, blades, and saws due to its inherent hardness and edge retention properties, ensuring precise and efficient cutting performance over prolonged usage. Bearings, vital components in machinery and automotive systems, benefit from high-carbon steel's strength and resistance to wear, ensuring reliable and long-lasting performance under heavy loads and friction. The robustness of high-carbon steel also makes it suitable for use in railway tracks, wire ropes for lifting equipment, and various automotive parts subjected to high stress. Its application extends to chisels, drills, and other cutting implements, where hardness, sharpness, and durability are paramount for accurate cutting tasks. In industrial machinery, components like gears, shafts, and bearings are often made from high-carbon steel to withstand rigorous usage, resist wear, and maintain operational efficiency. It's important to note that plain high-carbon steel, lacking significant alloying elements, serves specific applications where high hardness and strength without specific alloy enhancements are required.

Types of high-carbon steel

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

Standard	Grade	Application
ASTM A29/A29M	AISI/SAE 1060	Springs, gears, axles, heavy-duty machinery components
ASTM A29/A29M	AISI/SAE 1065	Springs, cutting tools, industrial knives and blades
ASTM A29/A29M	AISI/SAE 1070	Springs, automotive suspension components, agricultural machinery parts
ASTM A29/A29M	AISI/SAE 1080	Heavy-duty springs, automotive components, heavy machinery parts
ASTM A295	AISI/SAE 52100	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

Property	Value
Density	0.0163 – 0.298 lb/in³
Tensile Strength, Yield	39900 – 484000 psi
Fracture Toughness	12.0 – 150 ksi-in½
Shear Modulus	11300 – 12000 ksi
Melting Point	2,800-2,900°F
Thermal Conductivity	1132 – 361 BTU-in/hr-ft²-°F

The differences between low, medium and high-carbon steel

	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

Conclusion

Low, medium, and high-carbon steels exhibit distinct differences in their carbon content and mechanical properties. Low-carbon steel is known for its high ductility and ease of fabrication, making it suitable for a wide range of applications where strength requirements are moderate. Medium-carbon steel strikes a balance between strength and ductility, requiring heat treatment for optimal performance and finding use in applications needing higher strength and toughness. High-carbon steel, while the hardest and strongest of the three, is also more brittle and challenging to work with but is preferred for applications demanding exceptional wear resistance and durability. Understanding these differences allows for informed material selection based on specific performance criteria and application requirements.

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