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A Comprehensive Guide to Medium-Carbon Steel
Medium-carbon steel is a type of steel alloy with a carbon content typically ranging between 0.30% and 0.60%. It holds a special place in the metallurgy industry due to its balanced composition, which combines strength, ductility, and machinability. As a result, it is a highly versatile material well-suited for various applications. This article will explore its importance across different industries, characteristics, and applications.
Definition
Medium-carbon steel possesses a carbon content ranging from 0.3% to 0.6%, striking a balance between low-carbon steel’s ductility and high-carbon steel’s strength.
The higher carbon content of medium-carbon steel gives it greater strength and hardness than low-carbon steel. However, this reduces its ductility and makes it less malleable, which means it requires more effort in forming and welding processes. Like quenching and tempering, heat treatment is often needed to achieve the desired mechanical properties.
Besides, medium-carbon steel usually contains manganese, further enhancing its strength and hardenability. The manganese content in this steel ranges from 0.30% to 0.60%, contributing to its overall performance characteristics.
Making Process of Medium-Carbon Steel
The production of medium-carbon steel typically involves the use of carbon steel. The process begins with mining iron ore, which is then melted down into pig iron in a blast furnace. Controlled amounts of carbon, usually ranging from 0.3% to 0.6%, and other alloying elements are added to the molten pig iron to achieve the desired medium-carbon content. The alloy is then refined and cast into various shapes. Compared to low-carbon steel, medium-carbon steel produced in this manner is stronger and harder.
Chemical Composition of Medium-Carbon Steel
If you are interested in the exact chemical composition of Medium-Carbon Steel, it is as follows:
Table 1: Chemical Composition of Medium-Carbon Steel
| Element | Percentage |
| Aluminum, Al | 0.020 – 1.15 % |
| Boron, B | 0.00050 – 0.0030 % |
| Carbon, C | 0.10 – 1.29 % |
| Chromium, Cr | 0.13 – 4.5 % |
| Cobalt, Co | 4.5 – 8.0 % |
| Copper, Cu | 0.20 – 0.50 % |
| Iron, Fe | 78.7 – 100 % |
| Manganese, Mn | 0.10 – 3.0 % |
| Molybdenum, Mo | 0.030 – 4.25 % |
| Nickel, Ni | 0.15 – 10 % |
| Phosphorus, P | 0.0080 – 0.40 % |
| Silicon, Si | 0.050 – 2.2 % |
| Sulfur, S | 0.0020 – 0.50 % |
| Vanadium, V | 0.030 – 1.0 % |
The Properties of Medium-Carbon Steel
Table 2: Physical Properties of Medium-Carbon Steel
| Property | Value |
| Density | 7.75 – 7.89 g/cc （0.280 – 0.285 lb/in³ ） |
| Particle Size | 6.70 – 12.0 µm |
Table 3: Mechanical Properties of Medium-Carbon Steel
| Property | Value |
| Hardness, Brinell | 126 – 578 |
| Hardness, Knoop | 145 – 616 |
| Hardness, Rockwell B | 71.0 – 112 |
| Hardness, Rockwell C | 9.00 – 71.0 |
| Hardness, Vickers | 131 – 614 |
| Tensile Strength, Ultimate | 450 – 2730 MPa |
| Tensile Strength, Yield | 230 – 1740 MPa |
| Elongation at Break | 5.00 – 34.2 % |
| Reduction of Area | 20.0 – 71.4 % |
| Modulus of Elasticity | 187 – 213 GPa |
| Bulk Modulus | 152 – 163 GPa |
| Poissons Ratio | 0.280 – 0.300 |
| Fatigue Strength | 138 – 614 MPa |
| Fracture Toughness | 80.9 – 143 MPa-m½ |
| Machinability | 40.0 – 80.0 % |
| Shear Modulus | 72.0 – 82.0 GPa |
| Izod Impact | 9.00 – 135 J |
| Charpy Impact | 10.8 – 65.0 J |
| Charpy Impact, Unnotched | 2.71 – 86.0 J |
Table 4: Thermal Properties of Medium-Carbon Steel
| Property | Value |
| Electrical Resistivity | 0.0000166 – 0.0000263 ohm-cm |
| CTE, linear | 10.4 – 15.1 µm/m-°C |
| Specific Heat Capacity | 0.470 – 0.519 J/g-°C |
| Thermal Conductivity | 21.9 – 52.0 W/m-K |
| Melting Point | 1420 – 1460 °C |
| Maximum Service Temperature, Air | 400 °C |
Some Other Properties of Medium-Carbon Steel
The properties of medium-carbon steel are mainly determined by its carbon content and the addition of other alloying elements. The carbon content is the crucial factor influencing the steel’s mechanical properties, like elongation, tensile strength, and yield strength.
- Tensile Strength and Yield Strength
Medium-carbon steel has higher tensile and yield strengths compared to low-carbon steel. This is because of the increased carbon content, which creates harder carbide particles within the steel matrix. These carbide particles act as strengthening agents, making the steel more resistant to deformation under load.
- Ductility and Toughness
Medium-carbon steel is known for its increased strength as well as its ability to retain a reasonable level of ductility, allowing it to be formed and shaped into various geometries. Additionally, it exhibits high toughness, which can absorb energy and resist fracture, making it well-suited for applications where impact resistance is crucial.
- Machinability
Medium-carbon steel is well-known for its excellent machinability. The carbon content, as well as the presence of alloying elements like manganese and sulfur, contribute to the formation of a chip that breaks cleanly in machining operations, leading to smooth and precise cuts.
- Heat Treatability
Medium-carbon steel can be hardened and tempered through heat treatment processes like tempering and quenching to enhance its hardness, mechanical properties, wear resistance, and fatigue strength.
- Weldability
Medium-carbon steel is typically weldable, but its weldability is somewhat restricted compared to low-carbon steel. The higher carbon content can result in weld cracking and other defects if proper welding techniques and procedures are not followed. Preheating and post-weld heat treatment may be needful to address these issues.
Equivalent Forms of Medium-Carbon Steel
Table 5: Equivalents of Medium-Carbon Steel
| Country | Equivalent Grade |
| United States | AISI 1045 |
| Germany | 1.1191 (Ck45) |
| Japan | S45C |
| European Union | C45E |
| China | 45# or 45G |
Common Forms of Medium-Carbon Steel
Here are three common forms of medium-carbon steel materials:
- Medium-Carbon Steel Bars
Medium-carbon steel bars are valued for their high strength and wear resistance, making them well-suited for applications such as shafts, axles, and gears. The microstructure of these bars typically consists of a combination of ferrite and pearlite, which contributes to their strong mechanical properties.
- Medium-Carbon Steel Wire
It is known for its high tensile strength, which is well-suited for springs and cable applications. When the tensile strain reaches ε = 6.4, the tensile strength of medium-carbon ferrite-pearlite steel wire increases significantly from 750 MPa to 4,120 MPa.
- Medium-Carbon Steel Sheets
Medium-carbon steel sheets have a carbon content range similar to carbon steel bars. They provide moderate strength and formability, making them suitable for automotive panels and various structural components. The microstructure of these sheets often shows a mixture of ferrite and pearlite, offering a balance of strength and workability.
Types of Medium-Carbon Steel
The following are different forms of medium-carbon steel:
- 4140 Steel
This is a type of chromium-molybdenum alloy with a carbon content of 0.38–0.43%. It is known for its outstanding strength, wear resistance, and toughness, even in cryogenic temperatures. Additionally, it has good weldability and corrosion resistance due to its higher chromium content. These properties make it an ideal material for heavy machinery components such as hydraulic cylinders and shafts.
- 1045 Steel
1045 steel contains 0.45% carbon and provides moderate strength and hardness. It is easily machinable and weldable but does not offer exceptional resistance to corrosion and wear. This type of steel is commonly used for parts requiring high strength or wear resistance, like shafts, gears, axles, and sprockets. Its cost-effectiveness and the ability to be heat-treated effectively are advantageous.
- 1060 Steel
This carbon steel, with a carbon content of around 0.60%, is preferred for making high-hardness blades, especially for cutting-focused knives. Although it is more brittle than 1045 steel, proper tempering can achieve the desired toughness. 1060 steel is known for being easy to sharpen and maintain.
Applications of Medium-Carbon Steel
The versatile nature of medium-carbon steel makes it suitable for various applications across different industries. Here are some of its most common uses: The diverse properties of medium carbon steel make it ideal for multiple applications across multiple industries. Here are some of the most common uses:
- Automotive Industry
Medium-carbon steel is widely used in the automotive industry to manufacture components such as gears, shafts, and axles. Its high strength and machinability allow for the production of precise and durable parts that can withstand the rigors of automotive operations.
- Machinery and Equipment
The high machinability and strength of medium-carbon steel make it ideal for producing machinery and equipment components. It is commonly utilized to manufacture gears, bearings, and other precision parts that demand high performance and durability.
- Tools and Dies
Medium-carbon steel is frequently used to produce tools and dies because of its capability to maintain a sharp edge and endure high-pressure forming processes. Tools crafted from medium carbon steel are well-suited for cutting, shaping, and working with various materials.
- Railway Components
The high strength and toughness of medium-carbon steel make it well-suited for uses in railway components like rails, axles, and wheels. These components must sustain the heavy loads and vibrations encountered during railway operations.
- Structural Applications
Medium-carbon steel is also utilized in structural applications where strength and durability are crucial. It can be employed to manufacture columns, beams, and other structural components in buildings and bridges.
Advantages & Disadvantages
Advantages
Many industries favor medium-carbon steel because it provides several advantages over other types of steel. It is heat-treatable and could be easily welded because of its low melting point. It also has outstanding machinability qualities, making it perfect for parts requiring intricate shapes or details. Besides, this type of steel has exceptional durability because of its high tensile strength, making it useful for components needing to withstand heavy loads or wear and tear.
- Medium carbon steel is stronger than low carbon steel.
- Medium carbon steel is more difficult to weld than low carbon steel.
- Medium carbon steel is more resistant to wear and tear than low carbon steel.
- Medium-carbon steel is more challenging to machine than low-carbon steel.
- Medium carbon steel is more expensive than low carbon steel.
Disadvantages
Medium-carbon steel has several advantages over other steel types but has some drawbacks. One major disadvantage is its potential to become brittle at certain temperatures or pressure levels if not properly treated or processed. Another drawback is its tendency to rust quickly when exposed to moisture for extended periods without a protective coating. Additionally, medium carbon steel is generally more expensive than other types due to the additional alloying elements present in its composition.
- More expensive than low-carbon steel
- Not as strong as high-carbon steel
- Can be susceptible to rust and corrosion
- Not as easy to weld as low-carbon steel
- Not as easy to machine as low-carbon steel
Comparison Between Medium-Carbon Steel And Stainless Steel
Stainless steel containing high chromium concentration forms a protective barrier against rust and corrosion, while carbon steel, rich in carbon, can rust and corrode when exposed to moisture. The addition of chromium significantly enhances the corrosion resistance of stainless steel.
Medium-carbon steel typically costs about 600USD per ton, but prices can change based on factors such as grade, shape, and market conditions. For the most accurate and up-to-date pricing information, it is recommended that you consult specific vendors.
Summary
With its balanced combination of strength, ductility, and machinability, medium-carbon steel is a versatile material with numerous applications. Its properties and uses are determined by its carbon content as well as the addition of other alloying elements.
Medium-carbon steel offers many advantages, including strength and durability. However, it can be prone to brittleness if not processed correctly. With proper care, it is an ideal material for industrial applications like machine tools, automotive frames, bridge supports, and railway tracks.
