Description
25CrMo4 Alloy Steel Overview
25CrMo4 is a low-alloy steel that contains chromium and molybdenum as its primary alloying elements. This steel is recognized for its excellent strength, toughness, and hardenability, making it suitable for a wide range of applications where mechanical performance and resistance to fatigue are critical. The chromium in the alloy enhances its resistance to wear and corrosion, while the molybdenum improves its strength and toughness, especially at high temperatures. Additionally, 25CrMo4 offers good weldability and machinability, making it an ideal choice for applications in the automotive, aerospace, and machinery industries.
Key Features of 25CrMo4:
- High Strength: Capable of withstanding high mechanical stresses without deformation.
- Good Toughness: Resistant to cracking under impact or repeated stress.
- Wear Resistance: Chromium content provides excellent resistance to wear and tear.
- High Temperature Performance: Molybdenum increases strength and performance in high-temperature environments.
- Weldability and Machinability: Easy to weld and machine under appropriate conditions.
Applications of 25CrMo4 Alloy Steel
25CrMo4 alloy steel is used in a variety of applications requiring high strength, toughness, and wear resistance. Typical uses include:
- Automotive Industry: Components such as gears, crankshafts, and suspension parts.
- Aerospace Industry: High-stress parts such as shafts, landing gear components, and engine mounts.
- Mechanical Engineering: Shafts, axles, and spindles used in heavy machinery and equipment.
- Construction Equipment: Used in parts that require high strength and wear resistance, such as hydraulic cylinders and fasteners.
Equivalent Grades for 25CrMo4
The 25CrMo4 steel is recognized by various international standards, and its equivalent grades include:
| Standard | Equivalent Grade |
|---|---|
| DIN | 1.7218 |
| AISI/SAE | 4130 |
| EN | 25CrMo4 |
| UNS | G41300 |
| JIS | SCM430 |
Chemical Composition of 25CrMo4
The chemical composition of 25CrMo4 alloy steel is designed to offer a balance of strength, toughness, and resistance to wear. The typical composition is as follows:
| Element | Composition (%) |
|---|---|
| Carbon (C) | 0.22 – 0.29 |
| Silicon (Si) | 0.15 – 0.40 |
| Manganese (Mn) | 0.60 – 0.90 |
| Phosphorus (P) | 0.025 max |
| Sulfur (S) | 0.035 max |
| Chromium (Cr) | 0.90 – 1.20 |
| Molybdenum (Mo) | 0.15 – 0.30 |
Mechanical Properties of 25CrMo4
The mechanical properties of 25CrMo4 make it an ideal material for demanding applications. The typical values for these properties include:
| Property | Value (Typical) |
|---|---|
| Tensile Strength (MPa) | 700 – 900 |
| Yield Strength (MPa) | 550 – 700 |
| Elongation (%) | 14 – 22 |
| Impact Toughness (J) | 30 – 45 (at 20°C) |
| Hardness (HB) | 207 – 235 |
Heat Treatment of 25CrMo4
Heat treatment is essential for optimizing the mechanical properties of 25CrMo4. The following heat treatment processes can be applied:
- Annealing: Heat to 680 – 710°C, hold for a sufficient time, and cool slowly to relieve internal stresses and improve machinability.
- Hardening: Heat to 830 – 860°C, followed by quenching in oil or water to increase strength and hardness.
- Tempering: After hardening, tempering is performed at 540 – 680°C to reduce brittleness and enhance toughness.
Hardness of 25CrMo4
The hardness of 25CrMo4 steel can be adjusted through heat treatment. In its normalized condition, the hardness ranges between 207 – 235 HB, but after hardening and tempering, the hardness can reach values up to 250 – 300 HB depending on the heat treatment parameters.
Physical Properties of 25CrMo4
The physical properties of 25CrMo4 are as follows, and they contribute to the material’s suitability for high-performance applications:
| Property | Value |
|---|---|
| Density (g/cm³) | 7.85 |
| Thermal Conductivity (W/m·K) | 37 – 45 |
| Specific Heat Capacity (J/kg·K) | 450 |
| Electrical Resistivity (µΩ·cm) | 20.7 |
| Melting Point (°C) | 1425 – 1460 |
Forging Properties of 25CrMo4
25CrMo4 alloy steel is highly suitable for forging. The optimal forging temperature range is between 1150 – 850°C. After forging, components should be cooled slowly in sand or another medium to prevent the formation of internal stresses and cracks.
Stress Relieving for 25CrMo4
To eliminate residual stresses resulting from machining or forming, stress relieving should be done by heating the steel to 550 – 600°C, holding for 1-2 hours, and then cooling slowly.
Normalizing 25CrMo4
Normalizing involves heating the steel to 850 – 880°C, followed by air cooling. This process refines the grain structure, improving mechanical properties and toughness.
Annealing 25CrMo4
Annealing of 25CrMo4 is carried out at 680 – 710°C. After reaching the temperature, the steel is slowly cooled in the furnace. Annealing helps to improve machinability and relieve internal stresses.
Machinability of 25CrMo4
25CrMo4 offers good machinability, particularly in the annealed or normalized condition. It can be machined using conventional techniques, but high-speed tools and appropriate cutting parameters are recommended for improved tool life and surface finish.
Welding of 25CrMo4
Welding 25CrMo4 is possible with proper precautions. Preheating to 150 – 250°C is advised to prevent cracking, especially for large sections. Post-weld heat treatment is also recommended to restore the material’s properties.
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