Product Description
1.7709, AFNOR 20CDV5.7, 21CrMoV5.7
Standard reference:
EUROPE EN 10269: 2003
ITALY (UNI 7845-78)
GERMANY (DIN 17200-86) / DIN 17240
FRANCE (NF A 35-552-86)
UK (BS 970 pt.3-96)
USA ASTM A 29
AD 2000 W7
Chemical Analysis (Mass-%)
| Element |
C |
Si |
Mn |
P |
S |
Cr |
NI |
Mo |
V |
Al |
| min. |
0.17 |
0.15 |
0.4 |
- |
- |
1.2 |
- |
0.65 |
0.25 |
- |
| Max. |
0.25 |
0.35 |
0.8 |
0.025 |
0.03 |
1.5 |
0.6 |
0.8 |
0.35 |
0.03 |
### Overview of 1.7709, AFNOR 20CDV5.7, 21CrMoV5.7 Steels
Steel is an essential material in various industrial applications, and its specific properties determine its suitability for different uses. Among the numerous steel grades available, 1.7709, also known as AFNOR 20CDV5.7 or 21CrMoV5.7, stands out due to its unique composition and mechanical properties. This essay delves into the characteristics, applications, and benefits of this particular steel grade.
#### Chemical Composition
1.7709 steel is a Cr-Mo-V (Chromium-Molybdenum-Vanadium) alloyed heat-resistant structural steel. Its chemical composition includes carbon (C), silicon (Si), manganese (Mn), phosphorus (P), sulfur (S), chromium (Cr), nickel (Ni), molybdenum (Mo), vanadium (V), and aluminum (Al). The precise composition ensures a balance between strength, toughness, and resistance to high temperatures. The typical chemical composition ranges are:
- Carbon (C): 0.17-0.25%
- Silicon (Si): 0.15-0.35%
- Manganese (Mn): 0.40-0.80%
- Phosphorus (P): max 0.025%
- Sulfur (S): max 0.030%
- Chromium (Cr): 1.20-1.50%
- Nickel (Ni): max 0.60%
- Molybdenum (Mo): 0.65-0.80%
- Vanadium (V): 0.25-0.35%
- Aluminum (Al): max 0.03%
These elements contribute to the steel's high strength, toughness, and resistance to wear and corrosion.
#### Mechanical Properties
The mechanical properties of 1.7709 steel are defined by its condition, typically in a quenched and tempered state (+QT). The properties include yield strength, tensile strength, elongation, reduction of area, and impact energy. For instance, in the quenched and tempered condition, the steel exhibits:
- Yield Strength: ≥ 550 N/mm²
- Tensile Strength: 700-850 N/mm²
- Elongation: ≥ 16%
- Reduction of Area: ≥ 60%
- Impact Energy (Charpy-V): ≥ 63 J
These properties make it suitable for applications requiring high strength and toughness, especially at elevated temperatures.
#### Applications
1.7709 steel is widely used in industries where components are subjected to high temperatures and stress. Its applications include:
1. **Connecting Elements:** The steel's high strength and toughness make it ideal for manufacturing bolts, nuts, and other fasteners used in high-stress environments.
2. **Turbine Shafts:** The ability to withstand high temperatures and maintain mechanical properties makes it suitable for turbine shafts in power plants and jet engines.
3. **Flanges and Rings:** The steel's resistance to deformation and wear is crucial for components like flanges and rings used in high-pressure systems.
4. **Components for Thermal Power Plants:** Its heat resistance makes it suitable for various parts in thermal power plants, including boiler components and heat exchangers.
#### Heat Treatment
The heat treatment process for 1.7709 steel involves hardening and tempering. The typical heat treatment parameters are:
- Hardening: Heating to 880-950°C followed by quenching in air, oil, polymer, or water.
- Tempering: Heating to 680-720°C for at least 2 hours, followed by air cooling.
This process enhances the steel's mechanical properties, ensuring it can perform effectively under high stress and temperature conditions.
#### Benefits
1.7709 steel offers several benefits that make it a preferred choice in demanding applications. These include:
1. **High Strength and Toughness:** The steel's composition and heat treatment result in excellent mechanical properties, making it suitable for high-stress applications.
2. **Heat Resistance:** The ability to retain strength and toughness at elevated temperatures makes it ideal for components exposed to high thermal loads.
3. **Wear and Corrosion Resistance:** The presence of chromium and molybdenum enhances the steel's resistance to wear and corrosion, extending the lifespan of components.
4. **Versatility:** The steel's properties make it suitable for a wide range of applications, from fasteners to critical components in power plants and turbines.
#### Conclusion
1.7709, also known as AFNOR 20CDV5.7 or 21CrMoV5.7, is a versatile and high-performance steel grade designed for applications requiring high strength, toughness, and resistance to high temperatures. Its unique chemical composition and mechanical properties make it suitable for critical components in various industries, including power generation and aerospace. Through proper heat treatment, the steel's performance can be further enhanced, ensuring reliability and durability in demanding environments.
Detailed Photos
Audited Supplier 
){kind=link}
){kind=link}