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High-Performance 10Cr11Co3W3NiMoVNbNB Steel – China Suppliers & Factory for Ultra-Supercritical Steam Turbines
Core Features and Applications
Main Features
- Excellent high-temperature strength and creep endurance strength: It can maintain high endurance strength at high temperatures (such as 660°C). For example, at a test temperature of 660°C and a test stress of 245MPa, the material's fracture time is required to be ≥100h.
- Good anti-relaxation performance: This is crucial for high-temperature bolts and can ensure that sufficient sealing preload is maintained during long-term operation.
- Excellent oxidation and corrosion resistance: Contains about 11% chromium, which gives it good stability in high-temperature steam environments.
- Higher toughness: Through proper heat treatment, a good balance of strength and toughness can be achieved.
- Stringent chemical composition and purity requirements: Extremely strict control of harmful elements such as silicon (Si) and aluminum (Al) (Si≤0.10%, Al≤0.015%), and pursuit of extremely high steel purity to reduce non-metallic inclusions.
Typical Applications
- Steam turbine high-temperature bolts and nuts: Mainly used for connecting the high-temperature section of ultra-supercritical units, which is its most typical application.
- Steam turbine blades: used to manufacture high-pressure or medium-pressure rotor blades for ultra-supercritical units.
- Other high-temperature components: such as valves, shafts and other key components that need to work in high-temperature and high-pressure environments.
Chemical Composition
The chemical composition of 10Cr11Co3W3NiMoVNbNB is precisely designed, and the content range of each element is strictly controlled to ensure its high performance. The specific composition is shown in the following table:
| Element | Specified range (wt%) | Main Function |
|---|---|---|
| C | 0.08～0.13 | Ensure the strength of the martensite matrix and form carbides |
| Si | ≤0.10 | Strictly controlled to mitigate adverse effects on thermal strength and toughness |
| Mn | 0.35～0.65 | Improves hardenability and is beneficial for hot working |
| P | ≤0.015 | Strictly controlled harmful elements (impurities) |
| S | ≤0.010 | Strictly controlled harmful elements (impurities) |
| Cr | 10.00～12.00 | Provides basic resistance to oxidation and corrosion |
| Ni | 0.30～0.70 | Stabilize austenite, improve toughness and hardenability |
| Mo | 0.10～0.40 | Solid solution strengthening, suppressing temper brittleness and improving strength |
| Co | 2.50～3.50 | Improve solid solution strengthening effect, increase martensitic transformation temperature, improve high temperature strength and tempering stability |
| W | 2.40～3.00 | Strong carbide-forming element, solid solution strengthening, significantly improving hot strength and recrystallization temperature |
| V | 0.15～0.25 | Formation of fine carbonitrides, precipitation strengthening, and grain refinement |
| Nb | 0.05～0.12 | Form stable NbC and NbN, refine grains, precipitation strengthen, and improve strength and creep resistance |
| N | 0.010～0.035 | Refine the grains and form nitrides to play a precipitation strengthening role |
| Al | ≤0.015 | Strictly controlled, usually remains as a deoxidizer, excessive amount will damage toughness |
| B | 0.01～0.04 | A very small amount can significantly improve the grain boundary strength and has great benefits for high temperature creep rupture performance |
Mechanical Properties
The properties of steel need to be obtained through heat treatment. Its mechanical properties depend on the specific heat treatment system.
1) Room-Temperature Mechanical Properties
After proper quenching and tempering heat treatment, its room temperature mechanical properties must generally meet or exceed the following exemplary requirements (specific requirements are subject to product standards or technical agreements):
| Performance indicators | Numerical range | Test conditions |
|---|---|---|
| Tensile strength (Rm) | ≥ 883 MPa | Room temperature |
| Yield strength (Rp0.2) | ≥ 619 MPa | Room temperature |
| Elongation after break (A) | ≥ 15% | Room temperature |
| Sectional reduction (Z) | ≥ 45% | Room temperature |
| Impact energy (AKv) | ≥ 10.7 J | Room temperature |
| Hardness (HBW) | 269 – 321 HBW | Room temperature |
2) High Temperature Mechanical Properties
Its high-temperature endurance strength is a key indicator. For example, it is required that the fracture time under the stress conditions of 660℃/245MPa should be no less than 100 hours.
Heat Treatment System
Heat treatment plays a vital role in the performance of 10Cr11Co3W3NiMoVNb steel. The effects of different heat treatment systems on its properties were studied:
- Quenching (Austenitizing): Heating and holding (oil or air cooling) is typically performed within the 1080°C to 1120°C range. Research has shown that increasing the quenching temperature within this range can improve the material's high-temperature durability (under the 660°C tempering condition). For example, after quenching at 1130°C and 1140°C, the material's time to fracture at 660°C/275MPa is greater than 100 hours.
- Tempering: The tempering temperature significantly affects the strength-toughness balance of a material. After quenching at 1100°C, tempering between 600°C and 700°C reveals a significant decrease in tensile strength and yield strength, while a significant increase in impact toughness (impact energy). The choice of tempering temperature must balance the combined requirements of strength, ductility, and toughness.
Important Note: The optimal heat treatment process (temperature, holding time, cooling method) must be determined through testing based on the specific product form (bar, forging, finished bolt), size, and final performance requirements, and follow the recommendations of the material manufacturer or relevant technical specifications.
Smelting Process
The smelting of 10Cr11Co3W3NiMoVNbNB is extremely challenging due to its extremely low Si and Al content requirements and the need for precise control of the boron element, while also ensuring extremely high steel purity. While traditional vacuum induction furnace smelting methods are effective, they are costly and inefficient.
Currently, advanced smelting technology utilizes a dual-process approach combining an AOD (Argon Oxygen Decarburization) furnace and a LF (Ladle Refining Furnace). Through a series of oxygen, silicon, aluminum, and slag control techniques, this technology successfully achieves precise control of the composition of the easily eroded elements Si, Al, and B, while maintaining high steel purity. Finished steel produced using this process exhibits extremely low levels of non-metallic inclusions (all inclusions have a coarseness rating of ≤1.0) and an oxygen content of ≤35ppm, fully meeting the requirements of high-end applications.
Summary and Outlook
10Cr11Co3W3NiMoVNbNB (Co3W3) is a high-tech, high-performance martensitic heat- resistant steel. Through multi-component composite strengthening and extremely strict purity control, it achieves a combination of high strength, high creep resistance, and excellent toughness at temperatures up to 630°C, making it a preferred material for key high-temperature components in ultra-supercritical thermal power generation units.
As the global energy industry continues to pursue efficient and clean power generation technologies, demand for higher-performance ultra-supercritical units will continue to grow. This places higher demands on advanced high-temperature materials like 10Cr11Co3W3NiMoVNbNB, demonstrating their broad application prospects. Further optimizing smelting processes to reduce costs and deepening research and stabilizing heat treatment regimes to fully tap the material's performance potential will remain key research areas.