1. Basic Definition and Alloy Design
12Cr2MoWVTiB is a multi-component composite-strengthened boiler tube specified in the GB 5310 standard. It is a martensitic heat-resistant steel. Its nomenclature and compositional characteristics are as follows:
"12": Carbon content 0.08-0.15% (low-carbon crack control design);
"Cr2": Chromium content 1.50-2.00% (high-temperature oxidation resistance);
"MoW": Molybdenum 0.50-0.70% + Tungsten 0.30-0.55% (solid solution strengthening);
"VTiB": Vanadium 0.25-0.35% + Titanium 0.08-0.15% + Boron 0.005-0.010% (grain boundary strengthening);
Special Requirements: Phosphorus ≤ 0.020%, Sulfur ≤ 0.010%, and 620°C endurance strength data are required.
2. Core Performance and Advantages
Ultra-High-Temperature Performance: Can operate for long periods at 620-650°C (design life 100,000 hours);
Creep Resistance: Time to Fracture ≥ 40,000 hours at 620°C/100 MPa;
Microstructural Stability: TiB composite precipitation inhibits grain boundary migration;
Processing Characteristics:
Welding requires preheating at 350-400°C, followed by post-weld tempering at 760-780°C;
Cold working requires intermediate annealing (HB ≤ 220).
3. Typical Applications
Ultra-Supercritical Boilers: Final Superheater (wall temperature ≥ 600°C);
Nuclear Power Systems: Connecting Pipes for Steam Generators in Generation IV Reactors;
Special Applications:
Heat Exchangers in High-Sulfur Flue Gas Environments;
Pressure-Bearing Components in Units with Frequent Start-Ups and Shutdowns.
4. Comparison with Similar Materials
vs. 12Cr2MoG:
Tungsten-Titanium-Boron Composite Reinforcement: 30% Higher High-Temperature Strength;
Maximum Operating Temperature Increased by 50°C;
Cost Approximately 40-50% Higher. vs. T92 (9Cr-2W):
Higher chromium content, stronger steam corrosion resistance;
Excellent thermal fatigue performance (ΔT > 300°C).
5. Procurement and Testing Key Points
Key Certificates: Must include testing for delta ferrite content (≤3%) and grain size (≥ Grade 6);
Testing Requirements:
100% ultrasonic + eddy current combined flaw detection;
Hardness gradient testing (cross-section hardness difference ≤ 30 HB);
