1.4906, X12CrMoWVNbN10-1-1, T505SC
1.4906/X12CrMoWVNbN10-1-1 and T505SC represent advanced martensitic stainless steels specifically developed for high-temperature turbine applications. Their balanced composition provides an excellent combination of strength, creep resistance, and corrosion resistance at operating temperatures up to 600°C. The strict quality control requirements and heat treatment specifications ensure reliable performance in critical power generation components.
Table of Contents
What is 1.4906, X12CrMoWVNbN10-1-1, T505SC?
Turbine blade steels are critical materials in power generation, requiring exceptional high-temperature strength, creep resistance, and corrosion resistance. This guide provides a comprehensive technical analysis of three important grades: 1.4906 (X12CrMoWVNbN10-1-1), T505SC, and their equivalents.
Microstructural Requirements
- Martensitic Structure: Fully martensitic after heat treatment
- Delta Ferrite: <5% allowed
- Grain Size: ASTM 4 or finer (after all heat treatments)
- Inclusions: Controlled per ASTM E45
- Homogeneity: Must be free from porosity, excessive segregation
Equivalent Grades
| Country/Standard | Equivalent Grade |
|---|---|
| Germany (DIN) | 1.4906, X12CrMoWVNbN10-1-1 |
| Japan (JIS) | T505SC |
| USA (ASTM/UNS) | S50490, S50491 |
| China (GB) | 1Cr11NiMoW2VNbN |
| Russia (GOST) | ЭП993 |
| Europe (EN) | X12CrMoWVNbN10-1-1 |
Quality Control and Testing Requirements
- Chemical Analysis: Melt analysis required for all specified elements
- Mechanical Testing:
- Tensile, impact, hardness testing required
- 10% of bars (min. 10) tested for hardness uniformity
- Non-Destructive Testing:
- Ultrasonic testing for bars ≥30mm diameter (EN 10308)
- Quality classes: Class 4 for ≤200mm, Class 3 for >200mm
- High-Temperature Testing:
- Elevated temperature tensile tests at 600°C
- Creep rupture testing for qualification
Recent Developments and Modifications
Recent updates to specifications (as seen in the TLV document) include:
- Change from average to minimum value for impact energy requirements
- Updated heat treatment parameters
- Enhanced product and process qualification requirements
- More stringent documentation requirements
Applications
X12CrMoWVNbN10-1-1, 1.4906 Applications
- Classification: Martensitic stainless steel
- Applications: High-pressure steam turbine blades, rotors, and components in conventional and nuclear power plants
- Key Features:
- Excellent high-temperature strength (Rp0.2 ≥ 750 N/mm² at room temperature)
- Good creep resistance at temperatures up to 600°C
- Fully martensitic microstructure after heat treatment
- Used in quenched and tempered condition (+QT)
T505SC Applications
- Classification: Martensitic stainless steel (Japanese standard)
- Applications: Steam turbine blades and rotors in thermal power plants
- Key Features:
- Similar composition to 1.4906 with slight variations
- Optimized for long-term creep resistance
- Used in quenched and tempered condition
Chemical Composition (%)
| Element | X12CrMoWVNbN10-1-1 / 1.4906 |
T505SC |
Similar Grades |
|---|---|---|---|
| C | 0.11-0.13 | 0.10-0.15 | 0.10-0.15 |
| Si | ≤0.12 | ≤0.50 | ≤0.50 |
| Mn | 0.40-0.50 | 0.30-0.80 | 0.30-1.00 |
| P | ≤0.010 | ≤0.025 | ≤0.025 |
| S | ≤0.005 | ≤0.010 | ≤0.010 |
| Cr | 10.2-10.8 | 10.0-11.5 | 9.0-12.0 |
| Mo | 1.00-1.10 | 0.80-1.20 | 0.80-1.50 |
| W | 0.95-1.05 | 0.90-1.20 | 0.80-1.50 |
| V | 0.15-0.25 | 0.15-0.30 | 0.10-0.30 |
| Nb | 0.04-0.06 | 0.03-0.08 | 0.02-0.10 |
| N | 0.045-0.060 | 0.040-0.080 | 0.030-0.090 |
| Ni | 0.70-0.80 | 0.30-1.00 | 0.30-1.50 |
Note: Trace elements Cu, As, Sb, Sn, and Ti should be reported but are not specified in most standards.
Material Properties
Room Temperature Mechanical Properties
| Property | 1.4906 / X12CrMoWVNbN10-1-1 | T505SC |
|---|---|---|
| 0.2% Proof Strength (MPa) | 750-830 | 750-880 |
| Tensile Strength (MPa) | 870-1020 | 880-1080 |
| Elongation A (%) | ≥14 (d≤100mm), ≥13 (d>100mm) | ≥15 |
| Reduction of Area (%) | ≥45 (d≤100mm), ≥40 (d>100mm) | ≥50 |
| Impact Energy (J) | ≥55 (d≤100mm), ≥24 (d>100mm) | ≥60 |
| Hardness (HB) | 270-310 | 270-320 |
High-Temperature Mechanical Properties (600°C)
| Property | 1.4906 / X12CrMoWVNbN10-1-1 | T505SC |
|---|---|---|
| 0.2% Proof Strength (MPa) | ≥405 | ≥420 |
| Tensile Strength (MPa) | ≥420 | ≥440 |
| Elongation A5 (%) | ≥18 | ≥20 |
| Reduction of Area (%) | ≥65 | ≥70 |
Creep and Rupture Properties
1.4906 / X12CrMoWVNbN10-1-1 Creep Performance
Creep Rupture Strength at 600°C:
- 10,000 hours: ≥100 MPa (typical requirement)
- 100,000 hours: ≥80 MPa (estimated)
Creep Rate: Typically <1×10⁻⁷ %/h at 600°C under 100 MPa stress
T505SC Creep Performance
- Generally shows slightly better creep resistance than 1.4906 at temperatures above 550°C
- 100,000 hour rupture strength at 600°C typically ≥85 MPa
Physical Properties
| Property | 1.4906 / X12CrMoWVNbN10-1-1 |
|---|---|
| Density (g/cm³) | 7.8 |
| Thermal Conductivity (W/m·K) | 25 (at 20°C), 28 (at 600°C) |
| Specific Heat (J/kg·K) | 460 (at 20°C), 600 (at 600°C) |
| Thermal Expansion (10⁻⁶/K) | 10.5 (20-100°C), 12.8 (20-600°C) |
| Electrical Resistivity (Ω·m) | 0.85 × 10⁻⁶ |
| Elastic Modulus (GPa) | 210 (at 20°C), 170 (at 600°C) |
Heat Treatment
1.4906 / X12CrMoWVNbN10-1-1 Heat Treatment
Hardening
- Temperature: 1050-1100°C
- Quenching: Air or liquid cooling
- Must be cooled to ≤100°C in the core to ensure complete martensitic transformation
Tempering
- First temper: 570-680°C
- Second temper: 680-720°C
- Stress relief (if straightening is required): 20-50K below tempering temperature with slow cooling
Final Condition: Quenched and Tempered (+QT)
T505SC Typical Heat Treatment
- Hardening: 1050-1100°C followed by air or oil quenching
- Tempering: Double tempering at 680-750°C
- Final Condition: Quenched and Tempered (+QT)
Processing Performance
Forging and Hot Working
- Recommended hot working temperature range: 1100-900°C
- Should be cooled slowly after hot working to prevent cracking
- Requires annealing if interrupted during hot working
Machinability
- Machinability rating: ~50% of free-cutting steels
- Recommended tools: Carbide tools with positive rake angles
- Cutting speeds: 30-50 m/min for turning operations
- Requires generous use of cutting fluids
Welding Characteristics
- Weldability: Fair to good with proper precautions
- Recommended Processes: GTAW (TIG), SMAW (shielded metal arc)
- Preheat: 200-300°C
- Post-Weld Heat Treatment: Full heat treatment cycle recommended
- Filler Metals: Matching composition or higher alloy grades