ASTM A234 WP92 Pipe Fittings – Technical Specifications
1. Material Overview
ASTM A234 WP92 is an advanced 9Cr-1.75W-V-Nb alloy steel** for ultra-supercritical service (up to 620°C/1150°F). These high-performance fittings feature:
– Enhanced creep strength (100,000h rupture strength @ 600°C: 100MPa)
– Superior oxidation resistance
– Excellent microstructural stability
– Optimized tungsten-enhanced properties
2. Chemical Composition (%)
| Element | Composition Range | Metallurgical Function |
|———|——————-|———————–|
| C | 0.07-0.13 | Strength & carbide formation |
| Mn | 0.30-0.60 | Austenite stabilization |
| P | ≤0.020 | Purity control |
| S | ≤0.010 | Purity control |
| Si | 0.50 max | Deoxidation |
| Cr | 8.50-9.50 | Oxidation resistance |
| Mo | 0.30-0.60 | Solid solution strengthening |
| W | 1.50-2.00 | Laves phase formation |
| V | 0.15-0.25 | Carbide stabilization |
| Nb | 0.04-0.09 | Precipitation strengthening |
| N | 0.03-0.07 | Nitride formation |
| B | 0.001-0.006 | Grain boundary strengthening |
3. Mechanical Properties
| Property | Requirement | Test Standard |
|———-|————-|—————|
| Tensile Strength | 620-840 MPa | ASTM A370 |
| Yield Strength | 440 MPa min | ASTM A370 |
| Elongation | 20% min | ASTM A370 |
| Hardness | 250 HB max | ASTM E10 |
| Impact Energy | 41J min @ RT | ASTM A370 |
4. Temperature Performance
– **Maximum Design Temp**: 620°C (1150°F)
– **Creep Threshold**: 565°C (1050°F)
– **Short-term Peak**: 650°C (1200°F)
– **Minimum Temp**: -30°C (-20°F) with testing
5. Manufacturing Standards
– **Base Specification**: ASTM A234
– **Dimensional Standards**:
– ASME B16.9 (Butt-welding fittings)
– ASME B16.28 (Short radius elbows)
– **Heat Treatment**:
– Normalizing: 1040-1080°C (1900-1975°F)
– Tempering: 730-780°C (1350-1435°F)
6. Available Fitting Types
1. **Power Plant Elbows** (45°/90° LR/SR)
2. **Heavy-Wall Tees** (Equal/Reducing)
3. **High-Pressure Reducers**
4. **Thick-Wall Caps**
5. **Reinforced Stub Ends**
7. Heat Treatment Protocol
– **Normalizing**:
– 1065°C ±15°C (1950°F ±25°F)
– Forced air cooling
– **Tempering**:
– 750°C ±15°C (1380°F ±25°F)
– Minimum 2 hours
– **PWHT Requirements**:
– 750-775°C (1380-1425°F)
– 4 hours minimum hold
8. Welding Technology
– **Preheat**: 200-250°C (400-480°F)
– **Interpass Temp**: ≤300°C (≤570°F)
– **Filler Metals**:
– SMAW: E9015-B9 (modified)
– GTAW: ER90S-B9
– **Critical Controls**:
– Heat input: 15-25 kJ/cm
– Post-weld hardness ≤250 HB
– 100% RT/UT examination
9. Quality Assurance
– **Mandatory Tests**:
– Hydrostatic (1.5x design pressure)
– Full-section tensile tests
– Hardness mapping
– **Special Examinations**:
– Creep rupture testing
– Phase balance analysis
– Advanced NDE (TOFD, PAUT）
10. Microstructural Characteristics
– **Optimal Structure**: Tempered lath martensite
– **Precipitates**:
– M23C6 carbides
– MX carbonitrides
– Laves phase (Fe2W)
– **Grain Size**: ASTM No. 5 or finer
11. Applications
– Ultra-Supercritical Power Plants：
– Main steam lines
– Hot reheat systems
– Advanced boiler components
– **Specialty Services**:
– High-temperature reactors
– Thermal cracking units
– Advanced energy systems
12. Comparative Analysis
| Grade | Key Alloys | 10^5h Creep Strength @600°C |
|——-|————|—————————–|
| WP91 | 9Cr-1Mo-V | 90 MPa |
| WP92 | 9Cr-1.75W | 120 MPa |
| WP911 | 9Cr-1W | 110 MPa |
13. Purchasing Specifications
Essential requirements:
1. **Material Certification**: EN 10204 3.2
2. **Heat Treatment Records**: Complete cycle documentation
3. **PMI Reports**: Full chemistry verification
4. **NDE Packages**:
– 100% RT + UT
– Surface examination (PT/MT)
5. **Hardness Maps**: Full component survey
14. Installation Best Practices
1. **Storage**: Climate-controlled to prevent condensation
2. **Handling**: Non-magnetic tools to prevent contamination
3. **Alignment**: Laser-assisted for precision
4. **Welding**: Automated processes preferred
5. **PWHT**: Furnace treatment with thermocouple monitoring
15. Lifecycle Management
– **Inspection Technologies**:
– Replica metallography
– Ultrasonic creep monitoring
– Oxide thickness measurement
– **Remaining Life Assessment**:
– Annual evaluations after 100,000h service
– Advanced microstructural analysis
– **Retirement Criteria**:
– 20% wall thinning
– Creep damage ≥Level 3
– Macro-crack detection
WP92 represents the current generation of advanced ferritic steels for ultra-supercritical applications. For new projects exceeding 600°C service, consider nickel-based alloys for optimal performance. Always comply with ASME B31.1 Power Piping Code for installation and ASME Section IX for welding procedure qualifications.
