ASME SA387 Grade 911 Class 2 (SA387 Gr 911 Cl 2) Steel Plate
ASME SA387 Grade 911 Class 2 (SA387 Gr 911 Cl 2) steel plates are advanced chrome moly alloy plates with 9Cr-1Mo-V-Nb-N-B composition, offering superior creep strength and weldability for ultra-supercritical boilers.
Specification
ASME SA-387/SA-387M for chromium-molybdenum alloy steel plates in pressure vessels
Dimensions
6-100mm thick, 4600mm max wide, 12000mm max long
Hardness/Density
ASME SA387 Gr 911 Cl 2 Hardness 200 HB, Density 7.85 g/cm³
Equivalent Material
X12CrMoWVNbN10-1-1 (EN10028-2), 9Cr-1Mo-V-Nb-B (JIS G3462), 10Cr9Mo1VNbN-B (GB/T 713)
What is ASME SA387 Grade 911 Class 2?
ASME SA387 Grade 911 Class 2 (SA387 Gr 911 Cl 2) steel plates represent an advanced evolution of Grade 91 alloy steel, specifically developed for ultra-supercritical (USC) power plants and high-temperature petrochemical pressure vessels.
With its unique 9Cr-1Mo-V-Nb-N-B alloy composition, Grade 911 achieves significantly higher creep rupture strength, long-term stability, and oxidation resistance compared to conventional Grade 91.
This material is designed for service temperatures up to 650–700°C, making it an excellent choice for steam headers, superheaters, reheaters, and heavy welded pressure vessels in modern high-efficiency power plants.
Material Specification
| Specification Element | Requirement | SHH STEEL Supply |
| Standard | ASME SA387 / ASTM A387 | Pressure vessel quality alloy steel |
| Grade | 911 | Modified 9Cr-1Mo-V-Nb-N-B steel |
| Class | 2 | High-strength grade |
| Thickness Range | 6 – 120 mm | Custom up to 150 mm |
| Width/Length | Up to 4200 mm / 18000 mm | Large-format plates |
| Heat Treatment | Normalized + Tempered | Furnace controlled |
| Inspection | UT, Charpy, Creep Testing | SGS / BV / TUV available |
Chemical Composition
| Element | Heat Analysis (%) | Product Analysis (%) | Remarks |
| Carbon (C) | 0.08 – 0.12 | 0.07 – 0.13 | Provides strength without excess brittleness |
| Manganese (Mn) | 0.30 – 0.60 | 0.28 – 0.65 | Improves toughness |
| Phosphorus (P) | ≤ 0.020 | ≤ 0.025 | Strict control for toughness |
| Sulfur (S) | ≤ 0.010 | ≤ 0.015 | Low sulfur ensures weldability |
| Silicon (Si) | 0.20 – 0.50 | 0.18 – 0.55 | Enhances oxidation resistance |
| Chromium (Cr) | 8.0 – 9.5 | 7.8 – 9.7 | Provides creep and oxidation resistance |
| Molybdenum (Mo) | 0.85 – 1.05 | 0.83 – 1.10 | Strengthens high-temperature creep resistance |
| Vanadium (V) | 0.18 – 0.25 | 0.17 – 0.27 | Improves creep strength |
| Niobium (Nb) | 0.06 – 0.10 | 0.05 – 0.11 | Enhances long-term stability |
| Nitrogen (N) | 0.030 – 0.070 | 0.028 – 0.072 | Improves creep and toughness |
| Boron (B) | 0.001 – 0.006 | 0.001 – 0.007 | Extends creep rupture life, unique to Grade 911 |
Mechanical Properties
| Property | Requirement | Test Method |
| Tensile Strength | 620 – 820 MPa | ASTM A370 |
| Yield Strength | ≥ 440 MPa | ASTM A370 |
| Elongation (200 mm) | ≥ 18% | ASTM A370 |
| Charpy V-Notch Impact | ≥ 27J at -20°C | ASTM A370 |
| Hardness | 200 – 250 HB | ASTM E18 |
| Creep Rupture Strength | ≥ 120 MPa at 650°C (100,000 h) | ASME Code |
Heat Treatment
- Normalized at ~1050°C
- Tempered at 730–780°C
Delivery
- Always supplied in Normalized + Tempered (N+T) condition
Tolerances
- Thickness: ±1.5mm (≤40mm), ±2.0mm (>40mm)
- Width/Length: ±10mm standard
- Flatness: ≤3mm/m
Weldability
- Good weldability but requires strict preheat (200–300°C)
- PWHT (post weld heat treatment) mandatory for thick weldments
- Requires low-hydrogen electrodes (E9018-B9, E10018-B9)
Equivalent Grades
| Standard | Grade | Notes |
| ASTM A387 | Grade 911 | Equivalent designation |
| EN 10216 | X12CrMoWVNbN10-1-1 | European equivalent |
| DIN | X12CrMoWVNbN10-1-1 | German equivalent |
| JIS | G3462 9Cr-1Mo-V-Nb-B | Japanese equivalent |
| GB/T | 10Cr9Mo1VNbN-B | Chinese equivalent |
Supplementary Requirements
- Ultrasonic testing (ASTM A435/A578)
- Charpy impact testing at -20°C
- Creep rupture testing for long-term service
- Third-party inspection (SGS, TUV, BV)
- Protective coating: shot blasting + primer
Applications
| Application | Service Temp | Industry |
| Ultra-Supercritical Boilers | 600–700°C | Power generation |
| Pressure Vessels | Elevated | Petrochemical |
| Steam Headers & Piping | High stress | Thermal power plants |
| Heat Exchangers | Creep service | Refinery & LNG |
| Nuclear Components | High safety | Nuclear energy |
| Offshore Platforms | Severe service | Oil & gas |
Why Choose SHH STEEL
- Leading ASME SA387 Grade 911 Class 2 supplier with 15+ years of experience
- Large stock and global distribution
- Mill test certificates EN 10204 3.1/3.2 available
- Customized cutting, machining, and beveling services
- Strong track record in power plant and refinery projects
FAQ
- What is ASME SA387 Grade 911 Class 2 used for?It is mainly used in ultra-supercritical boilers, high-pressure steam piping, and long-term creep service components in power and petrochemical plants.
- How does Grade 911 differ from Grade 91?Grade 911 includes boron (B) and optimized N, V, Nb content, providing higher creep rupture strength and longer service life than Grade 91.
- What is the chemical composition of SA387 Gr 911 Cl 2?It has 9% Cr, 1% Mo, V, Nb, N, and Boron, designed for creep resistance at 650–700°C.
- What are the mechanical properties?Tensile 620–820 MPa, yield ≥440 MPa, elongation ≥18%, impact ≥27J, creep ≥120 MPa at 650°C (100,000 h).
- Is SA387 Gr 911 Cl 2 weldable?Yes, but requires strict preheating, low-hydrogen electrodes, and post-weld heat treatment (PWHT) for thick weldments.
- What industries use SA387 Gr 911 Cl 2?It is widely used in power generation, nuclear energy, oil & gas, and petrochemical industries.
- What is the service temperature range?Typically used between 550–700°C for long-term service.
- What is the difference between Class 1 and Class 2?Class 2 has higher strength requirements than Class 1, suitable for more demanding applications.
- Can it replace stainless steels in boilers?Yes, it provides better cost-performance than stainless steel for high-temperature pressure vessels, though not for corrosive acids.
- Yes, it provides better cost-performance than stainless steel for high-temperature pressure vessels, though not for corrosive acids.UT, impact, hardness, tensile, and creep rupture testing are standard for Grade 911.
Conclusion
ASME SA387 Grade 911 Class 2 (SA387 Gr 911 Cl 2) steel plates are the advanced generation of 9Cr alloy steels, specifically designed for ultra-supercritical boilers, steam piping, and high-temperature pressure vessels. With Boron-enhanced chemistry, superior creep rupture strength, and reliable weldability, they ensure safe and efficient performance at 650–700°C.
As a trusted SA387 Gr 911 Cl 2 supplier, SHH STEEL provides certified plates, global delivery, and project-proven reliability for the world’s most demanding energy projects.
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