ASME SA387 Grade 911 Class 2 (SA387 Gr 911 Cl 2) Steel Plate

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.

asme sa387 grade 2 class 2	sme sa387 grade 11 class 2	asme sa387 grade 911 class 2
asme sa387 grade 91 class 2	asme sa387 grade 22 class 2	asme sa387 grade 21 class 2
asme sa387 grade 22l class 1	asme sa387 grade 12 class 1	asme sa387 grade 11 class 1
asme sa387 grade 9 class 2	asme sa387 grade 22 class 1	asme sa387 grade 12 class 2
asme sa387 grade 9 class 1	asme sa387 grade 5 class 2	asme sa387 grade 2 class 1
asme sa387 grade 5 class 1	asme sa387 grade 21 class 1	asme sa387 grade 21l class 1

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.

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.