ASME SA387 Grade 91 Class 2 (SA387 Gr 91 Cl 2) Steel Plate

What is ASME SA387 Grade 91 Class 2?

ASME SA387 Grade 91 Class 2 (SA387 Gr 91 Cl 2) alloy steel plates are an advanced 9Cr-1Mo-V grade in the ASME SA387 specification, designed for extreme thermal and pressure conditions. This SA387 Gr 91 Cl 2 grade is quenched and tempered, offering tensile strength (585–760 MPa) and yield strength (minimum 415 MPa) with outstanding creep rupture strength and resistance to oxidation.

The SA387 Grade 91 Class 2 plates are manufactured using precise quenching and tempering heat treatment, stabilizing the martensitic microstructure for superior toughness and longevity at ultra-high temperatures, making them essential for supercritical boilers, power plant piping, and refinery systems facing intense operational demands.

SHH STEEL supplies ASME SA387 Gr 91 Cl 2 alloy steel plates in a wide size range from 6mm to 100mm thickness, up to 4600mm width, and up to 12000mm length, meeting both ASME Section VIII pressure vessel code and customer-specific requirements.

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

As a production and export expert at SHH STEEL, we can confirm that ASME SA387 Grade 91 Class 2 alloy steel plates are governed by ASME SA-387/SA-387M, the standard for pressure vessel plates, alloy steel, chromium-molybdenum.

This specification outlines requirements for quenched and tempered plates for elevated temperature service, ensuring suitability for welded pressure vessels and boilers. SHH STEEL complies fully with this standard, providing plates in quenched and tempered conditions to optimize mechanical properties.

The specification supports thicknesses from 6mm to 100mm, widths up to 4600mm, and lengths to 12000mm, with custom dimensions available for vessel designs. Ultrasonic examination per ASME SA-578 Class 1 detects laminations, guaranteeing defect-free material, while dual certification with ASTM A387 Gr 91 Cl 2 or EN 10028-2 is offered for international compatibility.

This makes our ASME SA387 Gr 91 Cl 2 plates a reliable choice for global buyers, supported by mill test certificates for complete traceability.

Specification Element	Requirement	SHH STEEL Compliance	Keywords
Primary Standard	ASME SA-387/SA-387M	ASME Section VIII	SA387 Gr 91 Cl 2 specification
Thickness Range	6mm-100mm (custom)	Mill Test Certificate	SA387 Gr 91 Cl 2 dimensions
Width/Length	Up to 4600mm / 12000mm	Custom fabrication available	SA387 Gr 91 Cl 2 size options
Ultrasonic Testing	No laminations >0.25% thickness	Class 1 per ASME SA-578	SA387 Gr 91 Cl 2 inspection
Heat Treatment	Quenched and tempered	870-900°C quench, 760-790°C temper	SA387 Gr 91 Cl 2 heat treat

Chemical Composition

At SHH STEEL, we ensure the chemical composition of ASME SA387 Grade 91 Class 2 is tightly controlled per ASME SA-387/SA-387M to guarantee ultra-high temperature stability and weldability.

The carbon content is 0.08-0.12% for optimal hardenability, while manganese (0.30-0.60%) and silicon (≤0.50%) aid deoxidation. Phosphorus and sulfur are limited to 0.020% max each to prevent cracking, with chromium (8.00-9.50%), molybdenum (0.85-1.05%), vanadium (0.18-0.25%), niobium (0.06-0.10%), and nitrogen (0.03-0.07%) ensuring precipitation strengthening and creep resistance.

Our testing per ASME SA-350 maintains low impurities. Melt analysis (heat analysis) and product analysis differ slightly with tolerances. Melt analysis is stricter for ladle chemistry, while product analysis allows variation for finished plates.

This ensures consistency, making ASME SA387 Gr 91 Cl 2 plates a reliable choice for buyers searching for “ASME SA387 Gr 91 Cl 2 chemical composition.”

Element	Melt Analysis (%)	Product Analysis (%)	Standard Limit	Test Method	Role	Keywords
Carbon (C)	0.08-0.12	0.07-0.13	0.08-0.12	ASME SA-350	Hardenability	SA387 Gr 91 Cl 2 carbon
Manganese (Mn)	0.30-0.60	0.25-0.66	0.30-0.60	ASME SA-350	Toughness	SA387 Gr 91 Cl 2 manganese
Phosphorus (P)	≤0.020	≤0.020	0.020 max	ASME SA-350	Reduces brittleness	SA387 Gr 91 Cl 2 phosphorus
Sulfur (S)	≤0.020	≤0.020	0.020 max	ASME SA-350	Improves weldability	SA387 Gr 91 Cl 2 sulfur
Silicon (Si)	≤0.50	≤0.54	0.50 max	ASME SA-350	Deoxidation	SA387 Gr 91 Cl 2 silicon
Chromium (Cr)	8.00-9.50	7.90-9.60	8.00-9.50	ASME SA-350	Corrosion resistance	SA387 Gr 91 Cl 2 chromium
Molybdenum (Mo)	0.85-1.05	0.80-1.10	0.85-1.05	ASME SA-350	Creep resistance	SA387 Gr 91 Cl 2 molybdenum
Vanadium (V)	0.18-0.25	0.16-0.27	0.18-0.25	ASME SA-350	Precipitation strengthening	SA387 Gr 91 Cl 2 vanadium
Niobium (Nb)	0.06-0.10	0.05-0.11	0.06-0.10	ASME SA-350	Grain refinement	SA387 Gr 91 Cl 2 niobium
Nitrogen (N)	0.03-0.07	0.02-0.08	0.03-0.07	ASME SA-350	Nitride formation	SA387 Gr 91 Cl 2 nitrogen

Mechanical Properties

As a production and export expert at SHH STEEL, we can assure you that ASME SA387 Grade 91 Class 2 pressure vessel steel plates deliver strong mechanical properties, tested per ASME SA-370 for tensile/yield, ASME SA-23 for impact, and ASME SA-466 for fatigue.

With a minimum yield strength of 415 MPa and tensile range of 585-760 MPa, these plates support high load-bearing capacity, while 18% elongation ensures ductility for forming. The impact energy of 27J typical prevents brittle failure, and the modulus of elasticity (200 GPa) provides structural stability.

The fatigue limit (250 MPa est.) varies with surface finish, optimized by our grinding process. This makes ASME SA387 Gr 91 Cl 2 plates a reliable choice for buyers searching for “ASME SA387 Gr 91 Cl 2 mechanical properties.”

Property	Value	Test Method	Temperature (°C)	Thickness Effect	Keywords
Tensile Strength	585-760 MPa	ASME SA-370	Ambient	-5% >100mm	SA387 Gr 91 Cl 2 tensile
Yield Strength	415 MPa (min)	ASME SA-370	Ambient	Stable to 100mm	SA387 Gr 91 Cl 2 yield
Elongation	18% (min)	ASME SA-370	Ambient	16-20% (6-25mm)	SA387 Gr 91 Cl 2 elongation
Impact Energy	27J typical	ASME SA-23	Ambient	All thicknesses	SA387 Gr 91 Cl 2 impact
Modulus of Elasticity	200 GPa	ASME SA-111	Ambient	Constant	SA387 Gr 91 Cl 2 modulus
Fatigue Limit	250 MPa (est.)	ASME SA-466	Ambient	Varies with surface	SA387 Gr 91 Cl 2 fatigue

Heat Treatment

SHH STEEL provides ASME SA387 Gr 91 Cl 2 plates in normalized, quenched, and tempered condition as standard, normalized at 1040-1090°C, quenched at 870-900°C, and tempered at 760-790°C to achieve optimal creep strength for ultra-high temperature applications.

Factor Value/Condition Standard Recommended Keywords

Heat Treatment Normalize 1040-1090°C, Quench 870-900°C, Temper 760-790°C ASME SA387 Q&T standard SA387 Gr 91 Cl 2 heat treat

Factor	Value/Condition	Standard	Recommended	Keywords
Heat Treatment	Normalize 1040-1090°C, Quench 870-900°C, Temper 760-790°C	ASME SA387	Q&T standard	SA387 Gr 91 Cl 2 heat treat

Delivery

Plates are delivered with normalized options for flexibility, including heat numbers for traceability. Our global shipping ensures timely delivery, with 3-7 days to Asia for standard orders.

Factor	Value/Condition	Standard	Recommended	Keywords
Delivery Condition	Quenched & Tempered	ASME SA-20	Transit 3-7 days Asia	SA387 Gr 91 Cl 2 delivery

Tolerances

We maintain strict tolerances per ASME SA-20: thickness ±1.5mm for <40mm and ±2.0mm for thicker up to 100mm; width/length ±10mm (or ±5mm custom); flatness 3mm per meter. EN 10029 Class B available for European compatibility.

Factor	Value/Condition	Standard	Recommended	Keywords
Thickness Tolerance (<40mm)	±1.5mm	ASME SA-20	6-40mm	SA387 Gr 91 Cl 2 tolerance
Flatness	3mm per meter	ASME SA-20	All	SA387 Gr 91 Cl 2 flatness

Weldability

ASME SA387 Gr 91 Cl 2 is highly weldable with low CE ≤0.45 per AWS D1.1. SHH STEEL recommends preheating at 200-250°C for thicknesses over 25mm to prevent hydrogen-induced cracking, with post-weld heat treatment (PWHT) at 730-770°C for stress relief. Supported processes include GTAW, SMAW, and GMAW with E9018-B3 filler (AWS A5.1), achieving 90-95% joint efficiency per ASME Section IX. Low sulfur (≤0.020%) reduces hot shortness, and 18% elongation ensures ductility. Testing includes bend tests (ASTM E190) for 3t radius and ultrasonic for weld integrity per ASTM A435.

Weldability Factor	Value/Condition	Standard	Recommended Process	Keywords
Carbon Equivalent (CE)	≤0.45	AWS D1.1	GTAW, SMAW	SA387 Gr 91 Cl 2 weldability
Preheating (°C)	200-250 (>25mm)	ASME Section IX	GMAW	SA387 Gr 91 Cl 2 welding
PWHT (°C)	730-770	ASME SA-20	All	SA387 Gr 91 Cl 2 heat treat
Filler Metal	E9018-B3	AWS A5.1	SMAW	SA387 Gr 91 Cl 2 welding rod
Bend Test Radius (mm)	3t (t=thickness)	ASTM E190	All	SA387 Gr 91 Cl 2 bend test

Equivalent Grades

Global equivalents for ASME SA387 Gr 91 Cl 2 facilitate international projects, offering similar tensile and yield properties for pressure vessel use. For example, X10CrMoVNb9-1 (EN 10028-2) is a European equivalent with 585-760 MPa tensile and 415 MPa yield, suitable for EU power plants. STBA28 (JIS G4109) serves Japanese applications with 585-760 MPa tensile and 415 MPa yield, ideal for high-strength vessels. 10Cr9Mo1VNb (GB/T 713) is the Chinese standard equivalent, providing 585-760 MPa tensile and 415 MPa yield for cost-effective high-temperature equipment in Asian markets. These equivalents ensure cross-compatibility, allowing buyers to substitute ASME SA387 Gr 91 Cl 2 plates seamlessly in global supply chains.

Grade	Standard	Tensile (MPa)	Yield (MPa)	Elongation (%)	Impact (J @ -20°C)	Keywords
SA387 Gr 91 Cl 2	ASME SA-387/SA-387M	585-760	415	18	27	SA387 Gr 91 Cl 2 equivalent
X10CrMoVNb9-1	EN 10028-2	585-760	415	20	27	SA387 Gr 91 Cl 2 EN grade
STBA28	JIS G4109	585-760	415	20	27	SA387 Gr 91 Cl 2 JIS grade
10Cr9Mo1VNb	GB/T 713	585-760	415	19	27	SA387 Gr 91 Cl 2 GB grade
A387 Gr.91 Cl.2	ASTM A387	585-760	415	18	34	SA387 Gr 91 Cl 2 alternative
A516 Gr.60	ASTM A516	415-550	220	21	27	SA387 Gr 91 Cl 2 similar alt

Supplementary Requirements

Supplementary requirements for ASME SA387 Gr 91 Cl 2 pressure vessel steel plates enhance performance for specialized applications. They offer buyers tailored options.

These include ultrasonic testing (Class 1 per ASTM A435 for no laminations >0.25% thickness). Charpy impact at -50°C (27J min per ASTM A20 for cold service) is another. Heat analysis per heat number (ASTM E350 for traceability) ensures quality. Product analysis allows ±0.02% tolerance on elements. Shot blasting to Sa 2.5 (50-100μm profile per ISO 8501-1) is available for surface preparation.

Applications

Application	Service Temp	Industry
Boilers	550–650°C	Power generation
Pressure Vessels	Elevated temp	Petrochemical
Heat Exchangers	High stress	Refinery & LNG
Nuclear Components	Extreme service	Nuclear energy
Steam Piping	Superheaters, reheaters	Thermal power
Offshore Platforms	Harsh service	Oil & gas

Why Choose SHH STEEL

15+ years experience in supplying Grade 91 alloy steel plates
Large global stock, quick delivery
Mill test certificates EN 10204 3.1 / 3.2 available
Customized cutting, beveling, and machining
Strong track record in power generation and petrochemical projects

FAQ

What is ASME SA387 Grade 91 Class 2 used for?

It is used for high-temperature pressure vessels, steam boilers, nuclear reactors, petrochemical processing units, and heat exchangers, where long-term creep resistance is critical.

How is Grade 91 different from Grade 22?

Grade 22 (2.25Cr-1Mo) is suitable for 500–600°C, while Grade 91 (9Cr-1Mo-V-Nb) is engineered for higher strength and creep resistance up to 650°C.

What is the chemical composition of SA387 Gr 91 Cl 2?

It includes 9% Cr, 1% Mo, 0.18–0.25% V, 0.06–0.10% Nb, and 0.03–0.07% N, providing superior creep strength.

What mechanical properties does Grade 91 provide?

Tensile 585–760 MPa, yield ≥415 MPa, elongation ≥18%, hardness 200–250 HB, and creep rupture ≥100 MPa at 600°C for 100,000 h.

Is SA387 Grade 91 weldable?

Yes, but requires strict preheat (200–300°C), low-hydrogen consumables, and post-weld heat treatment. Improper welding may cause cracking.

What are the equivalents to SA387 Gr 91 Cl 2?

EN X10CrMoVNb9-1, DIN X10CrMoVNb9-1, JIS 9Cr-1Mo-V-Nb, GB 10Cr9Mo1VNb.

What thicknesses are available?

6–150mm standard supply, up to 180mm upon request.

What industries use SA387 Gr 91 Cl 2 most?

Power generation, nuclear energy, petrochemical refineries, and LNG plants.

What testing is typically required?

Ultrasonic testing, Charpy impact at -20°C, creep rupture testing, and third-party inspection.

Can SA387 Grade 91 be used in cryogenic applications?

No. It is designed for high-temperature service, not low-temperature cryogenic conditions.

Why choose Grade 91 instead of stainless steels?

Grade 91 provides better creep strength and cost-efficiency for boilers and pressure vessels compared to stainless steel, which is more expensive.

Conclusion

ASME SA387 Grade 91 Class 2 (SA387 Gr 91 Cl 2) steel plates are premium chrome moly alloy steel plates with superior creep resistance, oxidation resistance, and weldability. Designed for high-pressure boilers, nuclear reactors, and petrochemical vessels, they are the benchmark alloy for high-temperature performance.

With extensive stock and global delivery, SHH STEEL is a trusted supplier of SA387 Gr 91 Cl 2 steel plates, offering certified quality and reliable service for your projects.