Specifications for ASTM A387 Gr.91 Plates

The specifications below cover standards, sizes, finishes, and more for this pressure vessel grade steel.

ASTM A387 Gr.91 plates conform to ASTM A387/ASME SA-387 and are supplied in hot-rolled, normalised, and tempered formats.

Parameter Details
Standard ASTM A387 / ASME SA-387
Class Class 2
Length Range 3000 mm to 15000 mm
Surface Finish Hot Rolled, Sandblasted, Mill Finish

Available Sizes & Dimensions

The table below displays the standard sizes and dimensions of ASTM A387 Grade 91 plates stocked for boiler and pressure vessel fabrication.

Parameter Specification
Thickness 5 mm to 300 mm (0.2 in. to 11.8 in.)
Width 1,000 mm to 4,500 mm (39.4 in. to 177.2 in.)
Length 3,000 mm to 18,000 mm (118.1 in. to 708.7 in.)

ASTM A387 Grade 91 Plates Price

ASTM A387 Grade 91 plates cost between ₹200 and ₹500 per kg in India. In international markets, prices are usually $2.50 to $6.50 per kg on an FOB basis, with Class 2 and heat-treated plates costing more. The final price depends on thickness, width, length, order quantity, heat treatment, and tests such as impact, HIC or ultrasonic examination, as well as delivery terms like FOB, CIF and CFR, which affect landed cost.

Chemical Composition of ASTM A387 Grade 91 Plates

The table below lists the full chemical composition per heat analysis.

Vanadium and niobium form hard particles that stabilise the steel structure. Nitrogen strengthens the material. At the same time, lower amounts of phosphorus, sulfur, aluminium, and titanium help prevent it from brittling when used.

Carbon C
0.08 - 0.12%
Manganese Mn
0.30 - 0.60%
Phosphorus P
0.020% max
Sulfur S
0.010% max
Silicon Si
0.20 - 0.50%
Chromium Cr
8.00 - 9.50%
Molybdenum Mo
0.85 - 1.05%
Nickel Ni
0.40% max
Vanadium V
0.18 - 0.25%
Niobium Nb
0.06 - 0.10%
Nitrogen N
0.030 - 0.070%
Aluminium Al
0.02% max
Titanium Ti
0.01% max
Zirconium Zr
0.01% max

Mechanical Properties of ASTM A387 Grade 91 Class 2 Plates

The table below outlines the key mechanical properties of ASTM A387 Grade 91 as specified under ASTM A387 / ASME SA-387.

Grade 91 plates are supplied in a normalised and tempered condition to achieve the required creep strength.

85-110 / 585-760
ksi / MPa
Tensile Strength
60 / 415
ksi / MPa
Yield Strength, 0.2% Offset (min)
18
%
Elongation in 50 mm (2 in.), min

ASTM A387 Gr.91 Class 2

Property Value
Tensile Strength 585 to 760 MPa (85 to 110 ksi)
Yield Strength (0.2% offset), min 415 MPa (60 ksi)
Elongation in 50 mm (2 in.), min 18%
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Equivalent Designations for ASTM A387 Grade 91 Plates

The table below maps the global equivalent designations for ASTM A387 Grade 91 plates across multiple nations for easy cross-reference.

Standard Designation
ASTM A387 / ASME SA-387 Grade 91 Class 2
EN 10028-2 X10CrMoVNb9-1
Werkstoff Nr. 1.4903
DIN X10CrMoVNb9-1
JIS G 3203 SFVAF 28
BS Grade 91
ISO 9328-2 X10CrMoVNb9-1
UNS K91560

Applications of ASTM A387 Grade 91 Plates

ASTM A387 Grade 91 plates are primarily used for welded boilers and pressure vessels in elevated-temperature service. The following subsections cover specific applications across key sectors.

Power Generation

Grade 91 alloy steel plates are standard materials for headers, steam drums and superheater components in coal-fired and combined-cycle thermal power plants.

Oil & Gas

Refinery reactors, heat exchangers and high-temperature process columns rely on A387 Gr.91 plates. The 9% chromium content provides oxidation resistance in hydrogen-rich refinery environments.

Petrochemical & Chemical Processing

Reactor vessels and distillation columns handling corrosive feedstocks at elevated temperatures use these pressure vessel plates. Grade 91 suits environments where both mechanical loading and chemical attack are present simultaneously.

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ASTM A387 Grade 91 vs Other A387 Grades

The two tables below make it easier for buyers to choose the right grade for their operating conditions.

Grade 91 vs Grade 22

ASTM A387 Grade 91 plate handles higher temperatures than ASTM A387 Grade 22 plate, but it needs stricter welding and heat treatment.

Property ASTM A387 Grade 91 ASTM A387 Grade 22
Chromium Content 9.00% 2.25%
Molybdenum Content 0.85 – 1.05% 1.00%
Micro-Alloying Additions Vanadium, Niobium, Nitrogen None
Max Service Temperature Above 600°C Up to 565°C
Allowable Stress (High Temp) Superior Lower
Wall Thickness Required Thinner sections possible Thicker sections needed
Creep Rupture Strength Higher Moderate
Welding Controls Strict (mandatory PWHT 730–770°C) Less stringent
Typical Application Supercritical boiler systems Power generation pressure vessels
Cost Higher More economical
Best Chosen When High temp, high-pressure service needed Moderate temperature applications

Grade 91 vs Grade 9

ASTM A387 Grade 91 plate and ASTM A387 Grade 9 plate have similar basic chemistry, but differ greatly in alloying elements, creep strength and use.

Property ASTM A387 Grade 91 ASTM A387 Grade 9
Chromium Content 9.00% 9.00%
Molybdenum Content 0.85 – 1.05% 0.90 – 1.10%
Micro-Alloying Additions Vanadium, Niobium, Nitrogen None
Creep Rupture Strength Superior Lower
Max Service Temperature Above 600°C Up to 540°C
Long-Term High-Temp Service Highly suitable Not recommended
Typical Application Supercritical & ultra-supercritical power plants Moderate high-temperature service
Fabricability More complex (strict PWHT required) Relatively easier
Cost Higher Lower
Best Chosen When Maximum creep life is required Budget-conscious, lower temp applications

Shipping & Packaging

Main export packaging setup Heavy-duty wooden boxes Packing
Export Packaging Standard

We strictly follow seaworthy export handling standards to protect ASTM A387 Grade 91 Plates from transit damage, moisture ingress, and surface contamination during long-distance dispatch.

  • Heavy-duty wooden boxes with moisture barrier lining
  • HDPE stretch film wrapping on all bundles
  • Plastic end caps on threaded and plain-end plate
  • Silica gel desiccants to minimize moisture exposure
  • ISPM-15 fumigated wooden packaging for export
shipping preparation Plate Bundle Yard Staging
Shipping packaging Container End-Cap Protection
Shipping stock Wrapped Export-Ready Bundles

We Export Worldwide

Sachiya Steel International supplies ASTM A387 Grade 91 plates to major industrial markets across North America, Europe, the Middle East, Asia and Africa with export-ready documentation and logistics support.

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Frequently Asked Questions: ASTM A387 Gr.91 Plates

What are ASTM A387 grade 91 plates used for?+
ASTM A387 Grade 91 plates are used for welded boilers and pressure vessels designed for elevated-temperature service. Primary industries include power generation, oil and gas refining, and petrochemical processing.
What is the difference between class 1 and class 2 for A387 grade 91 plates?+
ASTM A387 Grade 91 is available only as Class 2 per the ASTM specification. Class 2 requires normalised and tempered heat treatment, with a minimum tensile strength of 585 MPa (85 ksi) and minimum yield of 415 MPa (60 ksi).
What thickness is available for ASTM A387 grade 91 plates?+
A387 Grade 91 plates are available in thicknesses from 5 mm to 300 mm, widths of 1,000 to 4,500 mm and lengths of 3,000 to 18,000 mm. Custom dimensions can be supplied on request.
What is the equivalent standard for ASTM A387 grade 91 plates?+
ASTM A387 Grade 91 is adopted by ASME as SA-387 Grade 91. The European equivalent is EN 10028-2 grade X10CrMoVNb9-1 (W.Nr. 1.4903). In Japan, the related designation is SFVAF 28 under JIS G 3203.
What is the price of ASTM A387 grade 91 plates?+
ASTM A387 Grade 91 plates typically range from ₹200 to ₹500 per kg in India, and internationally, it ranges from $2.50 to $6.50 per kg. Final price depends on thickness, quantity, testing requirements and delivery terms. Contact us for a current quotation.
Can ASTM A387 grade 91 plates be welded?+
A387 Grade 91 plates have good weldability when proper procedures are followed. Preheating to 200 to 300 °C is required before welding. Mandatory post-weld heat treatment (PWHT) at 730 to 770 °C restores mechanical properties and prevents hydrogen cracking.
What is the difference between type 1 and type 2 for ASTM A387 grade 91 plates?+
Type 2 has restricted composition limits compared to Type 1, specifically designed to improve creep resistance at elevated temperatures. For long-term high-temperature service, Type 2 is the preferred choice.
What testing is available for ASTM A387 grade 91 plates?+
Available testing includes tensile tests, Charpy V-notch impact tests, ultrasonic examination, positive material identification (PMI), HIC testing, drop-weight tests, vacuum treatment, and simulated post-weld heat treatment testing. Mill test certificates are provided with every order.

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