ASTM A387 Grade 22 Class 1 (equivalent to ASME SA‑387 Gr.22 Cl.1) is a 2.25Cr‑1Mo chromium‑molybdenum alloy pressure‑vessel steel plate intended for welded boilers and pressure‑vessel equipment under mild‑to‑moderate elevated‑temperature service conditions. This grade shares identical chemical composition with Class 2, yet Class 1 delivers lower strength and superior ductility. It is not recommended for severe sour‑gas service rich in H₂S; Grade 22 Class 2 shall be selected for such harsh operating conditions. Per ASTM A387 requirements, the minimum tempering temperature shall be 1250 °F (675 °C).
GNEE Steel is an export‑oriented supplier specializing in ASME/ASTM alloy pressure‑vessel steel plates, with 18 years of experience serving global clients in petrochemical, power‑generation and general process‑equipment sectors.
Please submit your equipment drawings and service‑condition parameters to receive a free material‑selection assessment report. Our metallurgical engineers will verify whether A387 Gr22 Cl1 is suitable for your project at no charge.
High‑Temperature Service Performance of A387 Gr22 Class 1 Steel Plate
A387 Gr22 Class 1 exhibits stable high‑temperature oxidation resistance and moderate creep resistance under moderate thermal environments. Nevertheless, its performance falls short compared to Class 2 for heavy‑duty or hydrogen‑sulfide‑bearing sour‑hydrogen service.
Continuous safe operating temperature:
maximum long‑term service temperature of 520 °C; short‑term peak temperature up to 570 °C. Operation above this threshold elevates the risk of creep deformation.
Oxidation resistance:
oxidation weight gain reaches 0.41 mg/cm² after 1000 hours of continuous thermal exposure at 520 °C, substantially outperforming carbon steel plates.
Microstructural stability:
after tempering at minimum 1250 °F (approx. 677 °C), the material retains a stable tempered‑bainite microstructure and mitigates high‑temperature embrittlement risk during prolonged thermal exposure.
ASTM A387 Grade 22 Class 1 2.25Cr‑1Mo Pressure Vessel Alloy Steel Plate Specification
| Item | Details |
|---|---|
| Full Product Name | ASTM A387 Grade 22 Class 1 2.25Cr‑1Mo Pressure Vessel Alloy Steel Plate |
| Governing Standard | ASTM A387 / A387M, ASME SA‑387 / SA‑387M |
| Thickness Scope | Stock: 6‑120 mm; Custom rolling: 4.7 mm (3/16")‑280 mm |
| Width Range | 1500‑4400 mm |
| Length Range | 2800‑17500 mm |
| Usual Delivery Condition | Normalized & Tempered (N&T, primary delivery state); Quenched & Tempered upon purchaser's special approval |
| Optional Supplementary Tests | Charpy impact at specified temperature, SPWHT simulated post‑weld heat treatment, PMI, metallographic inspection |
| Export Seaworthy Packing | Moisture‑proof paper + anti‑rust PE film + steel band fastening + solid wooden pallets, edge corner protection, complete packing list attached |
ASTM A387 Grade 22 Class 1 Pressure Vessels Plate chemical composition
| Element | Heat Analysis | Product Analysis |
|---|---|---|
| C | 0.05‑0.15 | 0.04‑0.15 |
| Mn | 0.30‑0.60 | 0.25‑0.66 |
| Si | ≤0.50 | ≤0.50 |
| P | ≤0.025 | ≤0.025 |
| S | ≤0.025 | ≤0.025 |
| Cr | 2.00‑2.50 | 1.88‑2.62 |
| Mo | 0.90‑1.10 | 0.85‑1.15 |
ASTM A387 Grade 22 Class 1 boiler plate mechanical property
| Performance Item | ASTM A387 Gr.22 Class 1 | ASTM A387 Gr.22 Class 2 (Reference) |
|---|---|---|
| Tensile Strength, MPa | 415‑585 | 515‑690 |
| Min Yield Strength (0.2 % offset), MPa | 205 | 310 |
| Min Elongation (50 mm gauge length) | 18 % | 18 % |
| Reduction of Area (round specimen), min | 45 % | 45 % |
| Reduction of Area (flat specimen), min | 40 % | 40 % |
| Typical Brinell Hardness HB | 170‑195 | 180‑210 |
| Max Hardness after SPWHT | ≤220 HB | ≤220 HB |
ASTM A387 Grade 22 Class 1 boiler steel plate size range
| 2" | 1/2" | 3/16" | 1" | 4" |
| 1-1/2" | 3/8" | 1/8" | 3/4" | 3" |
| 2-1/2" | 5/8" | 1/4" | 1-1/4" |
ASTM A387 Grade 22 Class 1 PVQ plate Tolerance Chart
| Nominal thickness | within a plate Maximum thickness difference | |||||
| Nominal width | ||||||
| > 600 < 2000 | > 2000 < 2500 | > 2500 < 3000 | > 3000 < 3500 | > 3500 < 4000 | > 4000 | |
| > 150 < 250 | 1.4 | 1.5 | 1.6 | 1.6 | 1.7 | - |
| > 3 < 5 | 0.8 | 0.9 | 0.9 | - | - | - |
| > 80 < 150 | 1.3 | 1.4 | 1.5 | 1.5 | 1.6 | 1.7 |
| > 5 < 8 | 0.9 | 0.9 | 1.0 | 1.0 | - | - |
| > 15 < 25 | 1.0 | 1.1 | 1.2 | 1.2 | 1.3 | 1.4 |
Typical Applications of ASTM A387 Gr22 Class 1 Alloy Steel Plate
Suited for medium‑and‑low‑pressure equipment operating under mild elevated‑temperature, non‑sour‑gas conditions.
Power Industry: medium‑pressure boiler drums, conventional waste‑heat exchangers, auxiliary steam piping and header assemblies for thermal power plants.
General Petrochemical: medium‑temperature surge vessels with non‑sour media, common heat‑exchanger shells, non‑hydrogenation process reaction vessels.
Chemical Processing: medium‑temperature reactors, heat‑exchange equipment without severe hydrogen‑sulfide corrosion risk.
General‑Industrial Pressure Components: boiler attachments, pressure flanges, pipe supports and blanks for heavy‑duty high‑temperature structural parts.
Material Sourcing & Procurement Guidelines
- Specify exact grade: designate ASTM A387 Grade 22 Class 1 on purchase orders. Do not confuse it with Class 2. Though chemically identical, they feature substantial differences in mechanical‑property requirements and associated testing protocols.
- Define heat‑treatment delivery condition: default delivery condition is Normalized and Tempered (N&T). Quenched and Tempered (Q&T) condition must be explicitly stated within procurement documents if required.
- Confirm test scope: standard supply includes tensile test, hardness test and 100 % UT (Ultrasonic Testing) complying with SA‑578. Supplementary tests such as Charpy V‑notch impact test, simulated PWHT and PMI (Positive Material Identification) verification shall be listed as additional inspection items when needed.
- Service‑condition screening: select Class 2 instead of Class 1 for equipment exposed to H₂S‑bearing sour gas, high‑partial‑pressure hydrogen environments or thick‑wall pressure vessels under high design pressure.
- Documentation requirements: EN 10204 3.2 MTC (Material Test Certificate) with heat‑number traceability shall be furnished for acceptance of export‑oriented projects.
For project‑based bulk‑purchase customers, third‑party witnessed shop inspection is available upon application. For orders exceeding 10 metric tons, GNEE Steel coordinates the full inspection procedure with no extra administrative fees applied.
Why Choose us?
Machining Services: flame / plasma cutting, bevel milling, levelling and blanking, with dimensional tolerance controlled within ±1.2 mm.
Inspection Coordination: arrange third‑party laboratory testing for impact test, PMI and metallographic analysis per customer requirements.
Sample Service: small‑size test samples can be provided; international freight cost shall be borne by the customer.
FAQ
What is the core difference between A387 Grade 22 Class 1 vs Class 2?
The core difference between ASTM A387 / ASME SA387 Grade 22 Class 1 and Class 2 is their mechanical strength and the heat treatment used to achieve it. Both classes share an identical chemical makeup (2.25% Chromium and 1% Molybdenum), but Class 2 is processed to offer significantly higher tensile and yield strength.
Is low‑temperature Charpy impact test mandatory for A387 Grade 22 Class 1?
No, a low-temperature Charpy V-notch (CVN) impact test is not mandatory in the base material specification for ASTM A387 / ASME SA387 Grade 22 Class 1. The standard specification covers chromium-molybdenum alloy steel plates intended primarily for elevated-temperature and high-pressure service, meaning standard production requires only chemical analysis and room-temperature tensile testing.
Is PWHT (post‑weld heat treatment) necessary for welding A387 Grade 22?
Yes, post-weld heat treatment (PWHT) is generally mandatory for welding ASTM A387 Grade 22 (a 2.25Cr–1Mo low-alloy steel, classified under P-No. 5A) under major construction codes like ASME Boiler and Pressure Vessel Code Section VIII, though specific exemptions can sometimes apply based on nominal thickness, pipe/tube dimensions, or specific code rules.
Can A387 Grade 22 Class 1 plates be used for H₂S sour‑gas environment?
ASTM A387 Grade 22 Class 1 plates can be used in H₂S sour-gas environments, provided they meet specific hardness, heat treatment, and supplemental testing limits required by standards like NACE MR0175 / ISO 15156. Its 2.25% chromium and 1% molybdenum composition offers good high-temperature and corrosion resistance.
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