ASTM A387 Grade 22 Class 1 is a specific type of chromium-molybdenum (Cr-Mo) alloy steel plate designed for welded boilers and high-temperature pressure vessels, offering good high-temperature strength and corrosion resistance, with "Class 1" indicating standard tensile strength levels and suitability for applications where lower-temperature impact toughness isn't critical, unlike the stronger Class 2. It contains approximately 2.25% chromium and 1.00% molybdenum, making it ideal for petrochemical, oil & gas, and power generation industries.
Standard Specification For ASTM A387 Gr.22 Class 1 Alloy Steel Plate
Specifications : ASTM A387 / ASME SA387
Standard : ASTM, ASME and API
Thickness : 5mm-150mm
Specialize : Shim Sheet, Perforated Sheet, B. Q. Profile.
Form : Coils, Foils, Rolls, Plain Sheet, Shim Sheet, Perforated Sheet, Chequered Plate, Strip, Flats, Blank (Circle), Ring (Flange)
Finish : Hot rolled plate (HR), Cold rolled sheet (CR), 2B, 2D, BA NO(8), SATIN (Met with Plastic Coated)
Hardness : Soft, Hard, Half Hard, Quarter Hard, Spring Hard etc.
Equivalent Grades Alloy Steel ASTM A387 Grade 22 Class 1 Plate
| GRADE | UNS NO | DIN | BS | EN |
| Gr 22 Class 1 | - | 10 CRMO910 | 622-515B | 10 CRMO910 |
Chemical Composition of ASTM A387 Gr.22 Class 1 Alloy Steel Plate
| Grade | C | Mn | P | S | Si | Cr | Mo |
| Gr 22 | 0.04 - 0.15 | 0.25 - 0.66 | 0.035 | 0.035 | 0.035 | 0.5 max | 0.85 - 1.15 |
Mechanical Properties of Alloy Steel Grade 22 Class 1 Plate
| Tensile Strength (ksi) | Tensile Strength (MPa) | Yield Strength (ksi) | Yield Strength (MPa) | Elongation in 50mm (%) | Elongation in 50mm (%) |
| 60-85 | 415-585 | 30 | 205 | 18 | 45 |
processing
1. Heat Treatment (Thermal Processing)
Under ASTM A387, all plates must be thermally treated using one of the following methods:
Annealing: Full softening for maximum ductility.
Normalizing and Tempering (N+T): The most common delivery condition to achieve a balance of strength and toughness.
Accelerated Cooling (Quenching and Tempering - Q+T): Permitted with purchaser agreement; involves liquid quenching or air blasting from the austenitizing temperature followed by tempering.
Tempering Temperature: For Grade 22, the minimum tempering temperature must be 1250°F (675°C).
2. Fabrication and Welding
The high chromium and molybdenum content requires strict control during fabrication to prevent cracking and ensure structural integrity.
Preheating: Essential before welding, typically recommended at more than 150°C to prevent hydrogen-induced cracking.
Post-Weld Heat Treatment (PWHT): Critical for reducing residual stresses and improving toughness. Standard procedures include slow cooling after keeping the welded portion at 300–350°C for 10 minutes or more, often followed by full PWHT per code.
Welding Processes: Commonly used methods include GTAW (Gas Tungsten Arc Welding), SMAW (Shielded Metal Arc Welding), and SAW (Submerged Arc Welding).
Simulated PWHT (SPWHT): Suppliers can perform third-party simulated heat treatments to ensure the material maintains its mechanical properties after the actual fabrication heat cycles.
3. Mechanical Requirements (Class 1)
Class 1 designates a specific tensile strength range, which is lower than Class 2:
Tensile Strength: 60 to 85 ksi [415 to 585 MPa].
Yield Strength (min): 30 ksi [205 MPa].
Elongation (min in 2 in.): 18%.
Key Applications
Boilers & Heat Exchangers:
Its resistance to scaling, deformation, and high temperatures makes it ideal for efficient heat transfer in boilers, superheaters, and heat recovery systems. The material maintains structural stability under prolonged thermal cycling, ensuring reliable performance and reducing maintenance needs in power and industrial boiler applications.
Oil & Gas Industry:
Used in equipment for oil refineries, natural gas processing, and petrochemical plants, including reactors, separators, and pressure vessels. Its ability to withstand hydrogen attack and high-temperature service makes it suitable for handling hydrocarbons and process fluids in demanding refinery and gas processing environments.
Power Generation:
Components for power plants requiring high-temperature strength and creep resistance, such as boiler headers, steam pipes, and pressure parts. The steel's creep properties ensure long service life even under continuous high-pressure and high-temperature conditions typical of thermal power generation.
Chemical Processing:
Equipment in chemical plants where elevated temperatures and corrosive environments are present, including hydrogenation reactors and process vessels. Its combination of toughness, weldability, and resistance to high-temperature degradation makes it a preferred choice for handling aggressive chemical streams and ensuring operational safety.
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Is A387 Grade 22 Class 1 weldable?
Yes, it is weldable via common methods like SMAW, GTAW, and GMAW. Preheating (150-260°C) and post-weld heat treatment (PWHT) are necessary to prevent cold cracking and relieve residual stress.
What is the corrosion resistance of A387 Grade 22 Class 1?
It resists oxidation and sulfidation in high-temperature environments. However, it is not suitable for strong acidic or chloride-containing media, as it lacks sufficient corrosion resistance in such conditions.
What industries mainly use A387 Grade 22 Class 1?
It is widely applied in petrochemical, refinery, power generation (boilers, turbines), and chemical processing industries, primarily for pressure vessels, heat exchangers, and piping systems.
What is the ductility of A387 Grade 22 Class 1?
It has good ductility with a minimum elongation of 22% in 50mm. This property allows it to withstand slight deformation without cracking, ensuring safety in pressure-bearing applications.
Can A387 Grade 22 Class 1 be cold-formed?
It can be cold-formed with caution, but preheating is recommended for thick plates to avoid cracking. Post-forming heat treatment is needed to restore mechanical properties and eliminate residual stress.
How does A387 Grade 22 Class 1 perform vs. A480 430 stainless steel?
430 is ferritic stainless steel with 17% Cr, better corrosion resistance but poorer creep strength. Grade 22 is designed for high-temperature pressure vessels, while 430 is for decorative or mild corrosive parts.
Compare A387 Grade 22 Class 1 with A1018 carbon steel.
A1018 is low-carbon steel for general use, lacking high-temperature resistance. Grade 22's Cr-Mo composition provides superior creep and oxidation resistance, making it fit for high-temperature pressure applications.
What is the coefficient of thermal expansion of A387 Grade 22 Class 1?
It has a linear thermal expansion coefficient of 11.7×10⁻⁶/°C (20-100°C). This needs consideration in design to avoid thermal stress caused by temperature changes.
What defects should be avoided in A387 Grade 22 Class 1 production?
Key defects to avoid include porosity, inclusions, and intergranular cracking. Strict control of smelting and heat treatment processes ensures the material meets pressure vessel quality standards.
What is the difference between A387 Grade 22 Class 1 and Class 2?
Class 1 requires normalizing + tempering, while Class 2 allows quenching + tempering. Class 2 has higher strength but similar toughness. Class 1 is more commonly used for general high-temperature pressure vessels.