ASTM A387 Grade 22 Class 1 is a chromium-molybdenum alloy steel plate designed for use in welded pressure vessels and high-temperature service. It belongs to the family of heat-resistant alloy steels known for their good creep strength and resistance to hydrogen attack at elevated temperatures. Class 1 designation indicates a higher level of toughness requirement compared to Class 2, with more stringent impact testing criteria to ensure reliable performance under demanding conditions. The material is typically supplied in the normalized and tempered or quenched and tempered condition to achieve the desired combination of strength, ductility, and toughness. Its chemical composition is carefully controlled to provide excellent weldability and structural integrity in applications involving high pressure and temperature, such as refinery equipment, petrochemical reactors, and power generation components.
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. Steelmaking and Refining
Melting: Typically produced via Electric Arc Furnace (EAF) or Basic Oxygen Furnace (BOF).
Refining: Secondary refining (such as Ladle Refining or Vacuum Degassing) is performed to control chemical composition and minimize impurities like Phosphorus (P) and Sulfur (S).
Rolling: Steel slabs are hot-rolled at temperatures around 1700°F (925°C) to achieve the required thickness.
2. Heat Treatment (Defining Class 1 Properties)
Class 1 material is characterized by its specific tensile strength range (60–85 ksi / 415–585 MPa). To achieve this, the plates must undergo:
Annealing: Heating above the critical temperature followed by slow cooling.
Normalizing and Tempering: Heating to at least 1650°F (900°C) and air cooling, followed by tempering at a minimum of 1250°F (675°C).
Accelerated Cooling: Liquid quenching or accelerated air cooling from the austenitizing temperature is permitted, followed by tempering.
3. Fabrication Processes
Cutting: Can be processed using thermal cutting (plasma or oxy-fuel) or mechanical cold cutting.
Forming: The alloy has good ductility for cold bending or hot pressing into vessel shells or heads.
Welding:
Consumables: Use matching filler metals (typically ER90S-B3 or E9018-B3 types).
Preheating: Essential to prevent cold cracking (typically preheated to 200°C–300°C depending on thickness).
Post-Weld Heat Treatment (PWHT): Mandatory for most pressure vessel applications to relieve residual stresses and restore toughness.
4. Testing and Quality Control
Mechanical Testing: Verification of tensile strength, yield strength (min 30 ksi / 205 MPa), and elongation.
Charpy V-Notch Impact Test: Conducted if low-temperature toughness is required by the specific project code.
API 934 Testing: For high-pressure/high-temperature hydrogen service, additional tests (like Step Cooling tests) may be required to assess temper embrittlement resistance.
Non-Destructive Examination (NDE): Ultrasonic testing (UT) per ASTM A435 or A578 to ensure internal plate soundness.
Primary Applications
Oil & Gas and Petrochemical: Used in the construction of reactors (specifically hydrogenation units), separators, and heat exchangers. It is particularly favored for sour gas service where hydrogen sulfide is present.
Power Generation: Employed for boiler drum shells, superheater tubes, and high-pressure piping in both fossil fuel and nuclear power plants.
Industrial Equipment: Found in high-temperature ducting, furnace components, flanges, and valves.
Marine & Offshore: Utilized in condensers and piping systems that must handle high pressure in harsh environments.
Key Advantages
Superior Creep Resistance: Maintains structural integrity and resists permanent deformation even after thousands of hours of service at temperatures up to 600°C.
Oxidation & Corrosion Resistance: The chromium content provides a protective layer against oxidation and various forms of chemical attack, including pitting and stress corrosion cracking.
Enhanced Weldability (Class 1 Specific): While Class 1 has lower tensile strength (415–585 MPa) compared to Class 2, it offers higher ductility and better formability, making it easier to weld and shape into complex vessel components.
Thermal Stability: Exhibits minimal thermal aging or scaling under continuous thermal cycling, ensuring efficient heat transfer and operational safety.
Durability in Fluctuating Conditions: Its brawny surface resists cracking and deformation caused by sudden pressure shocks or temperature fluctuations.
Full specification and details are available on request. The above information is provided for guidance purposes only. For specific design requirements please contact our technical sales staff.
Can A387 Grade 22 Class 1 be used in cryogenic environments?
No, it is not suitable for cryogenic service. Its toughness decreases sharply at low temperatures (below -20°C), easily causing brittle fracture. Cryogenic applications require austenitic steels instead.
What standards govern A387 Grade 22 Class 1?
It is regulated by ASTM A387, a standard for chromium-molybdenum alloy steel plates for pressure vessels. Class 1 specifies the heat treatment requirement (normalized and tempered) for the material.
What is the creep resistance of A387 Grade 22 Class 1?
It exhibits excellent creep resistance at 400-550°C, maintaining structural stability under long-term constant load and high temperature. This makes it ideal for high-temperature pressure-bearing components.
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.
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.
What is the contrast between A387 Grade 22 Class 1 and A240 304?
304 has better corrosion resistance but lower high-temperature strength and higher cost. Grade 22 excels in high-temperature pressure-bearing scenarios, while 304 is for general corrosive environments.
What is the thermal conductivity of A387 Grade 22 Class 1?
At room temperature, its thermal conductivity is about 42 W/(m·K), decreasing slightly with increasing temperature. This property ensures efficient heat transfer in heat exchanger 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.