SA387 Grade 22 Class 1 is a chromium‑molybdenum alloy steel plate under the ASME SA387 standard, used for pressure vessels and boilers in high‑temperature, high‑pressure service. Its chromium‑molybdenum content provides good high‑temperature strength, creep resistance, and resistance to hydrogen attack and sulfide corrosion. It is typically supplied normalized and tempered for balanced toughness and hardness, and it offers good weldability with appropriate preheating and post‑weld heat treatment.
Chemical Composition
Grade/ Material | Element | Composition( Max-A, Min-I) |
SA387 Grade 22 Class 1/ SA387 Gr22 Cl1 | C | 0.05-0.15 |
Mn | 0.30-0.60 | |
Si | A:0.50 | |
P | 0.035 | |
S | 0.035 |
Mechanical Properties
Grade/ Material | Tensile Test | Ksi/MPa |
SA387 Grade 22 Class 1/ SA387 Gr22 Cl1 | Tensile Strength | 60-85/415-585 |
Yield Strengh | 30/205 | |
Elongation | 18% | |
Impact Test( if any) |
|
processing
1. Heat Treatment Requirements
SA 387 Grade 22 is typically supplied in a Normalized and Tempered or Annealed condition.
Normalizing: Placed in a furnace to reach the austenitizing temperature, then air-cooled.
Tempering: Must be performed at a minimum temperature of 1250°F (675°C) to achieve the Class 1 mechanical properties.
Simulated PWHT (SPWHT): Manufacturers often perform simulated post-weld heat treatment on test coupons to ensure the material will still meet specifications after final fabrication.
2. Welding Procedures
Due to its high chromium (2.25%) and molybdenum (1%) content, this alloy is susceptible to cracking if not handled correctly.
Preheating: Necessary to prevent hydrogen-induced cracking. Welded joints often require a preheat temperature maintained until post-weld heat treatment is performed.
Filler Materials: Matching electrodes, such as 2.25% Cr - 1% Mo (e.g., E9018-B3), are typically used to match the base metal's strength and creep resistance.
Post-Weld Heat Treatment (PWHT): Mandatory for Grade 22. It involves reheating the welded area to approximately 300°F to 1125°F (150°C to 600°C) to relieve residual stresses. For critical applications, joints should not cool below 300°F (150°C) between welding and PWHT.
3. Forming and Machining
Hot Rolling: This is the primary method for manufacturing the plates, where slabs are heated to roughly 1,700°F before passing through rollers.
Cold/Hot Forming: Class 1 plates have lower tensile strength than Class 2, making them slightly easier to form into vessel heads or cylinders.
Cutting: Typically performed via flame or plasma cutting. Due to the alloy's hardening characteristics, edge preparation (grinding or machining) is often required after thermal cutting to remove the heat-affected zone (HAZ).
4. Surface Finishing
Available finishes include hot-rolled, cold-rolled, or polished options (e.g., mirror, 8K, sandblasted) depending on the end-user's environmental needs.
Primary Industrial Applications
Petrochemical & Oil Refining: Used extensively for vessels handling sour gas (hydrogen sulfide). Key components include:
Hydrocracking and Catalytic Reactors: Where high thermal stability is required.
Separators and Storage Vessels: For processing media under high pressure.
Heat Exchangers and Condensers: Utilizing the alloy's efficient heat transfer and oxidation resistance.
Power Generation: Essential for thermal and fossil fuel power stations. Applications include:
Industrial Boilers: Including boiler drums and superheater tubes.
Steam Headers and Turbine Casings: Which face significant cyclic thermal stress.
Nuclear Industry: Increasingly used for reactor components capable of withstanding extreme temperatures.
Chemical Processing: Used in the fabrication of chemical reactors, valves, and piping systems that must resist stress corrosion cracking and pitting in harsh media.
Specialized Component Use
Fluid Transport: High-pressure piping, flanges, and high-temperature ducting.
Hardware: Pipe clamps, valves, and base plates for wind or turbine supports.
Liners: Protective liners for chutes, tubs, bins, and truck bodies in heavy industrial settings.
Offshore Services: Applied in offshore oil drilling and seawater equipment where corrosion protection is paramount.
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What is the creep strength of SA387 Grade 22 Class 1 at 500°C?
At 500°C, its 100,000-hour creep strength is approximately 60 MPa. This indicates its ability to resist permanent deformation under long-term high-temperature loads.
What is the hardness range of SA387 Grade 22 Class 1 after heat treatment?
After standard heat treatment, its Brinell hardness (HB) ranges from 137 to 187. This hardness balance ensures machinability and resistance to deformation under operating loads.
Can SA387 Grade 22 Class 1 be used in low-temperature environments?
It is not ideal for low temperatures (below -20°C) as its impact toughness decreases. For cryogenic service, choose grades with better low-temperature performance like SA387 Grade 11.
What is the delivery condition of SA387 Grade 22 Class 1 plates?
It is usually delivered in normalized and tempered (N&T) condition. This heat treatment ensures consistent mechanical properties and microstructure for pressure vessel applications.
Is SA387 Grade 22 Class 1 magnetic?
Yes, it is ferromagnetic due to its iron-based composition. This property allows magnetic particle inspection (MPI) for detecting surface and near-surface defects.
What inspection methods are used for SA387 Grade 22 Class 1 plates?
Common methods include ultrasonic testing (UT) for internal defects, MPI for surface flaws, visual inspection (VI), and chemical composition analysis to ensure compliance with standards.
What is the Poisson's ratio of SA387 Grade 22 Class 1?
The Poisson's ratio is about 0.3 at room temperature. This value describes the lateral strain response to axial stress, essential for finite element analysis and structural modeling.
Can SA387 Grade 22 Class 1 be used in hydrogen service?
Yes, with proper PWHT, it resists hydrogen embrittlement. It is suitable for hydrogen-containing environments in refineries, provided operating temperature and pressure are controlled.
What is the difference between SA387 Grade 22 and Grade 11?
Grade 22 has higher molybdenum content (0.87-1.13% vs 0.45-0.65% for Grade 11), offering better high-temperature strength and creep resistance for more demanding service conditions.
What are the storage requirements for SA387 Grade 22 Class 1 plates?
Store in a dry, well-ventilated area to prevent rust. Keep plates elevated from the ground, covered with waterproof materials, and avoid contact with corrosive substances.