SA387 Grade 22 Class 1 is a chromium‑molybdenum alloy steel plate covered by the ASME SA387/SA387M standard. It is widely used for pressure vessel and boiler components that operate at elevated temperatures and pressures in industries such as petrochemical processing, refining, power generation, and chemical manufacturing. The steel derives its properties from a carefully balanced composition of chromium and molybdenum, which together provide good high‑temperature strength, creep resistance, and resistance to hydrogen attack and sulfide corrosion. It is usually supplied in the normalized and tempered condition to achieve a fine‑grained microstructure that offers a practical combination of toughness and hardness. The material also demonstrates good weldability when proper preheating and post‑weld heat treatment practices are applied.
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( Mpa)
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
Primary Manufacturing & Forming
The material is typically produced through the following processes:
Manufacturing Method: Primarily produced as Hot-Rolled (HR) plate.
Forming: Can be cold or hot formed; however, hot forming is common for heavy-wall vessel components to maintain structural integrity.
Cutting: Plates are often cut to size using precision methods like plasma or laser cutting, depending on thickness.
Heat Treatment (Thermal Processing)
Heat treatment is critical for SA 387 Grade 22 Class 1 to meet its mechanical property requirements. Standard protocols include:
Annealing or Normalizing & Tempering: The steel must be thermally treated by either annealing or normalizing and tempering.
Tempering Temperature: A minimum tempering temperature of 1250°F (675°C) is required to ensure stability.
Stress Relieving: Post-weld heat treatment (PWHT) or simulated PWHT is often performed to reduce internal stresses and prevent cracking, particularly in thicker sections.
Fabrication & Welding
Weldability: The alloy is designed for excellent weldability. It is frequently welded to form large pressure vessel superstructures.
Preheating: Preheating is often required before welding to prevent hydrogen-induced cracking, especially for thick plates.
Machinability: Due to its alloy content, it has moderate machinability but can be rock-hard if improperly cooled during processing.
Key Applications:
Pressure Vessels & Boilers: The primary use, handling high pressures and temperatures.
Oil & Gas Industry: For equipment in refining and natural gas processing.
Power Plants: Used in boilers and other components exposed to heat.
Chemical Plants: For reactors and piping in corrosive environments at high temperatures.
Heat Exchangers & Piping: Components requiring durability at elevated temperatures.
Key Characteristics:
High Temperature Service: Designed to withstand temperatures up to around 600°C (1100°F).
Corrosion & Oxidation Resistance: Molybdenum content enhances performance in high-temp, corrosive environments.
Mechanical Properties: Class 1 has lower tensile strength (60-85 ksi) compared to Class 2, but both are suitable for pressure service.
Heat Treatment: Typically supplied Normalized & Tempered or Quenched & Tempered for optimal properties.
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What is SA387 Grade 22 Class 1?
SA387 Grade 22 Class 1 is a low-alloy chromium-molybdenum steel plate, mainly used in pressure vessels. It has excellent high-temperature strength and good weldability, conforming to ASTM standards for harsh service conditions.
What are the main chemical components of SA387 Grade 22 Class 1?
Its key components include carbon (≤0.17%), chromium (1.90-2.60%), molybdenum (0.87-1.13%), manganese (0.40-0.65%), silicon (0.15-0.40%), with trace amounts of phosphorus and sulfur.
What is the maximum service temperature of SA387 Grade 22 Class 1?
The maximum continuous service temperature of SA387 Grade 22 Class 1 is around 593°C (1100°F). It maintains stable mechanical properties at this temperature, suitable for high-temperature pressure equipment.
What are the typical mechanical properties of SA387 Grade 22 Class 1 at room temperature?
At room temperature, its minimum yield strength is 207 MPa (30 ksi), minimum tensile strength is 414 MPa (60 ksi), and elongation at break is at least 22%, ensuring good toughness and load-bearing capacity.
Which standard does SA387 Grade 22 Class 1 comply with?
SA387 Grade 22 Class 1 complies with ASTM A387/A387M, a standard specifying low-alloy steel plates for welded pressure vessels in high-temperature and corrosion-prone environments.
What is the main application of SA387 Grade 22 Class 1?
It is widely used in manufacturing pressure vessels, boilers, heat exchangers, and reactor components in oil, gas, petrochemical, and power generation industries, adapting to high-temperature operations.
Is SA387 Grade 22 Class 1 weldable?
Yes, it has good weldability. Proper preheating (150-200°C) and post-weld heat treatment (PWHT) are recommended to avoid cold cracking and ensure the integrity of welded joints.
What post-weld heat treatment (PWHT) is required for SA387 Grade 22 Class 1?
Typical PWHT involves tempering at 620-675°C, holding for a sufficient time based on thickness, then cooling slowly. This relieves welding stress and improves joint toughness and corrosion resistance.
What is the difference between SA387 Grade 22 Class 1 and Class 2?
Answer: The main difference lies in impact toughness requirements. Class 2 has stricter Charpy V-notch impact standards at lower temperatures, while Class 1 meets basic impact performance for general applications.
Can SA387 Grade 22 Class 1 resist corrosion?
Answer: It has moderate corrosion resistance to mild acids, alkalis, and atmospheric conditions. For severe corrosion environments, additional coatings or alloy upgrades are recommended.