SA 387 Grade 22 Class 2 is a chromium-molybdenum alloy steel plate designed for use in pressure vessels and other equipment operating at elevated temperatures. It belongs to a family of heat-resistant steels known for their ability to resist creep deformation and oxidation over long service periods. The material offers a good combination of strength, toughness, and weldability, making it suitable for harsh environments found in refineries, petrochemical plants, power generation facilities, and other industrial applications where reliability under thermal stress is essential. Class 2 designation indicates more stringent impact toughness requirements compared to Class 1, ensuring better resistance to brittle fracture, particularly in thicker sections or under conditions involving temperature changes.
Chemical Properties:
|
SA387 |
Grade 22 |
|
Carbon |
0.04 – 0.15 |
|
Manganese |
0.25 – 0.66 |
|
Phosphorous |
0.035 |
|
Sulfur |
0.035 |
|
Silicon |
0.5 max |
|
Chromium |
1.88 – 2.62 |
|
Molybdenum |
0.85 – 1.15 |
Technical conditions of SA 387 Grade 22 Alloy Steel Plates
Ultrasonic tested as per SA 578 or any other as per requirement
MTC acc to EN 10204 / 3.2
Charpy Impact tested at -20 / - 46 DegC.
Furnace Normalised
BQ Plates with IBR form IV
SA 387 Grade 22 Class 2 Manufacturing Process Flow
Raw Material Preparation
High‑quality scrap steel, ferrochromium, ferromolybdenum, and other alloying elements are selected to ensure stable chemical composition and low impurity levels.
Melting (EAF or EAF + LF)
The raw materials are melted in an electric arc furnace. The molten steel is then transferred to a ladle furnace for preliminary refining, desulfurization, and composition adjustment.
Secondary Refining (LF / VD / VOD)
Further purification is achieved through vacuum degassing, argon stirring, and other processes to reduce gas content and inclusions, improving steel cleanliness and homogeneity.
Casting (Continuous Casting or Ingot Casting)
The refined steel is cast into slabs or ingots. Strict control of casting temperature and speed helps prevent segregation and internal defects.
Heating and Soaking
The slabs are heated in a furnace to a suitable temperature and soaked to ensure uniform microstructure and good workability before rolling.
Hot Rolling
The slabs are hot rolled to the desired thickness through multiple passes. Careful control of rolling temperature and reduction ratio ensures a fine, uniform grain structure.
Normalizing
The plates are heated to the appropriate temperature, held for a specified time, and then cooled in air. This step refines the microstructure and improves strength and toughness.
Tempering
After normalizing, the plates are reheated to a specific temperature, held, and then cooled slowly. This relieves internal stress, enhances toughness, and stabilizes dimensions.
Straightening
Mechanical or thermal straightening is performed to achieve the required flatness and ensure good machinability.
Ultrasonic Testing (UT)
Comprehensive ultrasonic inspection is carried out to detect internal defects such as laminations, shrinkage, or cracks.
Mechanical Testing
Tensile, impact, and hardness tests are conducted to verify that the material meets the mechanical property requirements of SA 387 Grade 22 Class 2.
Chemical Analysis
Chemical composition is verified through spectral analysis to ensure compliance with ASTM standards.
Final Inspection and Certification
The plates undergo a final visual inspection, dimensional check, and certification preparation before being dispatched to customers.
Key Advantages:
High-Temperature Performance: Designed for elevated temperatures, maintaining strength and integrity where other steels fail.
Corrosion & Oxidation Resistance: High Chromium (Cr) and Molybdenum (Mo) content provides excellent resistance in harsh environments, including sour gas.
Enhanced Strength: Offers superior tensile and yield strength compared to lower grades, especially at high temperatures, thanks to molybdenum.
Good Weldability: Can be reliably welded, crucial for fabricating complex pressure vessels.
Durability: High performance and durability ensure long service life in critical applications.
Versatility: Used in critical components like boilers, heat exchangers, and piping for petrochemical and energy sectors.
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What preheating temperature is recommended for welding SA 387 Gr. 22 Cl. 2?
Preheat temperatures typically range from 200–300°C, depending on plate thickness and welding procedure. Thicker plates may require higher preheat to reduce hydrogen-induced cracking.
What PWHT is required after welding SA 387 Gr. 22 Cl. 2?
A post-weld heat treatment of around 620–680°C for a sufficient duration is commonly applied to relieve residual stresses and improve toughness and creep properties.
What standards are equivalent to SA 387 Gr. 22 Cl. 2?
It is equivalent to ASTM A387 Grade 22 Class 2. In some international standards, it is comparable to 2.25Cr-1Mo steel grades used for pressure vessels.
What is the maximum service temperature for SA 387 Gr. 22 Cl. 2?
It is commonly used in service temperatures up to approximately 593°C (1100°F), where its creep strength and oxidation resistance are sufficient.
What inspection and testing are required for SA 387 Gr. 22 Cl. 2?
Typical requirements include ultrasonic testing (UT), radiographic testing (RT), tensile testing, bend testing, and impact testing as specified in ASTM A387/A387M and customer specifications.
Can SA 387 Gr. 22 Cl. 2 be used in low-temperature applications?While it is primarily designed for high-temperature service, Class 2 provides better low-temperature toughness than Class 1. However, it is not typically recommended for extremely low-temperature applications where nickel-alloyed steels are more suitable.
How does SA 387 Gr. 22 Cl. 2 compare to SA 387 Gr. 5 Cl. 2 in terms of alloy content and performance?
SA 387 Gr. 22 Cl. 2 has a higher chromium and molybdenum content (2.25Cr-1Mo) compared to SA 387 Gr. 5 Cl. 2 (0.5Cr-0.5Mo). This higher alloy content gives Gr. 22 superior high-temperature strength, creep resistance, and oxidation resistance, allowing it to be used in more severe service conditions. Gr. 5 is typically used in lower-temperature pressure vessel applications, while Gr. 22 is widely used in refineries, petrochemical plants, and power generation facilities for components operating at temperatures up to 593°C.
What is the difference in heat treatment between SA 387 Gr. 22 Cl. 2 and SA 537 Cl. 1?
SA 387 Gr. 22 Cl. 2 is supplied in the normalized and tempered condition to optimize its creep strength and toughness for high-temperature service. SA 537 Cl. 1, on the other hand, is quenched and tempered to achieve higher tensile strength for lower-temperature pressure vessel applications. The heat treatment difference reflects their intended service temperatures: SA 387 Gr. 22 is designed for long-term exposure to elevated temperatures, while SA 537 is optimized for high strength at ambient and moderately elevated temperatures.
How does SA 387 Gr. 22 Cl. 2 perform compared to stainless steel in high-temperature corrosion?
Stainless steels (such as 304, 316, or 321) generally offer better overall corrosion resistance, especially in acidic or chloride-containing environments. However, SA 387 Gr. 22 Cl. 2 provides superior creep strength and stress-rupture performance at temperatures above 500°C, making it more suitable for high-temperature pressure vessels and furnace components. SA 387 Gr. 22 is also more cost-effective and easier to weld and fabricate compared to many stainless steels. In refinery applications, SA 387 Gr. 22 is often used for reactor shells and heater tubes, while stainless steels are preferred for corrosion-resistant internals.
What is the difference in welding requirements between SA 387 Gr. 22 Cl. 2 and SA 387 Gr. 11 Cl. 2?
Both grades require preheating and post-weld heat treatment (PWHT) to prevent hydrogen-induced cracking and ensure good toughness. However, SA 387 Gr. 22 Cl. 2 typically requires higher preheat temperatures (200–300°C) and a more controlled PWHT due to its higher chromium and molybdenum content, which increases its hardenability. Welding consumables for Gr. 22 must also be matched to its alloy content to maintain strength and creep resistance in the weld zone. Gr. 11, with its lower alloy content, generally requires lower preheat and less stringent PWHT.