SA 387 Grade 22 Class 1 is a chromium-molybdenum alloy steel plate covered by the ASME Boiler and Pressure Vessel Code. It is widely used for pressure-retaining equipment that operates at high temperatures and pressures, such as pressure vessels, boilers, heat exchangers, and piping in refineries, petrochemical plants, and power generation facilities. The steel derives its high-temperature strength, creep resistance, and oxidation resistance from its carefully balanced chromium and molybdenum content, while its relatively low carbon level ensures good weldability. The Class 1 designation means that the material must undergo more stringent ultrasonic inspection to ensure a high degree of internal soundness, making it suitable for critical applications where reliability and resistance to temper embrittlement are essential.
Chemical Requirements for ASME SA387 Grade 22 Alloy Steel Plates
| Element | Chemical Composition (%) | |
| SA387 Grade 22 | ||
| Carbon: | Heat Analysis: | 0.05 - 0.15 |
| Product Analysis: | 0.04 - 0.15 | |
| Manganese: | Heat Analysis: | 0.30 - 0.60 |
| Product Analysis: | 0.25 - 0.66 | |
| Phosphorus: | Heat Analysis: | 0.035 |
| Product Analysis: | 0.035 | |
| Sulphur (max): | Heat Analysis: | 0.035 |
| Product Analysis: | 0.035 | |
| Silicon: | Heat Analysis: | 0.50 max |
| Product Analysis: | 0.50 max | |
| Chromium: | Heat Analysis: | 2.00 - 2.50 |
| Product Analysis: | 1.88 - 2.62 | |
| Molybdenum: | Heat Analysis: | 0.90 - 1.10 |
| Product Analysis: | 0.85 - 1.15 |
|
Grade |
SA387 Gr.22 CL.1 Mechanical Property |
|||
|
Thickness |
Yield |
Tensile |
Elongation |
|
|
SA387 Gr.22 Cl.1 |
mm |
Min Mpa |
Mpa |
Min % |
|
t≦50 |
205 |
415-585 |
18 |
|
|
50<t≦200 |
- |
- |
- |
|
Process Flow
Smelting and Composition Control:
The steel is melted in an electric arc furnace and refined in a ladle furnace, with strict control over carbon, silicon, manganese, phosphorus, sulfur, and the key alloying elements chromium and molybdenum. The carbon content is kept relatively low to improve weldability while ensuring the correct balance of chromium and molybdenum, which are essential for high-temperature strength and creep resistance.
Forming and Rolling:
The steel billet is heated to the appropriate rolling temperature and then rolled into plates of the required thickness. This process refines the grain structure and ensures uniform mechanical properties across the plate.
Heat Treatment (after hot working):
Normalizing: The plate is heated to the austenitizing temperature and air-cooled to homogenize the microstructure, relieve internal stresses, and achieve a fine-grained pearlite and ferrite structure.
Tempering: Performed after normalizing (or quenching), this step further adjusts hardness and toughness, stabilizes the microstructure, and ensures the material meets the required mechanical properties for high-temperature service.
Inspection and Testing:
Non-destructive testing, including ultrasonic testing and magnetic particle testing, is conducted to detect internal and surface defects. Mechanical tests such as tensile, impact, and hardness tests, along with chemical analysis, are carried out to ensure compliance with the ASME SA 387 Grade 22 Class 1 standard.
Main Characteristics (Influenced by Process):
The chromium-molybdenum alloy provides excellent high-temperature strength and oxidation resistance. The low carbon content enhances weldability, while the normalizing and tempering heat treatment optimizes the microstructure, ensuring good high-temperature performance and resistance to hydrogen attack, as well as controlling heat-affected zone embrittlement.
Application Scenarios:
SA 387 Grade 22 Class 1 is widely used in the petrochemical and oil refining industries for components such as hydrogenation reactors, high-temperature piping, and pressure vessels, where reliable performance under high temperatures and pressures is critical.
Advantages:
High-Temperature Performance:
Designed for elevated temperatures, resisting creep and maintaining strength where carbon steels weaken.
Corrosion & Oxidation Resistance:
Chromium and molybdenum content provide strong defense against oxidation and corrosive industrial environments, including sour gas (H₂S).
Enhanced Strength & Toughness:
Offers improved tensile strength and ductility compared to plain carbon steels, with good hardness and toughness.
Weldability:
Good weldability, even at higher temperatures, allowing for fabrication of complex pressure equipment.
Application Versatility:
Used in critical components for oil & gas, power generation (boilers, steam generators), and chemical processing.
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What are the main alloying elements?
The key alloying elements are chromium and molybdenum. Chromium improves oxidation resistance and high-temperature strength, while molybdenum enhances creep resistance and provides stability under long-term thermal loading. These elements work together to ensure the steel can withstand elevated temperatures without significant degradation. Other elements such as carbon, manganese, and silicon are also carefully controlled to maintain weldability and mechanical properties.
What does "Class 1" mean?
"Class 1" indicates that the steel plate must undergo a higher level of ultrasonic testing (UT) compared to Class 2. This stricter inspection ensures that the material has fewer internal defects such as laminations, inclusions, or voids. The goal is to provide a more reliable material for critical pressure vessel applications where structural integrity is essential. Plates that do not meet Class 1 standards may be reclassified as Class 2 if they meet the lower inspection requirements.
What is SA 387 GR 22 material?
The SA 387 Grade 22 Steel is a pressure vessel steel made up of high-quality raw material and high technology. Commonly used for high-temperature tasks based on its high heat tolerance this steel plate can be exposed up to 600° while maintaining superb oxidation and corrosion resistance.
What is the maximum service temperature?
SA 387 Gr.22 Cl 1 is commonly used in service temperatures up to approximately 593°C (1100°F). However, the actual maximum temperature depends on factors such as design code, stress level, creep requirements, and the presence of corrosive environments. For long-term creep applications, designers often use lower temperatures to ensure safety and durability over the equipment's lifetime.
How is it welded?
SA 387 Gr.22 Cl 1 can be welded using common processes such as SMAW (stick), GMAW (MIG), FCAW, and SAW. The choice of filler metal is important and usually involves matching Cr-Mo compositions, such as E8018-B2 or ER80S-B2. Proper preheating and post-weld heat treatment (PWHT) are essential to prevent cold cracking and ensure good mechanical properties in the heat-affected zone (HAZ).
What is SA 387 material equivalent to?
Sa 387 Gr 11 Equivalent Material is the ASME SA387 in the US markets with the European Union having modules in 13CrMoSi5-5 grade. The Sa 387 Gr 11 Cl 2 Equivalent Material is the SA387-11-2 of the ASME and ASTM standard.
How does SA 387 Gr.22 Cl 1 compare to carbon steel plates?
Unlike standard carbon steels, SA 387 Gr.22 Cl 1 contains chromium and molybdenum, which significantly improve its high-temperature strength, creep resistance, and resistance to temper embrittlement. Carbon steels soften and lose strength at elevated temperatures, making them unsuitable for many pressure vessel and boiler applications where Gr.22 excels.
How does SA 387 Gr.22 Cl 1 compare to SA 387 Gr.22 Cl 2?
Both grades have the same chemical composition, but Class 1 requires more stringent ultrasonic testing for internal soundness. Class 2 allows slightly more internal discontinuities. Class 1 is preferred for critical applications where failure could have severe consequences, while Class 2 is used when lower inspection levels are acceptable.