ASTM A387 Grade 22 Class 1 is a specific type of chromium-molybdenum (Cr-Mo) alloy steel plate designed for welded boilers and high-temperature pressure vessels, offering good high-temperature strength and corrosion resistance, with "Class 1" indicating standard tensile strength levels and suitability for applications where lower-temperature impact toughness isn't critical, unlike the stronger Class 2. It contains approximately 2.25% chromium and 1.00% molybdenum, making it ideal for petrochemical, oil & gas, and power generation industries.
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A387 Gr.22 CL.1 Chemical Composition |
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Grade |
The Element Max (%) |
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C |
Si |
Mn |
P |
S |
Cr |
Mo |
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A387 Gr.22 Cl.1 |
0.04-0.15 |
0.50 |
0.30-0.60 |
0.035 |
0.035 |
1.88-2.62 |
0.85-1.15 |
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Grade |
A387 Gr.22 CL.1 Mechanical Property |
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Thickness |
Yield |
Tensile |
Elongation |
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A387 Gr.22 Cl.1 |
mm |
Min Mpa |
Mpa |
Min % |
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t≦50 |
205 |
415-585 |
18 |
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50<t≦200 |
- |
- |
- |
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processing
Heat Treatment Requirements
Normalization and tempering are typically required for A387 Grade 22 Class 1 plates.
Normalization is usually performed in the temperature range of 900 to 950°C, followed by air cooling.
Tempering is carried out at a temperature generally between 620 and 700°C to achieve the required toughness and relieve residual stresses.
Quenching and Tempering (Q&T) Option
Some specifications or purchaser requirements may allow or specify quenching and tempering instead of normalization and tempering.
Quenching is done from the austenitizing temperature (typically 880 to 920°C) using water or oil.
Tempering after quenching is essential to improve toughness and reduce hardness to meet the Class 1 impact requirements.
Impact Test Requirements for Class 1
A387 Grade 22 Class 1 requires Charpy V-notch impact testing at a specified temperature (often 0°C or lower, depending on the purchase order or design code).
The impact energy values must meet the minimum requirements specified in ASTM A387 to ensure adequate toughness for low-temperature or high-stress service.
Welding Considerations
Preheating is generally recommended before welding to prevent cold cracking, typically in the range of 200 to 300°C.
Interpass temperature control is important during welding to avoid excessive heat input and maintain mechanical properties.
Post-weld heat treatment (PWHT) is usually required for welded components, typically at temperatures between 620 and 680°C, to reduce hardness in the heat-affected zone (HAZ) and relieve welding stresses.
Chemical Composition Control
Strict control of carbon, chromium, molybdenum, and other alloying elements is necessary to ensure the desired strength, toughness, and creep resistance.
The composition must conform to the limits specified in ASTM A387 for Grade 22.
Mechanical Property Requirements
Tensile strength, yield strength, elongation, and reduction of area must meet the minimum values specified in the standard.
For Class 1, special attention is paid to the impact toughness, which is the key differentiator from Class 2.
Inspection and Testing
Ultrasonic testing (UT) is commonly required for plates used in critical pressure vessel applications.
Visual inspection (VI), magnetic particle inspection (MPI), or liquid penetrant inspection (LPI) may be performed as per the specification or purchaser's requirements.
Hardness testing is often conducted to ensure that the material does not exceed the maximum allowable hardness after heat treatment or welding.
Key Industrial Applications
Petrochemical & Chemical Processing:
Used extensively for high-pressure reactors, separators, and storage vessels that handle volatile chemical processing media and sour gas.
Oil & Gas Industry:
Ideal for sour service environments due to its resistance to hydrogen-induced cracking and stress corrosion. It is used in both offshore and onshore piping, pressure vessels, and gas processing equipment.
Power Generation:
Found in thermal and nuclear power plants for boiler drums, superheater tubes, and furnace components. It maintains structural integrity under the prolonged thermal stress of high-pressure steam.
Heat Transfer Equipment:
Commonly employed in industrial boilers, heat exchangers, and condensers that must withstand continuous thermal cycling.
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What is A387 Grade 22 Class 1?
It is a low-alloy ferritic steel plate for pressure vessels, containing 2.25% chromium and 1% molybdenum. Designed for high-temperature service, it offers excellent creep and oxidation resistance, widely used in petrochemical and power industries.
What is the chemical composition core of A387 Grade 22 Class 1?
Its core components are 2.00-2.50% Cr, 0.87-1.13% Mo, ≤0.17% C, ≤0.50% Si, 0.40-0.65% Mn, with trace P and S. These elements enhance high-temperature strength and corrosion resistance.
What is the maximum service temperature of A387 Grade 22 Class 1?
It can withstand continuous service up to 593°C (1100°F). Beyond this temperature, its creep strength declines significantly, making it unsuitable for long-term high-temperature operations.
What heat treatment is required for A387 Grade 22 Class 1?
It typically undergoes normalizing (899-954°C) followed by tempering (677-760°C). This process refines grains, reduces internal stress, and optimizes its mechanical properties for pressure vessel applications.
What is the tensile strength range of A387 Grade 22 Class 1?
The minimum tensile strength is 415 MPa (60 ksi), and the yield strength is at least 205 MPa (30 ksi). It balances ductility and strength, meeting pressure vessel design standards.
Is A387 Grade 22 Class 1 weldable?
Yes, it is weldable via common methods like SMAW, GTAW, and GMAW. Preheating (150-260°C) and post-weld heat treatment (PWHT) are necessary to prevent cold cracking and relieve residual stress.
What is the corrosion resistance of A387 Grade 22 Class 1?
It resists oxidation and sulfidation in high-temperature environments. However, it is not suitable for strong acidic or chloride-containing media, as it lacks sufficient corrosion resistance in such conditions.
What industries mainly use A387 Grade 22 Class 1?
It is widely applied in petrochemical, refinery, power generation (boilers, turbines), and chemical processing industries, primarily for pressure vessels, heat exchangers, and piping systems.
How does A387 Grade 22 Class 1 differ from A387 Grade 12 Class 1?
Grade 12 has 1% Cr and 0.5% Mo, so Grade 22 has higher Cr-Mo content. Grade 22 offers better high-temperature strength and corrosion resistance, suitable for more severe service conditions than Grade 12.