A387 Grade 5 Class 2 is a type of pressure vessel steel plate designed for use in elevated-temperature service. It belongs to the chromium-molybdenum alloy steel family, which provides good strength and resistance to creep and oxidation at high temperatures. This grade is typically used in the fabrication of boilers, pressure vessels, and other equipment that must withstand harsh thermal conditions. The steel is produced with controlled chemistry and heat treatment to ensure consistent mechanical properties and reliable performance under stress. It is often specified in applications where durability and stability at elevated temperatures are critical requirements.
ASTM A387 GR 5 CLASS 2 Plate Specification
Grade : ASTM A387 Gr 5 CL.2 Alloy Steel Plates
Standard : ASTM A387 / ASME SA387
Width : 1000mm-4500mm
Thickness : 5mm-150mm
Length : 3000mm -18000mm
Impact tested : -52° C
Process : Hot-Rolled (HR)
ASTM A387 GR 5 CLASS 2 Chemical Composition
| Grade | C | Mn | P | S | Si | Cr | Mo |
|---|---|---|---|---|---|---|---|
| A387 Gr.5 | 0.05-0.21 | 0.55-0.80 | 0.025 | 0.025 | 0.15-0.40 | 0.50-0.80 | 0.45-0.60 |
ASTM A387 GR 5 CLASS 2 Mechanical Properties
| Class | Tensile (MPa) | Yield (MPa) | Elong. (50mm) | Elong. (200mm) | Reduc'n of Area* |
|---|---|---|---|---|---|
| Class 1 | 415 - 585 | 205 min | 18% min | - | 40% min |
| Class 2 | 515 - 690 | 310 min | 18% min | - | 40% min |
Equivalent Grades
| COUNTRY | USA | EUROPEAN | GERMANY | ENGLAND | FRANCE | RUSSIA |
|---|---|---|---|---|---|---|
| STANDARDS | ASTM | EN 10028 | DIN | BS | AFNOR 36206 | GOST |
| Grade 5 | A387 | X12CrMo5 | - | - | - | 15KH5M |
processing
1. Primary Heat Treatment (Crucial for Class 2)
As per 2026 technical requirements, the mechanical properties of Class 2 are achieved through controlled thermal cycles:
Normalizing: Heating the plates to an austenitizing temperature and cooling in air to refine the grain structure.
Tempering: Reheating to a minimum temperature of 1300°F [705°C]. This relieves internal stresses and achieves the specific tensile strength of 75–100 ksi.
Accelerated Cooling: If specified, liquid quenching followed by tempering is used to enhance toughness in thicker plates.
2. Mechanical Processing (Fabrication)
Hot Rolling: The process of reducing steel thickness while maintaining high temperatures to ensure uniform alloy distribution.
Edge Preparation: Beveling or machining plate edges to ensure proper fit-up and penetration during the welding stage.
Cold/Hot Forming: Shaping the plates into "shells" or "heads" for pressure vessels using hydraulic presses or rollers.
3. Welding & Thermal Conditioning
Preheating: Essential for Grade 5 (5% Cr) to minimize the risk of hydrogen-induced cracking during welding.
Post-Weld Heat Treatment (PWHT): A mandatory thermal cycle performed after welding to restore ductility and reduce hardness in the Heat Affected Zone (HAZ).
Simulated PWHT (SPWHT): A test procedure where samples are subjected to additional heat cycles to predict the final mechanical properties of the finished vessel.
4. Surface & Integrity Processing
Shot Blasting: Removing mill scale to provide a clean surface for inspection and coating.
Pickling and Passivation: Chemical cleaning to enhance the chromium-oxide protective layer for better corrosion resistance.
Vacuum Degassing: A refining process during the melting stage to eliminate trapped gases like hydrogen and oxygen.
5. Inspection & Verification
Non-Destructive Testing (NDT): Includes Ultrasonic Testing (UT) for internal flaws and Magnetic Particle Inspection (MPI) for surface cracks.
Charpy V-Notch Impact Testing: Evaluating the material's toughness at specific temperatures.
Positive Material Identification (PMI): Verifying the 5% Chromium and 0.5% Molybdenum content before shipment.
Applications For A387 Gr.5 Class 2 Alloy Steel Plate
Weldable Pressure Vessels and Industrial Boilers.
Sour Service Environments
Numerous Applications
Gas Applications
Benefits of ASTM A387 Grade 5 Class 2 Steel Plate
High Strength & Efficiency
High Performance
Longer Life Span
Flawless Finish
Durable
Corrosion Resistant Body
High Temperature Resistant Body
Good Weldability
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What is ASTM A387 Grade 5 Class 2?
ASTM A387 Grade 5 Class 2 is a chromium-molybdenum alloy steel plate specified for pressure vessel applications. It offers good strength and creep resistance at elevated temperatures. The material is typically normalized and tempered to achieve the required mechanical properties, ensuring reliability in high-temperature service environments.
What is the typical tensile strength range of ASTM A387 Grade 5 Class 2?
ASTM A387 Grade 5 Class 2 generally has a tensile strength between 60 ksi and 80 ksi. This range provides a good balance of strength and ductility, making it suitable for pressure vessel components that operate under moderate to high-temperature conditions.
What is the minimum yield strength requirement for ASTM A387 Grade 5 Class 2?
The minimum yield strength for ASTM A387 Grade 5 Class 2 is typically 30 ksi. This ensures that the material can withstand significant internal pressures and loading without undergoing excessive deformation in high-temperature service environments.
What heat treatment is required for ASTM A387 Grade 5 Class 2?
ASTM A387 Grade 5 Class 2 is usually supplied in the normalized and tempered condition. Normalizing refines the grain structure, while tempering reduces hardness and improves toughness, ensuring the material meets the required mechanical properties for pressure vessel applications.
What are the common applications of ASTM A387 Grade 5 Class 2?
ASTM A387 Grade 5 Class 2 is widely used in pressure vessels, boilers, and heat exchangers in the oil, gas, and petrochemical industries. It is also found in refinery equipment such as reactors and piping systems that operate at moderate to high temperatures.
Is ASTM A387 Grade 5 Class 2 suitable for welding?
Yes, ASTM A387 Grade 5 Class 2 is considered readily weldable using common welding processes. Proper preheating and post-weld heat treatment are recommended to prevent hydrogen-induced cracking and to ensure the desired mechanical properties in the heat-affected zone.
What preheating temperature is recommended for welding ASTM A387 Grade 5 Class 2?
Preheating temperatures for ASTM A387 Grade 5 Class 2 typically range from 200°F to 300°F. This helps reduce the cooling rate of the weld and heat-affected zone, minimizing the risk of cracking and ensuring sound weld quality.
What post-weld heat treatment is required for ASTM A387 Grade 5 Class 2?
Post-weld heat treatment for ASTM A387 Grade 5 Class 2 usually involves tempering at temperatures between 1100°F and 1200°F. This relieves residual stresses, improves toughness, and restores the material's mechanical properties after welding.
What is the difference between ASTM A387 Grade 5 Class 1 and Class 2?
The main difference lies in their strength levels and heat treatment requirements. Class 2 has higher strength and typically requires more stringent heat treatment to achieve the desired properties. Class 1 is often used in less demanding applications, while Class 2 is preferred for higher-pressure or higher-temperature service conditions.
What is the difference between ASTM A387 Grade 5 Class 2 and ASTM A516 Grade 70?
ASTM A387 Grade 5 Class 2 is a chromium-molybdenum alloy steel designed for high-temperature service, while ASTM A516 Grade 70 is a carbon steel for low to moderate temperature pressure vessels. Grade 5 Class 2 offers better creep resistance, while Grade 70 provides good toughness at lower temperatures.
How does ASTM A387 Grade 5 Class 2 compare to ASTM A285 Grade C?
ASTM A387 Grade 5 Class 2 is an alloy steel with chromium and molybdenum, offering superior high-temperature strength compared to ASTM A285 Grade C, a carbon steel. Grade 5 Class 2 is used in more demanding thermal environments, while Grade C is suitable for lower-temperature pressure vessel applications.
What is the difference between ASTM A387 Grade 5 Class 2 and ASME SA387 Grade 5 Class 2?
ASTM A387 Grade 5 Class 2 and ASME SA387 Grade 5 Class 2 are essentially the same material. SA387 is the ASME designation adopted from ASTM A387 for use in boiler and pressure vessel codes, ensuring compliance with ASME standards for construction and certification.