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 CL.2 BQ Steel 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 CL.2 Alloy Steel Plates Equivalent Grades
| COUNTRY | USA | EUROPEAN | GERMANY | ENGLAND | FRANCE | RUSSIA |
| STANDARDS | ASTM | EN 10028 | DIN | BS | AFNOR 36206 | GOST |
| Grade 5 | A387 | X12CrMo5 | - | - | - | 15KH5M |
ASTM A387 Grade 5 CL.2 Alloy Steel Plates 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 CL.2 Alloy Steel Plates 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 |
applications
1. Oil, Gas, and Petrochemical Refining
The high chromium (5%) and molybdenum (0.5%) content make it essential for equipment exposed to corrosive media and high operating heat.
Hydrocracking Units: Used for vessels that break down heavy crude oil into lighter products.
Sour Service Environments: Ideal for equipment handling hydrogen sulfide (𝐻2𝑆) because of its resistance to corrosion and cracking.
Separators and Reactors: Fabrication of phase separator skids and chemical reactors that operate under extreme pressure.
2. Power Generation
Its thermal stability and creep resistance are vital for fossil fuel and thermal power plants.
Boiler Components: Manufacturing of boiler drums, superheater tubes, and steam generators.
High-Temperature Ducting: Used in piping systems that carry high-pressure steam at temperatures up to 1000°F (538°C).
Turbine Base Plates: Support applications for high-heat turbines.
3. Chemical Processing and Synthesis
Pressure Vessels: Construction of weldable vessels designed for elevated temperature service.
Heat Exchangers: Used in industrial shells and tubes that transfer heat between corrosive fluids.
Synthesis Towers: Crucial for ammonia and urea synthesis where high pressure and chemical durability are required.
4. Specialized Industrial Machinery
Furnace Equipment: Ideal for liners and structural components within industrial furnaces.
Marine and Seashore Applications: Resistant to corrosion in freshwater and some marine environments, though often used with additional protective measures.
Heavy Duty Infrastructure: High-temperature valves, pipe clamps, and flanges.
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.
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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.
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 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 standards govern the testing of ASTM A387 Grade 5 Class 2?
Testing of ASTM A387 Grade 5 Class 2 is governed by ASTM standards, including tensile, bend, and impact tests. Additional requirements may be specified by ASME Boiler and Pressure Vessel Code when used in certified pressure vessel construction.
What is the maximum temperature at which ASTM A387 Grade 5 Class 2 can operate?
ASTM A387 Grade 5 Class 2 is commonly used in applications up to approximately 900°F. Its chromium-molybdenum composition provides good creep resistance and structural stability at these elevated temperatures, making it suitable for refinery and petrochemical equipment.
How does ASTM A387 Grade 5 Class 2 compare to ASTM A387 Grade 9?
ASTM A387 Grade 5 Class 2 has lower chromium content than Grade 9, resulting in lower high-temperature strength and creep resistance. Grade 9, with higher chromium, is better suited for more severe elevated-temperature applications, while Grade 5 Class 2 is used in moderately high-temperature pressure vessel components.
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.
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.
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.