ASTM A387 Grade 5 Class 2 (also designated as ASME SA 387 Grade 5 Class 2) is a high-quality chromium-molybdenum alloy steel plate designed for use in welded boilers and pressure vessels operating at elevated temperatures.
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 | - | - | - | 15KH5 |
processing
1. Melting and Casting
Melting: Produced using Electric Arc Furnaces (EAF) or Basic Oxygen Furnaces (BOF).
Refining: Typically undergoes vacuum degassing to remove impurities and gases (hydrogen/nitrogen), ensuring a clean internal structure.
Chemistry: Precisely alloyed with 4.00–6.00% Chromium and 0.45–0.65% Molybdenum.
2. Hot Rolling
Steel slabs are heated to approximately 1,700°F (926°C) and passed through multiple rollers to achieve the final plate thickness, typically ranging from 6mm to 300mm.
3. Heat Treatment (Critical for Class 2)
Class 2 requires specific heat treatment to achieve higher tensile strength (75–100 ksi) compared to Class 1.
Normalizing: Heated above the critical temperature to refine the grain structure, followed by air cooling.
Tempering: Reheated to a minimum of 1,300°F (705°C) to achieve the required ductility and strength balance.
Alternative: When permitted, accelerated cooling (liquid quenching) from the austenitizing temperature followed by tempering may be used.
4. Fabrication (Machining & Forming)
Cutting: Plates are cut to size using flame, plasma, or laser cutting.
Forming: Mechanical shaping or drilling is performed as per specific vessel designs.
Welding: Designed for high weldability; however, Post-Weld Heat Treatment (PWHT) is often required to relieve stress and prevent cracking in the weld zone.
5. Inspection and Testing
To verify compliance with ASTM/ASME standards, the following tests are performed:
Mechanical: Tensile tests and Charpy V-Notch impact tests.
Non-Destructive: Ultrasonic Examination (UT) and Magnetic Particle Examination to detect internal or surface defects.
Certification: Each plate is typically issued a Mill Test Certificate (MTC).
Key Industrial Applications
Petrochemical Industry: Fabrication of high-pressure vessels, heat exchangers, separators, and storage tanks.
Oil Refining: Construction of refinery towers, catalytic cracking units, and hydrogenation units.
Power Generation: Used in industrial boilers and pressurized equipment designed for elevated temperature service.
Natural Gas & Fertilizer Production: Manufacturing of gas storage tanks, transmission pipelines, ammonia synthesis towers, and urea synthesis towers.
Specialized Equipment: fabrication of reactors, furnace equipment, and pipework.
Why It Is Used
The specific alloy composition (4.00–6.00% Chromium and 0.45–0.65% Molybdenum) provides:
High Temperature Stability: Maintains structural integrity at temperatures as high as 1000°F (538°C).
Corrosion Resistance: Effective in "sour service" environments containing corrosive media like hydrogen sulfide.
Superior Strength: Class 2 offers higher tensile strength (75–100 ksi) than Class 1, making it ideal for higher pressure applications.
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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 are the key chemical elements in ASTM A387 Grade 5 Class 2?
ASTM A387 Grade 5 Class 2 contains chromium and molybdenum as primary alloying elements, which enhance its high-temperature strength and corrosion resistance. Carbon, manganese, silicon, and small amounts of other elements are also present to optimize weldability and mechanical performance during fabrication and service.
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 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.
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 ASTM A36 steel?
ASTM A387 Grade 5 Class 2 is a specialized alloy steel for high-temperature pressure vessels, while ASTM A36 is a general-purpose carbon steel. Grade 5 Class 2 offers better heat resistance and creep strength, whereas A36 is used in structural applications at ambient temperatures.
How does ASTM A387 Grade 5 Class 2 compare to ASTM A537 Class 1?
ASTM A387 Grade 5 Class 2 is a chromium-molybdenum alloy steel designed for high-temperature service, while ASTM A537 Class 1 is a quenched and tempered carbon steel for pressure vessels. Grade 5 Class 2 provides better creep resistance, while Grade 537 Class 1 offers high strength at lower temperatures.