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.
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A387 Gr.5 CL.2 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.5 Cl.1 |
0.15 |
0.55 |
0.25-0.66 |
0.035 |
0.035 |
3.90-6.10 |
0.40-0.70 |
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Grade |
A387 Gr.5 CL.2 Mechanical Property |
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Thickness |
Yield |
Tensile |
Elongation |
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A387 Gr.5 Cl.2 |
mm |
Min Mpa |
Mpa |
Min % |
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t≦50 |
310 |
515-690 |
18 |
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50<t≦200 |
- |
- |
- |
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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).
advantages
1. Exceptional High-Temperature Performance
Thermal Stability: It maintains its mechanical integrity and structural strength at elevated temperatures up to 1000°F (538°C).
Creep Resistance: The molybdenum content significantly enhances its resistance to slow deformation (creep) under high-stress, high-heat conditions.
2. Superior Corrosion and Oxidation Resistance
Chemical Defense: The high chromium content (4.00–6.00%) provides robust protection against oxidation and various forms of corrosion, including pitting and crevice cracking.
Sour Service Suitability: It is highly effective in environments containing hydrogen sulfide (sour service), making it a preferred choice for oil and gas refineries.
3. High Mechanical Strength (Class 2 Advantage)
Greater Tensile Strength: Class 2 provides higher strength levels (75–100 ksi) than Class 1, allowing for the design of thinner, lighter components that can still withstand high pressure.
Impact Toughness: It undergoes rigorous testing to ensure durability and resistance to brittle fracture, even in challenging environments.
4. Excellent Fabrication Characteristics
Weldability: It is specifically engineered to be weldable, allowing for the construction of complex pressure vessels and boilers without compromising the alloy's mechanical properties.
Formability: Despite its high strength, the steel can be formed into various shapes and sizes required for specialized industrial equipment.
5. Economic Efficiency
Durability and Longevity: Its resistance to harsh environmental conditions results in a longer life span for equipment, reducing the frequency of maintenance and costly replacements.
Cost-Effectiveness: Compared to more expensive high-alloy alternatives, it provides a balanced, high-performance solution that meets stringent industry budgets.
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.
Request a professional quotation for A387 Grade 5 Class 2from GNEE Steel.
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.
How does ASTM A387 Grade 5 Class 2 compare to ASTM A387 Grade 91?
ASTM A387 Grade 5 Class 2 has significantly lower chromium and molybdenum than Grade 91, a high-strength ferritic alloy steel. Grade 91 provides excellent creep resistance at very high temperatures, while Grade 5 Class 2 is suitable for moderately elevated-temperature pressure vessel applications.
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 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.
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 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 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.
How does ASTM A387 Grade 5 Class 2 compare to ASTM A387 Grade 11 Class 2?
ASTM A387 Grade 5 Class 2 has lower chromium and molybdenum content than Grade 11 Class 2, resulting in lower high-temperature strength and creep resistance. Grade 11 Class 2 is better suited for higher-temperature and higher-pressure applications, while Grade 5 Class 2 is used in moderately severe conditions.
What is the difference between ASTM A387 Grade 5 Class 2 and ASTM A387 Grade 22?
ASTM A387 Grade 5 Class 2 has a lower alloy content compared to Grade 22, which contains higher amounts of chromium and molybdenum. Grade 22 offers superior creep strength and is used in more aggressive high-temperature environments, while Grade 5 Class 2 is used in less severe thermal service conditions.
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.