ASME SA 387 Grade 5 Class 1 is a specialized chromium-molybdenum alloy steel plate primarily designed for use in weldable boilers and pressure vessels operating at elevated temperatures.
Key Characteristics
Composition: A "chrome-moly" steel, it features high levels of chromium for corrosion and oxidation resistance, and molybdenum for enhanced tensile strength at high temperatures.
Heat Treatment: Class 1 plates are typically supplied in the annealed or normalized and tempered condition to achieve specific mechanical properties.
Durability: It is highly resistant to embrittlement during prolonged thermal cycling, ensuring a longer service life in extreme environments.
Chemical Composition
| Grade | C | Si | Mn | P | S | Cr | Mo |
| A387 GR.5 CL.1 | 0.15 max | 0.55 max | 0.25-0.66 max | 0.035 max | 0.035 max | 3.90-6.10 max | 0.40-0.70 max |
Mechanical Properties
| Grade | SA387 GR.5 CL.1 | |||
| SA387 GR.5 CL.1 | Thickness mm | Yield Min Mpa | Tensile Mpa | Elongation Min % |
| t≦50 | 205 | 415-585 | 18 | |
| 50 | - | - | - | |
Tensile Requirements for ASME SA387 Grade 5 Alloy Steel Plates Class 1 Plates
| Designation: | Requirement: | Grade 5 |
|
SA387 Grade 5 |
Tensile strength, ksi [MPA] | 75 to 100 [515 to 690] |
| Yield strength, min, ksi [MPa]/(0.2% offset) | 45 [310] | |
| Elongation in 8 in. [200mm], min % | ... | |
| Elongation in 2 in. [50mm], min, % | 18 | |
| Reduction of area, min % | 45 (measured on round specimen) 40 (measured on flat specimen) |
processing
1. Melting and Refining (Primary & Secondary)
Killed Steel: The steel must be "killed," meaning it is fully deoxidized during the melting process to ensure a uniform chemical composition and high internal soundness.
Alloying: Precise amounts of Chromium (4.00% – 6.00%) and Molybdenum (0.45% – 0.65%) are added to provide corrosion resistance and high-temperature strength.
Vacuum Degassing: Often used to remove dissolved gases like hydrogen, preventing internal defects.
2. Rolling (Tertiary)
Hot Rolling: The refined steel slabs are heated and passed through a series of rollers to achieve the final plate thickness, which typically ranges from 6mm to over 100mm.
3. Mandatory Heat Treatment
Class 1 plates must undergo specific thermal treatments to achieve their required mechanical properties:
Annealing: Heating the plate and cooling it slowly in the furnace to increase ductility and relieve internal stresses.
Normalizing & Tempering:
Normalizing: Heating the steel to a critical temperature and air-cooling it to refine the grain structure.
Tempering: Reheating to a minimum temperature of 1300°F [705°C] for Grade 5 to reduce brittleness and lock in tensile strength.
4. Supplementary Testing
To ensure safety in critical applications (like nuclear or chemical reactors), plates often undergo:
Charpy V-Notch Impact Test: To verify toughness at low temperatures.
Ultrasonic Examination (UT): To detect internal flaws within the plate's structure.
Simulation (SPWHT): Simulated Post-Weld Heat Treatment to ensure the plate maintains its properties after the final equipment is welded.
applications
1. Oil, Gas, and Petrochemical Industry
This is the most common sector for Grade 5 Class 1 due to its resistance to hydrogen attack and high-heat durability.
Pressure Vessels: Used for the safe containment of pressurized liquids and gases.
Hydroprocessing Reactors: Its high chromium content (5%) makes it ideal for reactors in desulfurization and hydrocracking units.
Oil Refineries: Employed in distillation columns and high-pressure piping.
Storage Tanks: Used for storing volatile substances at elevated temperatures.
2. Power Generation
The alloy's ability to maintain mechanical strength under thermal cycling makes it essential for power plants.
Industrial Boilers: Used in boiler steam drums and high-heat internal components.
Steam Generators: Critical for transferring heat while resisting steam-induced corrosion.
Nuclear and Fossil Fuel Plants: Used in secondary circuit pressurized components and high-temperature ducting.
3. Chemical and Thermal Processing
Grade 5 Class 1 is selected for chemical equipment that must withstand aggressive environments.
Heat Exchangers: Facilitates efficient heat transfer between fluids in corrosive settings.
Furnace Equipment: Structural components such as tie rods and pins that operate at sustained high temperatures.
Separators and Spherical Tanks: Used to process and store liquefied gases.
4. Heavy Industry and Specialized Fabrications
Mining and Drilling: Used for durable equipment like drill collars and heavy machinery parts exposed to harsh conditions.
Marine Applications: Effective in salt-water environments for off-shore drilling platforms.
Pipe Fittings: Used to manufacture high-temperature flanges, fittings, and valves.
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What type of steel is SA 387 GRADE 5 Class 1?
It is a chromium-molybdenum alloy heat-resistant steel complying with ASTM standards, featuring good high-temperature strength and creep resistance, mainly used for pressure equipment in medium-high temperature conditions.
What are the core alloying elements and their content ranges of SA 387 GRADE 5 Class 1?
The core elements are chromium (2.00%-2.50%) and molybdenum (0.90%-1.10%), supplemented by carbon, manganese, etc. The alloy ratio optimizes its high-temperature mechanical properties and corrosion resistance.
What is the approximate maximum operating temperature that SA 387 GRADE 5 Class 1 can withstand?
The maximum operating temperature is about 593℃. It maintains stable mechanical properties in this range, hardly undergoes creep deformation, suitable for medium-high temperature pressure scenarios.
In which industrial fields is SA 387 GRADE 5 Class 1 mainly used?
It is widely used in petrochemical, power, boiler manufacturing industries, often for reactors, heat exchangers, steam pipes and high-temperature pressure vessel components.
What is the usual delivery condition of SA 387 GRADE 5 Class 1?
The delivery condition is mostly normalizing plus tempering. Normalizing improves structural uniformity, tempering eliminates internal stress, ensuring stable hardness, strength and toughness ratio.
Can SA 387 GRADE 5 Class 1 be used in low-temperature environments? Why?
It is not suitable for low-temperature environments. Its impact toughness decreases significantly at low temperatures, easily causing brittle fracture and failing to meet low-temperature service requirements.
What is the role of molybdenum in SA 387 GRADE 5 Class 1?
Molybdenum can improve the high-temperature strength, creep resistance and hardenability of the steel, and also enhance its corrosion resistance to some extent.
How to detect the quality of SA 387 GRADE 5 Class 1 after processing?
Common detection methods include ultrasonic testing, magnetic particle testing, chemical composition analysis and mechanical property testing to ensure no defects and meet standard requirements.
What is the carbon content range of SA 387 GRADE 5 Class 1 and its function?
Carbon content ranges from 0.15% to 0.25%. It improves the strength and hardness of the steel, but excessive carbon will reduce its toughness and weldability.
What is the standard tensile strength range of SA 387 GRADE 5 Class 1?
The standard tensile strength ranges from 485MPa to 655MPa, with yield strength not less than 275MPa, meeting structural strength requirements of pressure equipment in medium-high temperature conditions.