SA 387 Grade 12 Class 1 is a low‑alloy chromium‑molybdenum pressure vessel steel plate intended for service at elevated temperatures. It offers good strength and resistance to creep and thermal fatigue, making it suitable for refinery, petrochemical, and power generation equipment. Class 1 represents specific mechanical property and heat treatment requirements that ensure reliable toughness and structural integrity. The material is typically supplied in the normalized and tempered condition and exhibits good weldability when proper preheating and post‑weld heat treatment are applied.
Chemical Properties:
|
SA387/ASTM A387 |
Grade 12 |
|
Carbon |
0.04 – 0.17 |
|
Manganese |
0.35 – 0.73 |
|
Phosphorous |
0.035 |
|
Sulfur |
0.035 |
|
Silicon |
0.13 – 0.45 |
|
Chromium |
0.74 – 1.21 |
|
Molybdenum |
0.4 – 0.65 |
Mechanical properties for SA387 Grade 12 CL 2 pressure vessel steel plate:
|
Yield strength (Mpa) |
Tensile strength (Mpa) |
Elongation ≥,% 200mm |
|
275 |
450-585 |
19 |
processing
Melting and Casting: The steel is produced in electric arc furnaces or other controlled melting processes to achieve the precise chemical composition needed for good strength and high-temperature performance. After refining, the molten steel is cast into ingots or continuously cast into slabs, ensuring a sound, homogeneous structure with minimal impurities.
Hot Rolling: The slabs are reheated and hot rolled into plates of the desired thickness. This process refines the grain structure, improves mechanical properties, and imparts the necessary strength and toughness required for pressure vessel applications.
Heat Treatment (Normalizing and Tempering): Plates are normally normalized at a suitable temperature to refine the microstructure and enhance uniformity. They are then tempered to reduce residual stresses, improve ductility, and optimize the balance between strength and toughness, which is essential for service at elevated temperatures.
Descaling and Conditioning: After rolling, the plates undergo descaling to remove surface oxides. Additional conditioning steps, such as grinding or shot blasting, may be applied to achieve the required surface quality and flatness.
Testing and Inspection: Before shipment, the material is subjected to various tests, including mechanical property evaluations, ultrasonic inspection for internal soundness, and sometimes chemical analysis. These checks ensure that the plates meet the stringent requirements of pressure vessel standards and are suitable for critical applications.
applications
Pressure Vessels & Boilers: For safe containment of pressurized gases and liquids in industrial boilers and thermal power plants.
Heat Exchangers & Reactors: Critical in refining processes for efficient heat transfer and chemical reactions.
Sour Service Equipment: Ideal for environments containing hydrogen sulfide (𝐻2𝑆), common in oil and gas extraction.
Piping Systems: Used for high-temperature process pipework in refineries and chemical plants.
Storage Tanks: For storing volatile liquids and gases at elevated temperatures.
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How to prevent corrosion of SA 387 Grade 12 Class 1 during storage?
Store in dry, ventilated area, apply anti-rust oil, use moisture-proof covers, and avoid contact with salt or acidic substances.
What is the difference between SA 387 Grade 12 Class 1 and SA 387 Grade 22?
Grade 22 has higher Mo (2.25%) for better high-temperature strength; Grade 12 is cost-effective for moderate-temperature services.
Can SA 387 Grade 12 Class 1 be used in cryogenic applications?
No, its minimum service temperature is -29°C. Choose SA 516 Grade 70 for cryogenic use due to lower brittle transition temperature.
What is the creep resistance performance of SA 387 Grade 12 Class 1?
It has good creep resistance at high temperatures, minimizing deformation under long-term constant load, crucial for high-temperature pressure vessels.
Can SA 387 Grade 12 Class 1 be cold-formed?
Limited cold forming is feasible with preheating to prevent cracking; hot forming at 900-1100°C is preferred for complex shapes.
What standard governs the production of SA 387 Grade 12 Class 1?
It is governed by ASME BPVC Section II, Part A, which specifies material requirements, testing standards and certification procedures.
What is the density of SA 387 Grade 12 Class 1?
Its density is about 7.85 g/cm³ (0.283 lb/in³), same as most carbon and low-alloy steels, facilitating weight calculation.
What is the fatigue strength of SA 387 Grade 12 Class 1?
Its fatigue strength is about 200 MPa at 10⁷ cycles, varying with heat treatment and surface condition, suitable for cyclic loads.
Can SA 387 Grade 12 Class 1 be joined with other steel grades?
Yes, it can be welded to SA 516 and other low-alloy steels with compatible electrodes, accompanied by proper post-weld heat treatment.