SA387 grade 5 class 2 Steel Plate - Pressure Vessel

SA 387 Grade 5 Class 2 is a chromium-molybdenum alloy steel plate specified in the ASME Boiler and Pressure Vessel Code. It is primarily used for welded pressure vessels and boiler components operating at elevated temperatures. This material offers good strength, creep resistance, and oxidation resistance, making it suitable for refineries, petrochemical plants, and power generation applications. Its chemical composition and mechanical properties are tightly controlled to ensure reliability under high-temperature and high-pressure conditions.

Equivalents

Specifications ASME SA387 Grade 5 Alloy Steel Plates

Tensile Requirements for ASME SA387 Grade 5 Alloy Steel Plates Class 2 Plates

Chemical Requirements for ASME SA387 Grade 5 Alloy Steel Plates

Primary Processing Methods

Manufacturing Process: These plates are primarily produced through Hot-Rolling (HR). Some suppliers also offer cold-rolled (CR) variants for specific sheet applications.

Heat Treatment: To achieve Class 2 mechanical properties (which require higher strength than Class 1), the material typically undergoes specialized heat treatments:

Normalizing and Tempering (N+T): The most common condition for Class 2, where the steel is heated to a critical temperature and then cooled to refine its grain structure before being tempered.

Quenching and Tempering (Q+T): Used to further enhance hardness and tensile strength.

Annealing: Though more common for Class 1 (as it "softens" the steel), annealing can be part of the initial processing stages.

Minimum Tempering Temperature: For Grade 5, the minimum tempering temperature is typically 1300°F (705°C) to ensure thermal stability.

Fabrication and Secondary Processing

Once the raw plate is manufactured, it undergoes various fabrication steps:

Cutting: Precise sizing using methods like plasma cutting, laser, or waterjet to meet specific project dimensions.

Forming and Machining: The material has good formability, allowing it to be shaped into vessel heads or cylinders. Drilling and grinding are used for surface smoothing and hole placement.

Welding: It possesses good weldability using conventional methods such as TIG, MIG, and SMAW. However, preheating is mandatory to prevent cracking, and post-weld heat treatment (PWHT) is often simulated during testing.

Quality Testing and Inspections

Rigorous processing includes multiple non-destructive and mechanical tests to ensure integrity:

Mechanical Testing: Tensile strength (515–690 MPa), yield strength (310 MPa), and elongation tests.

Non-Destructive Testing (NDT): Ultrasonic examination (UT) for internal flaws and magnetic particle examination (MPI) for surface defects.

Impact Testing: Charpy V-Notch testing, often down to -52°C, to ensure toughness in varied environments.

Primary Industrial Applications

Petrochemical and Chemical Processing: These plates are fundamental in constructing equipment that handles corrosive chemicals at extreme temperatures. Key uses include:

Pressure Vessels: Used for storage and processing under high pressure.

Heat Exchangers: Crucial for efficient thermal management in refining processes.

Reactors and Distillation Columns: Components that must resist hydrogen attack and oxidation.

Oil and Gas Industry: Widely used in upstream and downstream operations, including:

Refineries: In systems like hydrocrackers and catalytic reformers where "sour service" (H2S environments) is common.

Storage Tanks: Specifically those designed for weldable carbon steel applications at elevated temperatures.

Power Generation: Essential for fossil fuel and nuclear power plants in high-heat areas:

Boiler Drums and Industrial Boilers: Withstanding continuous steam pressure and high heat.

Steam Generators: Used in turbine systems and piping.

Piping and Ducting: For high-temperature gas and fluid transport.

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What post-weld heat treatment is required for SA 387 Grade 5 Class 2?

Post-weld heat treatment for SA 387 Grade 5 Class 2 typically involves heating the joint to 1100°F to 1200°F (595°C to 650°C) and holding for a time based on thickness. This process relieves residual stresses, improves ductility, and enhances resistance to temper embrittlement. PWHT is often mandatory for pressure vessel applications to ensure structural integrity and compliance with ASME code requirements, especially for thick sections.

What welding processes are commonly used for SA 387 Grade 5 Class 2?

Common welding processes for SA 387 Grade 5 Class 2 include SMAW, GTAW, GMAW, and SAW. The choice depends on joint design, thickness, and production needs. Low-hydrogen electrodes and fluxes are preferred to minimize cracking risk. Proper procedure qualification and welder certification are essential to ensure reliable welds. Each process has specific advantages, such as GTAW for root passes and SAW for high-deposition filling in thick plates.

What are the typical forms and dimensions of SA 387 Grade 5 Class 2?

SA 387 Grade 5 Class 2 is primarily produced as steel plates in various thicknesses and widths, as specified by ASME SA-387. Plates can range from thin sheets to several inches thick, depending on the application. The material may also be available as forgings or castings for specialized components. Dimensions and tolerances are controlled to meet pressure vessel fabrication and design code requirements.

What are the testing requirements for SA 387 Grade 5 Class 2 plates?

SA 387 Grade 5 Class 2 plates undergo tensile, bend, impact, and ultrasonic tests. Tensile tests verify strength properties, while bend tests assess ductility. Impact tests evaluate toughness and resistance to brittle fracture. Ultrasonic testing detects internal defects. Additional tests such as hardness and chemical analysis may be performed to ensure compliance with standards. These tests help guarantee the material's quality and reliability for critical applications.

What is the hardness range of SA 387 Grade 5 Class 2?

The hardness of SA 387 Grade 5 Class 2 is typically between 170 and 220 HB after proper heat treatment. This range provides a good balance of strength and toughness, suitable for high-temperature pressure vessel service. Hardness testing is done on base material and welds to check for excessive hardening in the heat-affected zone, which could indicate potential cracking issues.

How does SA 387 Grade 5 Class 2 perform in terms of creep resistance?

SA 387 Grade 5 Class 2 has good creep resistance at elevated temperatures due to its chromium and molybdenum content. These elements stabilize the microstructure and reduce deformation under long-term stress and heat. The material is used in components where creep must be minimized, such as steam headers and high-temperature pressure vessels. Proper heat treatment and design are necessary to ensure reliable creep performance over the service life.

What is the oxidation resistance of SA 387 Grade 5 Class 2?

SA 387 Grade 5 Class 2 has moderate oxidation resistance due to its chromium content, which forms a protective oxide layer at high temperatures. This resistance is sufficient for many refinery and petrochemical applications but may be limited in very high-temperature or highly oxidizing environments. In such cases, coatings or higher-chromium alloys may be needed. Oxidation behavior is an important consideration in high-temperature service design.

What is the corrosion resistance of SA 387 Grade 5 Class 2?

SA 387 Grade 5 Class 2 is not specifically designed for highly corrosive environments but offers reasonable resistance to mild atmospheric and industrial corrosion. Its performance depends on temperature, environment, and stress. In aggressive environments with acids, salts, or sulfides, additional protection or alternative materials may be required. Proper surface treatment and coatings can enhance its corrosion resistance in certain applications.

Can SA 387 Grade 5 Class 2 be used in low-temperature applications?

SA 387 Grade 5 Class 2 is primarily intended for high-temperature service and may not be ideal for low-temperature use where high toughness is needed. Its impact resistance can decrease at low temperatures, increasing brittle fracture risk. For cryogenic or low-temperature service, materials like SA 516 Grade 70 or nickel-alloyed steels are more suitable. The design temperature range must be carefully evaluated for code compliance.

What is the fatigue resistance of SA 387 Grade 5 Class 2?

SA 387 Grade 5 Class 2 has acceptable fatigue resistance for many pressure vessel and boiler applications when properly designed and fabricated. Fatigue performance depends on stress level, temperature, surface finish, and weld quality. Welded joints can reduce fatigue life due to stress concentrations and residual stresses. Proper welding, post-weld heat treatment, and quality control are essential to maximize fatigue resistance under cyclic loading.