SA387 Grade 11 Class 2 is a chromium‑molybdenum alloy steel plate covered by the ASME SA387 specification, intended mainly for welded pressure vessels and service at elevated temperatures. Its alloy content gives it good high‑temperature strength, creep resistance, and toughness, along with favorable weldability, so it is widely used in refineries, petrochemical plants, and boiler components where reliable performance under heat and stress is essential.
Key Characteristics:
Key Elements: Approximately 1.00-1.50% Chromium (Cr) and 0.45-0.65% Molybdenum (Mo).
Properties: Excellent oxidation resistance, corrosion resistance (especially in sour gas), high strength at elevated temperatures.
Class 2 Mechanical Properties: Higher tensile strength (75-100 ksi or 515-690 MPa) and yield strength (min 43 ksi or 310 MPa) than Class 1.
Material Type: Chrome-Moly Alloy Steel Plate.
Applications: Boilers, pressure vessels, heat exchangers, and piping for elevated temperature service.
Standards & Equivalents:
Specified under ASTM A387 and ASME SA387.
Can be supplied with specific heat treatments like Normalized & Tempered (N&T) or Quenched & Tempered (Q&T) for more severe conditions.
Sa 387 Gr 11 Specification
| Grade | SA 387 Gr 11 material |
| Pressure Vessel Plates Specification | ASME SA387 and ASTM A387 Gr 11 Chromium-Molybdenum, Alloy Steel |
| Contact our sales executive in these locations | Mexico, UAE, Abu Dhabi, Singapore, Indonesia, Malaysia, Canada, USA, Pennsylvania, France, UK, Qatar, Australia, South Africa |
| Dimensions |
Grade11 Width : 1000mm-4500mm Thickness : 5mm-150mm Length : 3000mm -18000mm |
| Impact tested | -52° C |
| Uses |
Pressure vessels Welded boilers and other industrial applications |
Chemical Requirements for ASME SA387 Grade 11 Alloy Steel Plates
| Element | Chemical Composition (%) | |
| SA387 Grade 11 | ||
| Carbon: | Heat Analysis: | 0.05 - 0.17 |
| Product Analysis: | 0.04 - 0.17 | |
| Manganese: | Heat Analysis: | 0.40 - 0.65 |
| Product Analysis: | 0.35 - 0.73 | |
| Phosphorus: | Heat Analysis: | 0.035 |
| Product Analysis: | 0.035 | |
| Sulphur (max): | Heat Analysis: | 0.035 |
| Product Analysis: | 0.035 | |
| Silicon: | Heat Analysis: | 0.50 - 0.80 |
| Product Analysis: | 0.44 - 0.86 | |
| Chromium: | Heat Analysis: | 1.00 - 1.50 |
| Product Analysis: | 0.94 - 1.56 | |
| Molybdenum: | Heat Analysis: | 0.45 - 0.65 |
| Product Analysis: | 0.45 - 0.70 |
the process used
1. Steelmaking and Refining
Melting Process: The steel is typically produced using the Electric Arc Furnace (EAF) or Basic Oxygen Furnace (BOF) route.
Refining: To ensure high purity and low inclusion levels, it undergoes Ladle Furnace (LF) refining and Vacuum Degassing (VD). This is crucial for controlling the chemical composition (nominally 1.25% Chromium and 0.5% Molybdenum) and minimizing harmful trace elements like Phosphorus and Sulfur.
2. Rolling and Forming
Hot Rolling: The refined steel ingots or slabs are reheated and rolled into plates of specific thicknesses using a heavy plate mill.
Microstructure Control: Controlled rolling parameters are maintained to ensure a uniform grain structure before the final heat treatment.
3. Heat Treatment (Crucial for Class 2)
The "Class 2" designation refers to specific tensile strength requirements (higher than Class 1), achieved through the following heat treatment processes:
Normalizing and Tempering (N+T): The plates are heated to an austenitizing temperature (typically above 900°C/1650°F), air-cooled, and then tempered at a minimum temperature of 1150°F (620°C).
Quenching and Tempering (Q+T): For thicker sections, accelerated cooling (liquid quenching) followed by tempering is used to ensure through-thickness mechanical properties.
4. Fabrication Processes
Welding: Due to its alloy content, the material is susceptible to cold cracking. Fabrication requires preheating (typically 150°C to 250°C) and the use of low-hydrogen electrodes.
Post-Weld Heat Treatment (PWHT): Mandatory for most pressure vessel applications to relieve residual stresses and refine the grain structure in the Heat Affected Zone (HAZ).
Cutting: CNC Plasma or Flame cutting is standard, though edges usually require grinding to remove the heat-affected layer before welding.
5. Mechanical Property Requirements
Under the ASME Section II Part A (SA-387) or ASTM A387/A387M specifications:
Tensile Strength: 75 to 100 ksi (515 to 690 MPa).
Yield Strength: Minimum 45 ksi (310 MPa).
Elongation: Minimum 18% to 22% (depending on gauge length).
applications
Pressure vessels：
Used in welded pressure vessels requiring strength and creep resistance at elevated temperatures, where stable mechanical properties and resistance to thermal cycling are essential for long-term reliability and safety under demanding operating conditions.
Refinery equipment：
Applied in refinery columns, reactors, and heat exchangers operating under high-temperature conditions, where the material must withstand continuous exposure to heat, pressure, and various process fluids while maintaining structural integrity and minimizing the risk of deformation or failure over extended service life.
Petrochemical and chemical processing：
Used for process vessels and piping components in petrochemical plants and chemical processing facilities, where the steel must provide good resistance to high-temperature degradation and maintain toughness and weldability in environments involving corrosive media and cyclic loading.
Boilers and boiler components：
Suitable for boiler drums, headers, and other parts subject to heat and pressure, where the material must exhibit excellent strength retention at elevated temperatures, along with sufficient ductility and fatigue resistance to handle repeated heating and cooling cycles.
Power generation：
Employed in power plant equipment where high-temperature service and reliability are critical, such as in components exposed to sustained heat and mechanical stress, requiring materials that can maintain performance and structural stability over many years of operation.
General high-temperature service：
Used in various components that must perform consistently under sustained heat and mechanical stress, including furnace parts, pressure-containing structures, and other heavy-duty equipment operating in harsh thermal environments.
Full specification and details are available on request. The above information is provided for guidance purposes only. For specific design requirements please contact our technical sales staff.
What is SA387 Grade 11 Class 2?
SA387 Grade 11 Class 2 is a chromium-molybdenum alloy steel plate under the ASME SA387 standard, mainly for welded pressure vessels and high-temperature service. It offers good high-temperature strength, creep resistance, and weldability, making it suitable for refineries, petrochemical plants, and boilers where reliable performance under heat and stress is required.
What are the key alloying elements in SA387 Grade 11 Class 2?
SA387 Grade 11 Class 2 primarily contains chromium and molybdenum, which enhance its high-temperature strength and creep resistance. These elements also improve hardenability and toughness, allowing the steel to maintain mechanical properties under prolonged heat exposure. Carbon and manganese are present to support strength and formability, while other residual elements are controlled to ensure weldability and structural stability.
What standards cover SA387 Grade 11 Class 2?
SA387 Grade 11 Class 2 is specified in the ASME SA387 standard, which governs chromium-molybdenum alloy steel plates for pressure vessel applications. It is also referenced in various ASME Boiler and Pressure Vessel Code sections, ensuring compliance with material, testing, and fabrication requirements. Additional industry standards may be applied depending on the end use and regulatory jurisdiction.
What heat treatment is typically applied to SA387 Grade 11 Class 2?
SA387 Grade 11 Class 2 is usually supplied in the normalized and tempered condition. Normalizing refines the grain structure and improves strength, while tempering reduces hardness and enhances toughness, minimizing the risk of cracking during welding or service. This heat treatment ensures the steel meets the required mechanical properties for high-temperature pressure vessel applications.
What are the typical mechanical properties of SA387 Grade 11 Class 2?
SA387 Grade 11 Class 2 exhibits good tensile strength, yield strength, and impact toughness, especially at elevated temperatures. It maintains its strength under prolonged heat exposure and shows resistance to creep deformation. The steel also has adequate ductility and fatigue resistance, allowing it to withstand thermal cycling and mechanical stress in pressure vessel service.
What are the main applications of SA387 Grade 11 Class 2?
SA387 Grade 11 Class 2 is widely used in welded pressure vessels, refinery columns, reactors, and heat exchangers. It is also suitable for boiler drums, headers, and power plant components operating at high temperatures. Its ability to resist creep and maintain strength makes it ideal for petrochemical and chemical processing equipment in harsh thermal environments.
Why is SA387 Grade 11 Class 2 suitable for high-temperature service?
SA387 Grade 11 Class 2 contains chromium and molybdenum, which improve its resistance to creep and high-temperature degradation. These alloying elements stabilize the microstructure and prevent softening under prolonged heat exposure. The steel's heat treatment further enhances its strength retention and toughness, ensuring reliable performance in elevated-temperature pressure vessel applications.
How does SA387 Grade 11 Class 2 perform in welding?
SA387 Grade 11 Class 2 has good weldability when proper procedures are followed. Preheating and post-weld heat treatment are often recommended to reduce hardness and prevent cracking in the heat-affected zone. Matching consumables with similar chromium and molybdenum content ensure sound welds with adequate strength and toughness for high-temperature service.
What are the differences between Grade 11 Class 1 and Class 2 in SA387?
SA387 Grade 11 Class 1 and Class 2 have similar chemistry but differ in tensile strength and toughness requirements. Class 2 offers higher strength and improved impact properties, making it more suitable for demanding pressure vessel applications. Class 1 is often used where lower strength is acceptable, while Class 2 is preferred for thicker plates and more severe service conditions.
What quality control tests are performed on SA387 Grade 11 Class 2?
SA387 Grade 11 Class 2 typically undergoes ultrasonic testing to detect internal flaws, tensile and impact tests to verify mechanical properties, and hardness testing to ensure heat treatment effectiveness. Chemical analysis confirms alloy content, and radiographic or other nondestructive tests may be conducted based on customer or code requirements to ensure structural integrity.
What are the limitations of SA387 Grade 11 Class 2?
SA387 Grade 11 Class 2 has limited corrosion resistance in highly corrosive environments and may require additional protection such as coatings or cladding. It is also not recommended for extremely high temperatures where more highly alloyed steels are necessary. Welding requires careful procedure control to avoid cracking, and thicker sections may need extended heat treatment to ensure uniform properties.