SA 387 Grade 11 Class 2 is a chromium-molybdenum alloy steel plate specified in the ASME SA-387/SA-387M standard, primarily used for pressure vessels and boilers operating at elevated temperatures, where it provides good strength retention, creep resistance, and resistance to hydrogen attack and other high-temperature degradation mechanisms.
Tensile Requirements for ASME SA387 Grade 11 Alloy Steel Plates Class 2 Plates
| Designation: | Requirement: | Grade 11 |
| SA387 Grade 11 | Tensile strength, ksi [MPa] | 75 to 100 [515 to 690] |
| Yield strength, min, ksi [MPa]/(0.2% offset) | 43 [310] | |
| Elongation in 8 in. [200mm], min % | 18 | |
| Elongation in 2 in. [50mm], min, % | 22 | |
| Reduction of area, min % | ––– |
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 |
Manufacturing of the plates:
SA 387 GR 11 CL-2 Alloy Steel Plate is manufactured by using the superior quality of raw material that is sourced from the reputable market mills supplying pure quality of alloy only. The producers before utilizing those are doing the testing of the alloy so that the superior quality of plate fabrication can be guaranteed. The fabrication and designing process is executed under the strict guidance of experts that are always ready to guide the workforce in all possible way to develop the quality of plates. Moreover, the designing of plates is done by keeping in mind raw material quality standards and manufacturing guidelines. Also, the quality control team is hired looking at the product quality maintenance through quality control measurements. The proper utilization of sophisticated technology and modern tools has helped us developing the superior quality of plate. Thus the very good comprehensive ranges of plates are supplied and exported to the global buyers. During the time of product creation, it passes through various processes like cutting, forming, drilling, machining, grinding and testing.
Applications
Boilers and pressure vessels
Used for shells, heads, and pressure-retaining parts of boilers, pressure vessels, and heat exchangers that operate at moderate to high temperatures.
Oil and gas industry
Applied in refinery equipment, hydrogenation reactors, reformers, and components exposed to high-temperature hydrogen, hydrocarbons, and sour service conditions.
Power generation
Used in power plant boilers, superheater components, and other high-temperature structural parts in fossil-fuel and some nuclear-related auxiliary equipment.
Chemical and petrochemical processing
Suitable for reactors, columns, and piping systems handling high-temperature and high-pressure process fluids, including hydrogen-rich and corrosive media.
General high-temperature service
Used in any welded pressure equipment where good creep resistance, strength retention, and resistance to hydrogen attack at elevated temperatures are required.
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What is SA 387 Grade 11 Class 2?
SA 387 Grade 11 Class 2 is a chromium-molybdenum alloy steel plate designed for high-temperature pressure vessel applications. It is part of the ASME SA-387 series, which covers heat-resistant chromium-molybdenum alloy steel plates for welded boilers and pressure vessels. Class 2 indicates stricter toughness and impurity control compared to Class 1, making it suitable for more demanding service conditions.
Which standard covers SA 387 Grade 11 Class 2?
SA 387 Grade 11 Class 2 is covered by the ASME SA-387/SA-387M standard, which specifies requirements for chemical composition, mechanical properties, heat treatment, and testing of chromium-molybdenum steel plates used in pressure vessels and boilers. The standard is widely recognized in the oil and gas, petrochemical, and power generation industries.
What type of steel is SA 387 Grade 11 Class 2?
It is a low-alloy Cr-Mo steel, specifically a 1.25% chromium – 0.5% molybdenum alloy. This composition provides excellent high-temperature strength, creep resistance, and resistance to hydrogen attack, making it ideal for elevated-temperature service in pressure equipment.
What are the main alloying elements in SA 387 Grade 11 Class 2?
The key alloying elements are chromium (Cr) and molybdenum (Mo). Chromium improves oxidation resistance and high-temperature strength, while molybdenum enhances creep resistance and toughness. Other elements include carbon, manganese, silicon, phosphorus, and sulfur, with strict limits on impurities to ensure weldability and toughness.
What is the typical chemical composition range of SA 387 Grade 11 Class 2?
Typical ranges include: carbon 0.05–0.17%, manganese 0.40–0.65%, silicon 0.50–0.80%, chromium 1.00–1.50%, molybdenum 0.45–0.65%, phosphorus ≤ 0.035%, and sulfur ≤ 0.035%. These ranges are carefully controlled to balance strength, toughness, and weldability.
What is the minimum yield strength of SA 387 Grade 11 Class 2?
For plates up to 50 mm thick, the minimum yield strength is 310 MPa (45 ksi). For thicker plates, the yield strength may decrease slightly, but it remains sufficient for most high-temperature pressure vessel applications. The yield strength is a critical parameter for ensuring structural integrity under pressure.
How does SA 387 Grade 11 Class 2 differ from SA 387 Grade 11 Class 1?
SA 387 Grade 11 Class 2 has stricter requirements for toughness, lower impurity limits, and often more rigorous testing compared to Class 1. This makes Class 2 better suited for critical pressure vessel applications where resistance to brittle fracture is essential, while Class 1 is used in less demanding situations.
What is the difference in chemical composition between SA 387 Grade 11 Class 2 and SA 387 Grade 22?
SA 387 Grade 11 Class 2 is a 1.25Cr-0.5Mo steel, while Grade 22 is a 2.25Cr-1Mo alloy. The higher chromium and molybdenum content in Grade 22 provides better high-temperature strength and creep resistance, making it suitable for higher service temperatures than Grade 11 Class 2.
How does the maximum service temperature of SA 387 Grade 11 Class 2 compare to that of SA 387 Grade 91?
SA 387 Grade 11 Class 2 is typically used up to around 500°C, whereas SA 387 Grade 91 can operate at temperatures up to approximately 600°C or higher. Grade 91's higher chromium content and advanced heat treatment give it superior creep strength at elevated temperatures compared to Grade 11 Class 2.