What Is SA387 Grade 11 Class 2
SA387 Grade 11 Class 2 is a chromium-molybdenum alloy steel plate specified in ASTM A387 and its ASME adoption SA387, used for welded pressure vessels and boilers in elevated temperature service. The nominal composition is 1.25 percent chromium and 0.5 percent molybdenum, and the Class 2 designation requires the higher-strength normalized and tempered delivery condition.
Chemical Composition
Heat analysis limits are carbon 0.05 to 0.17 percent, manganese 0.40 to 0.65 percent, phosphorus 0.035 percent, sulfur 0.035 percent, silicon 0.50 to 0.80 percent, chromium 1.00 to 1.50 percent, and molybdenum 0.45 to 0.65 percent. Product analysis ranges are slightly wider, for example chromium 0.94 to 1.56 percent and molybdenum 0.40 to 0.70 percent.
Mechanical Properties
Class 2 plates have a tensile strength of 515 to 690 MPa, a minimum yield strength of 310 MPa at 0.2 percent offset, a minimum elongation of 18 percent in 200 mm and 22 percent in 50 mm. The higher strength compared with Class 1 allows thinner vessel walls for the same design pressure.
Heat Treatment
Class 2 plates are supplied in the normalized and tempered condition, with a minimum tempering temperature of 620 degrees C, or in the quenched and tempered condition. The resulting tempered microstructure combines high strength with the ductility and toughness required for pressure vessel fabrication.
Applications
The grade is used for pressure vessels in the oil and gas industry, boilers, heat exchangers, pipelines and equipment operating at elevated temperatures, flanges, high-temperature ducting, pipe clamps, and valves. It is particularly effective where liquids and gases are stored and processed at higher temperatures.
Fabrication Guidance
Welding requires preheating, typically 150 to 200 degrees C for thicker plates, low-hydrogen consumables, and post-weld heat treatment per the governing code to prevent hydrogen-induced cracking and restore toughness in the heat-affected zone. Hot forming within 850 to 950 degrees C is common, followed by heat treatment as required.
Frequently Asked Questions
Q: What is the composition of SA387 Grade 11?
A: About 1.25 percent chromium and 0.5 percent molybdenum.
Q: What is the yield strength of Grade 11 Class 2?
A: 310 MPa minimum.
Q: How does Class 2 differ from Class 1?
A: Class 2 is normalized and tempered to higher strength; Class 1 may be annealed or normalized at lower strength.
Q: Is SA387 Grade 11 Class 2 weldable?
A: Yes, with preheating, low-hydrogen consumables, and post-weld heat treatment.
Q: What applications use SA387 Grade 11 Class 2?
A: Pressure vessels, boilers, heat exchangers, flanges, and high-temperature ducting.
Q: What is the minimum tempering temperature?
A: 620 degrees C for the normalized and tempered condition.
Contact us with your specifications for SA387 Grade 11 Class 2 plates, including thickness, width, and testing requirements.