What Is SA387 Grade 22 Class 2
SA387 Grade 22 Class 2 is a chromium-molybdenum alloy steel plate specified in ASTM A387 and its ASME adoption SA387, designed for high-temperature service in welded boilers and pressure vessels. The nominal composition is 2.25 percent chromium and 1 percent molybdenum, and Class 2 is supplied in the normalized and tempered condition with significantly higher strength than Class 1.
Chemical Composition
Heat analysis limits are carbon 0.05 to 0.15 percent, manganese 0.30 to 0.60 percent, phosphorus 0.025 percent, sulfur 0.025 percent, silicon 0.50 percent maximum, chromium 2.00 to 2.50 percent, and molybdenum 0.90 to 1.10 percent. The composition delivers excellent resistance to heat, corrosion, and oxidation in severe service.
Mechanical Properties
Class 2 plates have a minimum yield strength of 310 MPa, a tensile strength of 515 to 690 MPa, a minimum elongation of 18 percent in 50 mm, and a minimum reduction of area of 40 percent. The higher as-delivered strength compared with Class 1 permits thinner vessel walls and lighter equipment for the same design conditions.
High-Temperature Performance
The 2.25Cr-1Mo composition provides excellent creep resistance, oxidation resistance, and resistance to hydrogen attack up to about 600 degrees C, evaluated per Nelson curve guidelines. This makes the grade a benchmark for heavy-wall refinery vessels and high-temperature power generation components.
Applications
SA387 Grade 22 Class 2 is used in the oil and gas industry for reactors, pressure vessels, heat exchangers, and separators; in chemical processing for reactors, sealed storage tanks, and transfer units handling aggressive media; in power generation for boilers, heat recovery steam generators, steam turbine casings, and steam headers; in petrochemical plants for heavy-duty pressure vessels and high-temperature process piping; and in general industry for high-temperature ducting and pipe clamps.
Equivalents
Key international equivalents include EN and DIN 10CrMo9-10, BS 622-515B, and JIS SCMV4, all offering similar strength and corrosion resistance for demanding oil, gas, and chemical applications. Equivalent comparisons are for reference only; the applicable standard governs.
Frequently Asked Questions
Q: What is the composition of SA387 Grade 22?
A: About 2.25 percent chromium and 1 percent molybdenum.
Q: What is the yield strength of Grade 22 Class 2?
A: 310 MPa minimum.
Q: How does Class 2 differ from Class 1?
A: Class 2 has significantly higher tensile and yield strength after normalization and tempering.
Q: What applications use SA387 Grade 22 Class 2?
A: Refinery reactors, heat exchangers, boilers, steam headers, and chemical vessels.
Q: What is SA387 Grade 22 Class 2 equivalent to?
A: 10CrMo9-10, BS 622-515B, and JIS SCMV4 among others.
Q: What temperature range suits this grade?
A: Continuous service up to about 600 degrees C depending on pressure and environment.
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