What are the mechanical properties of SA387 Grade 22 Class 2?
SA387 Grade 22 Class 2 is a specific grade of chrome-molybdenum (Cr-Mo) alloy steel plate designed for high-temperature and high-pressure service. It is primarily used in the construction of pressure vessels, boilers, and reactors in industries like oil refineries, petrochemical plants, and power generation.
The mechanical properties of SA387 Grade 22 Class 2 are defined by the ASTM/ASME SA-387 standard and are guaranteed by the material's Normalized and Tempered (+NT) heat treatment condition.
Minimum Required Properties (Per ASTM/ASME SA-387)
| Property | Requirement |
|---|---|
| Tensile Strength | 515 - 690 MPa (75 - 100 ksi) |
| Yield Strength (0.2% Offset) | ≥ 310 MPa (≥ 45 ksi) |
| Elongation (in 50mm / 2") | ≥ 18% (for plates ≤ 25mm / 1" thick) ≥ 20% (for plates > 25mm / 1" thick) |
| Reduction of Area | ≥ 45% (transverse test specimen) |
| Hardness (Brinell) | ≤ 220 HBW (typically ~163-220 HBW) |
| Impact Toughness (Charpy V-Notch) | Notch-Toughness Requirement: Must meet the supplementary requirement S8 if specified in the purchase order (e.g., 54J / 40 ft-lbf min. avg. at a specified temperature). |
Critical High-Temperature Properties
While not a single guaranteed value, SA387 Gr 22 Cl 2 is selected for its creep strength and elevated temperature yield strength. Design values are found in codes like ASME BPVC Section II, Part D (e.g., tables for maximum allowable stress values, "S" values).
Typical Maximum Useful Temperature: Up to ~540°C (~1000°F) for long-term service.
Key Advantage: Maintains a significant portion of its room-temperature strength at elevated temperatures, far superior to carbon steel.
Important Notes & Influencing Factors
Heat Treatment is Mandatory: The "Class 2" designation ensures the Normalized & Tempered condition, which achieves this specific balance of strength and ductility.
Thickness Effect: Mechanical properties, especially yield strength and elongation, can vary slightly with plate thickness. Thicker sections may exhibit lower strength.
Test Direction: Properties are typically reported in the transverse direction (perpendicular to rolling). Longitudinal values can be slightly higher.
Actual vs. Minimum: Mill Test Certificates (MTRs) report actual tested values from the specific heat, which must meet or exceed the minimums above. Actual yield strength often exceeds 310 MPa significantly.
In summary
SA387 Grade 22 Class 2 provides a minimum yield strength of 310 MPa (45 ksi) and tensile strength between 515-690 MPa (75-100 ksi), combined with good ductility and a controlled hardness that ensures weldability and toughness for high-temperature pressure vessel construction.
1. What is SA387 Grade 22 Class 2?
SA387 Grade 22 Class 2 is a specification for chromium-molybdenum alloy steel plates primarily used in pressure vessels and other high-temperature service applications.
2. What is the chemical composition of SA387 Grade 22 Class 2?
Its typical composition includes chromium (2.00-2.50%), molybdenum (0.90-1.10%), with carbon, manganese, phosphorus, sulfur, and silicon making up the remainder.
3. What are the mechanical properties of SA387 Gr 22 Cl 2?
Key mechanical properties include a minimum tensile strength of 515 MPa (75 ksi) and a minimum yield strength of 310 MPa (45 ksi) for plates over 65mm thick.
4. What is the difference between SA387 Grade 22 Class 1 and Class 2?
The primary difference is heat treatment; Class 2 material is required to be supplied in the normalized and tempered condition, while Class 1 does not have this mandatory requirement, affecting its strength and microstructure.
5. What is the maximum service temperature for SA387 Grade 22?
SA387 Grade 22 is commonly used for service temperatures up to approximately 550°C (1022°F), but specific limits depend on the pressure and stress conditions.
6. Is SA387 Grade 22 Class 2 equivalent to any other material grade?
Yes, it is broadly equivalent to ASTM A387 Gr22 Cl2, ASME SA387 Gr22 Cl2, and the common wrought material grade UNS K21590.
7. How to weld SA387 Grade 22 Class 2 steel?
Welding typically requires pre-heat and post-weld heat treatment (PWHT). Common filler metals include AWS E9015-B3 for SMAW or corresponding grades for other processes to match the base metal's properties.
8. What is the heat treatment for SA387 Gr22 Cl2?
SA387 Grade 22 Class 2 plates are supplied in the normalized (at 1650-1750°F) and tempered (at 1250-1350°F) condition to achieve the required mechanical properties.
9. Where is SA387 Grade 22 Class 2 commonly used?
It is extensively used in the fabrication of pressure vessels, boilers, and reactors for the power generation, petrochemical, and oil & gas industries, especially for components exposed to high temperatures and pressures.
10. What are the hardness requirements for SA387 Grade 22 Class 2?
While the ASTM/ASME specification does not mandate a specific hardness, it is typically controlled during heat treatment. A common requirement in service is to maintain a maximum hardness, often 225 Brinell (HBW) or lower, to prevent issues like hydrogen-induced cracking.
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.
