A387 Grade 11 Class 2 related information
ASTM A387 Grade 11 Class 2 is the same chromium-molybdenum alloy composition but supplied in the fully normalized and tempered (or quenched and tempered) heat treatment condition. This provides higher as-delivered strength and a more refined microstructure, making it suitable for applications where the final PWHT by the fabricator is impractical or where higher initial mechanical properties are required for the finished component.
ASTM A387 Grade 11 Class 2 Chemical Composition (%)
| Grade / Material | C | Mn | Si | P (max) | S (max) | Cr | Mo |
|---|---|---|---|---|---|---|---|
| A387 Grade 11 Class 2 (A387 Gr11 Cl2) | 0.05–0.17 | 0.40–0.65 | 0.15–0.40 | 0.035 | 0.035 | 1.00–1.50 | 0.45–0.65 |
Key alloy data highlights:
Chromium (Cr): 1.00–1.50% → improves oxidation & corrosion resistance
Molybdenum (Mo): 0.45–0.65% → enhances creep strength & hydrogen resistance
ASTM A387 Grade 11 Class 2 Mechanical Properties
| Grade / Material | Tensile Strength | Yield Strength (min) | Elongation (min) |
|---|---|---|---|
| MPa | MPa | % | |
| A387 Grade 11 Class 2 (A387 Gr11 Cl2) | 515–690 MPa | ≥ 310 MPa | ≥ 18% |
Compared with Class 1 (415–585 MPa tensile / 240 MPa yield),
Class 2 offers significantly higher strength, making it suitable for more demanding pressure and temperature conditions.
Impact Test
| Test Type | Typical Requirement |
|---|---|
| Charpy V-Notch Impact | As specified by project |
| Test Temperature | −20°C / −40°C / −60°C (optional) |
| Standard | ASTM / ASME / EN |
Heat Treatment Condition
| Item | Requirement |
|---|---|
| Delivery Condition | Normalized & Tempered (N+T) |
| Minimum Tempering Temperature | ≥ 620°C (1150°F) |
| Optional Treatments | Q+T, HIC, PWHT |
ASTM A387 Grade 11 Class 2 Equivalent Steel Grades
| Standard | Equivalent Grade |
|---|---|
| ASME | SA387 Grade 11 Class 2 |
| China (GB) | 14Cr1MoR |
| DIN / EN | 10CrMo9-10 |
These mechanical values allow the steel to safely withstand high internal pressure, thermal stress, and cyclic loading, making it suitable for critical pressure equipment.
1. How does the "Class 2" condition affect the welding procedure for A387 Grade 11?
This question explores the practical fabrication implications of using the pre-tempered Class 2 material, focusing on the specific adjustments needed for preheat, interpass temperature, and Post-Weld Heat Treatment (PWHT) compared to Class 1.
2. What are the main disadvantages of specifying A387 Grade 11 Class 2 over Class 1?
This question investigates the potential trade-offs, such as higher cost, less flexibility for subsequent hot forming, or the risk of property degradation if improper PWHT is applied to the already heat-treated plate.
3. In what specific applications is A387 Grade 11 Class 2 the mandatory or preferred choice?
This question seeks to define the engineering scenarios where the higher as-delivered strength and pre-treated microstructure of Class 2 provide a critical advantage, such as in repair projects or for components where full vessel PWHT is impossible.
4. What controls are necessary during the PWHT of a Class 2 material to prevent over-tempering?
This question addresses a key technical risk: ensuring that the mandatory post-weld stress relief does not lower the yield and tensile strength of the base metal below the minimum specified values for Class 2.
5. How does the impact toughness of Class 2 compare to Class 1 after proper fabrication?
This question compares the final service performance of the two classes, examining whether the different manufacturing routes result in significant differences in fracture resistance at operating temperatures.
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.
