Technical Profile: ASTM A671 CB70 Class 33
ASTM A671 Grade CB70 is a high-strength EFW pipe from ASTM A515 Grade 70 plate. It is intended for moderate-temperature pressure service. The Class 33 designation requires stress-relieving and 100% radiographic examination of the weld.
Class 33: Stress Relieving and Integrity
Class 33 follows a rigorous quality protocol:
Stress Relieving: Heated to ~1100°F to eliminate residual tension, ensuring dimensional stability.
NDT: 100% RT is mandatory to verify penetration and ensure a joint factor of 1.0.
Mechanical Properties
| Property | CB70 Class 33 Requirement |
|---|---|
| Tensile Strength | 485–620 MPa (70–90 ksi) |
| Yield Strength min. | 260 MPa (38 ksi) |
| Plate Standard | ASTM A515 Grade 70 |
FAQs
Class 33 vs Class 32?
Class 32 is Normalized; Class 33 is Stress Relieved. Normalizing refines grain; SR only reduces tension.
CB70 vs CC70?
CB70 uses A515 plate (moderate temps); CC70 uses A516 (lower temps).
Does A671 require hydro-testing?
Yes, 100% hydrostatic testing is mandatory for every length.
Use for cryogenic?
No, A515 is not designed for cryogenic toughness. Specify CC70 or CF70 series.
Filler metal required?
Must comply with AWS A5.1/A5.5, matching the A515 Grade 70 base plate.
