What Is ASTM A671 CC65 Class 30 Pipe?
ASTM A671/A671M is the standard specification for electric-fusion-welded carbon steel pipe intended for atmospheric and lower-temperature service. The pipe is produced from pressure-vessel-quality steel plate: the plate is formed into a cylinder and the longitudinal seam is welded with filler metal added during the electric fusion welding process. The designation CC65 Class 30 combines a grade, which defines the plate chemistry and strength, and a class, which defines the welding configuration, examination, and testing applied to the finished pipe.
Grade CC65: Material Definition
Grade CC65 is manufactured from carbon steel plate conforming to ASTM A516 Grade 65, a pressure-vessel-quality steel specified for moderate and lower-temperature service. The suffix 65 corresponds to a minimum tensile strength of 65 ksi, equal to 448 MPa. Grades with the 65 suffix must demonstrate low-temperature toughness, so the pipe is subject to Charpy V-notch impact testing at minus 50 degrees Fahrenheit, equal to minus 46 degrees Celsius, with the minimum absorbed energy defined by the applicable edition of the standard.
| Property | Typical Value per ASTM A516 Grade 65 |
|---|---|
| Minimum tensile strength | 65 ksi, equal to 448 MPa |
| Carbon, C, maximum | 0.28%, with limits varying by plate thickness |
| Manganese, Mn | 0.85% to 1.20% |
| Phosphorus, P, maximum | 0.035% |
| Sulfur, S, maximum | 0.035% |
| Silicon, Si | 0.15% to 0.40% |
What Class 30 Means
In the ASTM A671 class system, the class number defines the manufacturing and testing condition of the pipe. Class 30 requires 100 percent radiographic examination of the longitudinal weld seam, which provides a complete record of weld soundness. Radiography detects internal discontinuities such as porosity, lack of fusion, and inclusions, and it is the examination level selected for critical low-temperature and pressure service.
Manufacturing Process
The pipe is formed from plate by rolling or pressing into a cylinder, and the longitudinal seam is closed by electric fusion welding, typically submerged arc welding, from one or both sides. After welding, the pipe is sized, and the required heat treatment, examination, and pressure testing are performed according to the class. For Class 30, the weld is fully radiographed and the pipe is hydrostatically tested before shipment.
Typical Applications
A671 CC65 Class 30 pipe is used in low-temperature service where toughness at subzero temperatures is required. Typical installations include LNG terminal utility lines, low-temperature storage tank piping, refrigerated process lines, and power plant piping in cold environments. The combination of pressure-vessel-quality plate, impact testing, and full radiography makes it suitable for the most demanding low-temperature carbon steel applications.
FAQ
What does CC65 mean in ASTM A671?
CC identifies a carbon steel grade manufactured from A516 pressure-vessel plate, and 65 is the minimum tensile strength in ksi, equal to 448 MPa. The grade is impact tested at low temperature.
What is the difference between grade and class in A671?
The grade defines the steel chemistry and strength, while the class defines the weld configuration, heat treatment, examination level, and pressure testing of the finished pipe. Both must be stated in the order.
What examination is required for Class 30?
Class 30 requires 100 percent radiographic examination of the longitudinal weld seam. This is the highest routine examination level for single-welded A671 pipe and provides complete verification of weld soundness.
At what temperature is the impact test performed?
Grades with the 65 suffix are impact tested at minus 50 degrees Fahrenheit, equal to minus 46 degrees Celsius, in accordance with ASTM A671/A671M.
Can CC65 Class 30 pipe be welded in the field?
Yes. The girth welds are made on site with qualified procedures, and the low-temperature toughness of the base metal is preserved by proper joint preparation and welding control.
What certificates are provided?
Mill test reports document the chemistry, tensile and impact test results, radiographic examination, and hydrostatic test. The report is required for low-temperature pressure piping documentation.
