Overview of ASTM A671 CJP115 Class 33 Pipe
ASTM A671/A671M is the specification for electric-fusion-welded steel pipe made from pressure-vessel-quality plate, intended for high-pressure service at atmospheric and lower temperatures. The pipe is formed from plate and welded with a double-sided submerged arc weld, then heat treated and examined according to the class. It is produced in large diameters, normally 16 in, about 406 mm, and larger.
The designation CJP115 Class 33 has two independent parts. CJP115 names the plate material and its strength level: the pipe is made from A517/A517M Grade P plate, a high-strength alloy steel, quenched and tempered. Class 33 names the heat treatment and examination requirements applied to the finished pipe. Each part is explained below.
What the Grade Means
In the A671 designation the two-letter prefix identifies the pressure-vessel plate specification from which the pipe is made, and the number states the minimum tensile strength in ksi. The grade CJP115 therefore means pipe made from A517/A517M Grade P, with a minimum tensile strength of 115 ksi, about 790 MPa.
| Grade | Plate specification | Steel type | Minimum tensile strength |
|---|---|---|---|
| CJP115 | A517/A517M Grade P | high-strength alloy steel, quenched and tempered | 115 ksi, about 790 MPa |
CJP115 is made from A517 Grade P, a chromium-molybdenum-vanadium-boron alloy steel supplied in the quenched and tempered condition. The plate tensile range is 115 to 135 ksi, and the letters CJP are a material category code pointing to A517 Grade P plate, not the welding term complete joint penetration.
In terms of strength, The minimum yield strength is 100 ksi, about 690 MPa, for plate thicknesses up to 2.5 in..
How the A671 Class System Works
The class is a two-digit code. The first digit selects the heat-treatment family applied to the pipe after welding.
| Class family | Heat treatment applied to the pipe |
|---|---|
| 10 to 13 | None; delivered as welded |
| 20 to 23 | Stress relieved after welding |
| 30 to 33 | Normalized |
| 40 to 43 | Normalized and tempered |
| 50 to 53 | Quenched and tempered |
| 70 to 73 | Quenched and precipitation heat treated |
The second digit selects the examination level.
| Last digit | Radiography of the weld | Pressure test |
|---|---|---|
| 0 | Not required | Not required |
| 1 | Full-length radiography of each weld per ASME VIII UW-51 | Not required |
| 2 | Full-length radiography of each weld per ASME VIII UW-51 | Required per A530/A530M |
| 3 | Not required | Required per A530/A530M |
What Class 33 Means for This Pipe
Class 33 has two digits. The first digit 3 selects the heat-treatment family, which means the pipe is normalized after welding. The second digit 3 selects the examination level, which means no full-length radiography is required by the class, but a hydrostatic pressure test is required in accordance with A530/A530M.
Taken together, Class 33 pipe is the pipe is normalized after welding, and no full-length radiography is required by the class, but a hydrostatic pressure test is required in accordance with A530/A530M. These requirements are fixed at the time of ordering, recorded on the order documents and confirmed on the mill test certificate.
A517 plate is itself quenched and tempered, so the normalized classes 30 to 33 are unusual for this material; the quenched and tempered classes 50 to 53 are the typical fit, and the heat treatment must be confirmed with the engineer before ordering.
Typical Applications
CJP115 pipe is used where very high strength must be combined with toughness: heavy-wall high-pressure piping, pressure vessels, offshore structures and low-temperature service where a quenched and tempered alloy is specified.
Manufacturing, Testing and Documentation
A671 pipe starts as pressure-vessel-quality plate supplied under the applicable plate standard. The plate is formed into a cylinder and the longitudinal seam is welded by the submerged arc process from both the inside and the outside, producing a full-penetration weld. After welding, the pipe receives the heat treatment of the selected class and then the examination and tests required by the class and by A671/A671M.
Testing normally includes chemical analysis of the heat, tensile testing, and the radiography and hydrostatic pressure tests required by the class. Charpy V-notch impact testing is performed when the design code or the purchase order requires it, and the plate may be ultrasonically examined under A435 or a supplementary requirement. Every pipe is traceable to its plate heat number, and the mill test certificate records the chemical analysis, mechanical test results, heat treatment details and examination results.
The available outside diameters, wall thicknesses and lengths depend on the plate widths and the forming and welding capability of the producing mill, so the required OD, wall, length and end finish should be confirmed with the supplier before ordering.
FAQ
Q1. What does the grade CJP115 mean in the A671 designation?
The two-letter prefix identifies the plate specification, and the number states the minimum tensile strength in ksi. CJP115 means pipe made from A517/A517M Grade P plate, a high-strength alloy steel, quenched and tempered, with a minimum tensile strength of 115 ksi, about 790 MPa.
Q2. What does Class 33 mean?
Class 33 is read in two digits: the first digit selects the heat-treatment family, the pipe is normalized after welding, and the second digit selects the examination level, which means no full-length radiography is required by the class, but a hydrostatic pressure test is required in accordance with A530/A530M.
Q3. What is the minimum tensile strength of CJP115 pipe?
115 ksi, about 790 MPa. The number in the grade name states this value directly; it is a tensile value, not a yield value. The minimum yield strength is 100 ksi, about 690 MPa, for plate thicknesses up to 2.5 in.
Q4. Does Class 33 define a service temperature?
No. A class defines heat treatment and examination only, never a service temperature. The safe operating temperature is set by the plate material, the impact test requirements and the governing design code; for the CJP115 grade, the steel family and its qualified toughness determine the low-temperature limit.
Q5. What tests are performed on A671 pipe?
Every heat is verified by chemical analysis and tensile testing. The class determines whether full-length radiography of the longitudinal weld and a hydrostatic pressure test are required. Charpy impact testing, ultrasonic examination of the plate and other supplementary tests are added when the design code or the purchase order specifies them, and all results are reported on the mill test certificate.
Q6. How is A671 pipe manufactured and what sizes are available?
A671 pipe is formed from pressure-vessel-quality plate and welded with a double-sided submerged arc weld, then heat treated and examined per the class. It is produced in outside diameters of 16 in, about 406 mm, and larger, with wall thicknesses selected for the design pressure and lengths typically supplied in single or double random. Exact availability depends on the producing mill and must be confirmed before ordering.
