Line pipe grade designations come from API Spec 5L Specification for Line Pipe. Standard Line Pipe has grade designation A and B. Stronger grades have the designation X followed by the specified minimum yield strength of the pipe steel, measured in kilopounds per square inch (abbreviated ksi), e.g. X60 for pipe having a minimum yield strength of 60 ksi. See the table below for the standard available grades.
Line Pipe Physical Properties
| API 5L Grade | Yield Strength min. (ksi) | Tensile Strength min. (ksi) | Yield to Tensile Ratio (max.) | Elongation min. %1 |
| A | 30 | 48 | 0.93 | 28 |
| B | 35 | 60 | 0.93 | 23 |
| X42 | 42 | 60 | 0.93 | 23 |
| X46 | 46 | 63 | 0.93 | 22 |
| X52 | 52 | 66 | 0.93 | 21 |
| X56 | 56 | 71 | 0.93 | 19 |
| X60 | 60 | 75 | 0.93 | 19 |
| X65 | 65 | 77 | 0.93 | 18 |
| X70 | 70 | 82 | 0.93 | 17 |
| X80 | 80 | 90 | 0.93 | 16 |
| 1 | API 5L elongation figures vary with specimen dimensions. Values shown for 0.2 sq. in. specimen. |
Line pipe mechanical testing usually omits Reduction of Area (RA) measurement reporting, and Charpy V-Notch (CVN) testing. This prevents use of this pipe as body material above 36 ksi yield strength for API Spec 6A equipment without retesting for Reduction of Area, and in the case of low temperature service, Charpy V-Notch testing as well.
CAUTION: Do not confuse pipe manufactured to meet ASTM A106 Grade A or B as interchangeable with API 5L Grade A or B without close observation of the mill test reports. The two pipe specifications overlap, but vary. Pipe may or may not meet both specs.
