API 5CT — Casing and Tubing Specifications
Grades
H40, J55, K55, N80, L80, C90, T95, P110, Q125, V150
Chemical composition and mechanical properties
| Grade | Chemical composition | Mechanical properties |
|---|---|---|
| H40 | C≤0.50, Mn 1.20-1.65 (seamless tube only), P≤0.030, S≤0.030, Si (no requirements) | Rm ≥414 MPa, Rp0.2 276-552 MPa, A≥23% (gauge length 50mm), HB≤22HRC |
| J55 | C≤0.50, Mn 1.20-1.65, P≤0.030, S≤0.030 | Rm ≥517 MPa, Rp0.2 379-552 MPa, A≥23% (gauge length 50mm), HB≤22HRC |
| K55 | C≤0.50, Mn 1.20-1.65, P≤0.030, S≤0.030 | Rm ≥655 MPa, Rp0.2 379-552 MPa, A≥18% (gauge length 50mm), HB≤22HRC |
Application scope
API 5CT specifies casing and tubing for the oil and gas industry, i.e., well tubing, classifying them into steel grades from H40, J55, N80, L80, P110 to Q125, V150 based on strength and service conditions. The standard specifies requirements for composition, mechanical properties, and hardness, balancing pressure resistance, tensile strength, and extrusion resistance. Some steel grades also possess hydrogen sulfide resistance, catering to downhole oil and gas well operating conditions.
Typical applications
Primarily used for casing, tubing, and wellbore tubing in oil and gas production wells, casing is used for cementing and wall protection, while tubing is used for lifting oil and gas. Different steel grades are selected depending on the well depth and pressure. Based on strength, hardness, and corrosion resistance designed for downhole service, high-grade steel is suitable for deep and high-pressure wells, while sulfur-resistant steel is suitable for oil and gas wells containing hydrogen sulfide. These are key tubing materials for oil and gas drilling and production wellbores.
