What is the specification of API 5CT N80 oil well casing pipe
Apr 03, 2026
N80 oil casing is a medium-to-high strength seamless steel pipe conforming to API 5CT standards, primarily used for wellbore support and oil and gas transportation during oil and gas drilling. Its steel grade designation "N80" indicates a minimum yield strength of 80,000 psi (approximately 552 MPa), classifying it as a medium-strength material widely used in the completion and production stages of onshore and shallow-sea oil and gas wells.
API 5CT N80 Seamless Oil Casing Pipe Chemical Composition
| Steel Grade | Category | Carbon (C) | Manganese (Mn) | Phosphorus (P) | Sulfur (S) | Silicon (Si) |
| N80-1 | Normalized | Not Specified | Not Specified | ≤ 0.030% | ≤ 0.030% | Not Specified |
| N80-Q | Quenched & Tempered | Not Specified | Not Specified | ≤ 0.030% | ≤ 0.030% | Not Specified |
API 5CT N80 oil well casing Mechanical Properties
| Property | Unit (Metric) | Value | Unit (Imperial) | Value |
| Yield Strength | MPa | 552 ~ 758 | psi | 80,000 ~ 110,000 |
| Tensile Strength | MPa | ≥ 689 | psi | ≥ 100,000 |
| Hardness | - | Not Required | - | Not Required |
| Elongation | % | Calculated by formula | % | Calculated by formula |
API 5CT N80 OCTG Casing Pipe Heat Treatment (Key Differences)
| Grade Category | Heat Treatment Method | Performance Characteristics |
| N80-1 | Normalizing (N) or Normalizing + Tempering | Lower cost; standard collapse resistance. |
| N80-Q | Quenched & Tempered (Q&T) | More uniform microstructure; better toughness and superior collapse resistance compared to N80-1. |
API 5CT N80 seamless casing and tubing Impact Test Requirements
N80-1: API 5CT generally does not mandate Charpy V-notch (CVN) impact testing unless specified in the purchase order.
N80-Q: Impact testing is mandatory (unless otherwise agreed) to ensure toughness under high-stress or low-temperature conditions.
API 5CT N80 Oilfield Casing Hot Rolled Tube Color Identification
| Steel Grade | Color Band | Application Method |
| N80-1 | Red | One red band on the pipe body |
| N80-Q | Red + Green | One red band and one green band |
Common Dimensions and Load Capacities (Examples)
N80 Tubing (Examples)
| Outer Diameter (inch) | Wall Thickness (mm) | Yield Load (kN, Theo.) | Collapse Resistance (MPa) |
| 2-7/8" (73.02mm) | 5.51 | 650+ | 70+ |
| 3-1/2" (88.90mm) | 6.45 | 930+ | 65+ |
N80 Casing (Examples)
| Outer Diameter (inch) | Wall Thickness (mm) | Nominal Weight (lb/ft) | Internal Yield (psi) | Collapse (psi) |
| 5-1/2" | 7.72 | 17.00 | 7,740 | 6,290 |
| 7" | 9.19 | 26.00 | 7,240 | 5,410 |
| 9-5/8" | 10.03 | 40.00 | 5,750 | 3,090 |
Manufacturing and Inspection Requirements
| Item | Requirement |
| Manufacturing Process | Seamless (SML) or Electric Resistance Welded (ERW) |
| Hydrostatic Test | Mandatory for every joint; test pressures are significantly higher than J55. |
| NDT (Non-Destructive) | Mandatory Ultrasonic or Electromagnetic testing (typically L4 inspection level). |
| Straightness | Strict adherence to API 5CT; total deviation ≤ 0.2% of total length. |
API 5CT N80 octg in stock
GNEE Pipe test and inspection equipment
GNEE Pipe process line
FAQ
What is N80 material grade?
N80 is a steel grade defined by the American Petroleum Institute (API) specification for Oil Country Tubular Goods (OCTG). Known for its strength and resistance to corrosion and cracking, N80 steel provides exceptional performance in challenging drilling conditions.
What is the difference between L80 and N80?
N80: yield strength of 379MPa ~ 552MPa; tensile≥517MPa; minimum elongation of N80 is 19%. L80: yield strength of 379MPa ~ 552MPa; tensile≥655MPa; minimum elongation of L80 is 15%.
What size is N80 casing?
N80 casing covers a variety of sizes from small to large diameters. Common outer diameters for N80 casing are: 4-1/2", 5-1/2", 6-5/8", 7", 9-5/8", and 13-3/8". Common outer diameters for N80 tubing are: 2-3/8", 2-7/8", 3-1/2", 4", and 4-1/2".
