API 5CT N80Q Casing Pipe is a high-performance, intermediate-strength oilfield pipe. The "Q" in N80Q stands for Quenched and Tempered, which is a specific heat treatment process that makes this pipe superior to the standard N80-1 (Normalized) grade.
N80Q is a heat-treated steel grade within the API 5CT specification (Group 1).
Heat Treatment: Unlike N80-1, which is typically normalized, N80Q must be Quenched and Tempered.
Performance: The Q&T process results in a more refined grain structure, giving N80Q higher toughness, better impact resistance, and higher reliability under internal pressure (burst resistance).
Application: It is used in medium-to-deep wells where the load and pressure are too high for J55/K55, but the budget doesn't require the high-end P110 grade.
Engineered for the Toughest Formations. Our N80Q Casing Delivers the Burst Resistance Your High-Pressure Wells Demand. Get a Technical Evaluation.
API 5CT N80Q Casing Specification
| Item | Details |
| Standard | API Spec 5CT |
| Grade | N80 Type Q (N80Q) |
| Product Specification Level | PSL1, PSL2, PSL3 |
| Color Code | One Red Band + One Green Band |
| Grouping | Group 1 (General purpose) |
API 5CT N80Q Chemical Composition Table
API standards for N80Q primarily limit the content of Phosphorus (P) and Sulfur (S) to ensure the purity of the material. Specific levels of Carbon (C), Manganese (Mn), and other elements are typically controlled by the manufacturer based on their heat treatment process to ensure the required mechanical strength is met.
| Grade | Type | Phosphorus (P) Max | Sulfur (S) Max | Alloy Elements |
| N80Q | Quenched & Tempered | ≤ 0.030% | ≤ 0.030% | Added as needed (e.g., Cr, Mo, Mn) |
API 5CT N80Q Mechanical Strength Table
N80Q is an intermediate-to-high strength steel grade. Its yield strength range and minimum tensile strength requirements are listed below. Due to the tempering process, N80Q possesses better toughness and burst resistance than N80-1.
| Mechanical Property | US Customary (psi) | Metric / SI (MPa) |
| Yield Strength (Minimum) | 80,000 psi | 552 MPa |
| Yield Strength (Maximum) | 110,000 psi | 758 MPa |
| Tensile Strength (Minimum) | 100,000 psi | 689 MPa |
| Hardness Limit | No mandatory API limit | No mandatory API limit |
| Elongation | Based on API Formula* | Based on API Formula* |
*Note: Minimum elongation depends on the cross-sectional area of the tensile specimen and the tensile strength, usually requiring 15% to 20% or higher.
API 5CT N80Q Casing Size Table (Common Sizes)
| Nominal Size (in) | OD (mm) | Wall Thickness (mm) | Weight (lb/ft) | Drift Diameter (mm) |
| 4-1/2 | 114.30 | 6.35 | 11.60 | 99.21 |
| 5-1/2 | 139.70 | 7.72 | 17.00 | 121.87 |
| 7 | 177.80 | 9.19 | 26.00 | 156.24 |
| 9-5/8 | 244.48 | 10.03 | 40.00 | 220.45 |
| 9-5/8 | 244.48 | 11.99 | 47.00 | 216.53 |
| 13-3/8 | 339.72 | 12.19 | 61.00 | 311.37 |
Connection Types, Ends, and Couplings
N80Q casing is used to line the wellbore and must handle significant axial tension and collapse pressure.
Ends: Standard Threaded and Coupled (T&C).
Casing Connections:
STC (Short Round Thread): 8 threads per inch, good for general use.
LTC (Long Round Thread): Longer threads for better tensile strength in deeper wells.
BTC (Buttress Thread): Trapezoidal threads designed for high axial loads.
Couplings: Couplings for N80Q must also be Quenched and Tempered and painted with the red and green color bands.
API 5CT N80Q Manufacturing Processes
The production of N80Q involves rigorous steps to ensure metallurgical integrity:
Tube Forming: Can be Seamless (SML) or Electric Resistance Welded (ERW). Seamless is the most common for N80Q.
Quenching (The "Q"): The pipe is heated above the critical temperature and then rapidly cooled in a liquid (water or oil). This creates a very hard but brittle structure.
Tempering (The "T"): The hardened pipe is reheated to a specific temperature below the critical point to reduce brittleness and achieve the perfect balance of strength and toughness.
Straightening & Sizing: Ensuring the pipe meets strict API dimensional requirements.
Threading: Precise CNC machining of connections.
Hydrostatic and Leak Testing
Every single joint must be tested to ensure it can withstand high downhole pressures.
Hydrostatic Pressure Test:
Frequency: 100% of joints.
Requirement: Each pipe is filled with water and pressurized (typically for at least 5 seconds). There must be no leaks, weeping, or permanent deformation.
Pressure Level: Calculated based on the OD, wall thickness, and 80% of the minimum yield strength.
Non-Destructive Testing (NDT)
NDT is used to find internal or surface defects that are invisible to the naked eye.
| NDT Method | Requirement | Detection Target |
| Ultrasonic (UT) | Mandatory for PSL2/PSL3 | Detects internal longitudinal and transverse flaws and measures wall thickness. |
| Magnetic Particle (MPI) | Mandatory for PSL2/PSL3 | Detects surface cracks and imperfections, especially on the ends and threads. |
| Eddy Current (EC) | Alternative to UT/MPI | Used primarily for detecting surface and near-surface defects. |
Dimensional and Visual Inspections
These tests ensure the pipe fits perfectly with other downhole components.
Visual Inspection: 100% of pipes are inspected for surface defects such as pits, slivers, seams, or mechanical damage.
Dimensional Check: Verification of Outside Diameter (OD), Wall Thickness, and Pipe Length.
Drift Test (Mandatory): A standard mandrel (the "drift") is passed through the entire length of the pipe to ensure the internal diameter is clear for downhole tools.
Thread Inspection: Measurement of thread lead, taper, and height according to API 5B standards to ensure a leak-proof connection.
API 5CT N80Q Casing test equipments
API 5CT N80Q Casing Pipe factory
API 5CT N80Q OCTG Certificate
FAQ
What is the difference between N80-1 and N80Q in API 5CT casing?
The primary difference between N80-1 and N80Q lies in the heat treatment process, which results in different toughness levels and reliability.
Here are the 4 key differences:
1. Heat Treatment (The Main Difference)
N80-1: Usually Normalized (heated then air-cooled). It is a simpler and more economical process.
N80Q: Mandatory Quenched and Tempered (Q&T). The steel is rapidly cooled in liquid and then reheated to achieve a specific balance of strength and toughness.
2. Toughness and Performance
N80Q has a more refined grain structure, providing higher impact toughness and better resistance to brittle fracture.
N80Q is more reliable in high-pressure or critical environments where standard N80-1 might fail.
3. API Color Identification
N80-1: Identified by one Red band.
N80Q: Identified by one Red band and one Green band.
4. Application
N80-1: Suitable for general medium-depth wells with lower pressure risks.
N80Q: Preferred for more demanding drilling conditions, deep wells, or projects requiring higher quality standards (PSL2/PSL3).
Can N80Q casing be used in sour service wells?
No, standard API 5CT N80Q is not recommended for sour service ( H2S environments).
Here is why:
Sulfide Stress Cracking (SSC): Sour service requires materials with a strictly controlled hardness (typically max 23 HRC). N80Q has no mandatory API hardness limit, meaning it can be too hard and brittle, leading to sudden cracking and failure in the presence of Hydrogen Sulfide ( H2S).
Lack of Restricted Yield: Sour service grades (like L80) have a narrow, restricted yield strength range. N80Q has a wider range (80,000 to 110,000 psi), which is not safe for H2S environments.
The Correct Alternative: If your well contains H2S, you should use API 5CT L80. It has the same 80,000 psi strength as N80Q but is specifically engineered and tested to be "Sour Service" compliant (NACE MR0175/ISO 15156).
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