API 5CT L80 Oil Well Casing Steel Pipe is a restricted-yield steel grade specifically engineered for oil and gas wells where corrosion resistance and structural integrity are paramount. It is classified under Group 2 of the API 5CT specification.
Application: It is the primary choice for Sour Service (environments containing
H2SH2S
) because its controlled hardness prevents Sulfide Stress Cracking (SSC).
Variants:
L80-1: Carbon steel for general sour service.
L80-9Cr: Contains 9% Chromium for CO2 resistance.
L80-13Cr: Contains 13% Chromium for high-temperature, high-CO2 environments.
Stop Sulfide Stress Cracking (SSC). Our API 5CT L80 Casing is Strictly Hardness-Controlled <23 HRC. Request a Tech Sheet.
L80 OCTG Casing Identification of Color Band
API 5CT requires specific color coding to prevent the accidental use of incorrect grades.
| Grade Type | Color Band on Pipe Body | Color on Coupling |
| L80 Type 1 | One Red + One Brown | Entirely Brown |
| L80 9Cr | One Red + One Brown + Two Yellow | Entirely Brown |
| L80 13Cr | One Red + One Brown + One Yellow | Entirely Brown |
Chemical Composition of API 5CT L80 Casing Steel Pipe(Weight %)
The chemistry of L80 varies significantly between the standard carbon steel (Type 1) and the corrosion-resistant alloys (9Cr and 13Cr).
| Grade | Type | Carbon (C) | Manganese (Mn) | Phosphorus (P) | Sulfur (S) | Silicon (Si) | Chromium (Cr) | Nickel (Ni) | Molybdenum (Mo) |
| L80-1 | Carbon Steel | ≤ 0.43 | ≤ 1.90 | ≤ 0.030 | ≤ 0.030 | ≤ 0.45 | - | ≤ 0.25 | - |
| L80-9Cr | 9% Chrome | ≤ 0.15 | 0.30 - 0.60 | ≤ 0.020 | ≤ 0.010 | 0.90 - 1.10 | 8.0 - 10.0 | ≤ 0.50 | 0.90 - 1.10 |
| L80-13Cr | 13% Chrome | 0.15 - 0.22 | 0.30 - 1.00 | ≤ 0.020 | ≤ 0.010 | ≤ 1.00 | 12.0 - 14.0 | ≤ 0.50 | - |
Mechanical Properties of API 5CT L80 Oil Well Drilling Casing Pipe
All L80 types share the same mandatory yield and tensile strength requirements. The most critical factor for this grade is the Hardness Limit.
| Mechanical Property | US Customary (psi) | Metric / SI (MPa) |
| Yield Strength (Minimum) | 80,000 psi | 552 MPa |
| Yield Strength (Maximum) | 95,000 psi | 655 MPa |
| Tensile Strength (Minimum) | 95,000 psi | 655 MPa |
| Hardness (Maximum) | 23 HRC | 241 HBW |
| Elongation | Based on API Formula* | Based on API Formula* |
*Note: Minimum elongation is calculated based on the cross-sectional area of the tensile specimen. For L80, high ductility is required to ensure performance in sour environments.
API 5CT L80 Casing Size Table (Common Specifications)
| Nominal Size (inch) | Outside Diameter - OD (mm) | Wall Thickness (mm) | Nominal Weight (lb/ft) | Inside Diameter - ID (mm) | Drift Diameter (mm) |
| 4-1/2 | 114.30 | 5.69 | 10.50 | 102.92 | 100.53 |
| 4-1/2 | 114.30 | 6.35 | 11.60 | 101.60 | 99.21 |
| 4-1/2 | 114.30 | 7.37 | 13.50 | 99.56 | 97.18 |
| 5 | 127.00 | 7.52 | 15.00 | 111.96 | 109.58 |
| 5-1/2 | 139.70 | 6.98 | 15.50 | 125.74 | 123.36 |
| 5-1/2 | 139.70 | 7.72 | 17.00 | 124.26 | 121.87 |
| 5-1/2 | 139.70 | 9.17 | 20.00 | 121.36 | 118.97 |
| 7 | 177.80 | 8.05 | 23.00 | 161.70 | 158.52 |
| 7 | 177.80 | 9.19 | 26.00 | 159.42 | 156.24 |
| 7 | 177.80 | 10.36 | 29.00 | 157.08 | 153.90 |
| 7 | 177.80 | 11.51 | 32.00 | 154.78 | 151.60 |
| 7-5/8 | 193.68 | 11.05 | 33.70 | 171.58 | 168.40 |
| 9-5/8 | 244.48 | 10.03 | 40.00 | 224.42 | 220.45 |
| 9-5/8 | 244.48 | 11.05 | 43.50 | 222.38 | 218.41 |
| 9-5/8 | 244.48 | 11.99 | 47.00 | 220.50 | 216.53 |
| 9-5/8 | 244.48 | 13.84 | 53.50 | 216.80 | 212.83 |
| 10-3/4 | 273.05 | 11.43 | 45.50 | 250.19 | 246.23 |
| 13-3/8 | 339.72 | 10.92 | 54.50 | 317.88 | 313.91 |
| 13-3/8 | 339.72 | 12.19 | 61.00 | 315.34 | 311.37 |
| 13-3/8 | 339.72 | 13.06 | 68.00 | 313.60 | 309.63 |
| 20 | 508.00 | 11.13 | 94.00 | 485.74 | 479.40 |
API 5CT L80 Oilfield Casing Dimension and Tolerances Table
| Parameter | Tolerance Standard |
| Outside Diameter (OD) | < 4-1/2": ±0.031" / ≥ 4-1/2": -0.50% to +1.00% |
| Wall Thickness | -12.5% (Tolerance is critical for pressure ratings) |
| Weight | -3.5% to +6.5% for single lengths |
| Straightness | 0.2% of total pipe length |
API 5CT L80 Oilfield Casing Pipes Manufacturing Types Table
| Manufacturing Method | Applicability | Mandatory Requirements |
| Seamless (SML) | All L80 Types (1, 9Cr, 13Cr) | Mandatory for 9Cr and 13Cr. Preferred for L80-1. |
| Electric Resistance Welded (ERW) | L80 Type 1 Only | Must undergo full-body heat treatment (Quenching & Tempering). |
Connection Types, Ends, and Couplings
Ends: Standard Threaded & Coupled (T&C), or Plain End (PE) for custom fabrication.
Casing Connections: STC (Short Round), LTC (Long Round), BTC (Buttress). For L80-13Cr, Premium Gas-Tight Connections are highly recommended.
Couplings: Must be of the same steel grade (L80) and follow the Brown color-coding standard.
Surface Condition of API 5CT L80
Protective Coating: Pipes are treated with a temporary anti-corrosion oil or bitumen-based varnish for storage and sea transport.
Mandatory Marking: Clear paint stenciling and die-stamping including size, weight, grade, heat number, and API monogram.
Thread Protection: Plastic or composite steel-plastic protectors are installed on both ends to prevent physical damage and thread rust.
Reference Inspection for L80 Casing Pipe
Rigorous inspection ensures the pipe can withstand downhole pressures and corrosive elements:
Visual Inspection: Check for surface pits, laps, cracks, and thread integrity.
Dimensional Verification: Measuring OD, wall thickness, and length.
Mandrel Drift Test: Ensuring a standard drift tool passes through to verify the minimum internal diameter.
NDT (Non-Destructive Testing): Mandatory Ultrasonic (UT) or Magnetic Particle Inspection (MPI) to detect sub-surface flaws.
Thread Gauging: Verifying thread lead, taper, and height according to API 5B.
FAQ
What is API 5CT L80 equivalent to?
L80 Type 1 (Carbon Steel): Closest to AISI 4130 or AISI 4140 (Chromium-Molybdenum steels). It is heat-treated (Quenched & Tempered) to a specific hardness of max 23 HRC.
L80 13Cr (Stainless Type): Equivalent to AISI 420 Martensitic Stainless Steel.
What is the difference between L80 and P110?
The main difference between L80 and P110 is their strength and well environment suitability. L80 is designed for corrosion resistance (
H2S ), while P110 is designed for high-pressure, deep wells.
1. Yield Strength (The Power)
L80: Minimum yield strength of 80,000 psi. It is an intermediate-strength grade.
P110: Minimum yield strength of 110,000 psi. It is a high-strength grade used for much heavier loads.
2. Environment (Sour vs. Non-Sour)
L80: Designed for Sour Service (
H2SH2S
environments). It has a strictly controlled hardness (max 23 HRC) to prevent Sulfide Stress Cracking.
P110: Designed for Deep, High-Pressure Wells. It is generally not suitable for sour service because its high hardness makes it brittle and prone to cracking if
H2SH2S
is present.
3. Heat Treatment
L80: Must be Quenched and Tempered with strict temperature controls to keep the steel ductile.
P110: Also Quenched and Tempered, but with a chemical composition designed to maximize hardness and tensile strength.
4. Identification (Color Code)
L80: One Red band + One Brown band.
P110: One White band.
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