API 5CT L80 tubing is a quenched and tempered sour service tubing grade with a minimum yield strength of 552 MPa (80,000 psi) and a minimum tensile strength of 655 MPa (95,000 psi). A maximum hardness of 23 HRC and a restricted yield range make it suitable for wells containing hydrogen sulphide.
Download API 5CT L80 Tubing data sheet (PDF) One-page summary of the supply range, chemistry, mechanical properties and inspection documents on this page. The standard is the governing document.
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Size range and specification
- Outside diameter 1.050 inch – 4-1/2 inch (26.7 – 114.3 mm)
- Most quoted sizes 2-3/8, 2-7/8 and 3-1/2 inch
- Wall thickness 2.87 – 9.65 mm depending on size and weight
- Length R1 6.10 – 7.32 m, R2 8.53 – 9.75 m, R3 11.58 – 12.80 m
- Ends EUE, NUE or premium connection; coupling supplied with the pipe
- Surface treatment Black varnish, phosphate, or as agreed
- Manufacturing process Hot rolled seamless, quenched and tempered
- Delivery standard API 5CT / ISO 11960, PSL1 or PSL2
How this grade is supplied
- Inspection Inspected by the producing mill’s own inspection department, which is independent of production, against the delivery standard above. Third-party inspection — SGS, BV or TUV, or an inspector you send yourself — can be arranged at the mill or before shipment; give us the dates and the scope at the order stage.
- Certificate A mill test certificate to EN 10204 3.1 showing the heat number, the chemical composition and the mechanical results is standard on every order. EN 10204 3.2, countersigned by the inspector you nominate, is available on request.
- Documents with the goods The mill test certificate and the packing list travel with the shipment, and the heat number is traceable from cast through to the finished product.
- Packing Sea-worthy export packing: bundled by size with end protection, corrosion protection on request, stencilled with the size, grade and heat number.
- MOQ One bundle or one truckload; mixed sizes within a bundle accepted.
- Lead time Counted from order confirmation, not from the enquiry. Stock sizes 5–10 days; mill run or non-stock 3–5 weeks. The delivery window is fixed on the quotation.
- How we supply Sourced through partner mills; the producing mill is named on the quotation.
API 5CT L80 chemical composition (%, maximum unless a range is given)
| Element | L80 Type 1 | L80 Type 13Cr | Note |
|---|---|---|---|
| Carbon, C | 0.43 max | 0.15 – 0.22 | Type 1 carbon may be raised to 0.50 max for oil or polymer quenched pipe |
| Silicon, Si | 0.45 max | 1.00 max | |
| Manganese, Mn | 1.90 max | 0.25 – 1.00 | |
| Phosphorus, P | 0.030 max | 0.020 max | |
| Sulphur, S | 0.030 max | 0.010 max | |
| Chromium, Cr | not specified | 12.0 – 14.0 | L80 Type 13Cr is a martensitic stainless grade for CO2 service |
| Nickel, Ni | 0.25 max | 0.50 max |
L80 is supplied in four types: Type 1 carbon steel, Type 3Cr, Type 9Cr and Type 13Cr; the table gives the two most commonly ordered. Type 1 is a carbon steel in the ordinary sense and its limits are not especially tight – 0.43% carbon, 0.45% silicon, 1.90% manganese. The 9Cr and 13Cr types are corrosion resistant alloys, and it is those types that carry the tighter 0.020% phosphorus and 0.010% sulphur limits; the chromium addition is what suits them to wells where carbon dioxide corrosion is the dominant risk and hydrogen sulphide is only trace. The hardness cap applies to all four types and is the defining feature of the grade.
Source: chemical composition requirements of API 5CT / ISO 11960. The standard is the governing document.
API 5CT L80 mechanical properties and hardness
| Grade | Yield strength | Tensile strength min | Hardness max | Sour service |
|---|---|---|---|---|
| L80 Type 1 | 552 – 655 MPa (80,000 – 95,000 psi) | 655 MPa (95,000 psi) | 23 HRC (241 HBW) | qualified |
| L80 Type 9Cr | 552 – 655 MPa (80,000 – 95,000 psi) | 655 MPa (95,000 psi) | 23 HRC (241 HBW) | CO2 service (trace H2S) |
| L80 Type 13Cr | 552 – 655 MPa (80,000 – 95,000 psi) | 655 MPa (95,000 psi) | 23 HRC (241 HBW) | CO2 service (trace H2S) |
| N80Q (for comparison) | 552 – 758 MPa (80,000 – 110,000 psi) | 689 MPa (100,000 psi) | not specified | not suitable |
The hardness limit is the defining feature of L80. API 5CT caps the hardness at 23 HRC, while NACE MR0175 / ISO 15156 applies a 22 HRC limit for carbon steel in sour service, with the API figure acting as a production lot maximum. The yield range is deliberately restricted to 80 to 95 ksi rather than the 80 to 110 ksi used for N80Q, which keeps the maximum strength, and therefore the maximum hardness, under control. Type 1 is the type specified for wet hydrogen sulphide service; the 9Cr and 13Cr types are selected for carbon dioxide corrosion, and where hydrogen sulphide is also present their acceptability has to be assessed against ISO 15156-3 rather than assumed.
Source: tensile requirements of API 5CT / ISO 11960. The standard is the governing document.
What Is L80 Tubing?
L80 is a quenched and tempered carbon steel grade in API 5CT with a minimum yield strength of 80,000 psi, or 552 MPa. It is used mainly for tubing, the inner string through which the well produces, although it is also available as casing. What distinguishes L80 from N80Q, which has the same minimum yield strength, is that L80 is hardness controlled and qualified for sour service. The yield range is held to 80 to 95 ksi rather than 80 to 110 ksi, and the maximum hardness is capped at 23 HRC, so the material cannot reach a hardness at which sulphide stress cracking becomes likely.
Hardness Control and Sour Service
Sulphide stress cracking is a failure mode in which high-strength steel cracks under tensile stress in the presence of wet hydrogen sulphide. Susceptibility rises sharply with hardness and strength, so the standard way to qualify a steel for sour service is to limit its hardness. API 5CT caps L80 at 23 HRC, and NACE MR0175 / ISO 15156 applies a 22 HRC limit for carbon steels, reflecting the same principle. When a well contains hydrogen sulphide, or where the H2S partial pressure exceeds the threshold in the standard, supplementary requirements such as hardness surveys, impact testing and hydrogen induced cracking testing to NACE TM0284 are commonly specified alongside the grade.
L80 Compared With N80 and C90
L80 and N80Q share the same minimum yield strength of 552 MPa, and the choice between them is entirely about the service environment. If the well is sweet, N80Q is cheaper and offers a wider yield range up to 758 MPa, which allows a higher collapse rating in the same wall. If the well is sour, N80Q is not qualified and L80 must be used. C90 is the next step up for sour service, with a minimum yield strength of 621 MPa and a hardness limit of 25.4 HRC. C90 gives more strength than L80 but relies on a slightly higher hardness ceiling, so it should only be specified where L80 does not provide enough capacity.
Types of L80 and Their Uses
L80 Type 1 is the plain carbon steel version and covers the large majority of sour service orders. L80 Type 9Cr and Type 13Cr are martensitic stainless versions containing chromium, intended for wells where carbon dioxide corrosion is the controlling mechanism and hydrogen sulphide is present only in trace amounts. Type 13Cr is the more common of the two and is widely used in CO2-rich gas wells. Selecting between the types is a corrosion engineering decision based on the produced fluid composition, temperature and partial pressures, and it should not be made on price alone.
Inspection and Documentation
Because L80 is a sour service grade, documentation and traceability matter more than for a plain carbon grade. API 5CT requires tensile testing, dimensional inspection and hydrostatic testing, and the mill certificate must show the phosphorus and sulphur content against the tighter limits. Hardness testing is used to confirm compliance with the 23 HRC cap and can be specified as a supplementary requirement with a defined survey pattern. Mill test certificates to EN 10204 3.1 are standard, 3.2 certification is available, and third-party inspection by SGS, BV or TUV can be arranged at the order stage.
L80 types and what changes
| Type | Main alloying change | Typical use | Order note |
|---|---|---|---|
| L80 Type 1 | Standard carbon/low-alloy L80 | General sour-service tubing | Most common; confirm hardness and restricted yield range |
| L80 9Cr | 9% chromium | Sweet and mildly corrosive wells with CO2 | Not a direct substitute for L80 Type 1 without corrosion review |
| L80 13Cr | 13% chromium | CO2-rich, sweet service | Verify chloride, temperature and H2S limits before selection |
Source: API 5CT L80 type designations and general well-completion practice. The final choice belongs to the well design.
What to state on the enquiry
- Type L80 Type 1, L80 9Cr or L80 13Cr
- Size and weight Outside diameter, wall thickness or weight designation
- Connection EUE, NUE or a named premium connection
- Well conditions H2S, CO2, chloride, temperature and pressure
- Tests Hardness, Charpy if specified, NACE MR0175 / ISO 15156 requirements
- Documents EN 10204 3.1 or 3.2, with heat traceability
Typical applications
- Sour oil and gas wells
- Production tubing in H2S service
- CO2 rich gas wells (L80 13Cr)
- Injection wells
- Workover and completion tubing
Standards covered
Frequently asked questions
What is the difference between L80 and N80 tubing?
Both have a minimum yield strength of 552 MPa, so the choice is about the environment, not strength. N80 has a wider yield range up to 758 MPa but no hardness limit, so it is not qualified for sour service. L80 is hardness controlled at 23 HRC with a restricted yield range of 552 to 655 MPa, which qualifies it for wells containing hydrogen sulphide.
Why does L80 have a maximum hardness requirement?
Because susceptibility to sulphide stress cracking rises sharply with hardness and strength. Capping the hardness at 23 HRC prevents the material from reaching a condition in which it would crack under tensile stress in the presence of wet hydrogen sulphide. NACE MR0175 / ISO 15156 applies a 22 HRC limit for carbon steel in sour service, which is the same principle.
Is L80 available as casing as well as tubing?
Yes. L80 is primarily specified for tubing, but it is also supplied as casing in the sizes and weights listed in API 5CT. The choice between using it as tubing or casing is a well design decision. The grade requirements, including the hardness cap and the restricted yield range, are the same in both applications.
Where to go next
- OCTG: Casing and Tubing – which string, grade, connection and documents the well needs
- API 5CT Tubing Pipe – API 5CT production tubing
- API 5CT Tubing Coupling – tubing couplings to API 5CT
- Premium Connection Casing and Tubing – gas-tight premium connections
- API 5CT N80Q Casing – quenched and tempered well casing
- API 5CT P110 Casing – high-strength well casing
- Sour Service – what changes when H2S is present
- Get a Quote – send the grade, size, quantity and destination port
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