API 5CT J55 is the entry-level well casing grade, with a minimum yield strength of 55,000 psi (379 MPa) and a minimum tensile strength of 75,000 psi (517 MPa). The standard specifies no chemistry for J55 beyond the phosphorus and sulphur limits and no impact toughness requirement, and the grade is supplied seamless or ERW. It is the default choice for shallower, lower-pressure wells.
Download API 5CT J55 Casing 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.
Mejor Steel is the export agent for the mills that make your material: one contract, one delivery date, and the mill named on the quotation. How we supply
We reply within one business day, Monday to Friday 09:00-18:00 CST. Or write to info@mejorsteel.com / WhatsApp.
Size range and specification
- Outside diameter 4-1/2 inch – 13-3/8 inch (114.3 – 339.7 mm), other API 5CT sizes on request
- Wall thickness 4.83 – 22.22 mm as a wall thickness, or by the API 5CT weight designation in lb/ft
- Length R1 4.88 – 7.62 m, R2 7.62 – 10.36 m, R3 10.36 – 14.63 m
- Ends STC, LTC, BTC, or premium connection
- Surface treatment Bare, varnish, phosphate, or as specified
- Delivery condition Not fixed by the grade; the steelmaking route is the manufacturer’s choice provided the mechanical requirements are met
- Manufacturing process Seamless or ERW (electric resistance welded)
- Delivery standard API 5CT / ISO 11960, threads to API 5B
- Types One grade only – there is no impact-tested variant of J55, so toughness has to be added as an order requirement if it is needed
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 J55 chemical composition (%)
| Element | Requirement | Element | Requirement |
|---|---|---|---|
| Phosphorus, P | 0.030 max | Carbon, C | not specified |
| Sulphur, S | 0.030 max | Manganese, Mn | not specified |
| Silicon, Si | not specified | Chromium, Cr | not specified |
| Nickel, Ni | not specified | Molybdenum, Mo | not specified |
J55 is an open-chemistry grade. API 5CT fixes only the two elements that damage toughness and weldability – phosphorus and sulphur, each at 0.030 percent maximum – and leaves carbon, manganese and every alloying element to the manufacturer, who is free to reach the required yield and tensile strength by whatever steelmaking route is economical. Two consequences follow for a buyer. First, a J55 mill certificate will not look the same from one mill to another. Second, the grade should be specified by its mechanical properties and its dimensions rather than by an expected chemistry. Published tables that quote a carbon or manganese range for J55 are describing one mill’s practice, not a requirement of the standard.
Source: chemical composition requirements of API 5CT / ISO 11960. The standard is the governing document.
API 5CT J55 mechanical properties
| Grade | Yield strength | Tensile strength | Elongation | Impact test | Hardness |
|---|---|---|---|---|---|
| J55 (API 5CT) | 379 – 552 MPa (55,000 – 80,000 psi) | 517 MPa min (75,000 psi) | per the API 5CT formula | not required by the standard | not specified at delivery |
J55, like K55, has a yield strength range rather than a minimum only, so an over-strength heat is as much a deviation as an under-strength one. Elongation is calculated from the tensile test specimen cross-sectional area using the formula in API 5CT rather than tabulated as a single figure, so it is read together with the test report. The grade carries no Charpy impact requirement and no hardness limit at delivery. Where the casing is intended for a sour well, NACE MR0175 / ISO 15156 limits carbon steels of this strength level to a maximum hardness of 22 HRC (250 HV), and that requirement has to be written into the purchase order and verified on the certificate rather than assumed.
Source: tensile requirements of API 5CT / ISO 11960. The standard is the governing document.
What Is API 5CT J55 Casing?
API 5CT J55 is a carbon steel casing grade for oil and gas wells, with a minimum yield strength of 55,000 psi (379 MPa) and a minimum tensile strength of 75,000 psi (517 MPa). It is the entry point of the API 5CT casing list – above H40, below K55, N80 and the higher grades – and it is the grade most surface strings and many shallow intermediate strings are built from. Like K55, J55 is bought on its mechanical properties and its dimensions rather than on a composition, because the standard specifies nothing about the steel except the two residual limits that affect toughness. J55 is supplied either seamless or as electric resistance welded (ERW) pipe.
Why J55 Has No Specified Chemistry and No Impact Requirement
API 5CT fixes only two things about the J55 steel itself: phosphorus and sulphur, each at 0.030 percent maximum. Carbon, manganese and any alloying addition are left to the mill. The standard also sets no Charpy impact requirement for J55 and no hardness limit at delivery, and those two omissions are what actually define the grade in service. A J55 certificate therefore tells a buyer the yield and tensile results, the dimensions and the heat number, and very little about the microstructure or the low-temperature toughness of the steel. Where impact toughness or a hardness ceiling matters, the requirement has to be added to the order explicitly, or a grade that carries it by specification has to be chosen instead.
Where J55 Casing Is Used
J55 is specified for surface casing, for shallow to medium-depth intermediate and production strings, and for water, observation, geothermal and coal-bed methane wells where the collapse, burst and tensile loads are modest. In US trade sizes the grade is ordered most often as 4 1/2 in (114.3 mm), 5 1/2 in (139.7 mm), 7 in (177.8 mm), 9 5/8 in (244.5 mm) and 13 3/8 in (339.7 mm) casing, the last two being the common surface-casing sizes. It is also used as conductor pipe and for structural and piling duties where an OCTG dimension is wanted without OCTG strength. The grade for each string is chosen from the load cases: the design normally takes the lightest and least expensive grade that passes collapse, burst and tensile together.
J55 versus K55 and N80
J55 and K55 share the same yield range, 379 to 552 MPa, and the same open chemistry, and they are separated by minimum tensile strength – 517 MPa for J55 against 655 MPa for K55. N80 sits above both, with a minimum yield of 552 MPa and a minimum tensile of 689 MPa, and it is the first grade in the list to be split into an as-rolled and a quenched and tempered delivery condition. In practice J55 is rarely the grade that fails a design; it is the grade that stops being economical. Once the wall J55 needs to carry the load becomes thicker than the mill can roll or than the connection can tolerate, the string moves up to K55 or N80 rather than staying with a heavier J55.
The three grades are compared below on minimum tensile strength, together with the toughness requirement each one carries.
Threads, Couplings and What to Put on the Order
J55 casing is threaded to API 5B and supplied with short round thread (STC), long round thread (LTC) or buttress thread (BTC) couplings as standard, with premium connections ordered where gas-tightness or a higher torque capacity is needed. The coupling is a separate API 5CT item and must match the pipe in grade and thread form. The accessories that go with the string – couplings, thread protectors, centralizers, pup joints and crossover subs – are normally part of the same delivery and should be specified against the same standard. Because the grade leaves the steel open, a J55 order is written on outside diameter, wall thickness or the API weight designation, thread form, length range and the mechanical requirements, plus anything the well needs on top, such as a hardness limit for sour service or a specified impact test.
J55, K55 and N80: which grade for the string
| Grade | Yield strength | Minimum tensile | Toughness by specification | Typical role | When not to choose it |
|---|---|---|---|---|---|
| J55 | 379 – 552 MPa | 517 MPa | No impact requirement | Surface, conductor and shallow casing | Deep strings or where CVN is required |
| K55 | 379 – 552 MPa | 655 MPa | No impact requirement | Higher tensile and collapse load than J55 | Where a qualified impact test is required |
| N80-1 / N80Q | 552 – 758 MPa | 689 MPa | Only if specified; N80Q can be ordered with impact | Deeper and higher-pressure strings | Sour wells unless hardness and HIC/SSC requirements are satisfied |
Source: API 5CT mechanical property requirements and the supplementary requirements the purchaser can invoke. The standard is the governing document.
Order fields for J55 casing
- Grade and PSL API 5CT J55, PSL1 or PSL2
- Size and weight Outside diameter, wall thickness or weight designation
- Length range R1, R2, R3 or a fixed length
- Thread STC, LTC, BTC, or specify coupling type and drift
- Supplementary tests Charpy temperature and energy, hardness, sour-service requirements
- Documents EN 10204 3.1 or 3.2, plus any project-specific inspection plan
Typical applications
- Surface casing strings
- Shallow to medium-depth intermediate and production casing
- Water, observation and geothermal wells
- Coal-bed methane and low-pressure gas wells
- Conductor and structural casing
Standards covered
Frequently asked questions
What chemistry does API 5CT require for J55 casing?
Only phosphorus and sulphur, each at 0.030 percent maximum. Carbon, manganese and the alloying elements are not specified for J55, so the manufacturer is free to reach the required yield and tensile strength by any economical route. The practical effect is that the chemistry shown on a J55 mill certificate varies from mill to mill, and that the grade is bought on mechanical properties and dimensions rather than on composition.
Does J55 casing need impact testing?
Not by specification. API 5CT sets no Charpy V-notch requirement for J55, and it sets no hardness limit at delivery either. If the well needs demonstrated toughness – because of a low design temperature, or because the casing is to be used in a sour well – the impact requirement has to be written into the purchase order, with the test temperature and the acceptance energy stated. Where toughness is critical, the usual answer is to order a grade that carries the requirement by specification rather than to add it to J55.
What is the difference between J55 and K55 casing?
They have the same yield strength range, 379 to 552 MPa, and the same chemistry limits – only phosphorus and sulphur at 0.030 maximum. The difference is minimum tensile strength: J55 requires 517 MPa and K55 requires 655 MPa. K55 therefore carries more tensile capacity and more collapse resistance for the same wall, and it is chosen where the string load or the setting depth puts the J55 option too close to its limit.
Can J55 casing be used in sour service?
Only where the material as delivered meets the hardness limit that NACE MR0175 / ISO 15156 sets for carbon steels, which is 22 HRC (250 HV). API 5CT does not itself set a hardness limit for J55 and does not require an impact test for it, so neither the hardness nor the toughness is controlled unless the order says so. In a sour well the hardness limit, the hardness test results and the impact results are part of what is being bought, and they belong on the purchase order.
Where to go next
- OCTG: Casing and Tubing – which string, grade, connection and documents the well needs
- API 5CT K55 Casing – the medium-strength casing grade above J55
- API 5CT N80 Casing
- Premium Connection Casing and Tubing – gas-tight premium connections
- Oil & Gas – the four products in the oil and gas chain
- Steel Pipe Weight Chart
- Get a Quote – send the grade, size, quantity and destination port
- API 5CT Casing Pipe – API 5CT well casing
- API 5CT Casing Coupling – casing couplings to API 5CT
- API 5CT Tubing Pipe – API 5CT production tubing
Need a price for a specific size and grade? Send the standard and grade, the size and wall thickness, the quantity and the destination port. We reply with availability and pricing.
Request a quotation