The chemical requirement for J55 is a row of blanks. API 5CT Table C.4 in SI units, and its USC twin Table E.4, lists nine elements, and for J55 it gives a maximum for phosphorus and sulfur and nothing else. The same open treatment applies to H40, K55, N80 Type 1, N80Q and M65; the first real chemistry limits appear with L80.
| Element | Requirement for J55 | What that means when the heat arrives |
|---|---|---|
| C | No limit | Left to the mill's production route; may move heat to heat |
| Mn | No limit | Same |
| Si | No limit | Same, unless the project adds a deoxidation requirement |
| Cr, Ni, Cu, Mo | No limit | Residuals are not capped, so no assumption about them is safe |
| P | 0.030 % max, product analysis | One of the two limits that can reject a heat |
| S | 0.030 % max, product analysis | The other one |
| Nb | No limit, must be reported | Reporting is an eleventh-edition requirement for all grades |
A dash in Table C.4 is a decision in the standard, not missing data. The elements listed still have to appear in the product analysis; there is simply no criterion to test them against.
The logic behind the open row is straightforward. J55 is qualified by a tensile test, not by chemistry, and it is intended for containment and structural duty in shallow, low-pressure, sweet wells rather than for corrosion resistance or microstructure control. A mill is free to reach 379 to 552 MPa by whatever route suits its billet or strip.
J55 is defined by a window rather than a target. The minimum is the design value; the maximum keeps the steel ductile and keeps the relationship between yield and tensile within a workable range.
| Grade | Yield min (MPa) | Yield max (MPa) | Tensile min (MPa) | Total elongation under load | Hardness max | Heat treatment |
|---|---|---|---|---|---|---|
| H40 | 276 | 552 | 414 | 0.5 % | — | None required |
| J55 | 379 | 552 | 517 | 0.5 % | — | None required |
| K55 | 379 | 552 | 655 | 0.5 % | — | None required |
| N80 Type 1 | 552 | 758 | 689 | 0.5 % | — | Normalized or normalized and tempered |
| N80Q | 552 | 758 | 689 | 0.5 % | — | Quenched and tempered |
| L80 Type 1 | 552 | 655 | 655 | 0.5 % | 23 HRC | Quenched and tempered |
| C90 | 621 | 724 | 689 | 0.5 % | 25.4 HRC | Quenched and tempered |
| P110 | 758 | 965 | 862 | 0.6 % | — | Quenched and tempered |
The minimum elongation comes from Equation (2) of the standard: e = k × (A^0.2 / U^0.9), where k is 1942.57 in SI units (625,000 in USC), A is the cross-sectional area of the tensile specimen rounded to the nearest 10 mm² and capped at 490 mm², and U is the specified minimum tensile strength. The result is rounded to the nearest 0.5 % below 10 % and to the nearest whole percent at 10 % and above.
| Grade | U, min tensile (MPa) | A (mm²) | e, minimum (%) |
|---|---|---|---|
| J55 | 517 | 230 | 21 |
| L80 Type 1 | 655 | 230 | 17 |
| P110 | 862 | 230 | 13 |
Worked from a 9-5/8 in 47.00 lb/ft length at 11.99 mm wall, so A = 19.00 × 11.99 = 227.8 mm², rounded to 230 mm². The same size and the same specimen give a different requirement for each grade because U sits in the denominator.
The two grades are separated by one number, and it is not the one most comparisons lead with.
| Property | J55 | K55 | Difference |
|---|---|---|---|
| Minimum yield | 379 MPa (55,000 psi) | 379 MPa (55,000 psi) | None |
| Maximum yield | 552 MPa (80,000 psi) | 552 MPa (80,000 psi) | None |
| Minimum tensile | 517 MPa (75,000 psi) | 655 MPa (95,000 psi) | +138 MPa (20,000 psi) |
| Chemistry limits | P and S only | P and S only | None |
| Heat treatment | None required | None required | None |
| Hardness limit | None | None | None |
| Most common form | Casing | Casing and tubing | — |
J55 casing runs from 4-1/2 to 20 in outside diameter, and J55 tubing up to 4-1/2 in. The grade is rolled across most of the casing weight table but not across all of it: the heavier walls in the largest diameters are usually quench-and-tempered grades, and some intermediate weights are only produced to order.
| OD (in) | OD (mm) | J55 weight range (lb/ft) | Tabulated wall range (mm) |
|---|---|---|---|
| 4-1/2 | 114.30 | 9.50–15.10 | 5.21–9.56 |
| 5-1/2 | 139.70 | 14.00–23.00 | 6.20–10.54 |
| 7 | 177.80 | 17.00–38.00 | 5.87–13.72 |
| 9-5/8 | 244.48 | 32.30–58.40 | 7.92–15.11 |
| 13-3/8 | 339.72 | 48.00–72.00 | 8.38–13.06 |
J is a grade class designator with no chemical meaning, and 55 is the minimum yield strength in thousands of pounds per square inch. J55 therefore specifies a minimum yield of 55,000 psi (379 MPa), an upper yield limit of 80,000 psi (552 MPa) and a minimum tensile strength of 75,000 psi (517 MPa). The designation says nothing about carbon content, heat treatment or hardness, because the specification sets no requirement on any of them.
API 5CT limits only phosphorus and sulfur for J55, both at 0.030 % maximum in the product analysis. Carbon, manganese, silicon, chromium, nickel, copper and molybdenum carry no limit, and niobium has no limit but must be reported. Bands such as 0.34-0.39 % C and 1.25-1.50 % Mn on supplier data sheets are mill practice for a particular production route, not specification limits, and a heat outside those bands cannot be rejected under API 5CT alone.
Both forms are produced commercially, and the overwhelming majority of J55 casing and tubing supplied today is seamless. The two routes carry different weld-related requirements, inspection scope and price, so seam type belongs on the purchase order rather than in the mill's discretion. If welded J55 is offered against a seamless requirement, it is a deviation and needs the purchaser's approval.
The yield band is identical at 55,000 to 80,000 psi, and so are the chemistry, heat treatment and hardness requirements. The only difference is the minimum tensile strength: 75,000 psi (517 MPa) for J55 and 95,000 psi (655 MPa) for K55. Because pipe-body ratings are calculated from minimum yield, K55 does not give a higher tensile rating at the same size and wall; it raises the minimum ultimate strength, which matters to how the connection and the failure margin are assessed.
No. J55 carries no hardness limit, no chemistry control for sulfide stress cracking and no SSC test requirement, so the grade designation supplies none of the three controls ISO 15156-2 looks for. A supplier statement that J55 is acceptable for mild sour service is a project qualification and needs a 22 HRC maximum hardness survey and test reports behind it; a heat that happened to test soft is still not a qualified grade. L80 Type 1 carries a 23 HRC ceiling and quench-and-temper heat treatment in the specification itself.
Neither is required. API 5CT specifies no heat treatment for J55, so pipe may be supplied as-rolled or normalized at the manufacturer's option, and the base specification calls for no Charpy impact test. Both can be added by naming them on the purchase order, but neither should be assumed from the grade, and without an impact requirement there is no absorbed-energy figure to compare against a design temperature.
Not by that name. The 11th edition, published in December 2023, removed the PSL1, PSL2 and PSL3 designations, and the PSL body markings went with them. Requirements once attached to those levels now sit in the main clauses or in the Annex A supplementary requirements, so a legacy call-out for J55 PSL2 has to be translated into the base grade plus each named supplementary requirement, listed individually on the order.
Minus 12.5 % on the pipe body, with no positive limit. A 9-5/8 in 47.00 lb/ft length with a nominal wall of 11.99 mm can be delivered at 10.49 mm and still conform. Published collapse and burst ratings are calculated on nominal wall, so a design that needs protection against the tolerance band has to state a minimum-wall requirement, or piece-level wall recording, on the purchase order.
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