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Help CenterAPI 5CT Coupling Stock Coupling Material for API Casing & Tubing – OCTG Connections
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API 5CT Coupling Stock
Coupling Material for API Casing & Tubing – OCTG Connections
API Monogram Licensed – Grades J55, N80, L80, P110
Product Overview
API 5CT coupling stock is a specialized seamless tube used to manufacture couplings for connecting API casing and tubing pipe in oil and gas wells . Couplings are the threaded connectors that join individual pipe joints into a continuous string.
Our coupling stock is manufactured under strict API Q1 quality management system and carries the API Monogram, ensuring full traceability and compliance with API 5CT specifications .
Manufacturing process: Seamless tube → Heat treatment (for higher grades) → Threading → Coupling
✅ API 5CT certified – Latest edition (10th Edition / ISO 11960)
✅ API Monogram licensed – Full traceability to heat and mill
✅ Seamless construction – Thread integrity and pressure sealing
✅ Same grade as pipe – Mechanical properties match casing/tubing
✅ 100% hydrostatic and NDT tested
✅ EN 10204 Type 3.1 MTC with full traceability
✅ Factory direct | Stock available | Fast delivery
Key Specifications
| Parameter | Details | |
|---|---|---|
| Standard | API 5CT (10th Edition / ISO 11960) | |
| Product Type | Coupling Stock (Coupling Material for Casing & Tubing) | |
| Forms Available | Coupling blanks (rough machined) / Fully machined couplings / Coupling material tube | |
| Grades | J55, K55, N80, L80, C95, P110, Q125 | |
| Coupling Type | STC, LTC, BTC for casing | NUE, EUE for tubing |
| OD Range (Material) | 60mm – 400mm (depending on pipe size) | |
| Wall Thickness | As per API 5CT coupling dimensions | |
| Length | As per API 5CT or customer specification | |
| Surface Finish | Black / Phosphate coated / Clear coated / Zinc plated | |
| Marking | API stencil per API 5CT requirement |
Coupling Stock vs Finished Couplings – Supply Options
| Form | Description | Lead Time | Typical Use |
|---|---|---|---|
| Coupling Material Tube | Seamless tube, heat treated, ready for machining | Stock (7-15 days) | In-house coupling manufacturing |
| Coupling Blanks (Rough Machined) | Cut to length, rough turned, unthreaded | 15-25 days | Final threading by customer |
| Fully Machined Couplings | Cut, turned, threaded, inspected, ready to use | 20-30 days | Direct use on casing/tubing |
💡 Options: Coupling stock can be supplied as plain end tube (for in-house machining) or as fully machined API couplings (ready to use) .
Available Grades – API 5CT Coupling Stock
| Grade | Yield Strength (psi) | Yield Strength (MPa) | Tensile (MPa min) | Hardness (HRC max) | Application |
|---|---|---|---|---|---|
| J55 | 55,000 – 80,000 | 379 – 552 | ≥517 | — | Shallow well casing/tubing couplings |
| K55 | 55,000 – 80,000 | 379 – 552 | ≥517 | — | Surface casing couplings |
| N80 (Type 1/Q) | 80,000 – 110,000 | 552 – 758 | ≥689 | — | General purpose couplings |
| L80 Type 1 | 80,000 – 95,000 | 552 – 655 | ≥655 | 23 HRC max | Sour service couplings (H₂S) |
| C95 | 95,000 – 110,000 | 655 – 758 | ≥724 | 25 HRC max | Intermediate depth, sour service |
| P110 | 110,000 – 140,000 | 758 – 965 | ≥862 | 30 HRC max | Deep well, high pressure couplings |
| Q125 | 125,000 – 165,000 | 862 – 1,090 | ≥931 | 35 HRC max | Ultra-deep well, extreme conditions |
Physical property/laboratory test requirements per API 5CT: For coupling stock, physical property testing must be conducted on tube samples and must meet all requirements of the API 5CT grade specification.
📌 Key requirement: Coupling stock must be of the same or higher grade than the pipe being connected . Mechanical properties of the coupling must meet API 5CT requirements for that grade (same as casing/tubing) .
Coupling Dimensions by Pipe Size (Reference – API 5CT)
Casing Couplings (BTC/LTC/STC):
| Pipe OD (inch) | Coupling OD (inch) | Coupling Length (inch) | Thread Type |
|---|---|---|---|
| 4-1/2″ | 5.000″ | 7.75″ (LTC) / 6.75″ (STC) | 8 round / Buttress |
| 5″ | 5.563″ | 8.00″ (LTC) / 7.00″ (STC) | 8 round / Buttress |
| 5-1/2″ | 6.050″ | 8.50″ (LTC) / 7.50″ (STC) | 8 round / Buttress |
| 6-5/8″ | 7.390″ | 9.00″ (LTC) / 8.00″ (STC) | 8 round / Buttress |
| 7″ | 7.656″ | 9.50″ (LTC) / 8.00″ (STC) | 8 round / Buttress |
| 7-5/8″ | 8.500″ | 10.00″ (LTC) / 8.50″ (STC) | 8 round / Buttress |
| 8-5/8″ | 9.625″ | 10.50″ (LTC) / 9.00″ (STC) | 8 round / Buttress |
| 9-5/8″ | 10.625″ | 11.00″ (LTC) / 9.50″ (STC) | 8 round / Buttress |
| 10-3/4″ | 11.750″ | 11.50″ (LTC) / 10.00″ (STC) | 8 round / Buttress |
| 11-3/4″ | 12.750″ | 12.00″ (LTC) / 10.50″ (STC) | 8 round / Buttress |
| 13-3/8″ | 14.375″ | 12.50″ (LTC) / 11.00″ (STC) | 8 round / Buttress |
| 16″ | 17.000″ | 13.00″ (LTC) / 11.00″ (STC) | 8 round / Buttress |
| 18-5/8″ | 19.750″ | 13.50″ (LTC) / 12.00″ (STC) | 8 round / Buttress |
| 20″ | 21.000″ | 14.00″ (LTC) / 12.50″ (STC) | 8 round / Buttress |
Tubing Couplings (NUE/EUE):
| Tubing OD (inch) | Coupling OD (inch) | Coupling Length (inch) | Connection Type |
|---|---|---|---|
| 1.050″ | 1.563″ | 3.25″ | NUE |
| 1.315″ | 1.875″ | 3.25″ | NUE |
| 1.660″ | 2.250″ | 3.50″ | NUE/EUE |
| 1.900″ | 2.500″ | 3.75″ | NUE/EUE |
| 2-3/8″ | 3.063″ | 4.50″ (EUE) | NUE/EUE |
| 2-7/8″ | 3.668″ | 5.00″ (EUE) | NUE/EUE |
| 3-1/2″ | 4.500″ | 5.50″ (EUE) | NUE/EUE |
| 4″ | 5.000″ | 5.75″ | NUE/EUE |
| 4-1/2″ | 5.563″ | 6.00″ | NUE/EUE |
Chemical Composition – API 5CT Coupling Stock (Typical Max Values)
| Grade | C max | Mn max | P max | S max | Si max | Cr | Mo | Others |
|---|---|---|---|---|---|---|---|---|
| J55 / K55 | 0.30 | 1.50 | 0.020 | 0.015 | — | — | — | — |
| N80 | 0.43 | 1.90 | 0.020 | 0.015 | 0.45 | — | — | V, Nb, Ti |
| L80 Type 1 | 0.43 | 1.90 | 0.020 | 0.010 | 0.45 | — | — | — |
| C95 | 0.43 | 1.20 | 0.020 | 0.010 | 0.45 | — | 0.25-0.85 | V,Nb,Ti |
| P110 | 0.43 | 1.20 | 0.020 | 0.010 | 0.45 | 0.40-1.50 | 0.60-1.00 | — |
| Q125 | 0.35 | 1.20 | 0.020 | 0.010 | 0.55 | 0.40-1.50 | 0.60-1.00 | B, V, Ni |
⚠️ Note for sour service: Coupling stock for L80 must have hardness ≤23 HRC and meet sour service chemical limits (P ≤0.015%, S ≤0.010%) .
Mechanical Properties – API 5CT Coupling Stock
| Grade | Yield Strength (psi) | Yield Strength (MPa) | Tensile (MPa min) | Hardness (HRC max) |
|---|---|---|---|---|
| J55 | 55,000 – 80,000 | 379 – 552 | ≥517 | — |
| K55 | 55,000 – 80,000 | 379 – 552 | ≥517 | — |
| N80 | 80,000 – 110,000 | 552 – 758 | ≥689 | — |
| L80 Type 1 | 80,000 – 95,000 | 552 – 655 | ≥655 | 23 HRC max |
| C95 | 95,000 – 110,000 | 655 – 758 | ≥724 | 25 HRC max |
| P110 | 110,000 – 140,000 | 758 – 965 | ≥862 | 30 HRC max |
| Q125 | 125,000 – 165,000 | 862 – 1,090 | ≥931 | 35 HRC max |
📌 Hardness limits are critical for sour service couplings – L80 couplings must maintain ≤23 HRC throughout the heat treatment and threading process .
Key Advantages – API 5CT Coupling Stock
| Feature | Benefit |
|---|---|
| API Monogram certified | Full traceability to heat and mill – audit-ready documentation |
| Same grade as pipe | Mechanical properties match casing/tubing per API 5CT |
| Seamless construction | Thread integrity and pressure sealing reliability |
| Full range grades | J55, K55, N80, L80, C95, P110, Q125 – all available |
| Sour service capability | L80 coupling stock with ≤23 HRC meets NACE MR0175 |
| Multiple supply options | Tube stock / blanks / fully machined couplings |
| 100% hydrostatic and NDT tested | Guaranteed material integrity |
| Full traceability | EN 10204 Type 3.1 MTC with heat number |
| Stock availability | Common grades (J55, N80, L80, P110) ready to ship |
Coupling Stock Selection by Pipe Grade
| Pipe Grade | Required Coupling Grade | Sour Service? | Hardness Limit |
|---|---|---|---|
| J55 casing/tubing | J55 or higher | No | — |
| K55 casing | K55 or higher | No | — |
| N80 casing/tubing | N80 or higher | No | — |
| L80 casing/tubing | L80 (sour service) | Yes | ≤23 HRC |
| C95 casing | C95 or higher | Yes (optional) | ≤25 HRC |
| P110 casing/tubing | P110 or higher | No (not for sour) | — |
| Q125 casing | Q125 | Yes (controlled) | ≤35 HRC |
💡 Key rule: Coupling grade must be equal to or higher than the pipe grade being connected .
Quality Testing & Inspection – API 5CT Coupling Stock
| Test | Standard / Method | Coverage |
|---|---|---|
| Hydrostatic Test | API 5CT | 100% |
| Ultrasonic Testing (UT) | ASTM E213 | 100% |
| Electromagnetic (EMI) Inspection | API 5CT | 100% |
| Tensile Test | API 5CT / ISO 6892 | 1 per 200 tons or each heat |
| Hardness Test | Rockwell C (HRC) | 1 per 200 tons (critical for L80) |
| Flattening Test | API 5CT | Per API frequency |
| Dimensional Inspection | API thread gauges | 100% (for machined couplings) |
| Thread Inspection | Visual, API thread gauges | 100% (for machined couplings) |
Mill Test Certificate – API 5CT Coupling Stock
API 5CT Certificate of Compliance – Standard (API Monogram licensed)
EN 10204 Type 3.2 – Available upon request (third-party: SGS, BV, TUV, DNV)
Traceability: Full traceability from melt to finished coupling stock (heat number → tube → coupling)
Hardness test report – Required for L80 sour service couplings
Material Test Report (MTR) – Includes heat number, chemical analysis, mechanical properties, NDT results
Processing Services – Coupling Stock to Finished Couplings
| Service | Description |
|---|---|
| Cutting to length | Precision cutting of coupling stock to specified length |
| Heat treatment | Quenching and tempering (for N80-Q, L80, P110 grades) |
| Rough turning | External turning to coupling OD dimensions |
| Threading | API STC, LTC, BTC (casing) or NUE, EUE (tubing) |
| Phosphating / Coating | Surface treatment for corrosion resistance |
| Marking | API stencil per API 5CT requirement |
| Coupling supply | Fully machined couplings ready for pipe connection |
Packaging & Shipping – Coupling Stock
| Item | Details |
|---|---|
| Packaging | Wooden crates or steel pallets (for machined couplings) |
| Bundles | Hexagonal bundles (for coupling material tube) |
| Protection | Anti-rust oil + plastic end caps (tube) / Thread protectors (couplings) |
| Marking | API stencil: Grade, size, heat number, API monogram |
| Lead time | 7–15 days (coupling stock tube), 20–30 days (machined couplings) |
| Port | Tianjin / Shanghai / Guangzhou |
Why Choose Our API 5CT Coupling Stock?
| Advantage | Description |
|---|---|
| API Monogram licensed | Full API Q1 quality management system – audit-ready |
| Full grade range | J55, K55, N80, L80, C95, P110, Q125 – one-stop sourcing |
| Sour service capability | L80 with ≤23 HRC meets NACE MR0175 for H₂S environments |
| Same grade as pipe | Mechanical properties match API 5CT casing/tubing requirements |
| Flexible supply options | Tube stock / blanks / fully machined couplings |
| Full thread inspection | API thread gauges for machined couplings – 100% check |
| Full traceability | EN 10204 3.1 MTC with heat number |
| Stock availability | Common grades (J55, N80, L80, P110) ready to ship |
| Global export | Shipped to OCTG manufacturers and oilfields worldwide |
Contact for Quote – API 5CT Coupling Stock
Please provide the following details for your coupling stock requirements:
Grade : J55 / K55 / N80 / L80 / C95 / P110 / Q125
Sour service required? : Yes / No
Pipe OD (inch) : _______
Coupling Type : STC / LTC / BTC (casing) | NUE / EUE (tubing)
Form Required : Coupling material tube / Blanks / Fully machined couplings
Quantity : _______ (meters / tons / pieces)
Inspection : Standard / Third-party (SGS/BV/TUV/DNV)
📧 Email: yjhtrade@gmail.com
📞 WhatsApp: +86 15106174543
🌐 Website:
Reply within 24 hours.
FAQ – API 5CT Coupling Stock
Q1: What is API 5CT coupling stock?
A: Coupling stock is a seamless tube manufactured to API 5CT specifications, used to machine couplings that connect casing or tubing pipes in oil and gas wells .
Q2: What grades of coupling stock are available?
A: J55, K55, N80, L80, C95, P110, Q125 – same grade range as API 5CT casing and tubing .
Q3: Does coupling stock have to be the same grade as the pipe?
A: Yes, by API 5CT requirements . Coupling grade must be equal to or higher than the pipe grade being connected .
Q4: What is the difference between coupling stock and finished couplings?
A: Coupling stock – seamless tube material ready for machining . Finished couplings – fully machined, threaded, inspected, ready to use .
Q5: What hardness is required for L80 sour service couplings?
A: ≤23 HRC . L80 coupling stock for sour service must meet NACE MR0175 hardness limits .
Q6: Can coupling stock be used for both casing and tubing?
A: Yes . Coupling stock can be machined into STC, LTC, BTC (casing) or NUE, EUE (tubing) connections .
Q7: What testing is required for coupling stock?
A: 100% hydrostatic test, 100% UT, tensile test, flattening test, and (for L80) hardness test .
Q8: Do you provide third-party inspection?
A: Yes. SGS, BV, TUV, DNV, or any customer-specified agency.
Q9: Can you supply fully machined couplings ready for use?
A: Yes . We can supply both coupling stock (material) and finished machined couplings .
Q10: Do you offer free samples?
A: 30cm coupling stock sample available for inspection. Finished coupling samples available on request (cost applies).
Related Products – OCTG Connections
API 5CT Coupling Stock – Coupling material (this product)
API 5CT Casing – Casing pipe with threaded connections
API 5CT Tubing – Tubing pipe with threaded connections
API 5CT Couplings – Finished machined couplings
Premium Connections – VAM, Tenaris, etc.
Thread Protectors – Steel or plastic protectors
Tags: API 5CT Coupling Stock Coupling Material OCTG Casing Coupling Tubing Coupling J55 Coupling N80 Coupling L80 Coupling P110 Coupling Sour Service Coupling
Quick Reference: API 5CT Coupling Stock Grade Selection
| Pipe Grade | Coupling Grade Required | Sour Service? | Hardness Limit |
|---|---|---|---|
| J55 | J55 or higher | No | — |
| K55 | K55 or higher | No | — |
| N80 | N80 or higher | No | — |
| L80 | L80 | Yes | ≤23 HRC |
| C95 | C95 or higher | Yes (optional) | ≤25 HRC |
| P110 | P110 or higher | No (not for sour) | — |
| Q125 | Q125 | Yes (controlled) | ≤35 HRC |
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