Stainless Steel Oil Well Coil Tube — Sandvik-Grade Specification
1. Product Overview
The Stainless Steel Oil Well Coil Tube (also referred to as Coiltube or Coiled Stainless Steel Pipe) is a continuously formed, non-seamed or welded stainless steel tubing product designed for demanding oil and gas extraction environments. This product is manufactured in accordance with the metallurgical standards and production methodologies established by Sandvik (Sandvik AB, Sweden), one of the world's leading producers of high-performance stainless steels and specialty alloys. The coil tube is supplied in continuous coil form, enabling rapid deployment, minimal field welding, and superior corrosion resistance in harsh downhole and surface conditions.
Sourced and distributed by Wenzhou Jixing Metal Materials Co., Ltd, this product line represents a fusion of Scandinavian metallurgical excellence and modern Asian manufacturing precision, serving as a critical component in oil well completion systems, chemical processing lines, and high-pressure fluid transport applications.
2. Material & Properties
2.1 Base Alloy Composition
The coil tube is fabricated from austenitic stainless steel conforming to Sandvik's proprietary and internationally recognized alloy grades. The most common grades utilized include:
- Sandvik 304 (UNS S30400 / AISI 304) — General-purpose austenitic stainless steel with excellent corrosion resistance and formability.
- Sandvik 316 (UNS S31600 / AISI 316) — Enhanced resistance to pitting and crevice corrosion due to the addition of molybdenum (Mo).
- Sandvik 316L (UNS S31603 / AISI 316L) — Low-carbon variant of 316, offering superior weldability and resistance to intergranular corrosion.
- Sandvik 321 (UNS S32100 / AISI 321) — Titanium-stabilized austenitic grade for high-temperature service environments.
- Sandvik 904L (UNS N08904) — Super-austenitic grade for extreme corrosive environments.
2.2 Mechanical Properties (Typical)
| Property | Grade 304 / 304L | Grade 316 / 316L | Grade 321 |
|---|---|---|---|
| Tensile Strength (UTS) — MPa (ksi) | ≥ 515 (75) | ≥ 515 (75) | ≥ 515 (75) |
| Yield Strength (0.2% Offset) — MPa (ksi) | ≥ 205 (30) | ≥ 205 (30) | ≥ 205 (30) |
| Elongation — % (min, 50 mm gauge) | ≥ 40 | ≥ 40 | ≥ 40 |
| Hardness (HB max) | 217 | 217 | 217 |
| Density — g/cm³ | 8.0 | 8.0 | 8.0 |
| Thermal Conductivity (at 100°C) — W/(m·K) | 16.3 | 16.3 | 16.3 |
| Modulus of Elasticity — GPa | 193 | 193 | 193 |
2.3 Chemical Composition (Typical, wt%)
| Element | Grade 304 | Grade 316 | Grade 316L | Grade 321 |
|---|---|---|---|---|
| C (Carbon) | ≤ 0.08 | ≤ 0.08 | ≤ 0.03 | ≤ 0.08 |
| Si (Silicon) | ≤ 1.00 | ≤ 1.00 | ≤ 1.00 | ≤ 1.00 |
| Mn (Manganese) | ≤ 2.00 | ≤ 2.00 | ≤ 2.00 | ≤ 2.00 |
| P (Phosphorus) | ≤ 0.045 | ≤ 0.045 | ≤ 0.045 | ≤ 0.045 |
| S (Sulfur) | ≤ 0.030 | ≤ 0.030 | ≤ 0.030 | ≤ 0.030 |
| Cr (Chromium) | 18.00 – 20.00 | 16.00 – 18.00 | 16.00 – 18.00 | 17.00 – 19.00 |
| Ni (Nickel) | 8.00 – 10.50 | 10.00 – 14.00 | 10.00 – 14.00 | 9.00 – 13.00 |
| Mo (Molybdenum) | — | 2.00 – 3.00 | 2.00 – 3.00 | — |
| Ti (Titanium) | — | — | — | 5×(C–0.02) – 0.70 |
3. Dimensions & Specifications
| Parameter | Specification / Range |
|---|---|
| Outer Diameter (OD) — mm | 12.7 – 168.3 (0.5" – 6.5") |
| Wall Thickness — mm | 0.8 – 8.0 (0.031" – 0.315") |
| Coil Weight — kg | 500 – 3,000 (per coil) |
| Coil Length — m (continuous) | Up to 1,000 – 3,000 (depending on OD and wall thickness) |
| Coil Inner Diameter (Coil ID) — mm | 152 – 610 (6" – 24") |
| Surface Finish | 2B (Cold Rolled & Annealed), BA (Bright Annealed), No. 4 Brushed, No. 8 Mirror, Pickled & Passivated |
| Tolerance — OD | ± 0.05 mm (± 0.002") |
| Tolerance — Wall Thickness | ± 10% of nominal |
| Seam Type | Welded (AWT / ERW) or Seamless (depending on grade and size) |
| Standards Referenced | ASTM A213 / A269 / A778, ASME B36.19M, EN 10216-5, ISO 3506, Sandvik Technical Data Sheets |
| Temperature Range | −196°C to +870°C (−320°F to +1,600°F) |
| Pressure Rating | Up to 1,200 bar (17,400 psi) — dependent on OD, wall thickness, and grade |
| Packaging | Wooden crate or steel drum with moisture barrier; coil wrapped in PE film and desiccant-treated |
4. Manufacturing Process
The production of Sandvik-grade stainless steel oil well coil tubes follows a rigorous, multi-stage manufacturing sequence that ensures metallurgical integrity, dimensional accuracy, and corrosion resistance:
- Raw Material Procurement & Verification — Virgin stainless steel billets or slabs are sourced from certified Sandvik or equivalent mills. Incoming material is subjected to spectroscopic analysis (OES — Optical Emission Spectroscopy) to confirm chemical composition compliance.
- Hot Rolling & Annealing — The initial hot-rolled strip is annealed in a controlled atmosphere furnace (reducing atmosphere, typically hydrogen-nitrogen mix) to achieve the desired austenitic microstructure and eliminate residual stresses.
- Pickle & Descale — The hot-rolled strip is immersed in a mixed acid pickling bath (hydrochloric acid + nitric acid) to remove scale, oxide layers, and surface contaminants. This is followed by a thorough water rinse and passivation treatment.
- Cold Rolling — The descaled strip undergoes multi-pass cold rolling to achieve precise wall thickness and dimensional tolerances. Cold rolling enhances mechanical properties and surface finish quality.
- Coil Forming & Welding — The cold-rolled strip is fed through a coiling and welding line. For welded coil tubes, the strip edges are precisely formed into a tube shape and welded using Automatic Welding Technology (AWT), Electro Resistance Welding (ERW), or Submerged Arc Welding (SAW). For seamless coil tubes, the process utilizes Autoclave Annealing and Pilot Tube Milling methods.
- Post-Weld Heat Treatment & Annealing — Welded tubes undergo solution annealing at 1,010°C – 1,150°C (1,850°F – 2,100°F) followed by controlled water or air quenching to restore full austenitic structure and maximize corrosion resistance in the Heat-Affected Zone (HAZ).
- Non-Destructive Testing (NDT) — Every coil tube is inspected using multiple NDT methods:
- Eddy Current Testing (ECT) — For detection of surface and near-surface defects along the full length of the tube.
- Ultrasonic Testing (UT) — For wall thickness verification and internal defect detection.
- Hydrostatic Pressure Testing — Each tube is pressure-tested at 1.5× the maximum working pressure to ensure leak-tightness and structural integrity.
- Visual Inspection — Automated optical inspection systems scan the entire coil length for surface imperfections.
- Surface Finishing & Passivation — Final surface treatment includes mechanical polishing (if specified), chemical passivation (using nitric acid or citric acid solutions), and application of protective coatings (e.g., silicone oil, VCI — Vapor Corrosion Inhibitor film) to prevent post-production corrosion.
- Coiling & Packaging — The finished tube is coiled to the specified coil diameter, wrapped in protective PE film, and packed in moisture-protected containers. Each coil is labeled with a unique heat number, grade designation, and traceability code.
5. Applications
The Sandvik-grade stainless steel oil well coil tube is engineered for a broad spectrum of high-demand industrial applications:
5.1 Oil & Gas Industry
- Oil Well Completion Strings — Used as downhole tubing, casing, and production tubing in onshore and offshore oil wells. The continuous coil form eliminates the need for field welding of individual pipe segments, reducing installation time and potential failure points.
- Flowlines & Manifolds — Transport of crude oil, natural gas, and produced water in surface facilities.
- Subsea Pipelines — Resistant to chlorinated seawater environments, making them suitable for subsea applications.
- Well Intervention & Coiled Tubing Units (CTU) — The coil tube is the core component of coiled tubing operations, enabling continuous well intervention without breaking flow.
5.2 Chemical & Petrochemical Processing
- Transport and processing of aggressive chemicals, acids, and solvents.
- Reactor internals, heat exchanger tubes, and distillation column components.
- Storage tank piping and transfer lines for corrosive media.
5.3 Food & Pharmaceutical Industry
- Hygienic-grade piping systems for food processing, beverage production, and pharmaceutical manufacturing (BA finish available).
- Compliant with 3-A Sanitary Standards and EHEDG (European Hygienic Engineering & Design Group) guidelines.
5.4 Energy & Power Generation
- Boiler tubes, superheater tubes, and economizer tubes in fossil fuel and nuclear power plants.
- Geothermal well tubing and heat recovery systems.
5.5 Marine & Desalination
- Seawater intake piping, desalination plant heat exchangers, and marine propulsion systems.
- Grade 316L and 904L variants offer exceptional resistance to pitting in chlorinated marine environments.
6. Quality Certifications & Compliance
Every coil tube product supplied by Wenzhou Jixing Metal Materials Co., Ltd. undergoes comprehensive quality assurance and carries the following certifications and compliance documentation:
- ISO 9001:2015 — Quality Management System certification ensuring consistent product quality and process control.
- ISO 14001:2015 — Environmental Management System certification for sustainable manufacturing practices.
- API (American Petroleum Institute) Compliance