Stainless Steel Coil Tube (Coiltube) — Model JX-CT Series
Product Overview
The JX-CT Series Stainless Steel Coil Tube, manufactured by Wenzhou Jixing Metal Materials Co., Ltd., represents a next-generation coiled tubular product engineered for demanding industrial, commercial, and infrastructure applications. Unlike conventional straight-length stainless steel pipes, coil tubes are delivered in continuous helical or spiral configurations, offering superior flexibility in installation, reduced joint counts, and enhanced system integrity. The design philosophy of the JX-CT Series draws upon advanced research into flange pipe connection methodologies, incorporating improved joint compatibility, optimized wall thickness distributions, and refined surface finishes that collectively minimize leakage risks and extend service life.
Coiltube products occupy a critical niche in process engineering, HVAC systems, heat exchanger assemblies, and fluid transport networks where continuous, joint-minimized piping runs are essential for pressure integrity and operational reliability. The JX-CT Series is engineered to meet the rigorous demands of these environments while maintaining the corrosion resistance, mechanical strength, and dimensional accuracy characteristic of high-grade stainless steel alloys.
Material Composition & Mechanical Properties
Base Alloy Grades
The JX-CT Series is fabricated from premium austenitic and duplex stainless steel grades, selected to ensure optimal combinations of corrosion resistance, formability, and mechanical performance:
- 304 / 304L (UNS S30400 / S30403): The industry-standard austenitic grade offering excellent general corrosion resistance, high formability, and good weldability. Suitable for non-aggressive chemical environments, food processing, and architectural applications.
- 316 / 316L (UNS S31600 / S31603): Enhanced austenitic grade with molybdenum addition (2.0–3.0 wt%), providing superior resistance to pitting and crevice corrosion in chloride-containing environments. Ideal for marine, pharmaceutical, and chemical processing applications.
- 321 (UNS S32100): Stabilized austenitic grade with titanium stabilization, offering excellent resistance to intergranular corrosion in high-temperature service (up to 870°C / 1598°F).
- 316L (UNS S31603): Low-carbon variant of 316 with carbon content ≤ 0.03 wt%, designed for enhanced weldability and resistance to sensitization during welding operations.
- Duplex 2205 (UNS S32205): Duplex austenite-ferrite microstructure providing approximately twice the yield strength of 304/316 grades with superior resistance to chloride stress corrosion cracking (Cl-SCC).
Mechanical Properties (Typical Values for Annealed Condition)
| Property | Grade 304/304L | Grade 316/316L | Grade 321 | Grade 2205 Duplex |
|---|---|---|---|---|
| Yield Strength (0.2% Offset), MPa | ≥ 205 | ≥ 170 | ≥ 205 | ≥ 450 |
| Tensile Strength, MPa | 515 – 730 | 485 – 725 | 515 – 730 | 550 – 800 |
| Elongation (%), minimum | 40 | 40 | 40 | 25 |
| Density, g/cm³ | 8.0 | 8.0 | 8.0 | 8.0 |
| Thermal Conductivity, W/(m·K) at 20°C | 16.3 | 16.3 | 14.2 | 11.4 |
| Maximum Service Temperature, °C | 870 | 870 | 870 | 315 (continuous) |
Corrosion Resistance Characteristics
The JX-CT Series exhibits the following corrosion resistance profiles:
- Pitting Resistance: Quantified by PREN (Pitting Resistance Equivalent Number) values ranging from 18–20 for Grade 304, 24–26 for Grade 316, and 34–38 for Duplex 2205, calculated as PREN = %Cr + 3.3 × %Mo + 16 × %N.
- Crevice Corrosion: All grades demonstrate excellent resistance in non-oxidizing aqueous environments; Grade 316 and Duplex 2205 are specifically recommended for crevice-prone geometries such as flange gasket interfaces.
- Stress Corrosion Cracking (SCC): Duplex 2205 provides the highest resistance to chloride SCC among the offered grades, making it the preferred selection for high-chloride, high-temperature service.
- Intergranular Corrosion: Grades 304L, 316L, and 321 are stabilized against sensitization through low-carbon control or titanium stabilization, ensuring long-term grain boundary integrity.
Dimensional Specifications
| Parameter | Specification / Range | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | Φ6.0 mm – Φ114.3 mm (¼" – 4½") | ASTM A554 / GB/T 14976 |
| Wall Thickness | 0.5 mm – 6.0 mm (0.020" – 0.236") | ASTM A554 / EN 10216-5 |
| Coil Length (per coil) | 20 m – 500 m (configurable) | — |
| Coil Core Diameter | Φ150 mm – Φ300 mm | — |
| Coil Diameter (outer) | Φ500 mm – Φ1500 mm | — |
| OD Tolerance | ±0.05 mm (precision) / ±0.10 mm (standard) | ASTM A554 |
| Wall Thickness Tolerance | ±10% (standard) / ±5% (precision) | ASTM A554 |
| Surface Finish (Ra) | Ra 0.4 – 1.6 μm (polished) / Ra 3.2 – 6.3 μm (pickled) | ASTM A270 |
| End Form | Plain cut / Beveled / Flanged (upon request) | ASME B16.5 / EN 1092-1 |
| Heat Treatment Condition | Annealed (Solution Annealed at 1050–1150°C) | ASTM A554 |
| Delivery Condition | Coiled on wooden reel / Steel reel / Palletized | — |
Manufacturing Process
The JX-CT Series undergoes a rigorous, multi-stage manufacturing process designed to ensure dimensional precision, metallurgical integrity, and surface quality:
- Raw Material Procurement & Ingot Casting: High-purity stainless steel billets or slabs are sourced from certified mills, with chemistry verified by spectroscopic analysis to ensure compliance with ASTM and EN standards. Ingot casting is performed via vacuum arc remelting (VAR) or electro-slag remelting (ESR) for ultra-high purity grades.
- Hot Rolling & Annealing: Billets are reheated to 1150–1250°C and hot-rolled into seamless tube blanks. The hot-rolled blanks undergo solution annealing at 1050–1100°C followed by controlled air cooling or water quenching to establish a fully austenitic (or duplex) microstructure free of carbide precipitation.
- Cold Drawing & Sizing: The annealed blanks are cold-drawn through precision tungsten carbide dies to achieve the target outer diameter and wall thickness. Multiple drawing passes are employed to achieve tight dimensional tolerances (±0.05 mm) and uniform wall thickness distribution. Intermediate annealing at 1050°C is performed between drawing passes to relieve accumulated work hardening and restore ductility.
- Piercing & Coiling: The drawn tube is coiled onto a mandrel at controlled tension to form the helical coil configuration. Coiling is performed at elevated temperature (300–400°C) to minimize residual stresses and prevent microstructural distortion. The coiling tension is precisely regulated to maintain consistent coil diameter and prevent kinking or ovality.
- Pickling & Passivation: The coiled tube undergoes acid pickling using a hydrofluoric-nitric acid (HF-HNO₃) or citric acid bath to remove mill scale, oxide films, and surface contaminants. This is followed by passivation to establish a chromium-rich oxide layer (Cr₂O₃) that provides initial corrosion protection. The passivation treatment is verified by the ferric chloride (FeCl₃) surface test per ASTM A967.
- Precision Coiling & Stranding: The pickled and passivated tube is coiled into the final product configuration with controlled pitch, diameter, and strand arrangement. The coiling parameters are optimized to ensure the tube can be unwound without permanent deformation or surface damage.
- Flange Connection Integration (if applicable): For configurations requiring flanged connections, the tube ends are beveled per ASME B16.5 standards and may be fitted with integral or bolted flange assemblies. The improved flange connection methodology—incorporating enhanced gasket sealing surfaces, optimized bolt preload sequences, and corrosion-resistant fastener materials—ensures leak-tight joints even under thermal cycling conditions.
- Quality Inspection & Testing: Every coil undergoes comprehensive inspection including dimensional verification, visual surface examination, and non-destructive testing (NDT).
Quality Assurance & Testing Protocols
| Test Method | Standard | Frequency | Acceptance Criteria |
|---|---|---|---|
| Chemical Analysis (Spectrometry) | ASTM E415 / GB/T 223 | Per heat number | Composition within specified range |
| Hydrostatic Pressure Test | ASTM A554 / GB/T 244 | 100% of coils | No leakage at 2× working pressure for 60 s |
| Visual Surface Inspection | ASTM A270 / EN 10216-5 | 100% of coils | Free from pits, cracks, seams, and surface defects |
| Dimensional Measurement (OD, WT, Roundness) | ASTM A554 | Per coil (sampling) | Within specified tolerances |
| Mechanical Testing (Tensile, Hardness) | ASTM A370 / ASTM E10 | Per heat number | Meets minimum yield strength and elongation |
| Pickling & Passivation Verification (FeCl₃ Test) | ASTM A967 | Per coil | No staining within 60 s exposure |
| Intergranular Corrosion Test (Acid Solution) | ASTM A262 Practice E | Per heat number | No intergranular attack |
| Chromium Oxide Layer Thickness | XRF Analysis | Per coil | ≥ 1.5 nm Cr₂O₃ layer |
Applications
The JX-CT Series Stainless Steel Coil Tube is engineered for a broad spectrum of industrial and commercial applications:
Process & Chemical Engineering
- Continuous process piping in chemical, petrochemical, and pharmaceutical manufacturing plants where joint-minimized piping reduces leakage risk and simplifies maintenance.
- Transfer lines for aggressive chemicals, acids, and alkaline solutions requiring superior corrosion resistance (Grade 316L and Duplex 2205 recommended).
- Hygienic piping systems in food and beverage processing (FDA-compliant surface finish, Ra ≤ 0.4 μm).
Heat Exchange & Thermal Systems
- Coiled heat exchanger tubes (hairpin coils, spiral coils) for condensers, evaporators, and air-handling units in HVAC systems.
- Steam coil assemblies for industrial heating applications.
- Refrigerant coils for commercial refrigeration and cryogenic systems.
Infrastructure & Construction
- Building services piping for plumbing, fire suppression, and compressed air distribution in commercial and residential structures.
- Marine and offshore platform piping where chloride resistance is critical (Grade 316L or Duplex 2205).
- Structural coil applications in automotive exhaust systems, heat shields, and industrial equipment fabrication.
Specialty Applications
- Semi-conductor manufacturing cleanroom piping (ultra-low particulate, ultra-high purity surface finish).
- Biomedical equipment fluid transport lines.
- Energy sector applications including geothermal heat exchangers and solar thermal collectors.
Quality Certifications & Standards Compliance
The JX-CT Series is manufactured under a certified quality management system and complies with the following international standards and certifications:
- ISO 9001:2015 — Quality Management System Certification (Wenzhou Jixing Metal Materials Co., Ltd.)
- ISO 14001:2015 — Environmental Management System Certification
- ISO 45001:2018