Stainless Steel Coil Tube (Coiltube) — Industrial Grade Continuous Wound Pipe
Product Overview
The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd is a continuously wound, seamless or welded tubular product formed through precision cold-drawing and coiling techniques. Unlike straight-length seamless or ERW (Electric Resistance Welded) pipes, coil tubes are produced in continuous helical form, offering superior material utilization, consistent dimensional tolerances, and reduced cutting waste. This product line encompasses austenitic, ferritic, and duplex stainless steel grades, engineered to meet the demanding requirements of heat exchangers, refrigeration systems, chemical processing, food-grade applications, and cryogenic environments.
The coil tube format is particularly advantageous in applications requiring long, uninterrupted pipe runs without butt welds, thereby minimizing potential leak points and enhancing structural integrity. The helical winding configuration also facilitates compact storage and efficient downstream processing through automated coil unwinding and straightening equipment.
Material & Properties
Available Grades
- Austenitic Grades: SUS304 / 1.4301, SUS304L / 1.4307, SUS316 / 1.4401, SUS316L / 1.4404, SUS321 / 1.4541, SUS310S / 1.4845
- Ferritic Grades: SUS430 / 1.4006, SUS409 / 1.4521, SUS444 / 1.4510
- Duplex Grades: SUS316L-2N / 1.4462, SUS2205 / 1.4462, SUS2507 / 1.4410
- Custom Alloys: Available upon request per ASTM, EN, or proprietary specifications
Mechanical Properties (Typical — Annealed Condition)
| Property |
Unit |
SUS304 / 1.4301 |
SUS316L / 1.4404 |
SUS2205 / 1.4462 |
| Tensile Strength (Rm) |
MPa |
≥ 520 |
≥ 450 |
≥ 450 |
| Yield Strength (Rp0.2) |
MPa |
≥ 205 |
≥ 170 |
≥ 450 |
| Elongation (A50) |
% |
≥ 40 |
≥ 40 |
≥ 25 |
| Hardness (HV) |
HV |
≤ 200 |
≤ 200 |
≤ 250 |
| Operating Temperature Range |
°C |
−196 to +870 |
−196 to +870 |
−196 to +350 |
Chemical Composition (Typical — wt%)
| Element |
C |
Si |
Mn |
P |
S |
Cr |
Ni |
Mo |
N |
| SUS304 / 1.4301 |
≤ 0.08 |
≤ 1.00 |
≤ 2.00 |
≤ 0.045 |
≤ 0.030 |
18.00–20.00 |
8.00–10.50 |
— |
— |
| SUS316L / 1.4404 |
≤ 0.030 |
≤ 1.00 |
≤ 2.00 |
≤ 0.045 |
≤ 0.030 |
16.00–18.00 |
10.00–14.00 |
2.00–2.50 |
— |
| SUS2205 / 1.4462 |
≤ 0.030 |
≤ 1.00 |
≤ 2.00 |
≤ 0.030 |
≤ 0.020 |
22.00–23.00 |
4.50–6.50 |
3.00–3.50 |
0.14–0.20 |
Corrosion Resistance Characteristics
- Pitting Resistance: PREN (Pitting Resistance Equivalent Number) values ranging from 18 (304) to 38 (2205), providing excellent resistance to chloride-induced pitting and crevice corrosion.
- Intergranular Corrosion Resistance: Low-carbon (L) grades undergo stabilization heat treatment at 1050°C to prevent chromium carbide precipitation at weld zones.
- Stress Corrosion Cracking (SCC) Resistance: Duplex grades exhibit superior SCC resistance in halide-containing environments compared to austenitic counterparts.
- Crevice Corrosion Resistance: Enhanced by molybdenum (Mo) and nitrogen (N) additions, particularly in 316L and duplex grades.
Specifications
| Parameter |
Specification |
Standard Reference |
| Outer Diameter (OD) |
Φ 3.00 mm – Φ 50.80 mm |
ASTM A269, EN 10216-5 |
| Wall Thickness |
0.30 mm – 3.00 mm |
ASTM A269, EN 10217-7 |
| OD Tolerance |
± 0.05 mm (± 0.5%) |
EN 10216-5 Class B |
| Wall Thickness Tolerance |
± 10% (minimum ± 0.03 mm) |
ASTM A269 |
| Coil Inner Diameter (ID) |
Φ 100 mm – Φ 305 mm (4" – 12") |
Customer-specific |
| Coil Length (per coil) |
5 m – 100 m (continuous) |
— |
| Surface Finish |
2B, BA (Bright Annealed), No.4 Brushed, Mirror (Ra ≤ 0.05 μm) |
EN 10088-2, ASTM A403 |
| Heat Treatment Condition |
Annealed (Solution Treated), Pickled & Passivated |
ASTM A269 |
| Welding Method (if applicable) |
ERW (Electric Resistance Welding), TIG (Tungsten Inert Gas) Welded |
ASTM A213 |
| End Condition |
Plain cut, Beveled (per ASME B16.25), Threaded (per ASME B1.20.1) |
ASME B16.25 |
| Coating / Protection |
PASSIVATED (passivation treatment per ASTM A967), optional PTFE internal coating |
ASTM A967, ASTM A380 |
| Testing Methods |
Hydrostatic Test, Eddy Current (ECT), Ultrasonic (UT), Spectroscopic Analysis |
ASTM A269, EN 10204 |
| Pressure Rating |
Up to 40 MPa (6,000 PSI) depending on grade and dimensions |
ASME B31.3, EN 13480 |
| Packaging |
Wooden pallet with steel strap, moisture-proof wrapping, protective caps on open ends |
ISO 4180 |
Manufacturing Process
Process Flow Diagram (Descriptive)
- Raw Material Selection & Verification: High-purity stainless steel strip or seamless pipe blanks are sourced from certified mills (e.g., Outokumpu, Voestalpine, POSCO, Taigang). Incoming material undergoes spectroscopic verification (OES — Optical Emission Spectroscopy) and mechanical testing to confirm compliance with specified grade chemistry and properties.
- Strip Cleaning & Edge Preparation: The steel strip is subjected to chemical degreasing (alkaline cleaning solution at 60–80°C) to remove surface oils, scale, and contaminants. Edges are trimmed to precise width tolerances (± 0.05 mm) using a precision slitting line.
- Forming & Welding (for welded coil tubes): The flat strip is fed through a series of progressively reducing rollers that incrementally form the rectangular cross-section into a circular tube. The edges are brought together and fused via high-frequency electric resistance welding (ERW) with inline inductive preheating to ensure a metallurgically sound weld seam. Alternatively, for higher-end applications, TIG (Tungsten Inert Gas) welding is employed with argon shielding gas.
- Pilot Mounting & Sizing: A precision-ground pilot mandrel is inserted into the tube to maintain dimensional accuracy during subsequent processing. The tube passes through a series of sizing rollers that ensure consistent OD and wall thickness throughout the entire coil length.
- Coiling: The continuous tube is wound into a helical coil on a precision coiling head. Tension is carefully controlled to prevent kinking, ovality, or residual stress accumulation. The coil ID and number of layers are adjustable per customer requirements.
- Heat Treatment (Annealing): The coiled tube is subjected to solution annealing at 1050–1100°C in a protective atmosphere (endothermic gas or vacuum) to dissolve carbides, relieve cold-work hardening, and restore full austenitic microstructure. The cooling rate is controlled to prevent grain growth or intermetallic phase precipitation.
- Pickling & Passivation: After annealing, the tube surface is cleaned via hydrofluoric-nitric acid pickling to remove oxide scale. A subsequent passivation treatment (citric acid or nitric acid per ASTM A967) forms a stable chromium oxide passive layer, enhancing corrosion resistance.
- Quality Inspection & Non-Destructive Testing (NDT): Every coil undergoes comprehensive inspection including:
- Visual inspection for surface defects, weld seam quality, and dimensional conformity
- Eddy Current Testing (ECT) for internal and external discontinuities along the entire tube length
- Hydrostatic pressure testing at 1.5× the maximum design pressure, held for minimum 10 seconds with no leakage
- Spectroscopic verification (OES) for chemical composition confirmation
- Mechanical property testing (tensile, hardness) per ASTM E8/E8M
- Intergranular corrosion testing per ASTM A240 (for susceptible grades)
- Coil Straightening (Optional): For applications requiring straight pipe segments, the coil is unwound through a precision straightening line (roller straightener) with controlled feed speed to minimize work hardening and maintain dimensional accuracy.
- Packaging & Dispatch: Each coil is protected with moisture-absorbent packaging, wrapped in PE film, and secured on a wooden pallet with steel strapping. Shipping documentation includes mill test certificates (MTC), material certificates per EN 10204 Type 3.1, and dimensional inspection reports.
Key Process Parameters
| Process Step |
Parameter |
Range / Value |
| Forming Reduction |
Per-stand reduction ratio |
5% – 15% |
| ERW Welding |
Welding frequency |
50 – 400 kHz |