Stainless Steel Coil Tube — Wenzhou Jixing Metal Materials Co., Ltd.

1. Product Overview

The stainless steel coil tube (Coiltube), product catalog number 1258, manufactured by Wenzhou Jixing Metal Materials Co., Ltd., represents a precision-engineered continuous-form tubular product designed for applications demanding superior corrosion resistance, mechanical integrity, and formability. Unlike straight-length seamless or welded tubes, coil tubes are produced in continuous helical form, offering significant advantages in downstream processing efficiency, material utilization, and inventory management for end-users.

This product line draws upon decades of metallurgical research and industrial practice in tubular material science, informed by the broader evolution of coil tube manufacturing in China — a sector that has progressed from basic carbon steel and copper coil production to advanced stainless steel alloy systems with tightly controlled microstructural and compositional specifications.

2. Material & Properties

2.1 Material Grades

The coil tube product is available in a range of austenitic, ferritic, and duplex stainless steel grades, including but not limited to:

• Austenitic Grades: AISI 304 (UNS S30400), AISI 316 (UNS S31600), AISI 321 (UNS S32100), AISI 316L (UNS S31603)
• Ferritic Grades: AISI 430 (UNS S43000), AISI 409 (UNS S40900)
• Duplex Grades: 2205 (UNS S32205), 2507 (UNS S32750)
• Custom Alloy Grades: Available upon request per ASTM, EN, or customer-specific specifications

2.2 Key Material Properties

• Corrosion Resistance: Exceptional resistance to intergranular corrosion, pitting, crevice corrosion, and stress corrosion cracking (SCC) in chloride-containing environments, achieved through optimized chromium (Cr), nickel (Ni), molybdenum (Mo), and nitrogen (N) content.
• Mechanical Properties: Tensile strength (Tensile Strength) ranging from 520 MPa to 800 MPa depending on grade and cold-work condition; elongation (Elongation) of 30%–60% ensuring excellent ductility for forming operations.
• Thermal Stability: Maintains structural integrity in service temperatures from cryogenic (−196°C) to 870°C (austenitic grades), with controlled grain boundary stability post-heat treatment.
• Weldability: Low carbon variants (e.g., 304L, 316L) exhibit superior weldability with minimal risk of sensitization (δ-phase formation) in the heat-affected zone (HAZ).
• Magnetic Properties: Austenitic grades are non-magnetic in the annealed condition; ferritic grades are ferromagnetic — a critical consideration for electromagnetic applications.

3. Specifications

Parameter	Specification	Standard Reference
Outer Diameter (OD)	3.0 mm – 168.3 mm	ASTM A554 / EN 10217
Wall Thickness	0.3 mm – 6.0 mm	ASTM A554 / GB/T 12771
Coil Inner Diameter (Coil ID)	150 mm – 500 mm	Manufacturer Specification
Coil Length (per coil)	100 m – 2,000 m (customizable)	ASTM A554
Coil Weight	Up to 2,500 kg per coil	Manufacturer Specification
Surface Finish	No.1 (Hot-rolled), 2B (Bright annealed), BA (Bright annealed in bell jar), Pickled & Passivated, Custom	ASTM A478 / EN 10088
Dimensional Tolerance (OD)	±0.05 mm – ±0.15 mm (Grade A & B)	ASTM A554
Dimensional Tolerance (Wall)	±10% or ±0.05 mm (whichever is greater)	ASTM A554
Roundness Tolerance	≤ 2% of nominal wall thickness	ASTM A554
Straightness (per 1,000 mm)	≤ 3 mm	EN 10217
Heat Treatment Condition	Annealed (Solution Annealed), Cold-worked + Partial Recrystallization	ASTM A240 / EN 10088-1
End Condition	Open ends, closed ends (plugged), or custom	Customer Specification

4. Manufacturing Process

The production of stainless steel coil tube follows a rigorous multi-stage metallurgical and forming sequence, ensuring that each coil meets exacting dimensional, chemical, and mechanical requirements:

1. Raw Material Preparation: High-purity stainless steel billets or slabs are sourced from certified primary producers. Incoming material undergoes spectrographic analysis (Optical Emission Spectrometry — OES) to verify chemical composition compliance with ASTM or EN specifications.
2. Hot Rolling / Hot Extrusion: Billets are heated to 1,150°C – 1,250°C in controlled-atmosphere furnaces and hot-rolled or hot-extruded to produce seamless tube blanks with approximate final dimensions. This stage establishes the initial grain structure and eliminates casting defects.
3. Pickle Line Processing: Hot-rolled tube blanks pass through a continuous pickling and passivation (Pickling & Passivation) line using hydrofluoric acid (HF) and nitric acid (HNO₃) solutions to remove mill scale and oxide layers, followed by passivation to establish a protective chromium oxide film.
4. Cold Reduction (Multi-stand Draw & Bend or Rotary Piercing): The tube is cold-drawn through a series of calibrated dies and mandrels to achieve precise final dimensions. The draw-and-bend (Draw & Bend) process or rotary piercing method is employed to convert the hot-rolled blank into the coil form with tight dimensional control.
5. Intermediate Annealing: At critical deformation stages, the tube undergoes controlled annealing (typically 1,000°C – 1,150°C in a protective atmosphere of argon (Ar) or nitrogen (N₂)) to relieve accumulated cold-work stresses, restore ductility, and refine grain structure — preventing cracking during subsequent forming.
6. Final Cold Working & Coiling: The tube is cold-worked to final dimensions and wound into coils of specified inner diameter. Coiling tension is precisely controlled to prevent deformation or springback.
7. Final Annealing (if required): For applications requiring the full annealed condition, coils undergo a final solution annealing cycle followed by controlled cooling to optimize austenite stability and minimize residual stresses.
8. Non-Destructive Testing (NDT): Each coil undergoes 100% eddy current testing (Eddy Current Testing) and/or ultrasonic testing (Ultrasonic Testing) to detect internal and surface discontinuities including laminations, cracks, and wall thickness irregularities.
9. Final Inspection & Packaging: Dimensional verification (OD, wall thickness, roundness), surface quality inspection, and hydrostatic testing (Hydrostatic Pressure Testing) are performed. Coils are wrapped in protective film or paper, strapped with steel bands, and packaged for shipment.

5. Applications

The versatility of stainless steel coil tubes, combined with the processing advantages of the coil form, makes them indispensable across numerous industrial sectors:

• Heat Exchangers & Condensers: Coil tubes serve as the core component in plate-and-tube heat exchangers, condenser coils, and evaporator systems. The continuous coil form eliminates butt welds between tubes, reducing leak points and improving thermal efficiency. Critical applications include refrigeration systems, HVAC (Heating, Ventilation, and Air Conditioning), and marine cooling systems.
• Automotive Industry: Used in automotive exhaust systems (downpipes, catalytic converter inlets), turbocharger coolant lines, and fuel delivery systems where high-temperature resistance and corrosion durability are paramount.
• Food & Pharmaceutical Processing: Sanitary-grade coil tubes (304L, 316L) are employed in dairy processing equipment, beer brewing systems, pharmaceutical fluid transfer lines, and medical device manufacturing where hygienic surface finish and cleanability are regulatory requirements.
• Chemical Processing: Duplex and super-duplex coil tubes (2205, 2507) are used in chemical reactor piping, acid storage systems, and desalination plant components due to their superior resistance to chloride-induced stress corrosion cracking.
• Oil & Gas Industry: High-performance alloy coil tubes are utilized in subsea production systems, wellhead assemblies, and offshore platform piping where resistance to sour gas (H₂S-containing environments) and high-pressure service is required.
• Aerospace & Defense: Precision-dimensioned stainless steel coil tubes are employed in hydraulic systems, actuator assemblies, and high-temperature exhaust components in aerospace applications.
• Architectural & Decorative Applications: Bright-annealed (BA) finish coil tubes are used in elevator handrails, balustrades, structural framing, and architectural feature elements where aesthetic surface quality and long-term weathering resistance are desired.
• Solar Thermal Systems: Coil tubes are integral to solar water heating collectors and concentrated solar power (CSP) systems, where they function as heat transfer media requiring excellent thermal conductivity and resistance to thermal cycling fatigue.

6. Quality Certifications & Compliance

Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework ensuring that all coil tube products meet or exceed international standards:

• ISO 9001:2015 — Quality Management System certification demonstrating systematic commitment to quality excellence across all production processes.
• ISO 14001:2015 — Environmental Management System certification ensuring environmentally responsible manufacturing practices.
• ISO/TS 22163 — Quality management systems specific to the automotive industry (IATF 16949 aligned).
• EN 10204 Type 3.1 Certificates — Third-party inspection and material certification provided with each shipment, verifying chemical composition, mechanical properties, and dimensional compliance.
• Mill Test Reports (MTR): Comprehensive documentation including chemical analysis (OES results), mechanical test data (tensile, hardness, impact), NDT results, and dimensional inspection records.
• Compliance Standards: Products manufactured in accordance with ASTM A554 (Stainless Steel Tube — Continuous), ASTM A240, EN 10217, EN 10088, GB/T 12771, JIS G3446, and equivalent international standards.
• Third-Party Inspection: Available upon request by organizations such as Bureau Veritas, SGS, TÜV, or Lloyd's Register for independent verification of product conformity.
• Traceability: Full heat-to-heat traceability maintained from raw material receipt through final shipment, enabling complete supply chain accountability.

7. Unique Selling Points

Integrated Coil Form Advantage: By delivering tube in continuous coil form, Wenzhou Jixing eliminates the need for end-users to perform tube straightening, cutting, and butt-welding operations, resulting in 20%–40% reduction in fabrication labor costs, minimized material waste (scrap reduction), and significantly improved production throughput in downstream manufacturing.

• Wide Grade Availability: Comprehensive inventory spanning austenitic, ferritic, and duplex stainless steel grades enables one-source procurement, reducing supply chain complexity.
• Precision Dimensional Control: Advanced cold-drawing and draw-and-bend technology ensures dimensional tolerances as tight as ±0.05 mm, critical for heat exchanger and automotive applications.
• Custom Surface Finishes: Availability of No.1, 2B, BA, pickled-and-passivated, and custom finishes addresses diverse aesthetic and functional requirements without post-processing.
• Technical Advisory Support: Drawing upon extensive metallurgical expertise, the company provides material selection guidance, application engineering support, and specification consultation to optimize product-performance matching for customer-specific applications.
• Scalable Production Capacity: Flexible manufacturing capability accommodating both prototype/small-batch orders and high-volume industrial supply contracts, with lead times optimized through efficient coil-form inventory management.

8. Conclusion

The stainless steel coil tube product line from Wenzhou Jixing Metal Materials Co., Ltd. embodies the convergence of advanced metallurgical science, precision manufacturing engineering, and rigorous quality assurance. Rooted in the broader evolution of China's coil tube industry — which has progressed from rudimentary copper coil production to world-class stainless steel alloy tube manufacturing — this product delivers the reliability, performance, and value that modern industrial applications demand. For organizations seeking a trusted partner in precision tubular materials, this product line represents a technically superior and commercially competitive solution.