Stainless Steel Coil Tube — Fully Annealed (Soft Condition) | Wenzhou Jixing Metal Materials Co., Ltd.
Product Overview
The Wenzhou Jixing Fully Annealed Stainless Steel Coil Tube (Product Code No. 47) is a precision cold-drawn tubing product supplied in continuous coil form, designed for maximum formability and ductility. Supplied in the fully soft annealed condition (Condition Designation: "O"), this coil tube is engineered to deliver superior deep-drawing capability, exceptional bend performance, and outstanding resistance to cracking during secondary forming operations. The product is particularly suited for applications requiring complex geometries, tight radii bending, and extensive post-fabrication forming without the risk of material failure.
As a leading manufacturer in China's stainless steel pipe industry, Wenzhou Jixing Metal Materials Co., Ltd. adheres to rigorous international standards in the production of this coil tube, ensuring consistent mechanical properties, dimensional accuracy, and surface quality across every coil lot.
Material & Properties
The fully annealed coil tube is manufactured from austenitic stainless steel grades, most commonly 304 (UNS S30400) and 316 (UNS S31600), which are renowned for their excellent corrosion resistance, non-magnetic properties, and outstanding formability. The annealing process eliminates work-hardening effects introduced during cold drawing, restoring the material to its maximum ductility state.
Key Mechanical Properties:
- Vickers Hardness (HV): ≤ 180 — indicating a fully softened microstructure with minimal dislocation density, enabling unrestricted plastic deformation during forming.
- Elongation at Break: ≥ 40% — demonstrating exceptional ductility and the capacity for extensive uniform strain without fracture, which is critical for deep-drawing and hydroforming applications.
- Minimum Bending Radius: ≈ 3 × Outer Diameter (OD) — allowing for tight-radius bending operations with minimal risk of wall thinning, cracking, or ovality distortion.
- Flaring Rate (Expanding Ratio): ≥ 30% — enabling reliable end-flaring, bellmouth forming, and tube expansion operations for fitting and connection assembly.
The combination of low hardness and high elongation establishes a wide processing window, making this product ideal for manufacturers who require predictable, repeatable forming performance without the need for intermediate annealing cycles during production.
Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Product Name | Stainless Steel Coil Tube (Fully Soft Annealed) | — |
| Product Code | No. 47 | — |
| Material Grades | 304 / 304L / 316 / 316L / 321 (Custom Available) | ASTM A269 / ASTM A270 / EN 10217-7 |
| Mechanical Condition | Fully Annealed (Soft) — Condition "O" | ASTM A269 Clause 10 |
| Vickers Hardness (HV) | ≤ 180 | ASTM E92 |
| Elongation at Break | ≥ 40% | ASTM E8 / ISO 6892-1 |
| Minimum Bending Radius | ≈ 3 × OD | Internal Specification |
| Flaring / Expanding Ratio | ≥ 30% | Internal Specification |
| Supply Form | Continuous Coil (Coiltube) | — |
| Surface Finish | Pickled & Passivated (2B / No. 4 / Mirror Available) | ASTM A480 |
| Coil Weight | Customized per customer requirement | — |
Manufacturing Process
The production of fully annealed stainless steel coil tube involves a multi-stage manufacturing sequence designed to achieve optimal dimensional precision and mechanical softness:
- Raw Material Selection: High-purity stainless steel strip or bar stock is procured from certified mills, with full chemical composition verification (Ni, Cr, Mo, C, S, P limits) to ensure grade compliance.
- Cold Drawing / Cold Pilgering: The tube is drawn through precision tungsten carbide tooling to achieve target wall thickness and outer diameter dimensions with tight tolerances. The coiling process ensures continuous, uniform production output.
- Full Annealing (Solution Treatment): The cold-worked tube is heated to a controlled temperature range (typically 1050°C–1150°C for austenitic grades) and held for sufficient time to dissolve carbide precipitates and fully recrystallize the grain structure. This step is critical in achieving the HV ≤ 180 hardness specification and ≥ 40% elongation.
- Controlled Cooling: Rapid water quenching or controlled air cooling follows the annealing cycle to lock the austenitic structure and prevent sensitization or grain coarsening.
- Pickling & Passivation: The tube surface is chemically treated to remove scale, oxide films, and residual contaminants, followed by passivation to restore the natural chromium oxide protective layer.
- Dimensional Inspection & Coiling: Each coil undergoes OD/wall-thickness measurement, hardness verification, and elongation testing. The finished product is then coiled onto precision mandrels for packaging and shipment.
Applications
The exceptional formability and soft condition of this coil tube make it suitable for a broad range of industrial and commercial applications:
- Automotive Industry: Fuel lines, brake lines, exhaust system components, and high-precision structural tubing requiring tight bending and crimping operations.
- Medical & Pharmaceutical: Surgical instrument tubing, endoscope sheaths, and medical device housings where deep-drawing and complex forming are required without post-forming annealing.
- Food Processing & Beverage: Sanitary-grade piping systems, CIP (Clean-In-Place) loop tubing, and hygienic fittings requiring flaring and welding operations.
- Chemical & Petrochemical: Process piping systems, heat exchanger tubes, and reactor components where corrosion resistance and formability are both critical.
- Appliance Manufacturing: Refrigeration coils, air conditioning tubing, and appliance structural components requiring coil-fed automated forming lines.
- Hydraulic & Pneumatic Systems: High-pressure fluid lines, hydraulic hose reinforcement, and pneumatic fitting assemblies.
- Architectural & Decorative: Handrails, balustrades, and ornamental tubing requiring artistic bending and shaping.
Quality Certifications
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework to ensure product conformity and traceability:
- ISO 9001:2015 — Quality Management System certification ensuring consistent production quality and continuous improvement.
- ISO 14001:2015 — Environmental Management System certification demonstrating responsible manufacturing practices.
- EN 10204 3.1 Certificate — Third-party material test certificates available for each shipment, confirming chemical composition, mechanical properties, and dimensional compliance.
- Mill Test Reports (MTR) — Full traceability documentation including heat numbers, lot tracking, and independent laboratory test results.
- Non-Destructive Testing (NDT): Eddy current testing, ultrasonic testing, and hydrostatic pressure testing performed to ensure freedom from internal and external defects.
- Compliance Standards: Products manufactured in accordance with ASTM, EN, JIS, and GB standards as specified by customer requirements.
Unique Selling Points: The combination of HV ≤ 180 hardness, ≥ 40% elongation, 3×OD minimum bend radius, and ≥ 30% flaring capability positions this fully annealed coil tube as a premium-grade, high-formability product. Unlike cold-worked or solution-treated conditions, the fully soft state eliminates the need for intermediate annealing cycles during complex forming operations, reducing production costs, minimizing material waste, and ensuring dimensional accuracy in the final component. The continuous coil supply format further enhances manufacturing efficiency by enabling uninterrupted automated forming, cutting, and assembly lines.