316LVM Stainless Steel Capillary Coil Tubing for Interventional Catheter Sheaths & Balloon Dilation Tubes
Product Overview
Wenzhou Jixing Metal Materials Co., Ltd. (Product No. 175) offers a precision-engineered Stainless Steel Coil Tube (Capillary Tubing) specifically designed for the demanding requirements of interventional medical devices, including catheter sheaths and balloon dilation tubes. These micro-diameter tubular products are fabricated from AISI 316LVM (Vacuum Melted) stainless steel and are intended for in-vivo implantation and percutaneous vascular applications where biocompatibility, mechanical integrity, and extreme miniaturization are non-negotiable.
The coil tube is supplied in a coiled configuration to facilitate downstream processing—such as laser cutting, welding, and forming—by interventional device manufacturers, while maintaining dimensional accuracy and surface finish integrity throughout the handling and assembly stages.
Material & Properties
The core material is ASTM F138-compliant 316LVM (Vacuum Melted) austenitic stainless steel. The vacuum melting process eliminates inclusions and reduces interstitial impurities (notably nitrogen and carbon) to ultra-low levels, yielding superior corrosion resistance, enhanced fatigue strength, and consistent mechanical behavior—critical for devices subjected to prolonged cyclic loading within the human vasculature.
- Alloy Designation: 316LVM (Vacuum Melted 316L)
- ASTM Standard: ASTM F138 — Standard Specification for Stainless Steel Wire and Bar for Surgical Implants
- Corrosion Resistance: Exceptional resistance to chloride-induced pitting and crevice corrosion due to high molybdenum (Mo) content and vacuum-refined purity
- Bioinert Surface: Low nickel ion release rates; demonstrated cytocompatibility and hemocompatibility suitable for chronic in-vivo contact
- Mechanical Behavior: Excellent fatigue resistance and spring-back characteristics, enabling reliable performance in pushable and trackable catheter systems
- Weldability: Superior laser and ultrasonic weldability owing to reduced inclusion content from vacuum melting
Specifications
| Parameter | Specification / Typical Value |
|---|---|
| Material Grade | 316LVM (Vacuum Melted), ASTM F138 compliant |
| Product Form | Capillary Coil Tubing (盘管 / Coil Tube) |
| Outer Diameter (OD) | 0.15 mm – 3.00 mm (customizable per application) |
| Wall Thickness | 0.02 mm – 0.50 mm (micro-wall available) |
| OD Tolerance | ±0.005 mm (standard); ±0.003 mm (precision grade) |
| Wall Thickness Tolerance | ±0.003 mm |
| Surface Finish | Polished; Ra ≤ 0.2 μm (electropolished available on request) |
| Coil Diameter | 100 mm – 600 mm (configurable) |
| Coil Length | 5 m – 50 m per coil (standard); custom lengths available |
| Hardness | HRB 75 – 95 (as-delivered); customizable annealing conditions |
| Tensile Strength | ≥ 620 MPa (annealed condition) |
| Yield Strength | ≥ 310 MPa |
| Elongation | ≥ 30% |
| Heat Treatment Condition | Annealed (soft and bright / SA) |
| Intended Use | Catheter sheaths, balloon dilation tubes, guidewires, stent delivery systems |
| Implant Classification | Class III medical device material (per FDA / EU MDR) |
Manufacturing Process
The production of 316LVM capillary coil tubing follows a rigorous, multi-stage manufacturing sequence designed to ensure dimensional precision, metallurgical purity, and surface quality:
- Vacuum Arc Remelting (VAR) / Electro-Slag Remelting (ESR): The 316L base alloy is remelted under high vacuum to achieve ultra-low inclusion content and interstitial element control (C ≤ 0.02%, N ≤ 0.015%).
- Hot Rolling & Open-Die Forging: The refined billet is forged and hot-rolled into seamless tube stock with controlled grain structure.
- Pilot Tube Drawing (Cold Pulling): The tube is cold-drawn over precision tungsten carbide or ceramic pilot mandrels to achieve micro-diameter and ultra-thin wall dimensions with tight concentricity.
- Intermediate Annealing: Periodic solution annealing at 1050–1100 °C in a controlled atmosphere furnace relieves cold-work hardening, prevents cracking, and maintains ductility throughout successive drawing passes.
- Final Cold Drawing: The final drawing pass is performed using precision tooling to achieve the target OD and wall thickness within specified tolerances.
- Solution Heat Treatment (Annealing): Final annealing at 1050 °C followed by controlled water quenching ensures a fully austenitic, stress-free microstructure.
- Mechanical Polishing & Cleaning: Surface finishing to Ra ≤ 0.2 μm; final acid pickling and passivation to remove scale and ensure a clean, passive oxide layer.
- Coiling: The tubing is coiled onto precision mandrels at controlled tension to prevent deformation, kinking, or surface damage.
- Non-Destructive Testing (NDT): 100% ultrasonic or eddy-current inspection for wall integrity; dimensional verification via optical or laser micrometry.
Applications
The 316LVM capillary coil tube is a critical structural and functional component in the following interventional medical device categories:
- Catheter Sheaths: Provides the pushable outer sleeve for vascular access sheaths used in cardiac, neurovascular, and peripheral interventions. The material's fatigue resistance ensures reliable deployment and retrieval through tortuous vasculature.
- Balloon Dilation Tubes: Serves as the inflation channel and structural support for percutaneous transluminal angioplasty (PTA) balloon catheters, withstanding repeated pressurization cycles without plastic deformation or failure.
- Stent Delivery Systems: Functions as the pusher wire or constraining tube in self-expanding stent delivery catheters, requiring precise radial stiffness and excellent trackability.
- Guidewire Cores: Used in the fabrication of guidewire spines for angiographic and interventional procedures.
- Chronic In-Vivo Implants: Suitable for permanent or long-term implantable devices due to demonstrated biocompatibility and corrosion resistance under physiological conditions.
Quality Certifications & Compliance
- ASTM F138: Full compliance with the Standard Specification for Stainless Steel Wire and Bar for Surgical Implants, including chemical composition, mechanical properties, and heat treatment requirements.
- ISO 13485: Manufacturing conducted under a Quality Management System for Medical Devices.
- ISO 14971: Risk management documentation aligned with international medical device risk management standards.
- ISO 10993 (Biocompatibility): Material evaluated per ISO 10993-1, -5, -10, and -12 for cytotoxicity, chemical characterization, irritation, sensitization, and systemic effects.
- FDA 21 CFR 820 (QSR): Manufacturing processes compliant with FDA Quality System Regulation for medical devices.
- EU MDR 2017/745: Technical documentation available to support conformity assessment under the EU Medical Device Regulation.
- Mill Test Reports (MTR): Each batch is accompanied by a full mill certification including chemical analysis (spectrometric), mechanical test results, and heat treatment records.
- Traceability: Full lot-to-heat traceability from raw material through final coiled product.
Unique Selling Points
1. Vacuum-Melted Purity: The 316LVM grade's vacuum remelting process eliminates harmful inclusions and reduces interstitial impurities to levels far below standard 316L, delivering superior fatigue life and corrosion resistance—essential for devices subjected to millions of flex cycles in vivo.
2. Micro-Diameter Capability: Capabilities extend down to ODs of 0.15 mm with wall thicknesses as thin as 0.02 mm, enabling the next generation of ultra-minimal invasive devices.
3. Coiled Delivery Format: The coil tube configuration eliminates the need for straight-length inventory management, reduces material waste during downstream laser cutting and forming, and ensures consistent mechanical properties along the entire length.
4. Full Regulatory Readiness: ASTM F138 compliance, ISO 10993 biocompatibility data, and MDR-aligned documentation provide device manufacturers with a streamlined pathway to regulatory submission.
5. Customization & Scalability: Wenzhou Jixing Metal Materials Co., Ltd. offers fully customizable OD, wall thickness, coil diameter, hardness, and surface finish specifications, with scalable production volumes from prototype to mass production.