Vascular Stent Delivery System Coil Tube — Ultra-Fine Precision MRI-Compatible Seamless Stainless Steel Tube
Product Overview
The Vascular Stent Delivery System Coil Tube is a specialized ultra-fine seamless stainless steel tubing product engineered specifically for the interventional medical device industry, with primary application in the construction of vascular stent delivery systems (catheter-based deployment systems). This coil tube serves as the critical structural and functional backbone of stent delivery catheters, providing the mechanical integrity, pushability, and radiopacity required to safely navigate the human vasculature and deliver stent implants to target anatomical sites with sub-millimeter precision.
Designed and manufactured by Wenzhou Jixing Metal Materials Co., Ltd, this product line addresses the demanding requirements of modern interventional cardiology and peripheral vascular interventions, where device safety, biocompatibility, and imaging compatibility are paramount. The coil tube form factor offers significant advantages in terms of storage density, manufacturing efficiency, and processing flexibility for downstream catheter assembly operations.
Unique Selling Points
- Ultra-Fine Bore Dimensions: Capable of producing inner diameters as small as 0.3 mm, enabling minimally invasive delivery profiles that reduce vascular trauma and patient recovery time.
- High-Precision Dimensional Tolerance: Tight tolerances on wall thickness and diameter ensure consistent pushability, torque response, and kink resistance throughout the catheter length.
- MRI Compatibility: Verified non-magnetic properties ensure safe use in Magnetic Resonance Imaging (MRI) environments, eliminating concerns about image distortion, artifact generation, or device migration during imaging-guided procedures.
- Superior Surface Finish: Electrolytic polishing (electropolishing) achieves surface roughness values below Ra 0.05 μm, reducing thrombogenic potential and frictional drag during vascular navigation.
- Dual Material Options: Availability in both 316LVM and L605 seamless grades provides flexibility for applications requiring either enhanced corrosion resistance or superior mechanical strength.
Material & Properties
SAE 316LVM (UNS S31603 Modified)
316LVM is an ultra-low carbon modification of the SAE 316L austenitic stainless steel grade, specifically formulated for medical implant and interventional device applications. The ultra-low carbon content (≤0.020% C) minimizes intergranular carbide precipitation during welding and thermal processing, ensuring superior resistance to sensitization and intergranular corrosion. The "M" designation denotes additional modifications for enhanced biocompatibility and surface finish characteristics.
| Property | Specification |
|---|---|
| Chemical Composition (Max.) | C ≤ 0.020%, Mn ≤ 2.0%, Si ≤ 1.0%, P ≤ 0.035%, S ≤ 0.030% |
| Chromium (Cr) | 16.5% – 18.5% |
| Nickel (Ni) | 10.0% – 14.0% |
| Molybdenum (Mo) | 2.0% – 3.0% |
| Tensile Strength | ≥ 520 MPa |
| Yield Strength (0.2% offset) | ≥ 205 MPa |
| Elongation | ≥ 40% |
| Magnetic Susceptibility | < 1 × 10⁻⁵ cm³/g (effectively non-magnetic) |
| Corrosion Resistance | ASTM G48, ASTM A967 verified |
SAE L605 (UNS N06605)
L605 is a nickel-iron-chromium superalloy (austenitic) offering exceptional resistance to high-temperature oxidation, stress corrosion cracking, and pitting in aggressive chemical environments. While primarily recognized as a superalloy, its use in medical device applications leverages its outstanding mechanical properties, fatigue resistance, and biocompatibility. L605 provides significantly higher strength and fatigue life compared to 316LVM, making it suitable for demanding applications where repeated mechanical cycling is anticipated.
| Property | Specification |
|---|---|
| Chemical Composition | Ni ≥ 52%, Fe 6.5% – 9.0%, Cr 22.0% – 23.0%, Mo 8.0% – 9.0%, Al 0.4% – 1.0%, Ti 0.4% – 1.0% |
| Tensile Strength | ≥ 620 MPa |
| Yield Strength (0.2% offset) | ≥ 275 MPa |
| Elongation | ≥ 40% |
| Magnetic Susceptibility | < 1 × 10⁻⁵ cm³/g (effectively non-magnetic) |
| Corrosion Resistance | ASTM G48, ASTM G93 verified; superior pitting and crevice resistance |
Specifications
| Parameter | Specification |
|---|---|
| Product Name | Vascular Stent Delivery System Coil Tube |
| Material Grade | SAE 316LVM (UNS S31603 Modified) / SAE L605 (UNS N06605) |
| Tube Type | Seamless (Seamless Tube / 无缝管) |
| Supply Form | Coil Tube (盘管 / Coil) |
| Outer Diameter (OD) Range | 0.5 mm – 5.0 mm |
| Inner Diameter (ID) Range | 0.3 mm – 3.5 mm |
| Wall Thickness Range | 0.05 mm – 0.80 mm |
| OD Tolerance | ±0.01 mm (standard); ±0.005 mm (precision grade available) |
| Wall Thickness Tolerance | ±0.005 mm |
| Surface Finish | Electrolytic Polishing (Electropolishing); Ra ≤ 0.05 μm |
| Surface Roughness (ID) | Ra ≤ 0.05 μm |
| Surface Roughness (OD) | Ra ≤ 0.05 μm |
| Magnetic Property | Non-magnetic verified; magnetic permeability < 1.005 |
| MRI Compatibility | MRI Conditional / MRI Safe (verified non-magnetic) |
| Coil Winding Diameter | Customizable; typical 500 mm – 1200 mm |
| Coil Length per Spool | 50 m – 500 m (customizable) |
| Heat Treatment Condition | Solution Annealed (Solution Annealing); fully austenitic microstructure |
| Residual Stress | Minimal; stress-relieved post-forming |
| Biocompatibility | ISO 10993 compliant |
| Applicable Standards | ASTM F138, ASTM F139, ISO 5832-1, ISO 10993 |
| Application Category | Interventional Medical Devices — Vascular Stent Delivery Systems |
Manufacturing Process
The production of ultra-fine precision coil tubes for vascular stent delivery systems involves a multi-stage manufacturing process with stringent quality controls at each step:
- Raw Material Selection and Verification: High-purity nickel, chromium, iron, and molybdenum alloys are sourced from certified suppliers. Incoming materials undergo spectroscopic analysis (OES — Optical Emission Spectroscopy) and PMI (Positive Material Identification) verification to confirm chemical composition compliance with ASTM F138 / ASTM F139 specifications.
- Billet Preparation and Homogenization: Cast billets are homogenized at elevated temperatures to ensure uniform microstructure and eliminate segregation. The billet is then subjected to vacuum arc remelting (VAR) or electroslag remelting (ESR) for critical applications to achieve ultra-low interstitial gas content (C, N, O).
- Hot Rolling / Hot Extrusion: The homogenized billet is hot rolled or extruded through calibrated dies to produce seamless tube blanks with approximate target dimensions. This step establishes the initial seamless tubular geometry without weld seams, ensuring uniform material properties in all circumferential directions.
- Hot Drawing / Hot Pilger Milling: The tube blanks are progressively reduced through hot drawing or hot pilger processes to achieve intermediate dimensions. This step refines the grain structure and improves dimensional accuracy.
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Cold Drawing (Multi-Pass): Multiple passes of cold drawing through precision tungsten carbide (WC) or diamond dies progressively reduce the tube to near-final dimensions. Each pass involves:
- Interpass annealing at controlled temperatures to relieve cold work stresses and restore ductility
- Precise control of drawing speed and lubrication to minimize surface defects
- Progressive dimensional refinement to achieve final OD and wall thickness within specified tolerances
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Solution Annealing: The cold-drawn tube is solution annealed at 1050°C – 1150°C (for 316LVM) or 1150°C – 1200°C (for L605) followed by rapid water quenching. This process:
- Dissolves precipitated carbides and restores full austenitic structure
- Eliminates residual stresses from cold working
- Maximizes corrosion resistance and ductility
- Ensures non-magnetic microstructure (no ferrite or martensite phases)
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Electrolytic Polishing (Electropolishing): The annealed tube undergoes electrochemical polishing in a heated phosphoric acid-based electrolyte bath. This process:
- Removes a thin surface layer (typically 0.5 μm – 2.0 μm) containing surface contamination and micro-defects
- Produces a smooth, passivated surface with Ra ≤ 0.05 μm
- Enhances surface chromium oxide passivation layer for improved corrosion resistance
- Eliminates surface roughness peaks that could promote thrombus formation in blood-contacting applications
- Reduces friction coefficient for improved catheter trackability
- Precision Coiling: The finished tube is wound into coil form using precision coiling equipment that maintains dimensional integrity, prevents kinking, and ensures uniform winding tension. Coil winding parameters (winding diameter, inter-layer tension, layer count) are optimized for the specific tube dimensions and downstream processing requirements.
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Final Inspection and Non-Magnetic Verification: Each production batch undergoes comprehensive final inspection including:
- Dimensional measurement (OD, ID, wall thickness) using calibrated micrometers and bore gauges
- Surface roughness verification using contact profilometry
- Magnetic susceptibility testing using a vibrating sample magnetometer (VSM) or Gauss meter
- Chemical composition re-verification by OES
- Visual inspection for surface defects
- Optional: Hydrostatic pressure testing for integrity verification
Applications
Primary Application: Vascular Stent Delivery Systems
The coil tube serves as the primary structural component in the following interventional device configurations:
- Stent Delivery Catheters (Pusher Catheters): The ultra-fine coil tube forms the inner pusher or outer sheath of balloon-expandable stent delivery systems, providing the mechanical force transmission capability required to deploy stents within coronary arteries, peripheral arteries, carotid arteries, and other vascular sites.
- Self-Expanding Stent Delivery Systems: For nitinol-based self-expanding stent delivery systems, the stainless steel coil tube serves as the outer sheath that constrains the stent during navigation and releases it at the target site.
- Stent-Graft Delivery Systems: In endovascular aneurysm repair (EVAR) and thoracic endovascular aortic repair (TEVAR) applications, the coil tube provides the structural backbone of large-bore delivery sheaths.
- Drug-Eluting Stent Delivery Systems: The ultra-smooth electropolished surface of the coil tube minimizes drug coating disruption during stent deployment, ensuring uniform drug elution profiles for drug-eluting stent (DES) systems.
- Peripheral Vascular