316LVM S31673 1.4441 Medical implant-grade precision capillary tubes
Material Definition & Grade
(1) Definition of Grade Suffixes
L: Extra-low carbon (C ≤ 0.030%), eliminating intergranular corrosion and compatible with repeated high-temperature sterilization
VM: Vacuum Arc Remelted (VAR), distinguished from standard 316L stainless steel
(2) Standard Grade Designations
UNS S31673
EN Standard: 1.4441 / X2CrNiMo18-15-3
Medical Compliance Standards: ASTM F138, ASTM F139, ISO 5832-1
(3) Nominal Chemical Composition (wt%)
C ≤ 0.030, Cr 17.0–19.0, Ni 13.0–15.0, Mo 2.25–3.00, %Cr + 3.3 x %Mo ≥26.0
S ≤ 0.005 (ultra-low sulfur for superior cleanliness), trace nitrogen added to enhance pitting corrosion resistance
Core Advantages Over Standard 316L (Capillary Application)
(1) Ultra-High Purity
Vacuum remelting removes slag and non-metallic inclusions with no free ferrite, delivering uniform microstructure. Inner bore is burr-free and free of impurity precipitation to prevent ion contamination when exposed to body fluids or pharmaceutical liquids, with implant-grade biocompatibility.
(2) Markedly Improved Corrosion Resistance
Combined molybdenum and nitrogen alloying provides outstanding resistance to chloride-induced pitting and crevice corrosion. Withstands repeated sterilization via high-pressure steam, ethylene oxide and alcohol; minimal nickel leaching and low sensitization risk under long-term immersion in bodily fluids.
(3) Superior Fatigue Performance
Stable mechanical strength after cold drawing. Resists cracking during bending, repeated puncturing and stent expansion, ideal for minimally invasive interventional devices subjected to cyclic deformation.
(4) Superior Mirror Polishing Performance
Internal and external surfaces can achieve Ra ≤ 0.01 μm ultra-smooth finish. Smooth bore prevents liquid adhesion and thrombosis during blood or drug delivery.
(5) Low Magnetic Permeability
Retains weak magnetism post cold working, compatible with MRI medical equipment.
Standard Specifications (Seamless Precision Drawn Capillary Tube)
Outer Diameter (OD)
0.20 mm ~ 10.0 mm; ultra-fine microtubes down to 0.1 mm available
Wall Thickness (WT)
Minimum 0.05 mm ultra-thin wall; dimensional tolerance ±0.003~±0.01 mm
Length Options
Straight cut-to-length pieces, coiled tubing, short precision cut blanks for needles and implant components
Surface Finishes
Bright Annealed (BA), Electropolished (EP) internal/external mirror finish, pickled clean grade. Medical-grade tubes manufactured with oil-free drawing and full ultrasonic degreasing under dust-free conditions.
Deep Machining Capabilities
Taper forming, tip grinding, side hole drilling, flaring, edge turning, laser micro-perforation, micro-chamfering, burr-free cutting
Manufacturing Process (Medical-Grade Workflow)
VIM+VAR ingot → hot rolled tube blanks → multi-pass precision cold drawing for diameter reduction → vacuum bright annealing → internal & external electropolishing → ultrapure water ultrasonic cleaning → dust-free sealed packaging. Strict control over sulfur content and inclusion rating throughout production; intergranular corrosion and biocompatibility testing conducted per batch.
Key Application Sectors (Primary for Medical Implants & Minimally Invasive Surgery)
(1) Cardiovascular Interventional Devices (Premium Mainstream Application)
Stent substrates, guidewire liners, microcatheters, contrast injection tubing, interventional sheaths
(2) Orthopedic Implants
Hollow cannulated bone screws, minimally invasive intramedullary nails, spinal fixation system tubing
(3) Surgical Instruments
Shafts for surgical cutters, puncture needles, blood collection needles, laparoscopic microchannels, biopsy cannulas, hollow dental implant posts
(4) Minimally Invasive Consumables
Insulin micro-needles, infusion capillaries, thin anesthetic catheters, ophthalmic microsurgical tubing
(5) High-Precision Non-Medical Applications
Lab microfluidic pipelines, chromatographic analysis capillaries, sensor probes, high-end watch components, precision instrument tubing for trace fluid transport
Critical Quality Control Points for Procurement
(1) Request material certification including VAR furnace batch number and inclusion rating inspection reports
(2) Medical tubing must be accompanied by ASTM F138 material test certificates and internal bore cleanliness testing reports for electropolished surfaces
(3) Verify dimensional tolerance, ovality and wall thickness uniformity for ultra-fine thin-walled tubes
(4) Implant-grade products require biocompatibility and cytotoxicity test documentation
