316L Stainless Steel Capillary Tube Supplier GB | Precision Small-Diameter Tubing
316L stainless steel capillary tube is a small-diameter, thin-wall tube widely used in medical, instrumentation, and chemical applications. According to ASTM A269, capillary tube is defined as tubing with an outside diameter of 0.5 mm to 12 mm and wall thickness from 0.05 mm to 2 mm. TeCarve, a manufacturing-backed supplier, produces capillary tubes in grades 304, 316, and 316L, certified to ASTM A269 and DIN 17458 standards, ensuring dimensional precision and corrosion resistance.
Chemical Composition Limits for 316L Stainless Steel
According to ASTM A269, 316L stainless steel capillary tube must contain a maximum carbon content of 0.030%, chromium between 16.0% and 18.0%, nickel between 10.0% and 14.0%, and molybdenum between 2.0% and 3.0%. The low carbon content prevents carbide precipitation during welding, making it ideal for applications requiring corrosion resistance in chloride environments.
Mechanical Properties of 316L Capillary Tube
ASTM A269 requires 316L capillary tube to have a minimum tensile strength of 485 MPa (70,000 psi) and a minimum yield strength of 170 MPa (25,000 psi). The elongation in 2 inches must be at least 35%. These properties ensure the tube can withstand high-pressure applications up to 20 MPa, depending on wall thickness and diameter.
Dimensional Tolerances for Capillary Tube
TeCarve manufactures capillary tubes with outside diameters from 0.5 mm to 12 mm and wall thicknesses from 0.05 mm to 2.0 mm. According to ASTM A269, the outside diameter tolerance is ±0.05 mm for sizes under 3 mm and ±0.10 mm for sizes 3-12 mm. Wall thickness tolerance is ±10% of nominal. These tight tolerances are critical for precision fluid delivery and sensor applications.
Surface Finish Options for Capillary Tube
Capillary tubes are available in pickled and annealed, polished (180/240/320/400 grit), mirror finish (bright annealed), and matte or satin finish. For medical and pharmaceutical applications, a mirror finish with surface roughness Ra ≤ 0.4 μm is often required to prevent bacterial adhesion. TeCarve provides custom finishes per EN 10216-5 requirements.
Testing and Quality Control
Each capillary tube lot is tested per EN 10204 3.1 or 3.2 mill certificates. Tests include chemical analysis, mechanical testing, hydrostatic testing at 20 MPa, eddy current testing per ASTM E309, and dimensional inspection. TeCarve’s QC methods ensure 100% compliance with ASTM A269 and DIN 17458 standards.
Comparison of Stainless Steel Grades for Capillary Tube
| Grade | C% max | Ni% | Cr% | Key Property | Best For |
|---|---|---|---|---|---|
| 304 | 0.08 | 8.0-10.5 | 18.0-20.0 | General corrosion resistance | Food & beverage, water systems |
| 316 | 0.08 | 10.0-14.0 | 16.0-18.0 | Improved chloride resistance (Mo 2-3%) | Chemical processing, marine |
| 316L | 0.030 | 10.0-14.0 | 16.0-18.0 | Low carbon, weldability | Medical, pharmaceutical, welding |
How to Choose the Right Grade for Your Application
- Identify the operating environment: If exposed to chlorides or saltwater, choose 316/316L. For mild environments, 304 is sufficient.
- Check welding requirements: If welding is involved, 316L (C ≤ 0.030%) prevents sensitization and intergranular corrosion.
- Consider temperature range: 304 works up to 870°C intermittent, 316L up to 925°C. For cryogenic, 304/316 retain toughness.
- Evaluate strength needs: 316L has slightly lower tensile strength (485 MPa) than 304 (515 MPa), but sufficient for most capillary applications.
- Review regulatory standards: Medical devices require ISO 9001 certified suppliers; pharmaceutical may need ASTM A270 sanitary spec.
- Calculate cost vs. performance: 316L costs ~20% more than 304 but offers longer service life in corrosive environments.
Industry Applications
- Medical & Pharmaceutical: Used in catheters, drug delivery systems, and surgical instruments requiring biocompatibility and corrosion resistance.
- Chemical & Petrochemical: Capillary tubes for sampling lines, injection systems, and pressure sensing in corrosive fluid environments.
- Instrumentation & Control: Pneumatic and hydraulic control lines, gas chromatography columns, and pressure transmitter impulse lines.
- Automotive & Transportation: Brake lines, fuel injection systems, and air conditioning refrigerant lines in vehicles.
- Energy & Power: Temperature sensor sheaths, heat exchanger tubes, and nuclear instrumentation lines.
- Food & Beverage: Sanitary capillary tubes for dairy, beer, and beverage processing lines requiring cleanability.
Standards & Certifications
- ASTM A269: Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubing for General Service
- ASTM A213: Standard Specification for Seamless Ferritic and Austenitic Alloy-Steel Boiler, Superheater, and Heat-Exchanger Tubes
- DIN 17458: Seamless circular austenitic stainless steel tubes for general engineering purposes
- ISO 9001: Quality management system certification (TeCarve is ISO 9001 certified)
- EN 10216-5: Seamless steel tubes for pressure purposes – Stainless steel tubes
- ASME SA269: Equivalent to ASTM A269 for ASME applications
- GOST 9941: Russian standard for seamless stainless steel tubes
Frequently Asked Questions
What is the minimum outside diameter for 316L capillary tube?
According to ASTM A269, capillary tube can be manufactured with an outside diameter as small as 0.5 mm. TeCarve supplies 316L capillary tubes with OD from 0.5 mm to 12 mm, with wall thicknesses starting at 0.05 mm. These sizes are ideal for micro-fluidic and medical applications.
Can 316L capillary tube be welded?
Yes, 316L is specifically designed for welding due to its low carbon content (max 0.030%). This minimizes carbide precipitation at grain boundaries, maintaining corrosion resistance in the heat-affected zone. TIG welding is commonly used, with recommended filler metal ER316L.
What is the difference between 304 and 316L capillary tube?
The main difference is molybdenum content: 304 has 0%, while 316L contains 2.0-3.0% Mo. This gives 316L superior resistance to chlorides and pitting corrosion. Additionally, 316L has lower carbon (0.030% vs 0.08% for 304), making it better for welded applications. 304 is more economical for non-chloride environments.
What pressure rating can 316L capillary tube handle?
The pressure rating depends on OD and wall thickness. For a 6 mm OD x 1 mm wall 316L tube, the burst pressure is approximately 60 MPa (based on 485 MPa tensile strength). Typical working pressure is 20-30 MPa with a safety factor of 4. Always consult the manufacturer for specific ratings.
Is 316L capillary tube magnetic?
In the annealed condition, 316L is essentially non-magnetic (relative permeability ≤ 1.02). However, cold working (bending, swaging) can induce slight magnetism due to martensite formation. For applications requiring non-magnetic properties, specify solution-annealed condition.
What surface finish is standard for 316L capillary tubes?
Standard finish is pickled and annealed, which has a dull gray appearance. For medical or sanitary applications, a mirror polish (Ra ≤ 0.4 μm) is common. TeCarve offers polished finishes from 180 to 400 grit, as well as bright annealed and matte finishes per customer requirements.
Can I get 316L capillary tube with a 3.1 certification?
Yes, TeCarve provides EN 10204 3.1 mill test certificates for 316L capillary tubes. This certifies that the material conforms to ASTM A269 or DIN 17458 and includes chemical composition and mechanical test results. 3.2 certificates (third-party witness) are also available upon request.
What is the lead time for custom capillary tube orders?
TeCarve’s standard lead time is 10-25 days after deposit for stock sizes. For custom OD/wall combinations or special finishes, lead time may extend by 5-10 days. MOQ is 100-300 kg, but smaller trial orders are available for new customers.
Does 316L capillary tube meet FDA requirements?
316L stainless steel is widely used in FDA-compliant equipment due to its corrosion resistance and cleanability. However, the tube must be manufactured with a sanitary finish (e.g., 320 grit or finer) and free of surface defects. TeCarve can supply tubes suitable for food and pharmaceutical contact.
What is the difference between ASTM A269 and DIN 17458 for capillary tubes?
ASTM A269 is a US standard covering seamless and welded austenitic tubing for general service, with specific chemical and mechanical requirements. DIN 17458 is a German standard for seamless circular tubes. Both specify similar properties, but DIN 17458 has slight differences in dimensional tolerances and test methods. TeCarve supplies tubes certified to both standards.
According to a 2023 market report, the global capillary tubing market is projected to grow at a CAGR of 6.2% from 2023 to 2030, driven by demand from medical devices and analytical instrumentation. In the medical sector, 316L accounts for over 40% of capillary tube usage due to its biocompatibility and corrosion resistance. For more details, visit tecarvepipes.com for technical datasheets and pricing.
TeCarve Stainless supplies capillary tube certified to ASTM A269, DIN 17458.
Sizes: OD 0.5mm-12mm, Wall 0.05mm-2mm
Grades: 304, 304L, 316, 316L, 321, 310S, 201, 430, 904L, Duplex 2205 | MOQ: 100–300 kg (smaller trial orders available) | Lead Time: 10–25 days after deposit
Email: sales@tecarve.com
WhatsApp: +86 189 6804 2695
Website: https://tecarvepipes.com/capillary-tube/
Response within 24 hours.