Laser-Welded Stainless Steel Coiltube — High-Precision Capillary & Thin-Wall Tubes
Product Overview
The Laser-Welded Stainless Steel Coiltube, produced by Wenzhou Jixing Metal Materials Co., Ltd., represents the pinnacle of advanced joining technology applied to continuous stainless steel tube manufacturing. Unlike conventional resistance-welded or arc-welded coil tubes, this product leverages Laser Beam Welding (LBW) to achieve an extraordinarily narrow Heat-Affected Zone (HAZ) and negligible thermal distortion, making it the premier solution for high-precision capillary tubes, micro-bore instrumentation tubing, and thin-wall precision applications where dimensional integrity and metallurgical purity are non-negotiable.
As a Continuous Coiled Welded Tube (CCWT), this product is formed through a seamless combination of cold-rolled strip feeding, precision roll-forming, and high-energy-density laser welding, followed by multi-pass post-weld treatment. The coiled format ensures efficient downstream processing, minimal material waste, and consistent mechanical properties along the entire tube length.
Material & Properties
Available Base Materials
- Austenitic Stainless Steels: AISI 304 (UNS S30400), AISI 304L (UNS S30403), AISI 316 (UNS S31600), AISI 316L (UNS S31603), AISI 321 (UNS S32100), AISI 347 (UNS S34700)
- Super-Austenitic Grades: AISI 904L (UNS N08904), Alloy 220 (UNS N02200), Alloy 625 (UNS N06625)
- Ferritic Stainless Steels: AISI 430 (UNS S43000), AISI 409 (UNS S40900)
- Duplex Stainless Steels: UNS S31803 (2205), UNS S32205
- Custom Alloy Specifications available upon request
Key Metallurgical Advantages of Laser Welding
- Ultra-Narrow HAZ: The laser beam's energy density (10⁶–10⁸ W/cm²) confines thermal input to a zone of typically < 0.1 mm on each side of the weld seam, compared to 1–3 mm in conventional TIG or MIG welding. This preserves the base material's microstructure, grain size, and mechanical properties in the vicinity of the weld.
- Minimal Thermal Distortion: Total heat input per unit length is reduced by up to 80–90% compared to arc welding processes, resulting in near-zero geometric deviation during continuous coiling.
- Deep Penetration with Narrow Bead: The keyhole effect (vaporization-driven plasma channel) enables full-penetration welds in wall thicknesses as thin as 0.05 mm, producing a weld bead with a depth-to-width ratio of 5:1 to 10:1.
- Excellent Weld Integrity: The rapid cooling rate (10³–10⁵ °C/s) suppresses grain coarsening, carbide precipitation, and sensitization, yielding a weld metal with mechanical properties closely matching the base metal.
- Non-Contact, Non-Deforming Process: No mechanical pressure is applied to the workpiece, ensuring dimensional accuracy for tubes with wall thicknesses as low as 0.05 mm.
Specifications
| Parameter | Specification Range | Notes |
|---|---|---|
| Outer Diameter (OD) | 0.1 mm – 100 mm | Capillary tubes down to 0.1 mm OD achievable |
| Wall Thickness | 0.05 mm – 10 mm | Thin-wall precision range: 0.05–0.5 mm |
| Weld Bead Height | ≤ 0.02 mm (flush to near-zero protrusion) | Post-weld grinding/polishing available |
| Heat-Affected Zone (HAZ) | < 0.1 mm (single-sided) | Ultra-narrow compared to arc welding (> 1 mm) |
| Thermal Distortion | ≤ 0.01 mm/m (straightness deviation) | Near-zero geometric deviation |
| Welding Speed | 1 – 20 m/min (material-dependent) | High productivity for continuous coiling |
| Weld Penetration | Full penetration (keyhole mode) | Depth-to-width ratio: 5:1 to 10:1 |
| Surface Finish | As-welded, ground, polished (Ra ≤ 0.4 μm), electropolished | Custom finishes available |
| Delivery Format | Continuous coil (Coiltube) | Coil weight: 5 kg – 500 kg |
| Dimensional Tolerance (OD) | ±0.01 mm – ±0.05 mm | Per ASTM A269 / EN 10216 standards |
| Dimensional Tolerance (Wall) | ±5% of nominal thickness | Tighter tolerances available on request |
| Applicable Standards | ASTM A269, ASTM A778, EN 10216-5, JIS G3459, GB/T 12771 | Multi-standard compliance |
Manufacturing Process
Step 1: Precision Cold-Rolled Strip Preparation
High-purity stainless steel strip is cold-rolled to the target thickness with controlled surface quality (typically 2B or No.4 finish). Strip edge quality is critical; laser-cut or sheared edges with burr height < 0.02 mm ensure consistent weld initiation and seam integrity. Chemical composition and mechanical properties are verified per batch via Spectroscopic Analysis and Tensile Testing.
Step 2: Precision Roll-Forming
The flat strip is guided through a series of precision-calibrated forming rollers that progressively bend the material into the target circular cross-section. Rollers are manufactured from hardened tool steel with surface roughness Ra < 0.1 μm to prevent surface transfer defects. Forming tolerances are maintained at ±0.02 mm for OD accuracy.
Step 3: Laser Beam Welding
A high-power Fiber Laser (typically 2–12 kW, wavelength 1070 nm) or CO₂ Laser (wavelength 10.6 μm) is focused through a high-numerical-aperture welding lens to produce a spot diameter of 0.05–0.2 mm. The weld is executed in Keyhole Mode under a protective atmosphere of high-purity Argon (Ar, 99.999%) or Nitrogen (N₂, 99.999%), with:
- Front-side shielding: Concentric gas nozzle with 2–5 L/min flow
- Back-side shielding: Internal gas lance or trailing nozzle with 3–8 L/min flow
- Weld speed: Optimized per material thickness (typically 1–20 m/min)
Step 4: Post-Weld Heat Treatment (if required)
Depending on the application and material grade, the welded coil may undergo:
- Solution Annealing: 1040–1120 °C, followed by rapid water quench (for austenitic grades)
- Stress Relief: 300–400 °C for 1–2 hours (for dimensional stabilization)
- Pickling & Passivation: HNO₃/HF mixed acid bath to remove weld discoloration and form protective Cr₂O₃ layer
Step 5: Post-Weld Finishing
For applications requiring internal surface smoothness (e.g., fluid transfer, medical devices):
- Internal Grinding: Precision diamond or ceramic grinding tools reduce weld bead to flush or near-flush condition
- Electropolishing (EP): Removes 10–50 μm of surface layer, achieving Ra ≤ 0.2 μm and enhanced corrosion resistance
- Passivation: Final citric acid or nitric acid passivation treatment
Step 6: Quality Inspection & Coiling
Every coil undergoes rigorous multi-stage inspection:
- Visual Inspection (VT): 100% full-length examination of weld seam
- Dimensional Measurement: Laser OD gauge, ultrasonic wall thickness gauge — continuous in-line monitoring
- Weld Penetration Testing: Eddy current or ultrasonic testing (UT) per ASTM E709 / ASTM E164
- Hydrostatic Testing: At 1.5× maximum working pressure for leak integrity verification
- Chemical Composition Verification: Optical Emission Spectroscopy (OES) per batch
Applications
Primary Target Applications
- High-Precision Capillary Tubes: Used in analytical instrumentation, gas chromatography, and laboratory sample delivery systems where internal diameter tolerances of ±0.005 mm and surface roughness Ra < 0.4 μm are mandatory.
- Thin-Wall Precision Tubes: Medical device tubing (hypodermic needles, catheter shafts, surgical instrument housings) requiring biocompatibility, fatigue resistance, and zero weld-induced geometric deviation.
- Semiconductor Industry: Ultra-pure gas delivery lines, vacuum chamber feedthroughs, and CVD/PECVD process lines where particulate contamination from weld defects is unacceptable.
- Automotive Fuel & Hydraulic Lines: High-pressure fuel injection rails, brake lines, and hydraulic actuator tubing requiring fatigue life > 10⁷ cycles.
- Food & Pharmaceutical Processing: CIP (Clean-in-Place) compatible tubing for dairy, beverage, and pharmaceutical fluid transfer where weld seam integrity prevents bacterial harboring.
- Oil & Gas Downhole Tools: Precision instrument tubing for logging tools, MWD (Measurement While Drilling) systems, and downhole sensor housings.
- Aerospace & Defense: Hydraulic lines, pneumatic control tubing, and fuel system components for aircraft and spacecraft.
- Electronics & Optics: Vacuum tubes for electron beam systems, fiber optic guide tubes, and precision thermal management channels.
Why Laser-Welded Coiltube is the Preferred Choice
For high-precision capillary tubes and thin-wall precision tubes, laser welding is not merely an option — it is the only viable technology. The ultra-narrow HAZ (< 0.1 mm) ensures that the base material's microstructure and mechanical properties remain unaltered within the critical wall thickness range. The near-zero thermal distortion preserves dimensional accuracy through the entire continuous coiling process. The keyhole weld geometry provides full-penetration strength without the need for post-weld mechanical finishing in many applications.
Quality Certifications & Compliance
System Certifications
- ISO 9001:2015 — Quality Management System
- ISO 14001:2015 — Environmental Management System
- ISO 45001:2018 — Occupational Health & Safety Management System
- EN 10204 3.1 — Third-party inspection certificate available
- EN 10204 3.2 — Product-specific inspection certificate available
Product-Specific Certifications
- ASTM A269/A269M — Standard Specification for Seamless, Welded, and Heavy-Walled Austenitic Stainless Steel Pipes and Tubes
- ASTM A778/A778M — Standard Specification for Stainless Steel Tubular Products for General Application
- EN 10216-5 — Non-alloy, heat-resisting alloy, and stainless steel tubes for mechanical and technical purposes
- JIS G3459 — Stainless steel seamless and welded tubes for general purposes
- GB/T 12771 — Stainless steel tubes for fluid transport (Chinese National Standard)
- GB/T 14976 — Cold-rolled or cold-drawn stainless steel seamless tubes
- ASME SA-213 — Heat exchanger and condenser tubes (upon request)
- ASME SA-269 — Corrosion-resistant chromium and chromium-nickel steel tubing (upon request)
Testing & Inspection Protocols
| Test Method | Standard Reference | Scope |
|---|---|---|
| Chemical Composition (OES) | ASTM E415 / ASTM E1410 | 100% per batch |
| Tensile Testing | ASTM A370 / ASTM E8 | Per heat / per coil |