TIG Autogenous Welded Stainless Steel Coil Tube (Coiltube)
Product Overview
The TIG Autogenous Welded Stainless Steel Coil Tube (Product No. 53) is a precision-engineered seamless-appearance tubular product manufactured by Wenzhou Jixing Metal Materials Co., Ltd. This product belongs to the Manufacturing Process > Forming Process > Welded Tube classification and represents the industry-leading approach to producing high-integrity stainless steel tubing for demanding industrial applications.
Unlike conventional welded tubing that relies on filler metal deposition, this product employs Tungsten Inert Gas (TIG) Autogenous Welding—a technique in which no external filler wire is introduced into the weld zone. The molten pool is formed exclusively from the base metal edges of the strip, resulting in a weld seam that is metallurgically identical to the parent material, thereby ensuring exceptional weld purity, superior corrosion resistance, and a pristine internal surface finish.
Unique Selling Points
- Zero Filler Wire (Autogenous Welding): No consumable filler metal is added, eliminating potential sources of impurity and ensuring the weld composition matches the base material exactly.
- Exceptional Weld Purity: The absence of filler wire results in a weld zone free of foreign alloying elements, inclusions, or compositional deviations.
- Smooth Internal Surface (Mirror-Grade ID): Back-side inert gas shielding combined with autogenous welding produces a remarkably flat and smooth inner wall—critical for sanitary, pharmaceutical, and food-grade applications.
- Industry-Standard for Thin-Wall Tubing: TIG autogenous welding is the dominant and preferred welding method for thin-wall stainless steel coil tubes, offering superior control over heat input and weld geometry.
- Continuous Production via Coil Forming: The coil tube configuration enables high-throughput, cost-effective manufacturing while maintaining consistent quality across long production runs.
Material & Properties
The base material for this product typically comprises austenitic stainless steel grades conforming to international standards. The following material specifications are representative:
- Common Grades: SUS304 / ASTM 304, SUS304L / ASTM 304L, SUS316L / ASTM 316L, SUS321 / ASTM 321
- Corrosion Resistance: Excellent resistance to intergranular corrosion, pitting, and crevice corrosion due to the homogeneity of the autogenous weld zone
- Mechanical Properties: Tensile strength, yield strength, and elongation meet or exceed ASTM A213 / EN 10216-5 requirements
- Weld Integrity: Weld zone hardness and microstructure are consistent with the heat-affected zone (HAZ) of the base material; no dilution effects from filler metal
- Surface Finish: Internal surface roughness (Ra) as low as 0.2–0.5 μm achievable, suitable for hygienic and high-purity fluid service
Specifications
| Parameter | Specification |
|---|---|
| Product Name | TIG Autogenous Welded Stainless Steel Coil Tube (Coiltube) |
| Product No. | 53 |
| Welding Method | TIG (Tungsten Inert Gas) Autogenous Welding — No Filler Wire |
| Classification | Manufacturing Process → Forming Process → Welded Tube |
| Applicable Wall Thickness | 0.3 mm – 3.0 mm (Thin-wall specialty) |
| Applicable Outer Diameter | Φ3.0 mm – Φ114.3 mm |
| Internal Surface Roughness | Ra ≤ 0.5 μm (as-welded); Ra ≤ 0.2 μm (post-polishing available) |
| Weld Seam Appearance | Flush, clean, continuous; no spatter, no filler metal trace |
| Shielding Gas | High-purity Argon (≥99.99%) — Front and Back Side |
| Welding Speed | Adjustable; typically 5–30 m/min depending on wall thickness and diameter |
| Delivery Form | Coil (continuous length); straight-cut lengths available upon request |
| Applicable Standards | ASTM A213, EN 10216-5, GB/T 14976, ISO 13679 |
| Manufacturer | Wenzhou Jixing Metal Materials Co., Ltd. |
Manufacturing Process
The production of TIG Autogenous Welded Stainless Steel Coil Tubes follows a rigorous multi-stage process designed to maximize weld quality and dimensional accuracy:
- Strip Uncoiling & Feeding: Precision stainless steel strip is uncoiled from a master coil and fed through a series of leveling and straightening rollers to ensure flatness and uniform edge quality prior to forming.
- Forming (Rolling): The flat strip is passed through a series of progressively reducing roller forming stations, which gradually bend the strip into a tubular cross-section while maintaining precise wall thickness and ovality tolerances.
- Edge Preparation & Alignment: The opposing edges of the formed strip are precisely aligned and brought into intimate contact. Edge quality is critical—any burr, scale, or contamination is removed prior to welding to ensure a defect-free weld.
- TIG Autogenous Welding: A tungsten electrode (non-consumable) generates an arc between the electrode tip and the workpiece edges. High-purity argon shielding gas is applied on both the front (weld side) and back (root side) to prevent oxidation. No filler wire is introduced—the weld pool is formed solely by melting the base metal edges. The arc parameters (current, voltage, travel speed) are precisely controlled to achieve full penetration with a smooth, uniform weld bead.
- Heat Treatment (Annealing): Welded tubes are subjected to solution annealing (typically at 1050–1100 °C) followed by rapid quenching to restore full austenitic microstructure, eliminate residual stresses, and ensure maximum corrosion resistance throughout the weld zone and HAZ.
- Pickling & Passivation: The tubes are acid-pickled (typically using a mixture of nitric and hydrofluoric acid) to remove the heat-tint oxide layer, followed by passivation to restore the protective chromium oxide film on both internal and external surfaces.
- Internal Polishing (Optional): For applications requiring ultra-smooth internal surfaces, mechanical or electrolytic internal polishing (e.g., electropolishing) may be applied to achieve Ra values below 0.2 μm.
- Quality Inspection: Each coil is subjected to comprehensive inspection including hydrostatic pressure testing, dimensional verification, surface defect detection (visual and automated), and chemical/spectral analysis of the weld zone.
- Coiling & Packaging: Finished tubes are recoiled to the required coil weight or cut to specified lengths, protected with internal and external packaging to prevent surface damage during transit.
Applications
The combination of high weld purity, smooth internal surfaces, and reliable mechanical integrity makes TIG Autogenous Welded Stainless Steel Coil Tubes suitable for a wide range of critical applications:
- Food & Beverage Industry: Fluid transfer lines, pasteurization systems, brewing equipment, and hygienic piping where smooth internal surfaces prevent bacterial adhesion and facilitate CIP (Clean-in-Place) processes.
- Pharmaceutical & Biotechnology: Process piping, reactor connections, and transfer lines requiring high-purity, low-contamination fluid handling.
- Chemical Processing: Corrosive fluid transport, reactor internals, and heat exchanger tubes where weld integrity is paramount.
- Medical Equipment: Tubing for medical gas delivery systems, dialysis machines, and surgical instrument components.
- Semiconductor & Electronics: Ultra-pure chemical delivery systems (UPCS) and vacuum piping where even trace contamination is unacceptable.
- Energy & Power Generation: Condenser tubes, feedwater systems, and heat exchangers in power plants.
- General Engineering: Structural tubing, fluid conveyance, and mechanical components in automotive, aerospace, and manufacturing sectors.
Quality Certifications & Testing
Wenzhou Jixing Metal Materials Co., Ltd. maintains rigorous quality management systems and adheres to internationally recognized standards:
- ISO 9001:2015 — Quality Management System certification ensuring consistent product quality and process control.
- ISO 14001:2015 — Environmental Management System certification for sustainable manufacturing practices.
- EN 10204 3.1 / 3.2 — Material test certificates available upon request, providing third-party verified conformity documentation.
- Hydrostatic Testing: All coils are hydrostatically pressure-tested to verify weld integrity and leak-tightness.
- Weld Seam Inspection: Automated visual inspection systems detect surface defects; ultrasonic testing (UT) or eddy current testing (ECT) may be applied for subsurface defect detection.
- Chemical Analysis: Spectroscopic verification of base material and weld zone composition to confirm grade conformity.
- Mechanical Testing: Tensile testing, hardness testing, and impact testing performed per applicable standards to validate mechanical properties.
Technical Note: TIG Autogenous Welding is specifically recommended for thin-wall stainless steel tubing (wall thickness ≤ 3.0 mm) where the absence of filler metal ensures the weld zone retains the full metallurgical and corrosion resistance characteristics of the parent material. The smooth internal surface produced by this method eliminates crevices and irregularities that could trap fluids or harbor microbial growth, making it the preferred welding technique for sanitary and high-purity applications.