Stainless Steel Coil Tube — Plasma Arc Welding (PAW) Process
Product Overview
The Plasma Arc Welded Stainless Steel Coil Tube (PAW Coil Tube) is a precision-engineered welded tubular product manufactured by Wenzhou Jixing Metal Materials Co., Ltd. This product represents the next generation of seamless-equivalent welded tubing, produced using Plasma Arc Welding (Plasma Arc Welding, PAW) technology. PAW is an advanced variant of Gas Tungsten Arc Welding (GTAW/TIG), characterized by the constriction of the electric arc through a nozzle orifice to form a high-velocity, high-energy-density plasma jet. This results in concentrated energy input, deep penetration, and significantly higher welding speeds compared to conventional TIG welding methods.
Coil tubes are supplied in continuous coil form, enabling high-volume downstream processing including cutting, bending, forming, and fabrication with minimal material waste. The PAW process ensures weld integrity comparable to seamless tubes while offering superior cost-efficiency, particularly for medium-to-heavy wall thickness applications where PAW welding efficiency substantially exceeds that of TIG.
Material & Properties
Available Grades
- 304 / 304L — General-purpose austenitic stainless steel with excellent corrosion resistance and formability
- 316 / 316L — Molybdenum-enhanced austenitic grade offering superior resistance to pitting and crevice corrosion
- 321 / 321H — Titanium-stabilized grade for elevated temperature service
- 310S — High-temperature austenitic grade for extreme thermal environments
- 316Ti / 316L — Titanium-stabilized 316 variant for enhanced resistance to intergranular corrosion
Mechanical Properties (Typical, 304 Grade)
| Property | Specification | Standard Reference |
|---|---|---|
| Tensile Strength (UTS) | ≥ 515 MPa | ASTM A213 / A269 |
| Yield Strength (0.2% Offset) | ≥ 205 MPa | ASTM A213 / A269 |
| Elongation | ≥ 40% | ASTM A213 / A269 |
| Hardness (HBW) | ≤ 217 | ASTM A213 / A269 |
| Heat Treatment | Solution Annealed (1050–1100°C, water quench) | ASTM A213 / A269 |
Specifications
| Parameter | Specification / Range |
|---|---|
| Outer Diameter (OD) | 6.0 mm – 219.1 mm (¼" – 8½") |
| Wall Thickness (WT) | 0.5 mm – 12.0 mm (0.020" – 0.472") |
| Coil Length | Customized per customer requirement (typically 3,000 – 6,000 mm) |
| Surface Finish | Ba & Fl (Bright Annealed & Pickled), No. 4 Brushed, Mirror (2B), Custom |
| Welding Process | Plasma Arc Welding (PAW) |
| Weld Penetration | Full penetration, deep weld profile |
| Welding Speed | Significantly higher than TIG (2× – 3× depending on wall thickness) |
| Applicable Wall Thickness (PAW Advantage) | Medium to Heavy Wall (≥ 1.5 mm) |
| Dimensional Tolerance | OD: ±0.15 mm; WT: ±0.05 mm (tight tolerance available) |
| Standards Compliance | ASTM A213, ASTM A269, ASME SA-213, EN 10216-5, JIS G3459 |
Manufacturing Process
Process Flow
- Steel Strip Supply & Inspection — Cold-rolled stainless steel strip of certified grade is inspected for chemical composition, mechanical properties, and surface quality.
- Coiling & Forming — The flat strip is formed into a helical coil shape using precision roll forming equipment to achieve the target outer diameter and wall geometry.
- Plasma Arc Welding (PAW) — The longitudinal seam is welded using a Plasma Arc Welding process. A tungsten electrode generates a high-current arc that is constricted through a copper nozzle, producing a focused plasma jet with energy density up to 10⁶ W/cm². This concentrated energy input enables:
- Deep penetration — The narrow, high-velocity plasma jet achieves deep weld fusion with minimal heat-affected zone (HAZ)
- High welding speed — Processing rates of 2×–3× TIG are achieved, especially for medium-to-heavy wall thicknesses
- Superior weld quality — Minimal spatter, reduced distortion, and consistent weld bead geometry
- Excellent weld appearance — Smooth, uniform weld with minimal post-weld finishing required
- Post-Weld Heat Treatment — Solution annealing at 1050–1100°C with rapid water quench to restore full austenitic microstructure and maximum corrosion resistance.
- Pickling & Passivation — Chemical treatment to remove weld discoloration and form a protective chromium oxide passive film on the surface.
- Final Inspection & Testing — Dimensional verification, hydrostatic pressure testing, visual inspection, and optional non-destructive testing (EDDY CURRENT, EC).
- Coiling & Packaging — Tubes are wound into coils with protective end caps and wrapped in moisture-barrier packaging for shipment.
PAW vs. TIG — Comparative Advantages
| Parameter | Plasma Arc Welding (PAW) | Gas Tungsten Arc Welding (TIG) |
|---|---|---|
| Energy Density | 10⁵ – 10⁶ W/cm² | 10⁴ – 10⁵ W/cm² |
| Weld Penetration | Deep, narrow profile | Moderate, broader profile |
| Welding Speed (Medium/Heavy Wall) | High (2× – 3× TIG) | Moderate |
| Heat-Affected Zone (HAZ) | Narrow | Broader |
| Distortion | Minimal | Moderate |
| Weld Appearance | Superior, uniform bead | Good |
| Equipment Complexity | Higher | Lower |
Applications
The PAW-welded stainless steel coil tube is suitable for demanding industrial applications where deep weld penetration, high production efficiency, and superior weld integrity are critical:
- Petrochemical & Oil/Gas Industry — Heat exchanger tubes, reactor piping, and process lines requiring high-strength welds in medium-to-heavy wall constructions
- Food & Beverage Processing — Hygienic piping systems, milk processing equipment, and beverage transfer lines (304L/316L grades)
- Pharmaceutical Industry — Clean-in-place (CIP) piping systems requiring high surface finish and corrosion resistance
- Automotive Industry — Exhaust system components, fuel delivery lines, and structural tubing requiring consistent weld quality at high production volumes
- Chemical Processing — Acid-resistant piping and equipment for aggressive chemical environments (316/316L grades)
- Power Generation — Boiler tubes, superheater elements, and steam piping in thermal power plants
- Building & Construction — Architectural decorative tubing, structural supports, and railings
Quality Certifications
Wenzhou Jixing Metal Materials Co., Ltd. maintains rigorous quality management systems and holds the following certifications and compliances:
- ISO 9001:2015 — Quality Management System certification
- ISO 14001 — Environmental Management System certification
- ASME "S" Stamp — Authorized Manufacturer for Pressure Vessel Components
- PED (Pressure Equipment Directive 2014/68/EU) — Conformity for pressure equipment
- EN 10204 3.1 Certificate — Third-party material testing and inspection reports available upon request
- Mill Test Reports (MTR) — Full chemical composition and mechanical property documentation provided with each shipment
Unique Selling Points
1. Superior Weld Efficiency for Medium-to-Heavy Wall Tubes: The Plasma Arc Welding (PAW) process delivers 2×–3× higher welding speed compared to TIG for medium-to-heavy wall thickness applications, significantly reducing production cycle time and manufacturing cost.
2. Deep Penetration with Minimal HAZ: The highly concentrated plasma jet achieves full-penetration welds with a narrow heat-affected zone, preserving the mechanical integrity and corrosion resistance of the base metal.
3. Seamless-Equivalent Weld Quality: PAW produces welds with mechanical properties and corrosion resistance equivalent to seamless tubing, eliminating the performance gap between welded and seamless products.
4. Consistent Production Quality: The automated PAW process ensures uniform weld geometry, minimal spatter, and reduced post-weld finishing, leading to consistent product quality across large production runs.
5. Versatile Coil Supply Format: Continuous coil supply enables high-volume downstream processing with minimal material waste, ideal for high-volume fabrication and production environments.
Technical Contact
For detailed specifications, custom requirements, or sample requests, please contact Wenzhou Jixing Metal Materials Co., Ltd. Our technical team provides full engineering support including material selection guidance, process consultation, and application-specific recommendations.