Plasma Arc Welded (PAW) Stainless Steel Coil Tube — High-Efficiency Medium & Thick-Wall Solution
Product Overview
Wenzhou Jixing Metal Materials Co., Ltd. presents its advanced Plasma Arc Welded (PAW) Stainless Steel Coil Tube, engineered specifically for medium-to-thick wall applications where superior welding efficiency, deep penetration, and high production speed are critical. Unlike conventional TIG (Tungsten Inert Gas) welding processes, the PAW technique concentrates plasma energy into an extremely narrow arc, delivering significantly greater heat input per unit area. This results in deeper weld penetration, faster welding speeds, and improved metallurgical quality — making it the preferred method for producing robust stainless steel coil tubes with enhanced structural integrity.
The PAW process represents a significant advancement in welded stainless steel tube manufacturing, offering a compelling alternative to TIG welding for wall thicknesses ranging from 1.0 mm to 12.0 mm. The concentrated plasma jet creates a highly stable, high-velocity arc that ensures consistent weld geometry and minimal distortion, even at elevated production rates.
Unique Selling Points
- Superior Energy Concentration: The plasma arc achieves energy densities 5–10 times higher than conventional TIG welding, enabling rapid melting and deep, uniform weld penetration.
- Enhanced Welding Speed: PAW delivers 2–4× faster welding rates compared to TIG for medium and thick-wall tubing, dramatically improving production throughput.
- Deep Penetration Capability: Achieves full-penetration welds in thick sections without the need for pre-grooving, reducing manufacturing complexity and cost.
- Consistent Weld Quality: The stable plasma arc produces uniform bead geometry with minimal spatter and reduced heat-affected zone (HAZ) width.
- Cost-Effective for Thick Walls: Significantly lower cost per linear meter compared to TIG for wall thicknesses above 1.5 mm.
Material & Properties
Available Grades
- 304 / 304L (UNS S30400 / S30403): General-purpose austenitic stainless steel with excellent corrosion resistance and formability.
- 316 / 316L (UNS S31600 / S31603): Molybdenum-bearing grade offering superior resistance to pitting and crevice corrosion in aggressive environments.
- 321 (UNS S32100): Titanium-stabilized grade with excellent resistance to intergranular corrosion at elevated temperatures.
- 310S (UNS S31008): High-temperature grade suitable for sustained service up to 1150 °C (2092 °F).
- 430 (UNS S43000): Ferritic grade offering good oxidation resistance and magnetic properties at economical pricing.
Mechanical Properties (Typical — Grade 304L)
| Property | Specification |
|---|---|
| Tensile Strength | ≥ 515 MPa (≥ 75 ksi) |
| Yield Strength (0.2% Offset) | ≥ 205 MPa (≥ 30 ksi) |
| Elongation (50 mm gauge length) | ≥ 40% |
| Hardness (Brinell) | ≤ 217 HB |
| Weld Seam Strength | ≥ 90% of base metal tensile strength |
| Maximum Service Temperature | 870 °C (1598 °F) |
Specifications
| Parameter | Range / Specification |
|---|---|
| Outer Diameter (OD) | 3.0 mm – 219.0 mm (0.12" – 8.63") |
| Wall Thickness | 0.5 mm – 12.0 mm (0.020" – 0.472") |
| Coil Length (per coil) | Custom — typically 50 m – 500 m (164 ft – 1,640 ft) |
| Coil Inner Diameter | 305 mm – 610 mm (12" – 24") |
| Weld Type | Plasma Arc Weld (PAW) — longitudinal continuous seam |
| Weld Penetration | Full penetration up to 12.0 mm wall thickness |
| Welding Speed | Up to 4× faster than equivalent TIG process |
| Surface Finish | Mirror polish, satin, brushed, matte, or pickled & passivated |
| Dimensional Tolerance (OD) | ±0.05 mm to ±0.50 mm (per ISO 4626 / ASTM A513) |
| Dimensional Tolerance (Wall) | ±10% or ±0.05 mm, whichever is greater |
| Straightness (after decoiling) | ≤ 1.0 mm/m (≤ 0.012"/ft) |
Manufacturing Process
Process Flow
- Raw Material Inspection: Incoming stainless steel strip is verified for chemical composition (spectroscopic analysis), mechanical properties, and surface quality in accordance with ASTM A473 / EN 10204 standards.
- Strip Preparation & Slitting: Cold-rolled stainless steel strip is slit to the required width with precision edge preparation to ensure consistent weld fit-up.
- Forming: The strip is progressively formed through a series of rolls into the desired circular cross-section with tight dimensional control.
- Plasma Arc Welding (PAW): The formed tube is welded longitudinally using a high-velocity plasma arc. The process utilizes a constricted tungsten electrode within a copper nozzle to produce a highly concentrated, stable plasma jet. Key process parameters include:
- Plasma gas: Argon (Ar) or Argon/Helium (Ar/He) mixture
- Shielding gas: Argon (Ar) — internal and external
- Welding current: 100 A – 500 A (depending on wall thickness)
- Arc transfer mode: Pulsed or DC continuous
- Welding speed: Optimized for 2–4× TIG equivalent rates
- Post-Weld Heat Treatment (as required): Solution annealing at 1040 °C – 1150 °C (1904 °F – 2092 °F) followed by rapid quenching to restore full austenitic microstructure and maximize corrosion resistance.
- Pickling & Passivation: Chemical treatment to remove oxide scale and form a protective chromium oxide passive layer on the weld seam and tube surfaces.
- Dimensional & Surface Inspection: Ultrasonic testing (UT) of the weld seam, dimensional verification, and surface quality assessment.
- Coiling & Packaging: Finished tubing is coiled on protective spools and packaged with rust-inhibitive wrapping for shipment.
PAW vs. TIG — Comparative Advantage
| Parameter | Plasma Arc Welding (PAW) | Tungsten Inert Gas (TIG) |
|---|---|---|
| Energy Density | 10⁶ – 10⁷ W/cm² | 10⁵ W/cm² |
| Weld Penetration (per pass) | Up to 12.0 mm | Up to 3.0 mm | Welding Speed | High (2–4× TIG) | Moderate |
| HAZ Width | Narrow | Narrow |
| Best Application Range | Medium to thick wall (1.0–12.0 mm) | Thin wall (0.3–3.0 mm) |
| Cost Efficiency (thick wall) | High | Moderate |
Applications
- Heat Exchangers & Boilers: Thick-wall PAW tubes provide excellent thermal conductivity and corrosion resistance in demanding heat transfer applications.
- Petroleum & Chemical Processing: 316L PAW coil tubes resist aggressive chemical environments including acids, chlorides, and hydrocarbons.
- Food & Pharmaceutical Processing: Sanitary-grade mirror-finish PAW tubing meets FDA and 3-A sanitary standards for hygienic fluid transfer.
- Power Generation: High-temperature grades (310S, 321) withstand extreme thermal cycling in boiler tubes, superheaters, and economizers.
- Automotive & Industrial Equipment: Precision PAW tubing for exhaust systems, fuel lines, and hydraulic circuits requiring durable weld integrity.
- Construction & Architectural: Structural tubing for decorative railings, handrails, and load-bearing applications.
- Medical Equipment: Biocompatible tubing for surgical instruments, dialysis equipment, and medical gas delivery systems.
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains rigorous quality management systems to ensure every batch of PAW stainless steel coil tube meets international standards:
- ISO 9001:2015 — Quality Management System certification
- ISO 14001 — Environmental Management System
- ASTM A513 / A511 — Standard specifications for welded austenitic stainless steel tube
- ASTM A554 — Standard specification for cold-rolled or cold-drawn austenitic stainless steel tube
- EN 10216-5 — European standard for welded stainless steel tubes — Part 5: Technical delivery conditions for non-ferrous
- ISO 4626 — Welded stainless steel tubes for technical purposes — Dimensions and tolerances
- ASME SA-213 — Standard specification for austenitic stainless steel tube for heat exchangers
- EN 10204 Type 3.1 — Inspection certificates provided with every shipment
- NDT Compliance: Ultrasonic testing (UT) and dye penetrant inspection (DPI) per ISO 17635 / ASTM E164
- Mill Test Reports (MTR): Full chemical and mechanical test data provided for each heat number
Technical Note
The Plasma Arc Welding (PAW) process employed by Wenzhou Jixing Metal Materials Co., Ltd. represents a purpose-built solution for medium-to-thick wall stainless steel tubing where production efficiency and weld integrity are paramount. With welding speeds up to 4× those of conventional TIG and full-penetration capability up to 12.0 mm (0.472"), PAW coil tubes deliver optimal value for demanding industrial applications requiring both high throughput and superior mechanical performance at the weld seam.