Stainless Steel Coiltube — Plasma Arc Welding (PAW) Manufactured
Product Code: WZJX-CT-PAW-54 | Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd.
1. Product Overview
The Plasma Arc Welded Stainless Steel Coiltube is a precision-engineered welded tube product produced through the advanced Plasma Arc Welding (Plasma Arc Welding, PAW) process. Coiltube refers to a continuous-length stainless steel pipe supplied in coil form, offering superior flexibility in downstream processing such as bending, cutting, and forming without the need for butt-welding of individual pipe segments.
Unlike conventional Tungsten Inert Gas Welding (TIG) methods, the PAW process delivers a highly concentrated plasma arc with significantly higher energy density, resulting in deeper penetration, faster welding speeds, and superior weld quality — particularly advantageous for medium-to-thick wall thickness applications. This makes the PAW-manufactured coiltube an ideal solution for industrial applications demanding both structural integrity and production efficiency.
2. Material & Properties
2.1 Base Materials
- Austenitic Grades: AISI 304, AISI 304L, AISI 316, AISI 316L, AISI 321, AISI 310S
- Duplex Grades: UNS S31803 (2205), UNS S32750 (2507)
- Super Duplex Grades: UNS S32750, UNS S32760
- Custom Alloys: Available upon request per customer specifications
2.2 Mechanical Properties (Typical for 304L, Annealed Condition)
- Tensile Strength (UTS): ≥ 485 MPa (70,000 psi)
- Yield Strength (0.2% Offset): ≥ 170 MPa (25,000 psi)
- Elongation: ≥ 40% (in 50 mm / 2 in gauge length)
- Hardness: ≤ 95 HRB (annealed condition)
2.3 Weld Seam Characteristics (PAW Process)
- Weld Penetration: Full penetration achievable with single-pass welding for wall thicknesses up to 6.0 mm
- Weld Bead Profile: Uniform, narrow bead with minimal spatter and excellent surface finish
- Heat-Affected Zone (HAZ): Significantly reduced compared to TIG, preserving base metal metallurgical properties
- Weld Dilution: Low — typically < 15% for medium wall thicknesses
- Weld Strength: Meets or exceeds base metal tensile strength (full-strength weld)
3. Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Outer Diameter (OD) | 6.0 mm – 168.3 mm (¼" – 6") | ASTM A554 / EN 10217-7 |
| Wall Thickness (WT) | 0.5 mm – 6.0 mm (0.020" – 0.236") | ASTM A554 / EN 10217-7 |
| OD Tolerance | ±0.05 mm (±0.002") | EN 10217-7 |
| WT Tolerance | ±10% of nominal | EN 10217-7 |
| Surface Finish | 2B, BA, No.4, Hairline, Mirror (Ra ≤ 0.4 μm) | ASTM A403 / EN 10088 |
| Coil Length | 10 m – 100 m per coil (custom lengths available) | — |
| Welding Process | Plasma Arc Welding (PAW), Helium or Argon shielding gas | ISO 13919 |
| Welding Speed | 50 – 300 m/hr (depending on OD and WT) | — |
| Plasma Current | 50 – 500 A (transferred arc mode) | ISO 13919 |
| Applicable Standards | ASTM A554, ASTM A269, EN 10217-7, ISO 13919, GB/T 12771 | — |
| Post-Weld Treatment | Solution annealing, pickling & passivation, cold drawing (optional) | ASTM A403 |
4. Manufacturing Process
4.1 Process Flow
- Strip Preparation: Cold-rolled stainless steel strip is slit to precise width and surface-conditioned to ensure consistent weldability. Surface oxides and contaminants are removed via pickling and passivation.
- Forming (Rolling): The flat strip is progressively rolled through a series of forming rolls into a semi-circular profile, then closed into a tubular shape with the edges overlapping.
- Plasma Arc Welding (PAW): The overlapping edges are welded using a high-current-density plasma arc. The plasma torch generates a highly focused, high-temperature arc (approximately 10,000–30,000 °C) that provides deep, narrow penetration with minimal heat input to surrounding material.
- Weld Seam Finishing: The external weld bead is ground or polished flush with the pipe surface. Internal weld seams may be smoothed via grinding or chemical machining (optional).
- Heat Treatment: Pipes are solution-annealed (typically at 1050–1100 °C followed by rapid water quench) to restore full austenitic microstructure, relieve residual stresses, and ensure corrosion resistance.
- Pickling & Passivation: Post-annealing pickling removes oxide scale; passivation establishes a protective chromium oxide layer for enhanced corrosion performance.
- Coiling & Packaging: Finished tubes are coiled to specified lengths and packaged with protective end caps, moisture barriers, and wooden or metal coil supports.
4.2 PAW Process Advantages Over Conventional TIG
| Parameter | Plasma Arc Welding (PAW) | Tungsten Inert Gas (TIG) |
|---|---|---|
| Energy Concentration | Very High (focused plasma jet) | Moderate (diffuse arc) |
| Weld Penetration | Deep, single-pass up to 6 mm | Shallow, multi-pass required for thick walls |
| Welding Speed | 2–3× faster than TIG | Baseline |
| Heat-Affected Zone (HAZ) | Narrow, minimal distortion | Wider, more distortion |
| Weld Quality | Uniform, low porosity, consistent geometry | Variable, higher operator dependence |
| Production Efficiency (Medium/Thick Wall) | Significantly Higher | Lower |
| Automation Compatibility | Excellent — ideal for continuous production | Limited — often manual or semi-automatic |
4.3 Key Process Parameters
- Plasma Gas: Helium (He) or Argon (Ar), or a mixture of Ar + H₂ (up to 5% H₂ for increased arc stability)
- Shielding Gas: Argon (Ar) or Argon + Helium mixture for optimal weld pool protection
- Transfer Mode: Transferred arc (for welding), non-transferred arc (for torch conditioning)
- Current Range: 50–500 A depending on material thickness
- Travel Speed: 50–300 m/hr, optimized for uniform weld geometry
- Weld Overlap: Typically 0.5–1.5 mm, controlled by forming roll geometry
5. Applications
The PAW-manufactured stainless steel coiltube is suited for demanding industrial applications requiring high corrosion resistance, structural strength, and precision dimensions:
- Petrochemical & Oil/Gas Industry: Heat exchanger tubes, process piping, condensate lines, and instrumentation tubing in aggressive chemical environments.
- Food & Beverage Processing: Hygienic-grade tubing for milk processing, brewing, pharmaceutical, and cosmetic production lines (FDA-compliant surfaces).
- Power Generation: Boiler tubes, superheater elements, and condensate extraction piping in coal-fired and nuclear power plants.
- Marine & Offshore Engineering: Ballast water systems, seawater cooling circuits, and offshore platform structural piping (Duplex/Super Duplex grades).
- Automotive & Aerospace: Exhaust system components, fuel lines, hydraulic tubing, and structural elements requiring high temperature resistance.
- Construction & Architecture: Decorative handrails, structural framing, and architectural cladding systems.
- Medical & Laboratory Equipment: Autoclave chambers, sterilization equipment, and analytical instrument tubing.
6. Quality Certifications & Testing
6.1 Certification Standards
- ISO 9001:2015 — Quality Management System
- ISO 14001:2015 — Environmental Management System
- EN 10204 — Type 3.1 / Type 3.2 Test Certificates available
- CE Marking — Compliance with European directives
- PED 2014/68/EU — Pressure Equipment Directive compliance (for pressure-rated applications)
- ASME / NB — National Board registration for pressure vessel components
- API 5L / API 5CT — For oil and gas industry applications
6.2 Inspection & Testing Methods
- Hydrostatic Testing: 100% of all coils tested at 1.5× design pressure (per ASTM A554 / EN 10217-7)
- Visual Inspection (VT): 100% external and internal weld seam inspection
- Magnetic Particle Inspection (MT): For detection of surface and near-surface discontinuities in ferritic/martensitic grades
- Eddy Current Testing (ET): Automated continuous inspection of weld seam for subsurface defects
- Dimensional Verification: Laser-based OD and WT measurement at 100% throughput
- Mechanical Testing: Tensile, hardness, and impact testing per ASTM A370 / EN 10204
- Chemical Analysis: Spectrometric verification of composition per ASTM E415
- Corrosion Testing: Intergranular corrosion testing per ASTM A262 (Method A/E), pitting resistance (PREN ≥ 19 for 316L, ≥ 38 for 2507)
- Surface Finish Measurement: Profilometry for Ra values per ASTM B776
6.3 Third-Party Inspection (TPI)
Independent third-party inspection by internationally accredited organizations (e.g., SGS, Bureau Veritas, DNV, Lloyd's Register) is available upon customer request throughout all production stages, from raw material receipt to final dispatch.
7. Unique Selling Points
"Deep penetration, high speed, superior quality — the PAW process redefines welded coiltube manufacturing for medium and thick-wall applications."
- Superior Energy Concentration: The plasma arc delivers 3–5× the energy density of conventional TIG, enabling single-pass full-penetration welds on wall thicknesses up to 6.0 mm — eliminating the need for multi-pass welding and reducing production time by up to 60%.
- Enhanced Production Efficiency: Welding speeds of 50–300 m/hr significantly outpace TIG methods, making PAW coiltube the most cost-effective solution for medium-to-thick wall production runs.
- Minimal Heat-Affected Zone: Narrow HAZ preserves the metallurgical integrity of the base metal, ensuring optimal corrosion resistance and mechanical properties throughout the pipe's service life.