Stainless Steel Coil Tube — Wenzhou Jixing Metal Materials Co., Ltd.
1. Product Overview
The Stainless Steel Coil Tube (盘管) produced by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered continuous-form tubular product designed for high-performance industrial applications requiring corrosion resistance, mechanical strength, and dimensional consistency. Unlike discrete pipe sections, coil tubes are manufactured in continuous lengths wound into coils, enabling efficient downstream processing through automated forming, cutting, and welding operations. This product line is particularly suited for structural, hydraulic, and mechanical assemblies where fatigue resistance and weld integrity are critical — as demonstrated in the design application of weld joint strength for 63-ton aggregate mixer trailer chassis components.
The coil tube product embodies the principle of continuous manufacturing, where raw stainless steel strip is cold-formed into tubular geometry through precision roll-forming, producing a seamless or welded tube in a continuous coil format that minimizes material waste and maximizes production throughput.
2. Material & Properties
2.1 Material Grades
- AISI 304 / ASTM A269 TP304 — The most widely specified austenitic stainless steel grade, offering excellent corrosion resistance, formability, and weldability. Chromium (18–20%) and Nickel (8–10.5%) content provide robust passive film formation in oxidizing environments.
- AISI 304L / ASTM A269 TP304L — Low-carbon variant (C ≤ 0.03%) designed for superior resistance to intergranular corrosion (IGC) during welding, making it the preferred grade for heavy-welding applications such as chassis structural joints.
- AISI 316 / ASTM A269 TP316 — Molybdenum-bearing (2–3% Mo) grade offering enhanced resistance to pitting and crevice corrosion in chloride-rich environments.
- AISI 316L / ASTM A269 TP316L — Low-carbon molybdenum grade combining the corrosion advantages of 316 with improved weldability for complex structural assemblies.
- Duplex 2205 / ASTM A790 — High-strength duplex austenite-ferrite microstructure providing yield strengths approximately 2× those of 304/316 grades with exceptional resistance to stress corrosion cracking (SCC).
2.2 Mechanical Properties (Typical for 304 Grade)
| Property | Unit | Value |
|---|---|---|
| Tensile Strength (UTS) | MPa | ≥ 515 |
| Yield Strength (0.2% Offset) | MPa | ≥ 205 |
| Elongation at Break | % | ≥ 40 |
| Hardness (Rockwell B) | HRB | ≤ 95 |
| Density | g/cm³ | 8.0 |
| Thermal Conductivity (20°C) | W/(m·K) | 16.3 |
| Modulus of Elasticity | GPa | 193 |
2.3 Corrosion Resistance
Stainless steel coil tubes derive their corrosion resistance from the formation of a self-healing chromium oxide passive film (Cr₂O₃) on the surface. The Pitting Resistance Equivalent Number (PREN) for 304L grade is approximately 19, while 316L achieves a PREN of 24–26, and Duplex 2205 reaches a PREN of 35–38, indicating progressively enhanced resistance to localized corrosion mechanisms including pitting, crevice corrosion, and intergranular corrosion.
3. Specifications
| Parameter | Specification |
|---|---|
| Outer Diameter (OD) | Φ6.0 mm – Φ114.3 mm (customizable) |
| Wall Thickness | 0.3 mm – 6.0 mm |
| Coil Weight | 1,500 kg – 5,000 kg per coil |
| Coil Inner Diameter | Φ300 mm – Φ600 mm |
| OD Tolerance | ±0.1 mm (precision grade); ±0.3 mm (standard grade) |
| Wall Thickness Tolerance | ±10% (standard); ±5% (precision) |
| Surface Finish | No. 1 (hot-rolled), 2B (cold-rolled + annealed), BA (bright annealed), No. 4 (brushed) |
| Surface Roughness (Ra) | 0.4 – 1.6 μm (2B finish); ≤ 0.2 μm (BA finish) |
| Applicable Standards | ASTM A269, ASTM A554, EN 10217-7, GB/T 12771, JIS G3459 |
| Temperature Range | −196°C to +870°C (304/316); −270°C to +400°C (Duplex 2205) |
| Welding Compatibility | TIG (GTAW), MIG (GMAW), Laser Welding, Resistance Welding |
4. Manufacturing Process
4.1 Process Flow
- Strip Preparation: Cold-rolled stainless steel strip is supplied in the solution-annealed (soft) condition. Incoming material undergoes chemical composition verification via Optical Emission Spectrometry (OES) and mechanical property confirmation through tensile testing.
- Strip Inspection & Cleaning: Surface defects are identified through automated optical inspection (AOI) systems. Strips are degreased and cleaned to remove rolling oils, ensuring a clean substrate for forming.
- Precision Roll Forming: The flat strip is fed through a series of progressive forming rollers that incrementally bend the strip into a tubular geometry. Roll configurations are CNC-programmed to achieve tight dimensional tolerances on OD and wall thickness.
- Welding (for welded coil tube): The formed tube undergoes longitudinal welding via either:
- MIG/GMAW welding with argon shielding gas for standard applications
- Laser welding for high-speed, narrow heat-affected zone (HAZ) applications
- Frequency Welding (FW) for high-throughput production
- Post-Weld Annealing & Pickling: The welded coil tube is annealed at 1050–1150°C followed by rapid water quenching to restore full austenitic microstructure and relieve welding-induced residual stresses. Subsequent pickling in a mixed acid bath (HNO₃/HF) removes the weld scale (heat tint) and re-establishes the passive chromium oxide film.
- Precision Sizing & Straightening: The coil tube passes through a sizing machine (sizer) to refine OD and roundness tolerances, followed by induction straightening to achieve straightness within 1.5 mm/m.
- Coiling & Packaging: Finished coil tube is wound onto a mandrel, wrapped with protective film, and secured with steel strapping. Each coil is labeled with mill test documentation.
4.2 Weld Joint Design Considerations (Chassis Application)
In the specific application of 63-ton aggregate mixer trailer chassis, the coil tube serves as a structural member requiring high weld joint integrity under cyclic loading. Key design parameters include:
- Weld Penetration: Full penetration welds are specified to ensure load transfer continuity across the joint. Weld toe geometry is ground smooth to minimize stress concentration factors (Kt ≤ 1.5).
- Heat-Affected Zone (HAZ) Control: Preheating at 100–150°C and interpass temperature control (≤ 250°C) minimize HAZ grain coarsening and prevent sensitization in the 450–850°C range.
- Filler Metal Selection: ER308L or ER316L filler wire is matched to the base metal composition to ensure adequate corrosion resistance and mechanical compatibility in the weld metal.
- Post-Weld Heat Treatment (PWHT): Solution treatment at 1050°C with water quenching restores full solution-annealed properties in the HAZ, eliminating any carbide precipitation.
5. Applications
- Heavy Equipment & Trailer Chassis: Structural tubes for aggregate mixer trailers, dump trailers, and special-purpose transport vehicles requiring high fatigue resistance and corrosion durability in outdoor environments.
- Hydraulic & Pneumatic Systems: High-pressure fluid conveyance lines in industrial machinery, construction equipment, and automotive power steering systems.
- Food & Pharmaceutical Processing: Sanitary-grade coil tubes for dairy processing, beverage production, and pharmaceutical equipment where CIP (Clean-in-Place) compatibility and biocompatibility are required.
- Automotive Exhaust & Turbo Systems: Heat-resistant coil tubes for exhaust manifolds, turbocharger ducting, and catalytic converter housings (utilizing 310S or 321 grades).
- Chemical Processing & Petrochemical: Corrosion-resistant tubing for chemical reactors, heat exchangers, and process piping in aggressive chemical environments.
- Architecture & Decoration: Precision-finished coil tubes for handrails, structural facades, and interior design elements requiring aesthetic surface quality.
- Energy & Power Generation: Boiler tubes, heat exchanger coils, and solar thermal collector tubing.
6. Quality Certifications & Testing
6.1 Certifications
- ISO 9001:2015 — Quality Management System certification ensuring consistent production quality and traceability.
- ISO 14001:2015 — Environmental Management System certification.
- CE Marking (PED 2014/68/EU) — Compliance with European Pressure Equipment Directive for pressure-bearing applications.
- EN 10204 3.1 — Material Testing Certificate providing verified chemical composition and mechanical property data.
- Mill Test Reports (MTR) — Per-coil documentation including heat number traceability, chemical analysis, mechanical test results, and dimensional verification.
6.2 Inspection & Testing Methods
| Test Method | Purpose | Standard |
|---|---|---|
| Hydrostatic Pressure Test | Verify weld integrity and absence of through-thickness defects | ASTM A269 |
| Eddy Current Testing (ET) | Non-destructive detection of surface and near-surface defects in weld seam | ASTM E309 |
| Ultrasonic Testing (UT) | Detection of internal volumetric defects (inclusions, voids) | ASTM E164 |
| Intergranular Corrosion Test (ASTM A269, Acid Solution Test) | Verify resistance to sensitization and IGC after welding | ASTM A269 |
| Impact Testing (Charpy V-Notch) | Assess ductile-to-brittle transition temperature and toughness | ASTM A370 |
| Dimensional Verification (CMM / Laser) | Confirm OD, wall thickness, roundness, and straightness tolerances | ISO 13715 |
7. Unique Selling Points
- Engineering-Validated Weld Joint Performance: Unlike generic coil tube suppliers, Wenzhou Jixing provides coil tube products with documented weld joint strength data validated for heavy-duty structural applications, including fatigue life assessment under cyclic loading conditions typical of trailer chassis service.
- Full Traceability & Certification: Every coil is accompanied by complete Mill Test Reports with heat-number traceability, enabling qualification for regulated industries including automotive, aerospace, and pressure vessel applications.
- Custom Dimensional Engineering: Capability to produce coil tubes with precise OD and wall thickness tolerances (±0.1 mm / ±5%) tailored to specific structural design requirements, reducing downstream machining costs.
- Multi-Grade Portfolio: Availability of standard austenitic (304, 304L, 316, 316L), duplex (2205), and specialty grades (310S, 321) from a single source, simplifying supply chain management for multi-material projects.
- High-Volume Continuous Production: Coil format enables automated downstream processing, significantly reducing fabrication labor costs compared to discrete pipe sections — a critical advantage for high-volume manufacturing of structural components.
Note: The coil tube product described herein is designed to meet the structural and corrosion-resistance demands of heavy-duty industrial applications. For specific project requirements, Wenzhou Jixing Metal Materials Co., Ltd. offers custom engineering consultation, including weld joint design validation, fatigue analysis, and material selection optimization to ensure long-term service reliability.