Stainless Steel Coil Tube for Decanting Machine Boiler Applications
Product Overview
The Stainless Steel Coil Tube (盘管) is a precision-engineered tubular component manufactured by Wenzhou Jixing Metal Materials Co., Ltd. (温州吉兴金属材料有限公司), specifically designed for use in decanting machine (清蜡机) boiler systems and high-temperature heat exchange environments. These coil tubes are fabricated through advanced continuous bending and forming processes, producing seamless or welded tubular geometries that maximize surface-area-to-volume ratios for superior thermal transfer efficiency.
The product line is distinguished by its application in CO₂ shielded automatic welding (CO₂ Shielded Metal Arc Welding, GMAW-C) processes for boiler coil tube assembly, ensuring consistent weld integrity, minimal distortion, and high production throughput in industrial manufacturing settings.
Material & Properties
Material Grades
- 304 Stainless Steel (UNS S30400) — Chromium-Nickel austenitic stainless steel with excellent corrosion resistance and formability
- 316 Stainless Steel (UNS S31600) — Molybdenum-enhanced austenitic grade offering superior resistance to pitting and crevice corrosion in aggressive chemical environments
- 321 Stainless Steel (UNS S32100) — Titanium-stabilized austenitic grade suitable for elevated-temperature service without intergranular corrosion risk
- 310S Stainless Steel (UNS S31008) — High-temperature austenitic grade for extreme thermal cycling applications
Mechanical Properties
| Property |
304 Grade |
316 Grade |
321 Grade |
310S Grade |
| Tensile Strength (MPa) |
≥ 520 |
≥ 520 |
≥ 520 |
≥ 520 |
| Yield Strength (MPa) |
≥ 205 |
≥ 205 |
≥ 205 |
≥ 205 |
| Elongation (%) |
≥ 40 |
≥ 40 |
≥ 40 |
≥ 40 |
| Maximum Service Temperature (°C) |
870 |
870 |
900 |
1150 |
| Thermal Conductivity (W/m·K at 100°C) |
16.3 |
16.3 |
16.3 |
18.0 |
| Corrosion Resistance |
Excellent |
Superior |
Excellent |
Outstanding (high-temp) |
Chemical Composition (Typical, wt%)
| Element |
304 |
316 |
321 |
310S |
| C (Carbon) |
≤ 0.08 |
≤ 0.08 |
≤ 0.08 |
≤ 0.08 |
| Cr (Chromium) |
18.0–20.0 |
16.0–18.0 |
17.0–19.0 |
24.0–26.0 |
| Ni (Nickel) |
8.0–10.5 |
10.0–14.0 |
9.0–12.0 |
19.0–22.0 |
| Mo (Molybdenum) |
— |
2.0–3.0 |
— |
— |
| Ti (Titanium) |
— |
— |
5×C – 0.70 |
— |
Specifications
| Parameter |
Specification |
| Product Category |
Stainless Steel Coil Tube (盘管) |
| Tube Outer Diameter (OD) |
φ6.0 mm – φ50.0 mm (customizable) |
| Tube Wall Thickness |
0.5 mm – 3.0 mm |
| Coil Bend Radius |
≥ 3D (three times the tube OD), minimum 10 mm |
| Coil Length |
Up to 300 m per continuous coil (standard); custom lengths available |
| Surface Finish |
No. 4 Brushed, 2B Annealed, BA (Bright Annealed), or Polished (Ra ≤ 0.4 μm) |
| Dimensional Tolerance (OD) |
±0.05 mm (±0.10 mm for OD > φ25 mm) |
| Dimensional Tolerance (Wall) |
±10% of nominal thickness |
| Coil Pitch Tolerance |
±0.5 mm per turn |
| Standards Compliance |
ASTM A269 / A270, ASME SA-213 / SA-269, EN 10217-7, GB/T 12771 |
| Welding Process |
CO₂ Shielded Metal Arc Welding (GMAW-C) — Automatic |
| Welding Wire |
ER308L / ER316L (matching base metal grade) |
| Shielding Gas |
100% CO₂ or CO₂/Ar mixtures (80% Ar + 20% CO₂) |
| Post-Weld Treatment |
Solid Solution Annealing (1050°C – 1150°C), Pickling & Passivation |
| Minimum Order Quantity |
500 kg (negotiable for long-term contracts) |
| Customization |
Coil geometry, coil pitch, end preparation, and surface finish available per customer drawings |
Manufacturing Process
Process Flow
- Raw Material Inspection: Incoming stainless steel strip or tube stock is verified for chemical composition (via optical emission spectrometry, OES) and mechanical properties in accordance with the specified ASTM/ASME/GB standards.
- Forming & Bending: Continuous coil forming is executed using CNC-controlled roll-forming machines. The bending process employs progressive die sets to achieve uniform bend radii without wall thinning, kinking, or ovalization. Coil pitch is maintained within ±0.5 mm per turn through servo-driven feed control.
- CO₂ Shielded Automatic Welding (GMAW-C): The core fabrication step involves automated CO₂ shielded metal arc welding for coil tube assembly and connection to boiler headers. Key parameters include:
- Welding Current: 120–220 A (DC+, depending on tube diameter)
- Welding Voltage: 18–24 V
- Welding Speed: 200–500 mm/min
- Wire Feed Rate: 3–8 m/min
- Shielding Gas Flow Rate: 15–20 L/min
- Weld Wire Diameter: 0.8 mm – 1.2 mm
- Weld Quality Control: Each weld joint undergoes visual inspection (VT) and, where specified, penetrant testing (PT) or eddy current testing (ECT). Radiographic testing (RT) is available for critical boiler applications per ASME Section IX.
- Post-Weld Annealing: Welded coil tubes are subjected to solid solution heat treatment at 1050°C–1150°C followed by rapid air or water quenching to dissolve precipitated chromium carbides, restore full corrosion resistance in the heat-affected zone (HAZ), and relieve residual welding stresses.
- Pickling & Passivation: Chemical pickling (using nitric-hydrofluoric acid solution) removes oxide scales and discoloration. Subsequent passivation (dilute nitric acid treatment) forms a stable chromium oxide protective film on the surface.
- Final Inspection & Packaging: Dimensional verification, surface finish assessment, and material certification are completed. Products are packaged with anti-corrosion wrapping and moisture-absorbing desiccants for shipment.
Key Welding Process Insights
The application of CO₂ shielded automatic welding for decanting machine boiler coil tubes offers distinct advantages over manual welding methods: consistent arc stability, reduced spatter through optimized shielding gas composition, high deposition rates (2.0–4.5 kg/h), and significantly lower operator fatigue. The automated process ensures uniform weld bead geometry, which is critical for maintaining the structural integrity of the coil tube under cyclic thermal loading conditions inherent in decanting machine operations. The use of low-carbon (L-grade) filler metals (ER308L/ER316L) minimizes the risk of sensitization and intergranular corrosion in the weld zone during service exposure to organic solvents and elevated temperatures.
Applications
- Decanting Machine Boilers (清蜡机锅炉): Primary application — coil tubes serve as heating elements for solvent-based wax removal processes in petroleum refining and chemical processing industries.
- Industrial Heat Exchangers: Compact coil geometries provide high heat transfer surface area for steam-water, gas-gas, and liquid-liquid heat exchange systems.
- Boiler Tube Banks: Used in industrial boiler construction where corrosion resistance and thermal cycling durability are paramount.
- Chemical Processing Equipment: Reactor coils, distillation column internals, and heat tracing systems in petrochemical and pharmaceutical plants.
- Food & Beverage Processing: Sanitary-grade coil assemblies for CIP (Clean-In-Place) compatible heating and pasteurization systems (FDA-compliant finishes available).
- Marine & Offshore Systems: Corrosion-resistant coil tubes for marine boiler systems and offshore platform heating applications.
- Power Generation: Auxiliary heating coils in power plant boiler systems and steam generator assemblies.
Quality Certifications
| Certification |
Description |
| 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 |
| ISO 45001:2018 |
Occupational Health & Safety Management System certification |
| ASME "S" Stamp |
Authorization for manufacturing sections, coils, and fittings for pressure vessels per ASME Boiler and Pressure Vessel Code (BPVC) Section II |
| NACE MR0175 / ISO 15156 |
Materials for use in H₂S-containing environments in oil and gas production (where applicable) |
| EN 10204 3.1 |
Material Test Certificate — third-party inspection and testing documentation |
| CE Marking |
Conformity with European Pressure Equipment Directive (PED 2014/68/EU) for pressure vessel components |
| GB/T 12771 |
Chinese national standard for welded stainless steel tubes for fluid transport |
Unique Selling Points
- Automated CO₂ Welding Expertise: Extensive experience in applying CO₂ shielded automatic welding specifically optimized for decanting machine boiler coil tube fabrication, ensuring superior weld quality and production efficiency.
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