Stainless Steel Heating Furnace Coil Tube (Coil Tube)
Product Overview
The Stainless Steel Heating Furnace Coil Tube (盘管 Coiltube), manufactured by Wenzhou Jixing Metal Materials Co., Ltd., is a high-performance tubular product engineered specifically for continuous heating furnace systems in the metallurgical and materials processing industries. Designed in a coiled configuration to maximize heat transfer surface area within a compact footprint, these coil tubes serve as critical thermal exchange elements in reheating furnaces, annealing furnaces, and other high-temperature industrial processes.
The product is distinguished by its exceptional resistance to scaling, corrosion, and thermal fatigue, enabling extended service intervals and reliable performance under the demanding conditions of industrial furnace environments. The coil tube design facilitates efficient radiant and convective heat transfer, making it indispensable in continuous production lines where thermal uniformity and process consistency are paramount.
Material & Properties
The coil tubes are fabricated from austenitic stainless steel grades selected for their superior high-temperature oxidation resistance, thermal stability, and mechanical integrity. The following table summarizes the key material properties:
| Property | Specification |
|---|---|
| Material Grades | SUS310S, SUS309S, SUS321, TP310H, TP309H, TP347H (ASTM A213/A269) |
| Outer Diameter (OD) | 25 mm – 114 mm (customizable) |
| Wall Thickness | 1.0 mm – 8.0 mm |
| Maximum Service Temperature | 1000 °C – 1200 °C (depending on grade) |
| Chromium (Cr) Content | ≥ 22% – 27% (by mass) |
| Nickel (Ni) Content | ≥ 19% – 25% (by mass) |
| Thermal Conductivity | 20 – 30 W/(m·K) at 1000 °C |
| Thermal Expansion Coefficient | 16 – 19 × 10⁻⁶ /°C (20–1000 °C) |
| Tensile Strength (at 1000 °C) | ≥ 150 MPa (depending on grade) |
| Scaling Resistance | Excellent; forms stable Cr₂O₃ protective oxide layer |
| Surface Finish | Mill finish or polished (Ra ≤ 0.8 μm available) |
Specifications
| Parameter | Specification |
|---|---|
| Product Category | Coil Tube (盘管) for Heating Furnace Applications |
| Coil Diameter | 300 mm – 2000 mm (configurable per furnace design) |
| Coil Length per Spool | 50 m – 200 m |
| Tube Forming Process | Hot-rolled or cold-drawn seamless tube, cold-formed coil |
| Welding Method | TIG (Tungsten Inert Gas) welding; seam weld or butt weld |
| End Preparation | Beveled ends for flange or socket-weld connection |
| Heat Treatment | Solution annealed (1050–1150 °C, water/quench cooled) |
| Coating/Passivation | Acid pickling and passivation; optional anti-scale coating |
| Standards Compliance | ASTM A213, ASTM A269, GB/T 12770, EN 10216-5 |
| Packaging | Wooden crate or steel drum with moisture-proof wrapping |
Manufacturing Process
The production of high-quality stainless steel coil tubes for heating furnace applications follows a rigorous multi-stage manufacturing workflow:
- Raw Material Selection: High-purity stainless steel ingots or slabs conforming to ASTM A213/A269 specifications are selected, with strict control over sulfur (S ≤ 0.03%), phosphorus (P ≤ 0.045%), and other impurity elements to ensure hot-workability and long-term oxidation resistance.
- Seamless Tube Production: Tubes are manufactured via hot-rolling (plug piercing) or cold-drawing processes to achieve precise dimensional tolerances and uniform wall thickness. The seamless construction eliminates weld-induced weak points that would compromise structural integrity at elevated temperatures.
- Solution Annealing: Tubes undergo solution heat treatment at temperatures between 1050 °C and 1150 °C, followed by controlled cooling, to dissolve carbides and restore full austenitic microstructure, ensuring optimal corrosion and scaling resistance.
- Pickling and Passivation: The tube surface is treated with nitric acid or citric acid solutions to remove oxide scale and form a thin, protective chromium oxide passive film, enhancing initial resistance to scaling accumulation.
- Coil Forming: The straight tubes are cold-bent into the required coil geometry using CNC-controlled bending machinery. The forming radius is carefully controlled to prevent wall thinning, ovality distortion, or residual stress concentrations that could lead to premature fatigue failure.
- Welding and Assembly: Coil tube segments are joined using TIG welding with matching filler metal (e.g., ER310 for TP310H tubes). Welds are inspected via radiographic testing (RT) or ultrasonic testing (UT) to ensure full penetration and absence of defects.
- Final Inspection: Each coil tube assembly undergoes dimensional verification, hydrostatic pressure testing (typically 1.5× working pressure), and surface quality assessment before shipment.
Applications
Stainless steel heating furnace coil tubes are deployed across a wide range of industrial thermal processing applications:
- Steel Reheating Furnaces: Coil tubes serve as radiant tube heating elements in continuous reheating furnaces for hot rolling mills, providing uniform heating of slabs and billets to rolling temperature (1050–1250 °C).
- Annealing and Normalizing Furnaces: Used in batch and continuous annealing furnaces for stainless steel strip, wire rod, and bar products requiring controlled thermal cycles.
- Heat Treatment Furnaces: Applied in quench-and-temper, tempering, and stress-relief furnaces for alloy steels and superalloys.
- Gas Fired Radiant Tubes: Function as gas combustion chambers in regenerative and recuperative burner systems, where the coil tube encloses the flame path and radiates heat to the process charge.
- Aluminum and Non-Ferrous Metal Processing: Employed in solution heat treatment and aging furnaces for aluminum alloys, copper alloys, and titanium products.
- Chemical Process Heating: Used in high-temperature process heaters and thermal oxidizers in petrochemical and chemical manufacturing plants.
Chemical Descaling and Maintenance — Technical Considerations
A critical operational aspect of heating furnace coil tubes is the management of scale formation during prolonged service. Scale buildup — composed primarily of iron oxides (FeO, Fe₂O₃, Fe₃O₄) and silicate compounds — degrades heat transfer efficiency and accelerates tube wall thinning. Wenzhou Jixing Metal Materials Co., Ltd. provides technical guidance on the Chemical Descaling (化学除垢) process for coil tubes, including:
- Acid-Based Descaling: Utilization of hydrochloric acid (HCl, 5–10%), sulfuric acid (H₂SO₄, 3–8%), or organic acid blends (citric acid, oxalic acid) to dissolve oxide scale deposits. The concentration, temperature (50–80 °C), and immersion time are precisely controlled to avoid base metal attack.
- Field Quantitative Evaluation Method: A systematic approach to evaluate descaling effectiveness through pre- and post-treatment measurements of scale thickness (via magnetic thickness gauge or ultrasonic testing), surface roughness (Ra), and heat transfer coefficient recovery. This method enables objective assessment of cleaning performance and optimization of descaling parameters.
- Post-Descaling Passivation: Following scale removal, the tube surface is re-passivated using dilute nitric acid (HNO₃, 10–20%) or hydrogen peroxide solutions to regenerate the protective Cr₂O₃ film and restore corrosion resistance.
- Preventive Coatings: Application of diffusion coatings (e.g., aluminized coatings via pack cementation or fluidized bed processes) to extend scale-free service intervals by 2–3× compared to uncoated tubes.
Quality Certifications
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system and holds the following certifications and complies with the following standards:
- ISO 9001:2015 — Quality Management System Certification
- ISO 14001:2015 — Environmental Management System Certification
- ISO 45001:2018 — Occupational Health and Safety Management System Certification
- EN 10204 3.1 — Third-party inspection and material certification
- ASTM A213 / A269 — Seamless austenitic stainless steel tube specifications
- GB/T 12770 — Chinese national standard for seamless stainless steel tubes
- PEI (Petroleum Equipment Institute) — API 5CT-equivalent testing for high-temperature applications (where applicable)
Each production batch is accompanied by a Mill Test Certificate (MTC) documenting chemical composition, mechanical properties, heat treatment records, and non-destructive testing (NDT) results. Third-party inspection by organizations such as SGS, Bureau Veritas, or TÜV is available upon customer request.
Unique Selling Points
- Extended Service Life: Optimized alloy chemistry and microstructure engineering deliver 30–50% longer furnace campaign intervals compared to conventional stainless steel coil tubes, reducing unplanned downtime and maintenance costs.
- Custom Coil Geometry: Flexible manufacturing capability allows tailoring of coil diameter, pitch, tube OD, and wall thickness to match specific furnace configurations and thermal design requirements.
- Integrated Descaling Technical Support: Unlike standard tube suppliers, Wenzhou Jixing provides end-to-end technical support including descaling protocol development, field evaluation methodology, and preventive coating solutions — minimizing total cost of ownership (TCO).
- Full Traceability: From raw material heat number through final coil assembly, complete traceability is maintained, enabling root-cause analysis and quality assurance at every stage.
- Proven Performance in Continuous Production: The coil tube products have been validated in continuous reheating furnace operations exceeding 50,000 hours of cumulative service, demonstrating reliability in the most demanding industrial environments.
Conclusion
The Stainless Steel Heating Furnace Coil Tube from Wenzhou Jixing Metal Materials Co., Ltd. represents a state-of-the-art thermal component solution for metallurgical and materials processing industries. By combining premium material selection, precision manufacturing, and comprehensive after-sales technical support — including scientifically grounded chemical descaling and field evaluation methodologies — the product delivers superior thermal efficiency, operational reliability, and economic value throughout its service lifecycle.