Stainless Steel Coil Tube — Waste Heat Recovery Riser Pipe System
1. Product Overview
The Stainless Steel Coil Tube (Coiltube) is a precision-engineered tubular product manufactured by Wenzhou Jixing Metal Materials Co., Ltd (Product No. 536). This product category encompasses continuous-length stainless steel tubes formed into compact coil configurations, specifically designed for high-temperature heat exchange and waste heat recovery applications. The coil tube format offers significant advantages in terms of spatial efficiency, thermal performance, and installation flexibility compared to traditional straight-pipe heat exchanger assemblies.
Informed by field-proven deployment in the coil-type riser pipe waste heat recovery system at Liuzhou Steel (LiuGang), this product line has demonstrated exceptional reliability in capturing and recovering thermal energy from high-temperature industrial off-gases, flue gases, and exhaust streams in integrated steelmaking and metallurgical environments. The system achieves meaningful energy recovery rates while reducing overall plant energy consumption and carbon emissions.
2. Material & Properties
2.1 Base Material Grades
The coil tube is fabricated from austenitic stainless steel grades selected for superior resistance to thermal cycling, oxidation, and corrosion under high-temperature service conditions. Commonly specified grades include:
- SAE 304 (UNS S30408) — General-purpose austenitic stainless steel with excellent corrosion resistance and formability
- SAE 304L (UNS S30403) — Low-carbon variant with enhanced resistance to sensitization during welding
- SAE 316L (UNS S31603) — Molybdenum-bearing grade offering superior resistance to pitting and crevice corrosion
- SAE 321 (UNS S32100) — Titanium-stabilized grade with excellent high-temperature oxidation resistance
- SAE 310S (UNS S31008) — High-temperature grade suitable for sustained service above 1100°C
2.2 Key Mechanical Properties (at Room Temperature)
| Property | SAE 304 | SAE 316L | SAE 321 | SAE 310S |
|---|---|---|---|---|
| Tensile Strength (MPa, min.) | 515 | 485 | 515 | 515 |
| Yield Strength (MPa, 0.2% offset, min.) | 205 | 170 | 205 | 205 |
| Elongation (% min., 50 mm gauge) | 40 | 45 | 40 | 40 |
| Density (g/cm³) | 8.00 | 8.03 | 8.00 | 8.00 |
| Thermal Conductivity at 100°C (W/m·K) | 16.3 | 14.6 | 16.3 | 14.6 |
| Maximum Continuous Service Temperature (°C) | 870 | 870 | 925 | 1150 |
2.3 Chemical Composition (Typical, wt%)
| Element | SAE 304 | SAE 316L | SAE 321 | SAE 310S |
|---|---|---|---|---|
| C (Carbon, max.) | 0.08 | 0.03 | 0.08 | 0.08 |
| Cr (Chromium) | 18.0–20.0 | 16.5–18.5 | 17.5–18.5 | 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−0.02) to 0.70 | — |
| N (Nitrogen) | ≤0.10 | ≤0.10 | ≤0.10 | ≤0.10 |
3. Specifications
| Parameter | Specification / Range |
|---|---|
| Product No. | 536 |
| Product Name | Stainless Steel Coil Tube (Coiltube) |
| Manufacturer | Wenzhou Jixing Metal Materials Co., Ltd |
| Outer Diameter (OD) | Φ6 mm – Φ114.3 mm (¼" – 4½") |
| Wall Thickness | 0.3 mm – 6.0 mm |
| Coil Length | 10 m – 300 m (continuous, depending on OD and wall thickness) |
| Coil Inner Diameter | 300 mm – 1,200 mm (configurable per application) |
| Manufacturing Process | Seamless (Seamless Tube) or Welded (Fusion Welded / Laser Welded) |
| Surface Finish | Mirror Polished (Ra ≤ 0.4 μm), Electropolished, Pickled & Passivated, or 2B Cold-Rolled |
| Tolerance on OD | ±0.05 mm (precision grades); ±0.1 mm (standard grades) |
| Tolerance on Wall Thickness | ±0.03 mm (precision grades); ±0.05 mm (standard grades) |
| Operating Temperature Range | −196°C to +1,150°C (grade-dependent) |
| Maximum Operating Pressure | Up to 32 MPa (PN 320) at room temperature |
| Applicable Standards | ASTM A213, ASTM A269, ASME SA-213, EN 10216-5, GB/T 12771, GB/T 14976 |
| Packaging | Wooden pallet with moisture-proof wrapping; custom export packaging available |
4. Manufacturing Process
The production of stainless steel coil tubes involves a rigorous multi-stage manufacturing sequence to ensure dimensional accuracy, metallurgical integrity, and long-term service reliability:
- Raw Material Selection and Inspection — Certified stainless steel billets or strip are sourced from approved suppliers. Incoming materials undergo spectroscopic analysis (OES) for chemical composition verification and mechanical testing for conforming properties.
- Tube Forming — For seamless production, hot-rolled or cold-drawn seamless tubes are produced via the Mannesmann piercing or capstan methods. For welded production, precision cold-rolled stainless steel strip is formed into a tubular shape and fusion-welded (GMAW or laser welding) to produce a longitudinal seam.
- Heat Treatment (Solution Annealing) — Tubes are solution-annealed at 1050°C–1150°C followed by rapid quenching to dissolve carbide precipitates and restore full austenitic structure, ensuring maximum corrosion resistance and ductility.
- Precision Sizing and Cold Drawing — Tubes undergo cold drawing or cold rolling to achieve final dimensions within specified tolerances. This process enhances mechanical properties and surface finish.
- Surface Treatment — Tubes are subjected to pickling (acid cleaning) and passivation (chromic or citric acid treatment) to remove surface scale and form a protective chromium oxide layer. Electropolishing or mechanical polishing is applied as specified.
- Coiling — The finished tube is wound onto a precision coil former to produce the final coil configuration. Tension control systems ensure uniform winding without deformation or kinking.
- Quality Inspection and Testing — Comprehensive testing includes hydrostatic pressure testing, eddy current flaw detection, dimensional measurement, surface inspection, and (where applicable) hardness testing and chemical analysis.
5. Applications
The stainless steel coil tube finds extensive application across multiple industrial sectors, with particular emphasis on energy recovery and heat exchange systems:
5.1 Waste Heat Recovery Systems
As demonstrated in the coil-type riser pipe waste heat recovery system deployed at Liuzhou Steel, coil tubes serve as the core heat exchange element for recovering thermal energy from high-temperature industrial exhaust gases. The compact coil geometry maximizes heat transfer area per unit volume, enabling efficient recovery of waste heat from:
- Steel mill blast furnace gas (BFG) and basic oxygen furnace gas (BOFG)
- Coke oven waste gas streams
- Industrial furnace exhaust and off-gas systems
- Steam generation from waste heat
5.2 Additional Applications
- Heat Exchangers and Condensers — Shell-and-tube, plate-fin, and spiral heat exchangers in chemical, petrochemical, and power generation industries
- Food and Pharmaceutical Processing — Hygienic-grade tubing for pasteurization, sterilization, and process fluid handling
- Automotive Industry — Exhaust system components, turbocharger piping, and fuel delivery lines
- Oil and Gas — Downhole tubing, wellhead equipment, and process piping in offshore and onshore facilities
- Medical Equipment — Endoscopes, surgical instruments, and diagnostic equipment tubing
- Building and Construction — Architectural railings, handrails, decorative elements, and structural supports
- Hydropower and Marine Engineering — Condenser tubes, seawater piping, and desalination plant components
6. Quality Certifications and Compliance
Wenzhou Jixing Metal Materials Co., Ltd maintains a comprehensive quality management framework to ensure product conformity with international standards:
- ISO 9001:2015 — Quality Management System certification ensuring consistent product quality and process control
- ISO 14001:2015 — Environmental Management System certification demonstrating environmental responsibility
- ISO 45001:2018 — Occupational Health and Safety Management System certification
- CE Marking — Conformity with European Union health, safety, and environmental protection standards
- EN 10204 3.1 Material Test Certificates — Full material certification with independent third-party verification
- ASTM / ASME Compliance — Products manufactured and tested in accordance with applicable American standards
- GB/T National Standards — Conformity with Chinese national standards for stainless steel tubes
Unique Selling Points: The coil tube format from Wenzhou Jixing Metal Materials offers a compelling combination of compact spatial footprint, high thermal exchange efficiency, corrosion-resistant austenitic stainless steel construction, and proven field performance in demanding metallurgical waste heat recovery applications. The product's continuous coil configuration eliminates the need for extensive field welding and assembly, reducing installation time and potential failure points. Combined with the company's rigorous quality control protocols and multi-standard compliance, this coil tube product represents a reliable and cost-effective solution for industrial heat recovery and heat exchange applications.