Stainless Steel Coil Tube — Water-Jacket Furnace Application Grade
1. Product Overview
The Stainless Steel Coil Tube (Coiltube) is a precision-engineered continuous tube product supplied in coiled form, designed specifically for use in water-jacket heating furnaces and process heat exchanger systems. Manufactured by Wenzhou Jixing Metal Materials Co., Ltd., this product addresses the critical engineering challenge of scaling (fouling) in water-jacket furnace coil tubes, a well-documented degradation mechanism that reduces thermal transfer efficiency, increases pressure drop, and shortens service life in high-temperature industrial environments.
The coil tube is formed through continuous rolling and coiling technology, producing a seamless, uniform tube that can be delivered in large-length coils to minimize welding joints and maximize system integrity. The product is engineered to withstand prolonged exposure to thermal cycling, corrosive media, and mechanical vibration inherent in furnace and heat-exchange applications.
2. Material & Properties
The coil tube is fabricated from austenitic stainless steel grades selected for superior resistance to high-temperature oxidation, intergranular corrosion, and scaling deposition. The following grades are commonly available:
- SAE 304 / AISI 304 (1.4301) — General-purpose austenitic stainless steel with excellent formability and moderate oxidation resistance up to 870 °C.
- SAE 316 / AISI 316 (1.4401) — Molybdenum-bearing grade offering enhanced resistance to pitting and crevice corrosion, ideal for environments with chlorides or acidic condensates.
- SAE 321 / AISI 321 (1.4541) — Titanium-stabilized grade with outstanding resistance to intergranular corrosion and scaling at temperatures up to 900 °C, making it particularly suitable for furnace applications.
- SAE 310S / AISI 310S (1.4845) — High-chromium, high-nickel grade providing exceptional oxidation and scaling resistance at temperatures exceeding 1100 °C.
Key Mechanical and Physical Properties (Typical — SAE 321)
- Tensile Strength (抗拉强度): ≥ 515 MPa
- Yield Strength (屈服强度): ≥ 205 MPa
- Elongation (延伸率): ≥ 40 %
- Thermal Conductivity (热导率) at 100 °C: 16.3 W/(m·K)
- Thermal Expansion Coefficient (热膨胀系数) at 20–100 °C: 17.3 × 10⁻⁶ /°C
- Maximum Continuous Service Temperature (最高连续使用温度): 900 °C
- Corrosion Resistance (耐腐蚀性): Excellent against intergranular attack, scaling, and oxidizing atmospheres
3. Specifications
| Parameter | Specification | Standard Reference |
|---|---|---|
| Tube Outer Diameter (OD) (外径) | φ 6 mm – φ 50 mm (customizable) | ASTM A213 / GB/T 14976 |
| Wall Thickness (壁厚) | 0.5 mm – 3.0 mm | ASTM A213 / GB/T 14976 |
| Coil Length (盘管长度) | 50 m – 500 m (per coil, negotiable) | Manufacturer standard |
| Coil Inner Diameter (盘管内径) | φ 300 mm – φ 1200 mm | Per customer requirement |
| Surface Finish (表面状态) | Pickled & Polished (酸洗抛光) / Annealed (退火) / Bright Annealed (光亮退火) | ASTM A478 / GB/T 14977 |
| Tolerance — OD (外径公差) | ± 0.05 mm (precision grade) | ASTM A213 |
| Tolerance — Wall Thickness (壁厚公差) | ± 10 % of nominal | ASTM A213 |
| End Condition (端部状态) | Plain end / Beveled end (平端/坡口端) | Per customer specification |
| Heat Treatment (热处理) | Solution Annealed (固溶退火), 1050–1150 °C, water quenched | ASTM A213 |
| Delivery Condition (交货状态) | Coiled (盘卷交货) | — |
4. Manufacturing Process
The coil tube is produced through a rigorous, multi-stage manufacturing workflow that ensures dimensional precision, metallurgical integrity, and surface quality:
- Raw Material Selection (原材料选择) — Ingot or wire rod material is verified for chemical composition via spectroscopic analysis (光谱分析) to ensure compliance with ASTM or GB standards.
- Hot Rolling & Seamless Tube Forming (热轧无缝管成型) — The steel is hot-rolled and pierced to form a seamless tube blank, eliminating weld seams and ensuring uniform microstructure throughout the cross-section.
- Cold Drawing / Cold Reduction (冷拔/冷轧) — The tube blank undergoes cold working to achieve precise dimensions, enhanced mechanical properties, and improved surface finish.
- Intermediate Annealing (中间退火) — Periodic annealing cycles are performed during cold working to relieve residual stresses and restore ductility, preventing cracking and deformation.
- Final Solution Annealing (最终固溶退火) — The tube is heated to 1050–1150 °C and rapidly water-quenched to dissolve carbides in solution, achieving the desired austenitic microstructure with maximum corrosion and scaling resistance.
- Pickling & Passivation (酸洗钝化) — The surface is cleaned of scale and oxidation products via acid pickling, followed by passivation to form a protective chromium oxide layer.
- Continuous Coiling (连续盘卷) — The finished tube is wound into coils of specified inner diameter and length using precision coiling machinery with tension control to prevent deformation.
- Quality Inspection & Packaging (质量检验与包装) — Each coil undergoes dimensional measurement, hydrostatic testing (水压试验), surface inspection, and chemical verification before protective packaging and shipment.
5. Applications
The Stainless Steel Coil Tube is engineered for demanding industrial applications where thermal efficiency, corrosion resistance, and scaling resistance are paramount:
- Water-Jacket Heating Furnaces (水套加热炉) — Primary application; the coil tube forms the heating element within the furnace water jacket, transferring heat to the process medium while resisting scale buildup on both the inner (water side) and outer (furnace side) surfaces.
- Industrial Heat Exchangers (工业换热器) — Used in shell-and-tube and plate-fin heat exchanger assemblies for chemical, petrochemical, and pharmaceutical processing.
- Boiler & Steam Generation Systems (锅炉与蒸汽发生系统) — Suitable for low-to-medium pressure steam systems requiring corrosion-resistant tubing.
- Chemical Processing & Reactor Cooling (化工处理与反应器冷却) — Resistant to aggressive chemical media and high-temperature operation.
- Food & Beverage Processing (食品加工) — Hygienic-grade finishes meet sanitary requirements for food-grade heat transfer equipment.
- Pharmaceutical Manufacturing (制药生产) — GMP-compliant surface quality for pharmaceutical process heating and sterilization systems.
6. Quality Certifications
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system ensuring product conformity with international and domestic 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
- ASTM A213 — Specification for seamless austenitic stainless steel boiler, superheater, and heat exchanger tubes
- GB/T 14976 — Chinese national standard for seamless stainless steel tubes for fluid transport
- GB/T 14977 — Chinese national standard for seamless stainless steel tubes for heat exchange and general use
- EN 10216-5 — European standard for seamless stainless steel tubes for heat exchangers
- Mill Test Certificate (MTC / 材质证明书) — Provided with each shipment, documenting chemical composition, mechanical properties, and heat treatment records
7. Unique Selling Points
Scaling-Resistant Design for Furnace Applications — The product is specifically engineered with metallurgical controls (titanium stabilization in 321 grade, high Cr/Ni content in 310S grade) to mitigate the scaling deposition mechanisms identified in water-jacket furnace coil tube degradation studies. This reduces maintenance intervals, extends service life, and improves overall thermal efficiency.
- Seamless Construction — Eliminates weld-induced weak points and corrosion initiation sites, ensuring uniform performance throughout the tube length.
- Continuous Coil Delivery — Minimizes the number of field welds required during installation, reducing leak risk and improving system reliability.
- Customizable Dimensions — Flexible manufacturing capability accommodates a wide range of OD, wall thickness, and coil configuration requirements.
- Multi-Grade Availability — Grade selection tailored to specific temperature, corrosion, and mechanical requirements of the application.
- Full Traceability — Each coil is traceable to its heat number, with complete documentation of raw material origin, processing parameters, and test results.
8. Technical Advisory Note
Based on engineering analysis of scaling mechanisms in water-jacket furnace coil tubes (水套加热炉盘管结垢解析), it is recommended that users implement the following operational practices to maximize service life:
- Maintain water quality parameters (pH 8.5–10.5, low dissolved oxygen, controlled hardness) on the coolant side to minimize mineral scale deposition.
- Ensure adequate coolant flow velocity (> 1 m/s) to prevent laminar boundary layer thickening and scale nucleation.
- Implement periodic chemical cleaning and passivation of the inner tube surface according to manufacturer guidelines.
- Monitor tube wall temperature differentials to detect incipient scale formation before significant thermal resistance develops.
- Select SAE 321 or SAE 310S grades for furnace-side temperatures exceeding 800 °C to maximize oxidation and scaling resistance.