Stainless Steel Coil Tube for Induction Secondary Cooling Systems
Product Overview
The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered coiled piping solution specifically designed for secondary cooling applications in induction heating and metalworking systems. This product series (Item No. 1661) addresses the critical engineering challenge of maintaining consistent cooling performance under variable flow rate conditions — a well-documented relationship between flow rate fluctuation and cooling capacity degradation in induction secondary cooling coil tubes.
These coil tubes serve as the primary heat exchange medium in secondary cooling zones, where controlled thermal management is essential to achieving desired metallurgical properties in continuously cast or formed metal products. The coil geometry provides maximum heat transfer surface area within a compact footprint, making it ideal for integration into space-constrained production lines.
Material & Properties
The coil tubes are fabricated from high-grade austenitic stainless steels selected for their superior combination of corrosion resistance, thermal conductivity, mechanical strength, and dimensional stability under repeated thermal cycling.
Available Grades
- ASTM A213 TP304 (UNS S30400) — General-purpose austenitic stainless steel offering excellent formability and weldability
- ASTM A213 TP316L (UNS S31603) — Enhanced corrosion resistance with molybdenum addition, suitable for aggressive cooling media
- ASTM A213 TP321 (UNS S32100) — Titanium-stabilized grade providing superior resistance to intergranular corrosion at elevated temperatures
- ASTM A213 TP310S (UNS S31008) — High-temperature grade for extreme thermal environments
Key Material Properties
- Thermal conductivity: 14–16 W/(m·K) at 20°C
- Operating temperature range: −196°C to +870°C (grade-dependent)
- Corrosion resistance: Excellent against atmospheric, aqueous, and mild chemical environments
- Mechanical strength: Yield strength ≥ 205 MPa (304 grade, annealed condition)
- Thermal cycling endurance: > 10,000 cycles without cracking or significant deformation
Specifications
| Parameter | Specification | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | 8 mm – 51 mm (custom sizes available) | ASTM A213 / ASME B36.19M |
| Wall Thickness | 0.8 mm – 4.0 mm | ASTM A213 |
| Bend Radius (Minimum) | 3D (3× outer diameter) | ASME B31.3 |
| Coil Length | 5 m – 100 m (configurable) | — |
| Surface Finish | Mirror polish (Ra ≤ 0.4 μm), Pickled & Passivated (Ra ≤ 1.6 μm), or Mill finish | ASTM A403 / ASTM A967 |
| Maximum Operating Pressure | Up to 1.6 MPa (design-dependent) | ASME B31.3 |
| Flow Rate Range | 0.5 – 50 L/min (per coil assembly) | — |
| Cooling Capacity | Proportional to flow rate; optimized for stable ΔT under ±20% flow variation | — |
| Tolerance on OD | ±0.15 mm (precision grade); ±0.30 mm (standard grade) | ASTM A213 |
| Tolerance on Wall Thickness | ±10% (standard); ±5% (precision grade) | ASTM A213 |
| End Preparation | Plain end, beveled, threaded (G/NPT), or flanged | ASME B31.3 |
| Coil Diameter | 150 mm – 1,500 mm (custom) | — |
Manufacturing Process
The production of these coil tubes follows a rigorously controlled multi-stage manufacturing process to ensure dimensional accuracy, mechanical integrity, and surface quality:
- Raw Material Selection & Incoming Inspection: Only certified stainless steel tubes from approved mills are used. Incoming material undergoes spectroscopic analysis (PMI), dimensional verification, and visual inspection per ASTM E162 and ASTM A213 requirements.
- Coil Straightening & Cutting: Tubes are straightened to within ±0.5 mm/m and cut to precise lengths using CNC-controlled cutting systems to minimize burr and deformation.
- Coil Forming (Bending): CNC-controlled coil bending machines form the tubes into precise spiral or helical geometries. The bending process employs mandrel-assisted forming to prevent ovalization and wrinkling, maintaining wall thickness uniformity throughout the bend radius.
- Welding (where applicable): Multi-pass orbital TIG welding (GTAW) is performed for joint fabrication, with full radiographic inspection (RT) or dye penetrant testing (PT) per ASME Section IX.
- Solution Annealing: Coils are solution-annealed at 1,050–1,150°C followed by rapid water quenching to achieve the desired austenitic microstructure and maximum corrosion resistance.
- Pickling & Passivation: Surface treatment involves acid pickling (HNO₃/HF mixture) followed by passivation per ASTM A967 to remove scale, restore corrosion resistance, and form a stable chromium oxide layer.
- Precision Machining & Surface Finishing: End preparation, threading, and polishing are performed to meet specified tolerances and surface finish requirements.
- Final Inspection & Testing: Includes hydrostatic pressure testing (per ASTM A213), dimensional verification, surface roughness measurement, and non-destructive testing (NDT).
Applications
These stainless steel coil tubes are engineered for demanding thermal management applications, with primary deployment in the following industrial sectors:
- Induction Heating Systems: Secondary cooling coils for induction furnaces, induction hardening equipment, and induction brazing systems where precise temperature control is critical.
- Continuous Casting Machines: Secondary cooling zone coils in continuous casting lines for steel, copper, and aluminum production, where the relationship between coolant flow rate and cooling intensity directly impacts product quality.
- Hot Rolling Mills: Coils for downstream cooling and controlled cooling systems in hot strip and wire rod mills.
- Petrochemical & Process Industries: Heat exchanger coils, condensers, and evaporator tubes in corrosive process environments.
- Food & Pharmaceutical Processing: Sanitary-grade coil heat exchangers requiring hygienic design and material compliance.
- Power Generation: Condenser tubes and heat recovery coils in thermal power plants.
Key Engineering Insight: Flow Rate vs. Cooling Capacity
Based on extensive study of the relationship between flow rate variation and cooling capacity change in induction secondary cooling coil tubes, the coil geometry, tube diameter, and wall thickness of this product series are specifically optimized to minimize cooling capacity fluctuation under variable flow conditions. This design philosophy ensures that even when flow rates vary by ±20%, the cooling intensity remains within acceptable limits, preventing thermal gradients that could compromise product metallurgical quality. The coil pitch, tube diameter, and number of turns are calculated to achieve a near-linear cooling capacity vs. flow rate relationship within the specified operating range.
Quality Certifications
Wenzhou Jixing Metal Materials Co., Ltd. maintains comprehensive quality management and product certification frameworks:
- ISO 9001:2015 — Quality Management System certification ensuring consistent product quality and process control
- ISO 14001:2015 — Environmental Management System certification
- ISO 45001:2018 — Occupational Health and Safety Management System
- EN 10204 3.1 — Material Test Reports per European standard, providing full traceability of material origin, heat treatment, and test results
- CE Marking — Conformity with European Union directives for pressure equipment and machinery
- Material Traceability: Each coil tube batch is accompanied by a Material Test Certificate (MTC) including chemical composition, mechanical properties, and heat treatment records
- NDT Capabilities: In-house radiographic testing (RT), ultrasonic testing (UT), and magnetic particle inspection (MT) facilities
Unique Selling Points
- Flow-Optimized Design: Coil geometry specifically engineered to maintain stable cooling performance under variable flow conditions — a critical advantage for induction secondary cooling applications.
- Custom Configuration: Full customization of coil diameter, pitch, tube dimensions, and end preparations to match specific equipment integration requirements.
- Multi-Grade Availability: Four premium stainless steel grades covering general-purpose to extreme-temperature and corrosion-resistant applications.
- Precision Manufacturing: CNC-controlled coil forming with mandrel assistance ensures dimensional accuracy and eliminates deformation-related flow restrictions.
- Complete Traceability: From raw material mill certification through final inspection, full material traceability is maintained per EN 10204 3.1.
- Engineering Support: Technical team provides flow rate analysis, thermal simulation, and coil layout design support for optimal system integration.
Technical Support & Compliance
All products comply with applicable international standards including ASTM A213, ASME B31.3, EN 10217, and GB/T 14976. Wenzhou Jixing Metal Materials Co., Ltd. provides comprehensive technical documentation, including P&ID integration drawings, flow rate performance curves, and thermal performance data sheets upon request. Engineering consultation is available for system-level optimization of induction secondary cooling configurations.