Stainless Steel Coil Tube for Marine Heating Systems — Coiltube

1. Product Overview

The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered tubular product specifically designed for marine heating applications, including shipboard heating coils, heat exchangers, and thermal management systems. The product is supplied in continuous coil form, enabling efficient downstream processing such as automatic layout, bending, and installation within marine heating systems.

This product has been extensively studied and validated in the context of the Ship Heating Coil Tube Automatic Layout System Design and Development project, which demonstrated the feasibility of automated arrangement and optimization of heating coil tubes aboard vessels. The coil tube serves as a critical component in marine thermal systems, facilitating heat transfer between fluid media while maintaining structural integrity under cyclic thermal and mechanical loading conditions.

2. Material & Properties

The coil tube is fabricated from austenitic stainless steel grades conforming to international standards, with primary emphasis on corrosion resistance, thermal conductivity, and mechanical durability under marine environmental conditions.

2.1 Primary Alloy Grades

2.2 Key Mechanical and Physical Properties

Property 304L 316L 321
Tensile Strength (MPa) ≥ 485 ≥ 485 ≥ 515
Yield Strength (MPa) ≥ 205 ≥ 205 ≥ 205
Elongation (%) ≥ 40 ≥ 40 ≥ 40
Thermal Conductivity at 100°C (W/m·K) 16.3 16.3 16.3
Maximum Service Temperature (°C) 870 870 900
Density (g/cm³) 8.0 8.0 8.0

2.3 Corrosion Resistance Characteristics

3. Specifications

Parameter Specification / Range
Product Type Stainless Steel Coil Tube (Continuous Coil Form)
Outer Diameter (OD) 6.0 mm – 50.8 mm (¼" – 2")
Wall Thickness 0.5 mm – 3.0 mm
Coil Width (for flat coil) 150 mm – 1200 mm
Coil Length per Spool Up to 3000 m (customizable)
Surface Finish 2B, No. 1, BA (Bright Annealed), Pickled & Passivated
Manufacturing Method Seamless (hot-rolled / cold-finished) or Welded (welded & annealed)
Applicable Standards ASTM A213 / A269, EN 10216-5, GB/T 14976, JIS G3459
Heat Treatment Solution Annealed (1050–1150°C) + Water Quenched
Delivery Condition Coiled on wooden spools, protected with VCI (Vapor Corrosion Inhibitor) paper
Customization Custom OD, wall thickness, coil dimensions, and surface finish available

4. Manufacturing Process

The production of stainless steel coil tubes follows a rigorous multi-stage manufacturing process to ensure dimensional accuracy, metallurgical homogeneity, and surface quality suitable for marine heating applications.

4.1 Seamless Tube Production Route

  1. Slab Heating and Hot Rolling: Stainless steel slabs are heated to 1200–1300°C and hot-rolled into hollow billets using the Mannesmann (plugging mill) or piercer method.
  2. Hot Finishing: The hot-rolled tube is passed through a continuous rolling mill to achieve preliminary dimensional accuracy.
  3. Solution Annealing: Tubes are annealed at 1050–1150°C followed by rapid water quenching to dissolve carbides and restore full austenitic microstructure.
  4. Pickling and Passivation: Acid pickling (HNO₃/HF blend) removes oxide scale; passivation restores the chromium oxide passive film.
  5. Cold Drawing / Cold Rolling: Tubes are cold-worked through a series of drawing passes to achieve final OD, wall thickness, and dimensional tolerances (±0.1 mm).
  6. Intermediate Annealing: Periodic annealing during cold working to relieve accumulated residual stresses and prevent cracking.
  7. Coiling: Finished tubes are wound into coils on precision-controlled winder equipment with controlled tension to prevent deformation.

4.2 Welded Tube Production Route

  1. Strip Coiling and Slitting: Cold-rolled stainless steel strip is slit to required width.
  2. Forming: Strip is formed into a tube shape using roll-forming equipment.
  3. Longitudinal Welding: TIG (Tungsten Inert Gas) welding or Laser welding is performed under inert gas shielding (Ar or Ar/He mixture).
  4. Weld Annealing: Full solution annealing to homogenize the weld zone microstructure.
  5. Calibration and Coiling: Final sizing via calibration rolls, followed by coiling.

4.3 Quality Control at Each Stage

5. Applications

5.1 Marine Heating Systems (Primary Application)

The coil tube is a core component in shipboard heating systems, including:

5.2 Automatic Layout System Integration

As demonstrated in the Ship Heating Coil Tube Automatic Layout System Design and Development study, the coil tube's continuous form factor enables:

5.3 Additional Applications

6. Quality Certifications and Compliance

6.1 Product Certifications

6.2 Marine Classification Society Approvals

6.3 Testing and Inspection Protocols

Test Type Standard Purpose
Hydrostatic Test ASTM A213 / EN 10216-5 Verify pressure integrity and wall soundness
Eddy Current Testing ASTM A269 Detect surface and near-surface defects in seamless tubes
Corrosion Testing ASTM G48 / G59 Assess pitting and crevice corrosion resistance
Mechanical Testing ASTM A370 / EN 10002 Verify tensile strength, yield strength, and elongation
Chemical Analysis ASTM E415 / E135 Confirm alloy composition compliance
Dimensional Inspection ASTM A213 / EN 10216-5 Verify OD, wall thickness, and straightness tolerances

7. Unique Selling Points

Marine-Grade Engineering Excellence: Wenzhou Jixing Metal Materials Co., Ltd. delivers stainless steel coil tubes engineered specifically for the demanding conditions of marine heating systems, validated through the advanced automatic layout system development program.

8. Technical Notes and Recommendations