Stainless Steel Coil Tube for Water-Jacketed Furnace Applications — Wenzhou Jixing Metal Materials Co., Ltd

1. Product Overview

The Stainless Steel Coil Tube (Product No. 539) manufactured by Wenzhou Jixing Metal Materials Co., Ltd is a precision-engineered continuous coil tubing specifically designed for use in Water-Jacketed Furnaces (WJF) within upstream oil and gas processing facilities. These coil tubes serve as critical heat-exchange components within the water-jacketed furnace system, where they facilitate the controlled heating of hydrocarbon process streams through indirect heat transfer via a circulating water jacket. The design philosophy centers on ensuring long-term metallurgical integrity under cyclic thermal loading, corrosive process environments, and sustained mechanical stress conditions typical of oilfield applications such as those documented in the Tahe Oilfield Water-Jacketed Furnace Coil Tube Corrosion and Protective Measures technical study.

Unlike conventional straight pipe sections, coil tubes are supplied in continuous helical or spiral-coiled configurations, enabling seamless integration into furnace designs that require serpentine flow paths for optimal thermal efficiency and space utilization. The coil geometry inherently accommodates thermal expansion through elastic deformation, reducing the need for expansion joints and minimizing mechanical fatigue failure points.

2. Material & Properties

2.1 Base Alloy Grades

The coil tubes are manufactured from high-performance austenitic stainless steel grades selected for their exceptional resistance to sulfidation, chloride-induced stress corrosion cracking (SCC), and high-temperature oxidation. The primary material specifications include:

2.2 Mechanical Properties (Typical Values at Room Temperature)

Property ASTM A213 TP304/304L ASTM A213 TP316/316L ASTM A213 TP321 ASTM A213 TP347
Tensile Strength (MPa) ≥ 515 ≥ 515 ≥ 515 ≥ 515
Yield Strength (0.2% Offset, MPa) ≥ 205 ≥ 205 ≥ 205 ≥ 205
Elongation (% in 50 mm) ≥ 40 ≥ 40 ≥ 40 ≥ 40
Modulus of Elasticity (GPa) ~193 ~193 ~193 ~193
Thermal Conductivity at 100°C (W/m·K) 16.3 14.6 16.3 16.3
Linear Thermal Expansion 20–100°C (×10⁻⁶/K) 17.3 16.0 17.3 17.3
Density (g/cm³) 8.00 8.03 8.00 8.00
Maximum Service Temperature (°C) 870 870 870 870

2.3 Chemical Composition (wt%)

Grade C Mn S P Cr Ni Mo Ti Nb N
304/304L ≤0.08 / ≤0.03 ≤2.00 ≤0.03 ≤0.045 18.0–20.0 8.0–10.5 — — — ≤0.10
316/316L ≤0.08 / ≤0.03 ≤2.00 ≤0.03 ≤0.045 16.0–18.0 10.0–14.0 2.00–3.00 — — ≤0.10
321 ≤0.08 ≤2.00 ≤0.03 ≤0.045 17.0–19.0 9.0–12.0 — 5×C–7.00 — ≤0.10
347 ≤0.08 ≤2.00 ≤0.03 ≤0.045 17.0–19.0 9.0–12.0 — — 10×C–1.00 ≤0.10

3. Specifications

3.1 Dimensional Specifications

Parameter Specification Range Standard Reference
Outer Diameter (OD) Φ14 mm – Φ108 mm (Φ1/2" – Φ4") ASTM A213 / GB/T 14976
Wall Thickness (WT) 0.50 mm – 6.00 mm ASTM A213 / GB/T 14976
Coil Winding Diameter Φ300 mm – Φ2,000 mm (adjustable) Manufacturer Specification
Coil Length (Continuous) Up to 500 m per coil (continuous production) —
OD Tolerance ±0.5% (OD ≤ 25 mm); ±0.75% (OD > 25 mm) ASTM A213
WT Tolerance ±10% ASTM A213
Min. Bend Radius 3D (D = Outer Diameter) ASME B31.3
Surface Finish Pickled & Passivated (Ra ≤ 0.8 μm); optional polished finish ASTM A328 / GB/T 13912
Delivery Condition Hot-Finished, Cold-Finished, or Annealed & Pickled ASTM A213
End Condition Plain end, beveled end, or threaded (upon request) —

3.2 Applicable Standards & Codes

4. Manufacturing Process

4.1 Production Workflow

The manufacturing process for stainless steel coil tubes follows a rigorous multi-stage workflow designed to ensure dimensional accuracy, metallurgical homogeneity, and corrosion resistance:

  1. Raw Material Selection & Inspection: Ingot or continuous casting billet sourced from certified mills (e.g., Outokumpu, POSCO, Taiyuan Iron & Steel). Each heat undergoes spectroscopic analysis (OES) to verify chemical composition within specification limits. Heat number traceability is maintained throughout production.
  2. Hot Rolling: Billets are reheated to 1,150–1,250°C and hot-rolled through multi-stand mills to produce seamless tubes (via Mannesmann piercing or plug-rolling methods) or welded tubes (via ERW or TIG welding). Hot-rolled coil stock is also available for cold-worked applications.
  3. Hot Coil Coiling: The hot-rolled tube is coiled onto a cooling spiral mill while maintaining controlled cooling rates (≤50°C/min) to prevent grain coarsening and minimize residual stress. Coiling diameter is selected based on downstream cold-forming requirements.
  4. Heat Treatment (Annealing): Tubes are solution-annealed at 1,050–1,150°C followed by controlled water quenching to dissolve carbide precipitates, restore full austenitic microstructure, and achieve maximum corrosion resistance and ductility. For stabilized grades (321, 347), precipitation annealing may be applied at 850–870°C.
  5. Cold Drawing / Cold Rolling: Tubes are drawn through calibrated tungsten carbide (WC) or polymer-lined dies to achieve precise OD and WT tolerances. Cold working introduces beneficial strain-hardening (dislocation density increase) while maintaining sufficient ductility for subsequent forming operations.
  6. Intermediate Annealing: If total cold-work reduction exceeds 15%, intermediate annealing at 1,050°C is performed to prevent cracking and maintain formability.
  7. Coil Winding (Precision Coiling): Tubes are wound into specified coil configurations using CNC-controlled coiling machines with servo-driven tension control. The coiling process ensures uniform curvature, prevents kinking, and maintains consistent bend radius throughout the coil length.
  8. Pickling & Passivation: Tubes undergo acid pickling (HNO₃/HF mixture) to remove mill scale, oxide layers, and surface contamination. Passivation treatment (HNO₃ or citric acid) establishes a stable chromium oxide (Cr₂O₃) passive film (10–20 nm thickness) critical