Stainless Steel Coil Tube for Resistance Heating Furnace Applications

Product Overview

The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd (Product No. 1390) is a precision-engineered tubular component designed for use in industrial resistance heating furnaces and high-temperature process environments. Coil tubes are continuous-length stainless steel tubes formed into helical or serpentine configurations to maximize heat transfer surface area within a compact furnace volume. These products serve as critical thermal exchange elements in metallurgical, petrochemical, and energy sectors where reliable operation under sustained thermal cycling is paramount.

This product line is specifically engineered to address the failure modes identified in industrial case studies, most notably the rupture of coil tubes in resistance heating furnaces — a well-documented failure mechanism involving thermal fatigue, creep deformation, oxidation spalling, and stress concentration at weld joints and bends.

Material & Properties

Coil tubes for resistance heating furnace service are fabricated from austenitic stainless steels selected for their exceptional high-temperature strength, oxidation resistance, and dimensional stability. The primary alloy grades employed include:

Key material properties for furnace-grade coil tubes include:

Specifications

Parameter Specification
Outer Diameter (OD) 12 mm – 150 mm (0.5" – 6")
Wall Thickness 0.5 mm – 8 mm (0.020" – 0.315")
Helical Coil Diameter 200 mm – 3000 mm (8" – 120")
Coil Length Custom, typically 5 m – 50 m per coil assembly
Surface Finish Pickled & Passivated (2B / No.4), Ra ≤ 0.8 μm
Welding Process Automatic Argon Arc Welding (TIG / GTAW), full-penetration butt joints
Heat Treatment Solution Annealing (1050–1150 °C) + Rapid Quench
Pressure Rating Up to 6.0 MPa (870 PSI) at operating temperature
Dimensional Tolerance OD: ±0.15 mm; Wall: ±0.10 mm; Coil diameter: ±2 mm
Applicable Standards ASTM A213 / A269 / A312; GB/T 12771; EN 10217-7
Material Grade SAE 304, 304L, 310, 310S, 321, 347 (custom grades available)

Manufacturing Process

The production of high-integrity coil tubes for resistance heating furnace applications follows a rigorous multi-stage manufacturing sequence designed to eliminate the failure mechanisms associated with coil tube rupture:

  1. Raw Material Selection & Inspection: High-purity stainless steel strips or seamless tubes are selected from certified mill sources. Incoming materials undergo spectrographic analysis (PMI), mechanical testing, and visual surface inspection to verify chemical composition and absence of defects.
  2. Coil Forming (Cold or Hot): Seamless stainless steel tubes are cold-bent or hot-formed into the required helical or serpentine geometry. Cold forming is preferred for tube diameters below 50 mm to preserve the cold-work hardening benefit; hot forming is employed for larger diameters or thicker walls to avoid residual stress concentration.
  3. Welding: Butt joints are produced using automated GTAW (Gas Tungsten Arc Welding) with 100% helium or argon shielding. Weld parameters are optimized to minimize the heat-affected zone (HAZ) width and prevent grain coarsening. Post-weld inspection includes visual examination (VT) and 100% radiographic testing (RT) or ultrasonic testing (UT) for volumetric defect detection.
  4. Solution Annealing: The formed coil assembly is subjected to solution heat treatment at 1050–1150 °C followed by rapid water quenching. This eliminates cold-work and welding residual stresses, restores full austenitic microstructure, and ensures uniform mechanical properties throughout the component.
  5. Pickling & Passivation: The annealed coil is immersed in a mixed acid bath (HNO₃ + HF) to remove oxide scale, followed by a passivation treatment to establish a protective chromium oxide surface film.
  6. Final Dimensional & Non-Destructive Testing: Completed coil tubes undergo dimensional verification, hydrostatic pressure testing (1.5× working pressure), and surface inspection to confirm compliance with all specifications.

Failure Prevention Design Features

Based on the analysis of coil tube rupture mechanisms in resistance heating furnaces, the following design and manufacturing features are incorporated to mitigate known failure modes:

Applications

Quality Certifications & Compliance

Wenzhou Jixing Metal Materials Co., Ltd maintains a comprehensive quality management system and product certification portfolio to ensure traceability and compliance with international standards:

All production batches are accompanied by full traceability documentation including chemical composition certificates, mechanical test reports, heat treatment records, and non-destructive examination reports, ensuring complete material traceability from raw steel mill to final installation.

Unique Selling Points