Stainless Steel Coil Tube (Coiltube) — Half-Coil Manufacturing Technology

1. Product Overview

The Stainless Steel Coil Tube (hereinafter referred to as "Coiltube") is a precision-engineered tubular product supplied in a continuous coiled configuration, designed for ease of downstream forming, cutting, and installation. Manufactured by Wenzhou Jixing Metal Materials Co., Ltd., this product line encompasses both full coil tubes and half-coil tubes, the latter representing an advanced manufacturing variant that addresses specific geometric and logistical challenges in industrial applications. The half-coil tube manufacturing process represents a significant technological advancement in coil tube production, enabling the fabrication of tubes with reduced coil diameter while maintaining structural integrity and dimensional accuracy.

Coiltubes are distinguished from conventional straight-length stainless steel tubes by their continuous coiled form, which offers superior material utilization, reduced cutting waste, and streamlined logistics. The half-coil variant specifically refers to a manufacturing configuration where the tube is coiled to a partial (half) diameter, facilitating easier handling, nesting, and transport while preserving the coiled advantage over straight tubes.

2. Material & Properties

The Coiltube product line is fabricated from a range of austenitic and duplex stainless steel grades, selected to meet demanding corrosion resistance, mechanical strength, and formability requirements:

Key Mechanical Properties (Typical for AISI 304/316 in Annealed Condition)

Property Unit AISI 304 / 304L AISI 316 / 316L
Tensile Strength (Rm) MPa ≥ 515 ≥ 515
Yield Strength (Rp0.2) MPa ≥ 205 ≥ 205
Elongation (A50mm) % ≥ 40 ≥ 40
Hardness (HBW) — ≤ 210 ≤ 210
Specific Gravity g/cm³ 7.93 8.00
Thermal Conductivity (20°C) W/(m·K) 16.3 14.6
Maximum Service Temperature °C 870 870

Corrosion Resistance Characteristics

3. Specifications

Parameter Specification Range Standard Reference
Outer Diameter (OD) Φ 6.0 mm – Φ 168.3 mm ASTM A554 / ASME SA-554
Wall Thickness (WT) 0.5 mm – 6.0 mm ASTM A554 / ASME SA-554
Coil Inner Diameter (CID) Full Coil: 600 mm – 1000 mm
Half Coil: 300 mm – 500 mm		 Enterprise Standard / Customer Spec.
Coil Length per Spool 50 m – 300 m (configurable) —
Surface Finish No. 1 (Annealed Bright), 2B, BA (Bright Annealed), Pickled & Passivated ASTM A473 / GB/T 4237
End Condition Plain cut, Beveled (45°), Threaded, Flanged Customer Requirement
Manufacturing Method Seamless (PWHT) / Welded (ERW, TIG, FAW) — Full & Half Coil ASTM A554 / EN 10216-5
Tolerance — OD ± 0.15 mm (≤ Φ 25 mm); ± 0.5% OD (> Φ 25 mm) ASTM A554 / EN 10216-5
Tolerance — Wall Thickness ± 10% WT ASTM A554 / EN 10216-5
Heat Treatment Solution Annealed (1050–1150°C) + Water Quenched ASTM A554
Packaging Wooden crate / Steel frame with VCI (Vapor Corrosion Inhibitor) film ISO 4180

4. Manufacturing Process

The production of half-coil tubes represents a specialized manufacturing advancement, integrating advanced forming technology with optimized tooling design. The process flow is outlined below:

4.1 Full Coil Tube Manufacturing Process

  1. Raw Material Preparation: High-purity stainless steel strip (cold-rolled) or seamless tube stock is inspected for chemical composition (per ASTM E415) and mechanical properties.
  2. Forming / Welding:
    • Welded route: Precision cold rolling of strip into a tubular blank, followed by TIG (Tungsten Inert Gas) or FAW (Fillet Arc Welding) seam welding under argon shielding.
    • Seamless route: Hot or cold pilgering / capillary drawing of round bar stock.
  3. Heat Treatment: Solution annealing at 1050–1150°C with rapid water quenching to achieve full austenitic structure and maximum corrosion resistance.
  4. Surface Finishing: Pickling (acid removal of scale) and passivation (chromate-free conversion coating) to establish a stable Cr₂O₃ passive film.
  5. Coiling: Continuous coiling onto a full-diameter mandrel using servo-controlled winding equipment to maintain uniform tension and prevent deformation.
  6. Quality Inspection: Hydrostatic testing (per ASTM A554, 1.5× working pressure), dimensional verification, and visual inspection.

4.2 Half-Coil Tube Manufacturing Process (Advanced Technology)

The half-coil tube manufacturing process addresses the challenge of producing tubes in a partial-coil configuration, which is particularly advantageous for specific downstream applications requiring compact storage or specific uncoiling geometries. This process involves:

  1. Tube Fabrication: Identical to the full-coil process through welding, heat treatment, and surface finishing stages.
  2. Intermediate Straightening: The tube is partially straightened to relieve residual coiling stresses while retaining a controlled curvature.
  3. Specialized Half-Coil Forming: Using custom-designed tooling (specialty mandrels and guide rollers) developed to achieve the half-coil geometry without inducing plastic deformation, ovality, or wall thinning beyond tolerance. The tooling design incorporates progressive bending profiles that distribute strain uniformly along the tube cross-section.
  4. Stress Relief Annealing: A post-forming temper at 400–500°C to eliminate residual stresses introduced during the half-coil forming operation while preserving mechanical properties.
  5. Final Coiling: The tube is wound onto a half-diameter coil configuration using precision tension-controlled equipment.
  6. Final Inspection: Comprehensive dimensional, visual, and non-destructive testing (EDDY current per ASTM E309) to verify compliance with specifications.
Key Innovation: The half-coil manufacturing technique employs proprietary tooling with optimized curvature radii and progressive forming sequences, enabling the production of half-coil tubes with dimensional accuracy comparable to full-coil products, while offering superior handling characteristics and reduced transport footprint.

4.3 Process Control Parameters

Process Stage Control Parameter Target Value Monitoring Method
Welding (TIG/FAW) Shielding gas flow rate 8–12 L/min Ar Flow meter + visual arc stability
Solution Annealing Furnace temperature 1080 ± 15°C Thermocouple (Type K) continuous
Quenching Quench transfer time ≤ 30 seconds Timer / conveyor speed control
Coiling Winding tension 0.5–2.0 kN (per OD) Load cell feedback loop
Half-Coil Forming Forming force ≤ 0.8 × Rp0.2 × A Hydraulic pressure monitoring
Hydrostatic Test Test pressure 1.5 × Pworking Calibrated pressure gauge (± 0.5%)

5. Applications

Stainless steel coil tubes find extensive application across multiple high-performance industries where corrosion resistance, formability, and reliability are paramount:

5.1 Primary Application Sectors

5.2 Half-Coil Tube Specific Applications

6. Quality Certifications & Standards Compliance

Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework ensuring full traceability and compliance with international standards:

6.1 Management System Certifications

6.2 Product Standards Compliance

Standard Description Applicability
ASTM A554 / ASME SA-554 Standard Specification for Stainless Steel Tube, Seamless, Welded, and Wrought (Cold-Drawn) Primary product standard
EN 10
"Professional Coil Tubes, Professionally Made"
© 2026 Wenzhou Jixing Metal Materials Co., Ltd · This content is for technical reference only. Final order specifications are subject to the signed contract and mill test certificate.