Stainless Steel Coil Tube — Single-Step Relaxation, Traction, Straightening & Interruption Process Equipment

1. Product Overview

The Stainless Steel Coil Tube (盘管) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. (Wenzhou Jixing) represents a high-precision, continuous-coil stainless steel tubing product engineered through an integrated One-Step Process Equipment system. This advanced manufacturing methodology combines four critical operations — coil relaxation (松圈), traction (牵引), straightening (矫直), and interruption control (中断) — into a single synchronized production line, eliminating the need for multi-stage transfer between independent machines.

Coil tubes are delivered in continuous helical coil form, offering significant advantages over cut-to-length pipe in terms of material utilization, welding joint reduction, and downstream forming efficiency. The one-step process ensures that each coil tube segment maintains consistent geometric tolerances, surface finish, and mechanical properties throughout the entire production run, making it suitable for demanding industrial applications requiring high dimensional accuracy and surface integrity.

2. Material & Properties

2.1 Applicable Grades

2.2 Mechanical Properties (Typical — Annealed Condition)

Property Unit Typical Value (304/316 Series) Test Standard
Tensile Strength (Rm) MPa ≥ 520 (52,000 psi) ASTM A270 / EN 10217-7
Yield Strength (Rp0.2) MPa ≥ 205 (29,700 psi) ASTM A270 / EN 10217-7
Elongation (A50) % ≥ 40 ASTM A270 / EN 10217-7
Hardness (HV10) — ≤ 230 ASTM E92
Density g/cm³ 7.93 – 8.00 —
Maximum Service Temperature °C 870 (1,600 °F) —
Cryogenic Service Temperature °C −196 (−321 °F) —

2.3 Surface Finish Options

3. Specifications

Parameter Specification Standard Reference
Outer Diameter (OD) Φ3.0 mm – Φ114.3 mm (1/8" – 4-1/2") ASTM A270 / EN 10217-7 / GB/T 12771
Wall Thickness (WT) 0.3 mm – 3.0 mm (0.012" – 0.118") ASTM A270 / EN 10217-7
OD Tolerance ±0.05 mm (±0.002") for OD ≤ Φ10 mm; ±0.1 mm for OD > Φ10 mm EN 10217-7
Wall Thickness Tolerance ±10% of nominal ASTM A270
Straightness (Post-Coil) ≤ 0.5 mm/m Internal Specification
Coil Weight Typical: 150 kg – 800 kg per coil —
Coil Inner Diameter (ID) Φ150 mm – Φ600 mm (adjustable) —
Production Length (Continuous) Up to 3,000 m per continuous run —
Manufacturing Method Seamless (Cold Drawn) or Welded (ERW/Automated) ASTM A269 / A270
Heat Treatment Solution Annealed (1010–1150 °C, water/quench) ASTM A270
End Condition Plain end, beveled (45°), or custom per drawing ASME B36.19M

4. Manufacturing Process

The defining technology behind Wenzhou Jixing's coil tube production is the One-Step Process Equipment (一步法工艺装备), which integrates four sequential operations into a single continuous production line. This represents a significant advancement over conventional multi-station manufacturing approaches.

4.1 Process Flow Diagram

  1. Coil Relaxation (松圈): The incoming stainless steel coil tube is fed into a controlled relaxation station where residual stresses from the prior coiling operation are relieved. A precision tension-controlled unwind mechanism gradually releases the stored elastic energy, preventing springback deformation and ensuring dimensional stability. The relaxation station is equipped with load cells and servo-controlled motors to maintain tension within ±2% of the setpoint.
  2. Traction / Pull-Through (牵引): A high-precision traction unit with synchronized drive motors pulls the tube through the processing line at a controlled speed. The traction system features independent speed regulation for each roller pair, ensuring uniform feed rate and preventing localized stretching or compression. Variable frequency drives (VFD) enable speed adjustment from 0.5 m/min to 12 m/min depending on tube diameter and wall thickness.
  3. Straightening (矫直): The tube passes through a multi-roller straightening die set, typically comprising 5–7 adjustable roller stations arranged in a progressive die configuration. Each station progressively reduces the curvature of the tube, achieving a final straightness of ≤ 0.5 mm/m. The straightening rollers are hardened and ground to Ra ≤ 0.2 μm to prevent surface marring, and are constructed from tool steel (HRC 60–62) or tungsten carbide for extended service life.
  4. Interruption Control (中断): The interruption control system enables seamless transition between continuous production and controlled stoppage without compromising product quality. This is achieved through a synchronized braking and clamping mechanism that arrests tube movement at a precise point while maintaining tension. The system includes automatic coil changeover capability, allowing uninterrupted production across multiple coil splices. Emergency stop and controlled shutdown protocols are integrated to prevent tube damage during production interruptions.

4.2 Key Process Parameters

Parameter Range Control Method
Traction Speed 0.5 – 12 m/min VFD with PLC feedback
Relaxation Tension 500 – 5,000 N Load cell closed-loop control
Straightening Roller Adjustment ±0.02 mm per station Hydraulic micrometer adjustment
Line Temperature 20 – 30 °C (ambient) Climate-controlled workshop
Cycle Time per Coil 45 – 120 minutes (depending on coil weight) Automated sequence control

4.3 Process Advantages Over Conventional Methods

5. Applications

5.1 Industry Segments

5.2 Application-Specific Benefits

Application Key Requirement Coil Tube Advantage
Hygienic Piping Low surface roughness, weld-free runs Continuous coil eliminates butt welds; polished finish Ra ≤ 0.4 μm
Automotive Exhaust High-temperature oxidation resistance 409/439 grades with coil form enable high-speed roll-forming
Subsea Piping Corrosion resistance, fatigue life Duplex 2205/2507 with full NDE traceability
Heat Exchangers Uniform wall thickness, tight OD tolerance One-step process maintains CV < 1.5% across entire length

6. Quality Certifications & Standards Compliance

6.1 International Standards