Stainless Steel Coil Tube (Coiltube) — Product Technical Specification
1. Product Overview
The Stainless Steel Coil Tube (Coiltube) is a precision-engineered hollow metal product manufactured by Wenzhou Jixing Metal Materials Co., Ltd. Unlike conventional cut-length pipe stock, coil tubes are produced in continuous, coiled configurations that offer superior material utilization, reduced cutting waste, and enhanced logistical flexibility. This product line is designed for applications demanding high corrosion resistance, mechanical integrity, and dimensional accuracy in both industrial and commercial environments.
Coiltube products are particularly advantageous for downstream processing operations such as bending, forming, welding, and machining, as the continuous coil format eliminates end-joint discontinuities and minimizes material loss during fabrication. Wenzhou Jixing Metal Materials Co., Ltd leverages advanced metallurgical expertise and state-of-the-art manufacturing infrastructure to deliver coil tubes that meet international quality benchmarks.
2. Material & Properties
2.1 Base Material Grades
The coil tubes are manufactured from austenitic and duplex stainless steel grades conforming to ASTM, EN, and GB standards. Commonly available grades include:
- A2 (304 / 06Cr19Ni10): The most widely used austenitic grade, offering excellent general corrosion resistance, formability, and weldability. Suitable for food processing, chemical, and architectural applications.
- A4 (316 / 06Cr17Ni12Mo2): Enhanced resistance to pitting and crevice corrosion due to molybdenum addition. Preferred in marine, pharmaceutical, and aggressive chemical environments.
- 316L (022Cr17Ni12Mo2): Low-carbon variant of 316 for improved weldability and resistance to intergranular corrosion.
- 321 (06Cr18Ni11Ti): Titanium-stabilized grade for elevated temperature service (up to 870°C) with resistance to stress corrosion cracking.
- 304L (022Cr19Ni10): Low-carbon version of 304 for superior welding performance and resistance to sensitization.
2.2 Mechanical Properties (Typical — Annealed Condition)
| Property | 304 (A2) | 316 (A4) | 321 | Unit |
|---|---|---|---|---|
| Tensile Strength (Rm) | ≥ 520 | ≥ 515 | ≥ 520 | MPa |
| Yield Strength (Rp0.2) | ≥ 205 | ≥ 170 | ≥ 205 | MPa |
| Elongation (A50) | ≥ 40 | ≥ 40 | ≥ 40 | % |
| Hardness (HV) | ≤ 200 | ≤ 200 | ≤ 200 | — |
| Density | 7.93 | 8.00 | 7.93 | g/cm³ |
| Thermal Conductivity (20°C) | 16.3 | 14.6 | 16.3 | W/(m·K) |
| Maximum Service Temperature | 870 | 870 | 870 | °C |
2.3 Surface Finish Options
- No. 1 (Hot Rolled Annealed & Pickled): Matte, non-directional surface suitable for industrial piping and heat exchanger tubes.
- No. 2B (Cold Rolled Annealed & Pickled): Smooth, bright finish with good formability; standard for general fabrication.
- No. 3 / No. 4 (Brushed): Directional satin finish for architectural and decorative applications.
- No. 8 (Mirror): High-polish reflective surface for food-grade and sanitary applications.
- Pickled & Passivated: Surface treated to remove scale and enhance passive chromium oxide film for maximum corrosion protection.
3. Specifications
3.1 Dimensional Parameters
| Parameter | Range / Options | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | 6.0 mm – 219.1 mm (¼" – 8") | ASTM A554 / GB/T 12771 |
| Wall Thickness (WT) | 0.3 mm – 12.0 mm | ASTM A554 / EN 10217 |
| Coil Length | Continuous coil; typically 300 m – 1,000 m per coil | — |
| Coil Inner Diameter (ID) | 500 mm / 610 mm (standard); custom upon request | — |
| OD Tolerance | ±0.1 mm (small diameter); ±0.5% (large diameter) | ASTM A554 |
| WT Tolerance | ±10% (min ±0.03 mm) | ASTM A554 |
| Straightness | ≤ 1.5 mm/m | — |
| End Condition | Plain ends; beveled ends available | — |
3.2 Applicable Standards
- ASTM A554 / A554M: Standard Specification for Cold-Formed Stainless Steel Tubing
- ASTM A312 / A312M: Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubing for High Temperature and High Pressure Service
- ASTM A269 / A269M: Standard Specification for Seamless and Welded Austenitic Stainless Steel Sanitary Tubing
- GB/T 12771: Chinese National Standard for Stainless Steel Seamless Tubes
- EN 10216-5: European Standard for Stainless Steel Tubes for General Purposes
- JIS G3459: Japanese Industrial Standard for Austenitic Stainless Steel Tubes
4. Manufacturing Process
4.1 Seamless Coil Tube Production
- Raw Material Preparation: Hot-rolled stainless steel strip or round bar billets are procured from certified mills, undergoing incoming inspection for chemical composition (via optical emission spectrometry) and mechanical properties.
- Hot Rolling / Extrusion (if from billet): Billets are heated to forging temperature (1,150–1,250°C) and extruded through dies to produce seamless tube blanks.
- Piercing & Elongation: The hot tube blank is pierced and elongated to approximate dimensions using Mannesmann piercing or continuous rolling mills.
- Cold Drawing / Cold Pilgering: The tube is cold-worked through precision dies to achieve final OD, wall thickness, and dimensional tolerances. This process also introduces beneficial work hardening and grain refinement.
- Intermediate Annealing: Periodic solution annealing (1,050–1,150°C followed by rapid cooling) restores ductility during multi-pass cold drawing operations.
- Final Solution Annealing & Pickling: Complete dissolution of carbides and restoration of the austenitic microstructure; acid pickling removes oxide scale and restores surface integrity.
- Passivation: Chemical treatment (nitric or citric acid) to enhance the passive chromium oxide film, ensuring optimal corrosion resistance.
- Coiling: The finished tube is wound onto precision coils with controlled tension to prevent deformation and surface damage.
4.2 Welded Coil Tube Production
- Strip Uncoiling & Leveling: Cold-rolled stainless steel strip is uncoiled, leveled, and fed into the forming line.
- Forming (Roll Forming): The flat strip is progressively formed into a tube shape through a series of roll stations.
- Welding: The formed tube seam is welded using TIG (Tungsten Inert Gas) welding or high-frequency resistance welding, depending on the application requirements.
- Post-Weld Heat Treatment: Solution annealing to homogenize the weld zone and eliminate residual stresses.
- Pickling & Passivation: Surface treatment identical to seamless production.
- Dimensional Inspection & Coiling: Final quality checks and coiling onto standard or custom coil diameters.
5. Applications
5.1 Industrial & Process Industries
- Chemical processing plant piping systems (acid, alkali, and solvent transport)
- Heat exchanger tubes and condensate lines
- Boiler feedwater and superheated steam lines
- Petrochemical and refinery process piping
5.2 Food & Beverage Industry
- Sanitary piping for dairy, brewery, and beverage processing
- Food-grade conveyor systems and structural supports
- CIP (Clean-In-Place) system tubing
5.3 Pharmaceutical & Medical
- Pharmaceutical process piping and equipment fabrication
- Medical device housings and instrument tubing
- Bioreactor and fermentation vessel components
5.4 Construction & Architecture
- Architectural handrails, balustrades, and decorative elements
- Structural bracing and facade components
- Staircase and railing fabrication (leveraging the coil tube's formability)
5.5 Automotive & Transportation
- Exhaust system components
- Automotive fuel lines and hydraulic tubing
- Structural tubing for lightweight vehicle components
5.6 Energy & Power Generation
- Nuclear power plant instrumentation tubing
- Solar thermal collector tubes
- Geothermal energy systems
6. Quality Certifications & Testing
6.1 Certifications Held
- ISO 9001:2015 — Quality Management System
- ISO 14001 — Environmental Management System
- CE Marking — Conformity with European Standards
- PED 2014/68/EU — Pressure Equipment Directive compliance
- NSF 61 — Drinking Water System Components (for food-grade applications)
- EN 10204 3.1 — Material Test Certificate
6.2 Quality Assurance Testing
| Test Category | Method / Standard | Frequency |
|---|---|---|
| Chemical Composition | Optical Emission Spectroscopy (OES) per ASTM E415 | Every heat batch |
| Tensile Testing | ASTM A370 / EN 10002-1 | Per coil / per lot |
| Dimensional Inspection | OD micrometer, wall thickness gauge, length measurement | 100% online inspection |
| Hydrostatic Testing | ASTM A269 / EN 10216-5 | Per coil (sampled or full) |
| Non-Destructive Testing (NDT) | Electromagnetic (Eddy Current) or Ultrasonic Inspection | 100% continuous |
| Pitting Corrosion Resistance | ASTM A967 / EN 10271 (Ferric Chloride Test) | Per grade certification |
| Intergranular Corrosion |