Stainless Steel Coil Tube (Coiltube) — Product Technical Specification
1. Product Overview
The Stainless Steel Coil Tube (Coiltube) is a precision-engineered tubular product manufactured in continuous coil form, designed for applications requiring high corrosion resistance, thermal stability, and mechanical integrity. Produced by Wenzhou Jixing Metal Materials Co., Ltd, this product line encompasses seamless and welded stainless steel tubing wound into coils for efficient handling, storage, and downstream processing. The coil tube format eliminates the need for straight-length cutting, reducing material waste and enabling continuous-form processing in advanced manufacturing environments.
Coil tubes find extensive application in heat exchanger systems, chemical processing plants, cryogenic engineering, food and pharmaceutical equipment, and de-icing/anti-icing thermal management systems. The product's inherent resistance to pitting, crevice, and intergranular corrosion makes it particularly suitable for aggressive chemical and environmental exposure conditions.
2. Material and Properties
2.1 Grade Classification
- Austenitic Grades: AISI 304 (UNS S30400), AISI 304L (UNS S30403), AISI 316 (UNS S31600), AISI 316L (UNS S31603), AISI 321 (UNS S32100)
- Duplex Grades: AISI 2205 (UNS S31803), AISI 2507 (UNS S32750)
- Super-Austenitic Grades: Alloy 20 (UNS N08020), Alloy 625 (UNS N06625)
2.2 Key Mechanical Properties
| Property | Typical Value (AISI 304) | Typical Value (AISI 316L) | Test Standard |
|---|---|---|---|
| Tensile Strength (Rm) | ≥ 515 MPa | ≥ 485 MPa | ASTM A269 / GB/T 228 |
| Yield Strength (Rp0.2) | ≥ 205 MPa | ≥ 170 MPa | ASTM A269 / GB/T 228 |
| Elongation (A5) | ≥ 40% | ≥ 40% | ASTM A269 / GB/T 228 |
| Hardness (HV) | ≤ 200 | ≤ 200 | ASTM A269 / ISO 6507 |
| Corrosion Resistance (Pitting, PREN) | 18–20 | 24–26 | ASTM G48 |
| Maximum Service Temperature | 870°C | 870°C | Manufacturer Data |
| Minimum Service Temperature | −196°C (LN₂) | −196°C (LN₂) | ASTM A269 |
2.3 Chemical Composition (Typical)
| Element | 304 (wt%) | 316L (wt%) | 2205 Duplex (wt%) |
|---|---|---|---|
| C (Carbon) | ≤ 0.08 | ≤ 0.03 | ≤ 0.03 |
| Cr (Chromium) | 18.0–20.0 | 16.0–18.0 | 22.0–23.0 |
| Ni (Nickel) | 8.0–10.5 | 10.0–14.0 | 4.5–6.5 |
| Mo (Molybdenum) | — | 2.0–3.0 | 3.0–3.5 |
| N (Nitrogen) | — | — | 0.14–0.20 |
| Si (Silicon) | ≤ 0.75 | ≤ 0.75 | ≤ 1.00 |
| Max S (Sulfur) | ≤ 0.03 | ≤ 0.03 | ≤ 0.02 |
3. Specifications
3.1 Dimensional Specifications
| Parameter | Range / Options | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | 3.0 mm – 168.3 mm | ASTM A269 / ASME SA-269 / GB/T 12771 |
| Wall Thickness | 0.3 mm – 6.0 mm | ASTM A269 / GB/T 12771 |
| Coil Length | 15 m – 100 m (configurable) | Manufacturer Specification |
| Coil Diameter | 300 mm – 800 mm (I.D.) | Customer Requirement |
| Weight Tolerance | ± 5% per coil | ASTM A269 |
| Surface Finish | 2B, No. 4 (Brushed), Mirror (Ra ≤ 0.4 μm), Pickled & Passivated | ASTM A480 / GB/T 4237 |
| End Condition | Open (Unfinished), Closed (Welded/Plug), Beveled | Customer Specification |
| Dimensional Tolerance (OD) | ± 0.05 mm (precision grade) | ASTM A269 / DIN 17456 |
| Dimensional Tolerance (Wall) | ± 0.05 mm (precision grade) | ASTM A269 / DIN 17456 |
3.2 Manufacturing Standards
- ASTM A269: Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubing for Chemical and Similar Severe Service
- ASME SA-269: Boiler and Pressure Vessel Code Section II, Part D
- EN 10216-5: Heat Exchangers and Similar Heat Transfer Equipment — Tubes Made of Stainless Steel
- GB/T 12771: Stainless Steel Seamless Tubes for Fluid Transport
- DIN 17456: Stainless Steel Tubes for General Purposes
- JIS G3459: Stainless Steel Seamless Tubes for General Purposes
4. Manufacturing Process
4.1 Seamless Coil Tube Production
- Raw Material Selection: Virgin stainless steel slabs or billets sourced from certified mills with full chemical traceability (mill test reports per ASTM A269 Appendix).
- Hot Rolling / Piercing: Slabs are heated to 1200–1300°C and pierced to produce hollow blanks. The piercing ratio is optimized to ensure uniform wall thickness and minimize internal defects.
- Pilgering / Mannesmann Process: The hollow blank is further reduced in diameter and wall thickness through rotary piercing or pilger mill passes, achieving near-final dimensions.
- Heat Treatment (Solution Annealing): Tubes are heated to 1040–1120°C in a protective atmosphere (endothermic gas or vacuum) and rapidly quenched to dissolve carbides and restore full austenitic microstructure. This step is critical for achieving maximum corrosion resistance and preventing sensitization.
- Pickling and Passivation: Tubes are immersed in a citric acid or dilute nitric acid solution to remove scale and form a protective chromium oxide passive film (typically 1–5 nm thickness).
- Coil Winding: The processed tube is wound onto a coil reel at controlled tension to maintain dimensional accuracy and prevent deformation. Tension control systems ensure uniform winding density.
- Final Inspection: Each coil undergoes dimensional verification, surface inspection, hydrostatic testing, and eddy current testing before packaging.
4.2 Welded Coil Tube Production (Alternative)
- Strip Milling: Cold-rolled stainless steel strip is slit to precise width.
- Forming: The strip is formed into a tubular shape through roll-forming or plate-to-tube (P2T) technology.
- Welding: TIG (Tungsten Inert Gas) welding or laser welding is performed with inert gas shielding (argon/helium) to prevent oxidation of the weld zone.
- Post-Weld Heat Treatment: Full solution annealing to homogenize the weld zone microstructure.
- Weld Seam Inspection: 100% eddy current or ultrasonic testing of the weld seam.
5. Applications
5.1 Thermal Management and De-Icing Systems
Coil tubes are extensively employed in internal ice-melting systems (内融冰系统) and external ice-melting systems (外融冰系统) for overhead transmission lines and industrial structures. In internal de-icing applications, the coil tube serves as a conduit for heated working fluid (water, glycol, or electrically resistive heating medium) that melts ice accumulation from within the tube structure. External systems utilize coil tubes as embedded heating elements or heat transfer surfaces. The high thermal conductivity of austenitic stainless steel (approximately 16 W/m·K for 304 grade) combined with superior cryogenic toughness ensures reliable operation at temperatures as low as −60°C.
5.2 Heat Exchangers and Boilers
- Shell-and-tube heat exchangers for chemical and petrochemical processes
- Plate-fin heat exchangers for cryogenic applications (LNG, LN₂)
- Boiler tubes and superheater tubes for power generation
- Condensers and evaporators in HVAC/R systems
5.3 Chemical and Pharmaceutical Processing
- Process piping and heat transfer coils in reactors
- Sterilization systems (SIP/CIP) in pharmaceutical manufacturing
- Food-grade brewing and dairy equipment
- Acid and alkali processing vessels
5.4 Other Industrial Applications
- Automotive exhaust systems and catalytic converter substrates
- Aerospace fuel lines and hydraulic tubing
- Oil and gas downhole tubing (duplex/super-duplex grades)
- Marine and offshore platforms (chloride-resistant grades)
- Architectural and decorative applications
6. Quality Certifications and Testing
6.1 Certifications
- ISO 9001:2015 — Quality Management System
- ISO 14001:2015 — Environmental Management System
- ISO/TS 22163 — Automotive Quality Management (IATF 16949 predecessor)
- EN 10204 3.1 / 3.2 — Inspection Document / Inspection Certificate
- ASME "S" Stamp — Section VIII, Division 1 (where applicable)
- PED 2014/68/EU — Pressure Equipment Directive (CE Marking)
- API Monogram — American Petroleum Institute (for oil & gas applications)
- DNV-GL / Lloyd's Register — Marine classification society approval
6.2 Quality Assurance Testing Protocol
| Test Method | Standard | Frequency | Purpose |
|---|---|---|---|
| Chemical Analysis (OES/AES) | ASTM E415 | Per heat | Verify composition conformance |
| Hydrostatic Pressure Test | ASTM A269 | 100% of coils | Detect internal defects and leaks |
| Eddy Current Testing | ASTM E309 | 100% of coils | Surface and subsurface defect detection |
| Ultrasonic Testing (UT) | ASTM E213 | 100% of coils | Internal volumetric defect detection |
| Tensile Testing | ASTM A269 / GB/T 228 | Per coil (or per lot) | Verify mechanical properties |
| Intergranular Corrosion Test | ASTM A269 Annex (ASTM A923 Practice E) | Per heat | Confirm sensitization resistance |
| Pitting Corrosion Test (ASTM G48) | ASTM G48 Practice B | Per grade qualification | Verify pitting resistance |
| Dimensional Inspection | ASTM A269 | 100% of coils | OD, wall thickness, roundness |
| Visual Surface Inspection | ASTM A480 | 100% of coils | Surface quality and finish grade |
| Cryo Impact Testing | ASTM E |