Stainless Steel Coil Tube (Coiltube) — Technical Product Specification
1. Product Overview
The Stainless Steel Coil Tube (Coiltube) is a continuous-length hollow metal product wound onto a spool or coil form, manufactured by Wenzhou Jixing Metal Materials Co., Ltd. Unlike straight-length seamless or welded pipes, coil tubes are produced in continuous coils, enabling downstream processing with minimal material waste, reduced handling costs, and improved production efficiency. This product category is fundamental to the fabrication of heat exchangers, condenser tubes, evaporator coils, refrigeration systems, and a wide range of process engineering applications.
Coil tubes are classified under ISO 11433:2014 (Non-ferrous metal tubes and pipes — Technical delivery conditions — Seamless tubes and pipes) and ASME B31.3 for process piping applications. The product is distinguished by its continuous geometry, tight dimensional tolerances, superior surface finish, and the inherent corrosion resistance of austenitic stainless steel alloys.
Unique Selling Points
- Continuous Coil Form: Eliminates butt welds between pipe segments, reducing failure points and improving thermal efficiency in heat exchanger applications.
- Minimal Material Waste: Coil production reduces offcuts by up to 15–20% compared to straight-length pipe processing.
- Multi-Process Supply Flexibility: Available through extrusion, rolling, and cold-drawing supply processes, allowing optimization based on order volume, dimensional requirements, and cost constraints.
- Premium Surface Quality: Achieves Ra ≤ 0.8 μm surface roughness through precision cold-drawing and internal/external polishing.
- Wide Grade Range: Covers austenitic (304, 316L, 321), duplex (2205), and specialty alloys (904L, 310S) to meet diverse environmental and mechanical demands.
2. Material & Properties
2.1 Applicable Grades
| Grade Designation | UNS Number | ASTM Equivalent | Key Alloying Elements (wt%) | Typical Application Environment |
|---|---|---|---|---|
| 304 / 304L | S30400 / S30403 | ASTM A213 TP304 / TP304L | Cr 18–20%, Ni 8–10.5% | General industrial, food processing, low-chloride environments |
| 316 / 316L | S31600 / S31603 | ASTM A213 TP316 / TP316L | Cr 16–18%, Ni 10–14%, Mo 2–3% | Marine, chemical processing, pharmaceutical, high-chloride environments |
| 321 | S32100 | ASTM A213 TP321 | Cr 17–19%, Ni 9–12%, Ti ≥ 5×C | High-temperature service, furnace components, heat exchangers |
| 2205 Duplex | S31803 | ASTM A790 | Cr 22–23%, Ni 4.5–6.5%, Mo 3–3.5%, N 0.14–0.20% | Offshore, high-strength structural, sour service |
| 904L | S90411 | ASTM A213 TP904L | Cr 19–23%, Ni 23–28%, Mo 4–5%, Cu 1–1.5% | Concentrated sulfuric acid, severe corrosive media |
| 310S | S31008 | ASTM A213 TP310S | Cr 24–26%, Ni 19–22% | Ultra-high temperature, furnace interiors, oxidation resistance |
2.2 Mechanical Properties (Annealed Condition, Representative Values)
| Property | 304L | 316L | 321 | 2205 | 904L |
|---|---|---|---|---|---|
| Tensile Strength (Rm, MPa) | ≥ 485 | ≥ 485 | ≥ 485 | ≥ 550 | ≥ 550 |
| Yield Strength (Rp0.2, MPa) | ≥ 170 | ≥ 170 | ≥ 170 | ≥ 450 | ≥ 205 |
| Elongation (A, %) | ≥ 40 | ≥ 40 | ≥ 40 | ≥ 25 | ≥ 35 |
| Hardness (HBW) | ≤ 201 | ≤ 201 | ≤ 201 | ≤ 310 | ≤ 241 |
| Density (g/cm³) | 7.93 | 8.00 | 7.93 | 7.80 | 8.10 |
| Thermal Conductivity (W/m·K, 20°C) | 16.3 | 16.3 | 16.3 | 16.0 | 15.0 |
2.3 Corrosion Resistance Characteristics
- Pitting Resistance (PREN — Pitting Resistance Equivalent Number): Calculated as PREN = %Cr + 3.3×%Mo + 16×%N. Grade 316L achieves PREN ≈ 24–26; Grade 2205 achieves PREN ≈ 34–38; Grade 904L achieves PREN ≈ 44–48.
- Intergranular Corrosion Resistance: Achieved through low carbon content (≤ 0.03% C for "L" grades) and/or titanium stabilization (Grade 321).
- Stress Corrosion Cracking (SCC) Resistance: Duplex 2205 and high-Ni alloys (904L) demonstrate superior resistance to chloride-induced SCC.
3. Specifications
3.1 Dimensional Specifications
| Parameter | Specification | Standard Reference |
|---|---|---|
| Outside Diameter (OD) | Φ3.0 mm – Φ159.0 mm | ISO 11433, ASTM A213 |
| Wall Thickness (WT) | 0.3 mm – 12.0 mm | ISO 11433, ASTM A213 |
| OD Tolerance | ±0.05 mm (OD ≤ 25 mm); ±0.10 mm (OD > 25 mm) | ISO 11433 Class A |
| Wall Thickness Tolerance | ±10% of nominal (minimum ±0.03 mm) | ISO 11433 |
| Roundness | ≤ 0.5% of nominal OD | ISO 11433 |
| Coil Length (per coil) | 10 m – 200 m (customizable) | — |
| Coil Inner Diameter | Φ150 mm / Φ300 mm / Φ500 mm (standard options) | — |
| Coil Weight | Up to 3,000 kg per coil (standard); up to 5,000 kg (special order) | — |
| Surface Finish | Mirror polish (Ra ≤ 0.2 μm), Satin (Ra 0.4–0.8 μm), Pickled (Ra 1.6–3.2 μm) | ASTM A478 |
| End Form | Plain cut, beveled, flared, or threaded | Customer specification |
3.2 Chemical Composition Requirements (Representative — Grade 316L)
| Element | Maximum / Minimum (%) | Notes |
|---|---|---|
| Carbon (C) | ≤ 0.030 | Low carbon for intergranular corrosion resistance |
| Chromium (Cr) | 16.0 – 18.0 | Primary corrosion resistance element |
| Nickel (Ni) | 10.0 – 14.0 | Austenite stabilizer |
| Molybdenum (Mo) | 2.0 – 3.0 | Pitting and crevice corrosion resistance |
| Iron (Fe) | Balance | — |
| Chlorine (Cl) | ≤ 0.030 | Impurity limit |
| Sulfur (S) | ≤ 0.030 | Impurity limit |
4. Manufacturing Process
4.1 Process Flow Overview
The manufacturing of stainless steel coil tubes involves a multi-stage process integrating raw material preparation, forming, heat treatment, cold working, and final finishing. The selection of the supply process (供坯工艺) — the method by which the initial tube blank is produced — is a critical decision that determines cost, quality, dimensional accuracy, and scalability. Three primary supply processes are employed:
- Extrusion Process (挤压工艺)
- Hot Rolling Process (热轧工艺)
- Cold Drawing Process (冷拔工艺)
4.2 Supply Process Comparison and Development Prospects
| Parameter | Extrusion (挤压) | Hot Rolling (热轧) | Cold Drawing (冷拔) |
|---|---|---|---|
| Applicable Diameter Range | Φ10 – Φ200 mm | Φ15 – Φ500 mm | Φ1 – Φ80 mm (from rolled/extruded blank) |
| Wall Thickness Capability | 0.5 – 30 mm | 2 – 50 mm | 0.1 – 10 mm |
| Dimensional Accuracy | Moderate (±15–20% WT) | Moderate (±15–20% WT) | High (±5–10% WT) |
| Surface Quality | Rough; requires subsequent finishing | Scaled; requires pickling | Smooth; minimal finishing needed |