Stainless Steel Coil Tube — Wenzhou Jixing Metal Materials Co., Ltd.
1. Product Overview
The Stainless Steel Coil Tube (SS Coil Tube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered, continuously formed tubular product delivered in coiled configuration for downstream processing and fabrication. This product category encompasses seamless and welded stainless steel tubing wound onto industrial spools, designed for applications demanding high corrosion resistance, mechanical integrity, and dimensional consistency. The coil tube format offers significant advantages over cut-length pipe in terms of material utilization efficiency, reduced waste, and streamlined manufacturing workflows for end-users.
Wenzhou Jixing Metal Materials Co., Ltd. draws upon extensive expertise in metallic materials processing, leveraging advanced rolling, forming, and heat treatment technologies to produce coil tubes that meet international quality benchmarks. The company's production methodology incorporates rigorous process control at every stage, from raw material selection through final quality inspection, ensuring that each coil meets specified dimensional tolerances, surface finish requirements, and metallurgical properties.
2. Material Composition & Properties
2.1 Grade Designations
- AISI 304 / ASTM A269 TP304 (UNS S30400): General-purpose austenitic stainless steel offering excellent corrosion resistance, formability, and weldability. The most widely specified grade for food processing, chemical, and architectural applications.
- AISI 316L / ASTM A269 TP316L (UNS S31603): Low-carbon variant of 316 with added molybdenum content (2.0–3.0%), providing superior resistance to pitting and crevice corrosion in chloride-containing environments.
- AISI 321 / ASTM A269 TP321 (UNS S32100): Titanium-stabilized austenitic grade suitable for elevated-temperature service up to 870°C (1600°F), with resistance to intergranular corrosion.
- AISI 304L / ASTM A269 TP304L (UNS S30403): Low-carbon version of 304 designed for enhanced weldability and resistance to sensitization in the heat-affected zone.
2.2 Mechanical Properties (Typical Values)
| Property |
304 / 304L |
316 / 316L |
321 |
Test Standard |
| Tensile Strength (UTS) |
≥ 515 MPa (74.7 ksi) |
≥ 515 MPa (74.7 ksi) |
≥ 515 MPa (74.7 ksi) |
ASTM A269 / ASTM A270 |
| Yield Strength (0.2% Offset) |
≥ 205 MPa (29.7 ksi) |
≥ 205 MPa (29.7 ksi) |
≥ 205 MPa (29.7 ksi) |
ASTM A269 / ASTM A270 |
| Elongation (at break) |
≥ 40% |
≥ 35% |
≥ 40% |
ASTM A269 / ASTM A270 |
| Hardness (Rockwell B) |
≤ 95 HRB |
≤ 95 HRB |
≤ 95 HRB |
ASTM E140 |
| Density |
8.00 g/cm³ |
8.00 g/cm³ |
8.00 g/cm³ |
— |
| Thermal Conductivity (20°C) |
16.3 W/(m·K) |
16.3 W/(m·K) |
14.2 W/(m·K) |
ASTM E153 |
| Max. Service Temperature |
870°C (1600°F) |
870°C (1600°F) |
925°C (1700°F) |
Manufacturer's Data |
2.3 Chemical Composition (Maximum/Wt%)
| Element |
304 / 304L |
316 / 316L |
321 |
| Carbon (C) |
≤ 0.08 / ≤ 0.03 |
≤ 0.08 / ≤ 0.03 |
≤ 0.08 |
| Chromium (Cr) |
18.0–20.0 |
16.0–18.0 |
17.0–19.0 |
| Nickel (Ni) |
8.0–10.5 |
10.0–14.0 |
9.0–13.0 |
| Molybdenum (Mo) |
— |
2.0–3.0 |
— |
| Titanium (Ti) |
— |
— |
5 × (C × 100) – 0.70 |
| Sulfur (S) |
≤ 0.03 |
≤ 0.03 |
≤ 0.03 |
| Phosphorus (P) |
≤ 0.045 |
≤ 0.045 |
≤ 0.045 |
| Silicon (Si) |
≤ 0.75 |
≤ 0.75 |
≤ 0.75 |
3. Dimensional Specifications
3.1 Tube Dimensions
| Parameter |
Specification / Range |
Standard Reference |
| Outer Diameter (OD) |
Φ 3.0 mm – Φ 168.0 mm (⅛" – 6½") |
ASTM A269 / ASTM A270 |
| Wall Thickness (WT) |
0.30 mm – 12.0 mm (0.012" – 0.472") |
ASTM A269 / ASTM A270 |
| OD Tolerance (≤ Φ 19 mm) |
± 0.10 mm (± 0.004") |
ASTM A269 |
| OD Tolerance (> Φ 19 mm) |
± 0.15 mm (± 0.006") |
ASTM A269 |
| Wall Thickness Tolerance |
± 10% of nominal |
ASTM A269 |
| Coil Length |
Custom, typically 10 m – 500 m per coil |
Customer Specification |
| Coil Weight |
Up to 2,000 kg (4,409 lb) per coil |
— |
| Straightness (per 1,000 mm) |
≤ 3.0 mm |
ASTM A269 |
3.2 Surface Finish Options
| Finish Designation |
Description |
Ra (μm) Typical |
Standard |
| 2B (Cold Rolled & Bright Annealed) |
Matt, reflective finish; standard commercial surface |
0.4 – 0.8 |
ASTM A480 |
| No. 4 Brushed |
Uniform unidirectional grain; aesthetic finish |
0.8 – 1.6 |
ASTM A480 |
| Mirror Polish (8K) |
Highly reflective, specular surface |
0.05 – 0.2 |
ASTM A480 |
| Pickled & Passivated (P&P) |
Chemically cleaned; free of scale and contaminants |
0.4 – 1.2 |
ASTM A380 |
| Electro-polished |
Ultra-smooth surface; enhanced corrosion resistance |
0.05 – 0.2 |
ASTM A967 |
4. Manufacturing Process
4.1 Process Flow Summary
- Raw Material Preparation: High-purity stainless steel slabs or strip are procured from certified mills, subjected to incoming quality inspection including chemical composition verification (via Optical Emission Spectroscopy, OES) and mechanical property testing.
- Hot Rolling & Annealing: Slab is hot-rolled to the target approximate dimensions, followed by solution annealing at 1050–1150°C (1922–2092°F) in a controlled atmosphere furnace to achieve a uniform austenitic microstructure and relieve residual stresses.
- Pickling & Descaling: Hot-rolled scale is removed through a combination of acid pickling (nitric-hydrofluoric acid blend) and mechanical descaling to achieve a clean base surface for cold working.
- Cold Rolling: The strip is cold-rolled through multiple passes in precision mills to achieve the target thickness within specified tolerances. Inter-pass annealing may be applied to prevent excessive work hardening.
- Solution Annealing: Cold-rolled strip undergoes final solution annealing at 1040–1120°C (1904–2048°F) followed by controlled cooling to restore full ductility and achieve the desired mechanical properties.
- Forming / Tube Making: The flat strip is formed into tubular configuration using one of the following methods:
- ERW (Electric Resistance Welding): Strip edges are pressed together and fused by high-frequency electrical resistance; weld seam is subsequently ground flush.
- Seamless Piercing & Rolling: Billet is pierced and cold-rolled through a series of reducing passes to achieve final dimensions without a longitudinal weld seam.
- Hydroforming: Internal hydraulic pressure is applied to form the tube from a pre-cut blank, enabling complex cross-sections.
- Coiling: Finished tube is wound onto precision steel coils with controlled tension to prevent deformation, kinking, or surface damage. Coiling speed and tension are computer-controlled to maintain dimensional integrity.
- Post-Forming Heat Treatment: Where required, the coiled tube undergoes stress-relief annealing or solution treatment to eliminate residual stresses introduced during coiling and forming operations.
- Passivation & Surface Treatment: Chemical passivation is performed to enhance the natural chromium oxide protective layer, improving corrosion resistance. This process complies with ASTM A967 requirements.
- Final Inspection & Packaging: Each coil undergoes dimensional measurement, visual inspection, and non-destructive testing (NDT) prior to protective packaging and shipment.
4.2 Key Process Control Points
- Temperature Control: All heat treatment operations are conducted with thermocouple-monitored furnaces maintaining ±10°C (±18°F) accuracy throughout the heating and cooling cycle.
- Atmosphere Control: Annealing furnaces are equipped with hydrogen/nitrogen protective atmosphere or vacuum systems to prevent oxidation and decarburization during high-temperature processing.
- In-line Dimensional Monitoring: Laser-based and ultrasonic thickness gauges provide real-time feedback to automated control systems, ensuring dimensional consistency throughout the production run.
- Weld Quality Assurance: For ERW products, ultrasonic testing (UT) and eddy current testing (ECT) are performed on the weld seam to detect discontinuities, inclusions, or porosity.
5. Applications
5.1 Primary Application Sectors
- Food & Beverage Processing: Tubular conveyors, heat exchanger coils, sanitary piping systems, and equipment frames in dairy, brewing, and pharmaceutical manufacturing. The 304L and 316L grades meet FDA and EHEDG hygiene standards.
- Chemical & Petrochemical Industry: Process piping, reactor internals, heat exchanger tubes, and instrument tubing where resistance to aggressive chemical media is required. The 316L grade provides superior performance in sulfuric acid, phosphoric acid, and chloride-containing environments.
- Automotive Manufacturing: Exhaust system components, fuel injection tubing, sensor housings, and structural coil springs. The coil format enables efficient continuous forming operations.
- Medical & Pharmaceutical Equipment: Autoclave components, medical device housings, dialysis machine tubing, and surgical instrument shafts requiring high purity and biocompatibility.
- Construction & Architecture: Structural tubing for railings, handrails, window frames, and decorative elements. The coil format reduces fabrication waste and enables automated cutting and forming.
- Energy & Power Generation: Boiler tubes, heat exchanger coils, solar thermal absorber tubes, and nuclear-grade tubing (316L for reactor coolant system components).
- Oil & Gas: Downhole tubing, flow lines, and subsea connectors where corrosion resistance and mechanical strength are critical in high-pressure, high-temperature (HPHT) environments.
5.2 Coil Format Advantages
The coiled delivery format provides material utilization rates exceeding 95%, compared to approximately 85–90% for cut-length pipe. This translates to significant cost savings for high-volume fabricators, reduced inventory management complexity, and minimized environmental impact through waste reduction.
6. Quality Certifications & Testing Standards
6.1 International Certifications