Stainless Steel Coil Tube (Coiltube) — Product Technical Specification

1. Product Overview

The Stainless Steel Coil Tube (Coiltube), manufactured by Wenzhou Jixing Metal Materials Co., Ltd., is a precision-engineered tubular product supplied in continuous coil form. Unlike discrete-length cut tubes, coil tubes are delivered in a tightly wound helical configuration, enabling seamless feeding into downstream processing equipment such as CNC tube cutters, bending machines, and automated welding systems. This format significantly reduces material waste, minimizes handling time, and improves production throughput in high-volume manufacturing environments.

The product is designed for applications requiring consistent dimensional accuracy, superior surface finish, and reliable mechanical performance under demanding operating conditions. The coil tube is available in a range of outer diameters, wall thicknesses, and grades of stainless steel, tailored to meet specific industry standards and customer specifications.

2. Material & Properties

Coil tubes are fabricated from high-quality austenitic and duplex stainless steel grades, selected for their exceptional corrosion resistance, mechanical strength, and formability. The following table summarizes the key material grades and their corresponding properties:

Stainless Steel Grade Equivalent Standards Composition (Typical, wt%) Key Properties
304 / 1.4301 ASTM A213, EN 10216-5, GB/T 14976 Cr 18–20%, Ni 8–10.5% Excellent general corrosion resistance; good formability and weldability; non-magnetic
316 / 1.4401 ASTM A213, EN 10216-5, GB/T 14976 Cr 16–18%, Ni 10–14%, Mo 2–3% Superior pitting and crevice corrosion resistance; suitable for aggressive chemical and marine environments
321 / 1.4541 ASTM A213, EN 10216-5, GB/T 14976 Cr 17–19%, Ni 9–12%, Ti ≥5×C Stabilized against intergranular corrosion; suitable for high-temperature service (up to 870°C)
316L / 1.4404 ASTM A213, EN 10216-5, GB/T 14976 Cr 16–18%, Ni 10–14%, Mo 2–3%, C ≤0.03% Low carbon variant of 316; enhanced weldability; resistance to intergranular corrosion
310S / 1.4845 ASTM A213, EN 10216-5, GB/T 14976 Cr 24–26%, Ni 19–22% Outstanding high-temperature oxidation resistance; suitable for furnace components and heat exchangers

2.1 Mechanical Properties (Aged Condition, Typical Values)

Grade Tensile Strength (MPa) Yield Strength (MPa) Elongation (%) Hardness (HB)
304 ≥520 ≥205 ≥40 ≤217
316 ≥515 ≥205 ≥40 ≤217
321 ≥485 ≥170 ≥40 ≤201
316L ≥485 ≥170 ≥40 ≤217
310S ≥515 ≥205 ≥40 ≤217

3. Specifications

The following table presents the dimensional and geometric specifications for the Stainless Steel Coil Tube product line:

Parameter Specification / Range Standard Reference
Outer Diameter (OD) 6.0 mm – 168.3 mm (¼" – 6") ASTM A213, EN 10216-5
Wall Thickness 0.5 mm – 6.0 mm ASTM A213, EN 10216-5
Coil Length 10 m – 120 m (customizable) Customer specification
Coil Inner Diameter 500 mm – 800 mm (standard) Industry practice
Surface Finish No. 1 (Pickled), 2B (Cold Rolled & Annealed), BA (Bright Annealed), No. 4 (Brushed), HL (Hairline), Mirror (8K) ASTM A480, GB/T 343
Tolerance (OD) ±0.05 mm – ±0.50 mm (depending on OD) ASTM A213
Tolerance (Wall Thickness) ±0.05 mm – ±0.20 mm ASTM A213
Roundness ≤0.5% of OD EN 10216-5
End Condition Open ends, closed ends, or beveled ends (per request) Customer specification
Heat Treatment Solution annealed (1050–1150°C followed by rapid cooling) ASTM A213
Welding Method Automatic TIG (Tungsten Inert Gas) welding for seamless tubes ISO 15614
Delivery Condition Coiled on wooden or steel pallets, wrapped in protective film and moisture-proof packaging Industry practice

4. Manufacturing Process

The production of Stainless Steel Coil Tubes at Wenzhou Jixing Metal Materials Co., Ltd. follows a rigorous, multi-stage manufacturing process designed to ensure dimensional precision, metallurgical integrity, and surface quality. The process flow is outlined below:

4.1 Process Flow

  1. Raw Material Procurement: Cold-rolled stainless steel strips are sourced from certified mills, with incoming quality inspection including chemical composition analysis (spectroscopic verification), mechanical property testing, and surface quality assessment.
  2. Strip Leveling & Slitting: Incoming coils are passed through a leveling unit to eliminate coil set and flatness defects. Strips are then slit to the required width with precision edge trimming to ensure uniformity.
  3. Forming (Roll Forming): The leveled strip is fed through a series of progressive forming rollers in a coil tube forming machine. Each roller station incrementally bends the flat strip into a partial circular cross-section. The number of forming stations (typically 12–20) is optimized based on the target OD and wall thickness to minimize residual stress and springback. This is the critical step highlighted in the learning experience: "Repeated deformation — the coil tube former delivers more power with less effort." The progressive multi-stage deformation ensures that the material is gradually shaped without exceeding its strain hardening limit, producing uniform wall thickness and consistent geometry.
  4. Welding: The formed semi-circular strip is longitudinally welded using high-frequency induction welding (HF) or automatic TIG welding. Welding parameters (current, speed, gas flow, and overlap) are precisely controlled to achieve full penetration, minimize heat-affected zone (HAZ) distortion, and produce a weld seam with mechanical strength equivalent to the base metal.
  5. Weld Seam Finishing: The weld seam is dressed by internal and external grinding or rolling to achieve a flush surface, reducing stress concentration points and ensuring smooth internal flow characteristics.
  6. Solution Annealing: Tubes are heat-treated at 1050–1150°C in a protective atmosphere (nitrogen or vacuum) to dissolve carbide precipitates, relieve residual stresses, and restore full corrosion resistance and ductility.
  7. Pickling & Passivation: Tubes undergo acid pickling (typically HNO₃/HF mixture) to remove oxide scale, followed by passivation to form a protective chromium oxide layer on the surface.
  8. Coiling & Packaging: Finished tubes are coiled onto a pay-off reel at controlled tension to prevent deformation. Coils are wrapped in protective film, moisture-proof paper, and secured on pallets for shipping.

4.2 Key Process Advantages

5. Applications

Stainless Steel Coil Tubes find extensive use across a broad spectrum of industrial and commercial applications, owing to their corrosion resistance, mechanical strength, hygienic properties, and ease of fabrication from coil form:

6. Quality Certifications & Standards Compliance

Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system and adheres to internationally recognized standards for stainless steel coil tube production:

6.1 Quality Assurance Measures

  1. Incoming Inspection: 100% verification of raw material certificates, spectroscopic chemical analysis, and surface inspection of cold-rolled strips.
  2. In-Process Control: Continuous monitoring of forming parameters, welding parameters, and dimensional tolerances via automated gauging systems. Statistical Process Control (SPC) is applied to critical characteristics.
  3. Final Inspection: Each coil batch undergoes hydrostatic pressure testing (1.5× working pressure), dimensional measurement (OD, wall thickness, length), surface inspection, and weld seam examination (dye penetrant testing or eddy current testing).
  4. Traceability: Each coil is marked with heat number, grade, dimensions, and production date, enabling full traceability from raw material to finished product.

7. Unique Selling Points