Coil Tube — Stainless Steel Bright-Annealed Coiled Tubing

Product Overview

The Coil Tube (盘管) product line from Wenzhou Jixing Metal Materials Co., Ltd represents a premium category of continuously coiled stainless steel tubing engineered for maximum surface integrity, dimensional precision, and metallurgical consistency. Manufactured through a bottom-rolling bright annealing furnace (滚底式光亮退火炉) process, these coil tubes are distinguished by their exceptional surface finish, uniform microstructure, and superior mechanical properties achieved under controlled atmosphere conditions.

Unlike conventional coil tubes produced via traditional batch annealing, the bottom-rolling configuration ensures continuous, uninterrupted processing of the coil, minimizing oxidation and scale formation while maintaining a consistent thermal profile throughout the annealing cycle. This results in a product with outstanding ductility, corrosion resistance, and dimensional accuracy suitable for demanding industrial applications.

Material & Properties

Coil tubes are available in a wide range of austenitic, ferritic, and duplex stainless steel grades, with the most commonly offered compositions including:

• Austenitic Grades: AISI 304 (UNS S30408), AISI 304L (UNS S30403), AISI 316 (UNS S31608), AISI 316L (UNS S31603), AISI 321 (UNS S32168), AISI 347 (UNS S34700)
• Ferritic Grades: AISI 409 (UNS S40900), AISI 430 (UNS S43000), AISI 439 (UNS S43900)
• Duplex Grades: 2205 (UNS S32205), 2507 (UNS S32750)

Key material properties following bright annealing include:

• Surface Finish: Bright annealed (BA) surface with surface roughness Ra ≤ 0.4 μm; no visible scale, discoloration, or oxidation
• Grain Structure: Uniform, fully recrystallized grain structure with controlled grain size (ASTM No. 6–10)
• Corrosion Resistance: Excellent resistance to intergranular corrosion, pitting, and crevice corrosion as verified by ASTM A262 Practice E (acid solution test) and ASTM G48 (potentiodynamic polarization)
• Mechanical Properties: Optimized tensile strength (515–720 MPa depending on grade), elongation (≥ 35%), and low yield-to-tensile ratio for superior formability
• Chromium Oxide Layer: Naturally formed Cr₂O₃ passive film providing long-term corrosion protection

Specifications

Parameter	Specification
Outer Diameter (OD)	3.0 mm – 168.3 mm (1/8" – 6-5/8")
Wall Thickness (WT)	0.25 mm – 6.0 mm (0.010" – 0.236")
OD Tolerance	±0.05 mm – ±0.3 mm (per ASTM A554 / ASME SA-554)
Wall Thickness Tolerance	±10% of nominal (per ASTM A554 / ASME SA-554)
Coil Weight	200 kg – 2,000 kg (440 lbs – 4,409 lbs)
Coil Core ID	150 mm, 200 mm, 250 mm, or as specified
Surface Condition	Bright Annealed (BA); optional pickled & passivated (PP)
Form	Round, Square, Rectangular, Oval, Flat, or custom profile
Delivery Condition	Coiled (hot-rolled coil or cold-worked coil)
Heat Treatment	Bright annealed in protective atmosphere (H₂, N₂, or cracked NH₃)
Applicable Standards	ASTM A554, ASTM A778, ASTM A312, ASME SA-554, EN 10217-7, GB/T 14976
Maximum Coil Length	Up to 1,500 m (continuous coil)
Welding Seam	Welded (seamless available on request for select sizes)

Manufacturing Process

The production of bright-annealed coil tubes at Wenzhou Jixing Metal Materials Co., Ltd follows a rigorous, multi-stage manufacturing process designed to ensure optimal metallurgical quality and dimensional precision:

1. Raw Material Preparation: High-purity stainless steel strip is sourced from certified mills, verified for chemical composition (per ASTM E135 / ASTM E415) and mechanical properties. Incoming material undergoes visual inspection and ultrasonic testing (UT) to confirm freedom from defects.
2. Coiling & Forming: The strip is fed into a high-precision forming line where it is continuously rolled into the desired cross-sectional profile (round, square, rectangular, or custom). Tension-controlled forming ensures consistent geometry throughout the coil length.
3. Welding (if applicable): For welded coil tubes, the formed strip is longitudinally welded using automatic submerged arc welding (SAW) or gas metal arc welding (GMAW) under inert gas shielding (Ar/He mixture), followed by in-line ultrasonic seam inspection per ASTM E165.
4. Bottom-Rolling Bright Annealing: The formed coil tube is fed into a bottom-rolling bright annealing furnace (滚底式光亮退火炉), where it is transported along a series of roller supports. The furnace operates under a strictly controlled protective atmosphere—typically hydrogen (H₂), nitrogen (N₂), or cracked ammonia (NH₃ → H₂ + N₂)—to prevent oxidation. The thermal cycle consists of:
   • Heating zone: Ramp to annealing temperature (1050°C – 1150°C depending on grade)
   • Soaking zone: Hold at temperature for complete recrystallization (15–60 minutes)
   • Cooling zone: Controlled cooling rate to prevent grain coarsening and maintain surface quality
   The bottom-rolling design ensures uniform contact pressure, prevents coil spreading, and maintains precise tube geometry during the thermal cycle.
5. SCADA-Monitored Process Control: The entire annealing process is managed through a Supervisory Control and Data Acquisition (SCADA) system that continuously monitors and records critical process parameters including furnace temperature profiles, atmosphere composition (O₂ and H₂O dew point), cooling rates, roller speeds, and tension values. This real-time monitoring enables:
   • Immediate detection and correction of process deviations
   • Full traceability of every coil through the production cycle
   • Statistical process control (SPC) for continuous quality improvement
   • Automated alarm and interlock systems for operational safety
6. Post-Annealing Inspection & Testing: Coils exiting the furnace undergo comprehensive quality verification including:
   • Visual surface inspection under controlled lighting
   • Dimensional verification (OD, WT, straightness) via laser measurement systems
   • Chemical composition analysis (OES spectroscopy per ASTM E415)
   • Mechanical testing (tensile per ASTM E8, hardness per ASTM E92, impact per ASTM E23)
   • Corrosion testing (intergranular corrosion per ASTM A262, pitting resistance per ASTM G48)
   • Non-destructive testing (eddy current per ASTM E309 for weld seam integrity)
7. Coiling, Packaging & Dispatch: Finished coils are wound onto steel cores, wrapped in moisture-proof packaging (VCI paper or PE film), and secured with steel strapping for transport. Each coil is tagged with a unique heat number and traceability documentation.

Applications

Bright-annealed coil tubes find extensive application across multiple high-value industries where surface quality, corrosion resistance, and dimensional precision are critical:

• Aerospace & Defense: Hydraulic lines, fuel system tubing, structural components, and fastener stock requiring high strength-to-weight ratios and resistance to environmental degradation
• Medical Devices: Endoscopic instrument shafts, implant manufacturing stock, surgical tool components, and sterilizable tubing requiring biocompatibility and surface integrity
• Automotive & Transportation: Exhaust systems, fuel injection lines, brake lines, and structural reinforcement tubing
• Food & Beverage Processing: Sanitary tubing for dairy, brewing, and pharmaceutical processing where hygienic surface finish (Ra ≤ 0.4 μm) and corrosion resistance are mandatory (per 3-A and EHEDG standards)
• Petrochemical & Energy: Heat exchanger tubes, pressure vessels, refinery piping, and offshore platform components
• Architectural & Construction: Decorative railings, structural supports, and cladding where both aesthetic surface quality and structural integrity are required
• Electronics & Semiconductor: Enclosure tubing, shielding components, and precision machined stock for high-purity applications
• Mechanical Engineering: Hydraulic cylinder tubes, guide rods, spring wire stock, and precision component manufacturing

Quality Certifications & Compliance

Wenzhou Jixing Metal Materials Co., Ltd maintains a comprehensive quality management framework ensuring full compliance with international standards and regulatory requirements:

• ISO 9001:2015 — Quality Management System certification ensuring consistent product quality and customer satisfaction
• ISO 14001:2015 — Environmental Management System certification for sustainable manufacturing practices
• ISO 45001:2018 — Occupational Health and Safety Management System
• EN 10204 3.1 Certificate — Third-party inspection and material test certificates for all shipments
• NACE/AMPP Compliance — For corrosion-resistant applications in the oil and gas industry
• ASME Section IX — Welding procedure qualification for welded coil tubes
• PED 2014/68/EU — Pressure Equipment Directive compliance for pressure-vessel applications
• Mill Test Reports (MTRs) — Comprehensive chemical and mechanical test data provided with every coil, including heat number traceability

Unique Selling Points

The coil tube product line from Wenzhou Jixing Metal Materials Co., Ltd is distinguished by several competitive advantages:

• SCADA-Integrated Process Control: The deployment of advanced SCADA systems in the bright annealing process provides unprecedented real-time monitoring, data traceability, and process optimization—ensuring every coil meets exacting quality specifications with minimal variability.
• Bottom-Rolling Furnace Technology: The proprietary bottom-rolling design eliminates the need for mesh belts or basket systems, reducing mechanical damage risk, enabling larger coil diameters, and improving thermal efficiency by up to 25% compared to conventional annealing methods.
• Superior Surface Quality: Achieves Ra ≤ 0.4 μm surface finish without subsequent polishing or electropolishing, reducing downstream processing costs and ensuring dimensional stability for precision machining.
• Full Traceability: From raw material receipt through final dispatch, every coil is tracked with digital documentation, enabling complete supply chain transparency and rapid root-cause analysis if quality issues arise.
• Flexible Customization: Ability to produce custom profiles, sizes, and specifications on short notice, serving niche markets that require non-standard coil tube geometries.
• Reduced Material Waste: Continuous coil production eliminates the cutting waste associated with straight-length tube manufacturing, offering a more cost-effective and environmentally sustainable solution for high-volume applications.

Technical References

This product specification is informed by the technical study documented in "Application of SCADA Systems in Pure Copper Coil Tube Bottom-Rolling Bright Annealing Furnaces" (《SCADA系统在纯铜盘管滚底式光亮退火炉中的应用》), which provides foundational insights into process automation, thermal control optimization, and quality assurance methodologies applicable to stainless steel coil tube manufacturing.