Stainless Steel Bright Annealed (BA) Coil Tube — Horizontal Continuous Furnace Process
Product Overview
The Bright Annealed (BA) stainless steel coil tube manufactured by Wenzhou Jixing Metal Materials Co., Ltd. represents the industry-standard solution for high-volume, cost-effective production of precision tubing with superior surface finish. Produced exclusively through a horizontal continuous bright annealing furnace, this coil tube delivers exceptional surface consistency, dimensional accuracy, and mechanical performance at competitive pricing.
The horizontal continuous BA furnace process is recognized as the mainstream production method for conventional bright annealed stainless steel tubing globally. Its inherent advantages — high throughput capacity, low per-unit manufacturing cost, and uniform surface quality across the entire coil length — make it the preferred choice for OEMs and fabricators demanding reliable, repeatable performance at scale.
Material & Properties
Available Grades
- 304 / 304L — General-purpose austenitic stainless steel with excellent corrosion resistance and formability
- 316 / 316L — Enhanced corrosion resistance with molybdenum addition, suitable for aggressive chemical environments
- 321 / 347 — Stabilized grades for elevated-temperature applications
- 430 / 409 — Ferritic grades for cost-sensitive, non-critical applications
Key Mechanical Properties (Annealed Condition)
- Tensile Strength: 515–720 MPa (74,700–104,400 psi) depending on grade and wall thickness
- Yield Strength: 205–310 MPa (29,700–44,950 psi)
- Elongation: ≥30% (minimum, per ASTM A213)
- Surface Roughness (Ra): ≤0.4 μm (16 μin) — typical for BA finish
- Surface Appearance: Bright, reflective, oxide-free finish with uniform luster along the entire coil length
Corrosion Resistance
The bright annealing process removes all surface oxides and scale formed during prior hot or cold working operations, restoring the full passive-layer corrosion resistance of the base alloy. The absence of pickling or mechanical finishing ensures a clean, contamination-free surface that achieves rapid re-passivation in atmospheric conditions.
Specifications
| Parameter | Specification |
|---|---|
| Outer Diameter (OD) | 6.0 mm – 114.3 mm (0.236 in – 4.500 in) |
| Wall Thickness | 0.5 mm – 3.0 mm (0.020 in – 0.118 in) |
| Coil Length | 30 m – 200 m (98 ft – 656 ft) per coil |
| Coil Inner Diameter | 150 mm – 300 mm (5.91 in – 11.81 in) |
| OD Tolerance | ±0.05 mm – ±0.15 mm (±0.002 in – ±0.006 in) |
| Wall Thickness Tolerance | ±0.02 mm – ±0.05 mm (±0.0008 in – ±0.002 in) |
| Roundness | ≤0.5% of OD |
| Surface Finish | Bright Annealed (BA) — Ra ≤ 0.4 μm |
| End Condition | Plain cut, or per customer specification |
| Applicable Standards | ASTM A213 / A269, ASME SA-213 / SA-269, EN 10217, JIS G3446 |
| Packaging | Wooden pallet with moisture-proof wrapping; export-standard crating available |
Manufacturing Process
Horizontal Continuous Bright Annealing Furnace
The core differentiator of this product line is the horizontal continuous bright annealing furnace, which represents the industry's most proven and widely adopted technology for producing BA stainless steel coil tube. The process operates as follows:
- Coil Loading: Cold-worked (cold-drawn or cold-rolled) stainless steel coil tube is loaded onto the furnace entry reel and fed continuously through the horizontal furnace.
- Pre-Heating Zone: The tube is gradually heated under a controlled reducing atmosphere (typically a mixture of hydrogen and nitrogen, or endothermic gas) to prevent oxidation. The atmosphere composition is precisely regulated to maintain a dew point of ≤ −40 °C (−40 °F).
- Annealing Zone: The tube is heated to the recrystallization temperature — typically 1050 °C – 1100 °C (1922 °F – 2012 °F) for austenitic grades — held for a controlled dwell time to achieve full grain recovery, stress relief, and microstructural homogenization.
- Cooling Zone: The annealed tube is rapidly cooled under the same reducing atmosphere, preserving the bright oxide-free surface finish. The cooling rate is controlled to prevent grain growth and minimize deformation.
- Coil Unloading & Inspection: The finished BA coil is unloaded, inspected for surface quality, dimensional accuracy, and mechanical properties, then packaged for shipment.
Why Horizontal Continuous Furnace?
- High Throughput Capacity: The continuous operation of the horizontal furnace enables production rates of 20–50 m/min (66–164 ft/min), significantly outperforming batch or box-furnace methods. This translates to the ability to supply large-volume orders on tight schedules.
- Low Manufacturing Cost: Continuous operation eliminates the thermal cycling losses associated with batch furnaces, reducing energy consumption per unit length by up to 30–40%. This cost advantage is passed directly to the customer.
- Superior Surface Consistency: The uniform, isothermal conditions along the entire horizontal furnace length ensure that every meter of the coil receives identical annealing treatment. Surface quality variation between the head, tail, and middle of the coil is minimized to negligible levels — a critical advantage over batch processes where edge effects and thermal gradients are common.
- Process Stability & Repeatability: The horizontal continuous configuration allows for precise, automated control of temperature, atmosphere, and speed — parameters that remain constant from coil to coil, ensuring lot-to-lot consistency.
Industry Recognition: The horizontal continuous BA furnace is universally acknowledged as the mainstream and preferred production method for conventional bright annealed stainless steel tubing. Its dominance in global production is a testament to its technical maturity, economic efficiency, and quality reliability.
Applications
Primary End-Use Sectors
- Food & Beverage Processing: Hygienic-grade tubing for dairy, brewery, and pharmaceutical processing equipment where smooth, non-porous surfaces prevent bacterial adhesion and facilitate CIP (Clean-in-Place) sanitation.
- Medical & Laboratory Equipment: Components for medical instruments, surgical tools, autoclave fittings, and laboratory apparatus requiring autoclavable, corrosion-resistant tubing.
- Heat Exchangers & HVAC: Coil tubes for condensers, evaporators, and refrigeration systems where thermal conductivity and corrosion resistance are paramount.
- Automotive & Aerospace: Precision tubing for fuel lines, brake lines, exhaust systems, and structural components in automotive and aerospace applications.
- Decorative & Architectural: Handrail systems, elevator components, furniture hardware, and architectural trim where the bright reflective surface is both functional and aesthetic.
- Chemical & Petrochemical: Process piping and heat transfer tubing in corrosive chemical environments, particularly with 316/316L grades.
- General Manufacturing: Precision tubing for machine tool builders, equipment manufacturers, and OEMs requiring consistent, cost-effective stainless steel coil for fabrication.
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework to ensure every coil meets international standards and customer specifications:
- ISO 9001:2015 — Quality Management System certification, demonstrating commitment to consistent quality and continuous improvement
- ISO 14001:2015 — Environmental Management System, reflecting responsible manufacturing practices
- EN 10204 3.1 — Material Test Reports (MTRs) provided with every shipment, including chemical composition analysis, mechanical test results, and dimensional verification
- Third-Party Inspection: Available upon request through SGS, Bureau Veritas, or TÜV for pre-shipment verification
- Material Traceability: Full heat-to-heat traceability from raw material mill certificate through final product, enabling complete supply chain accountability
Quality Control Measures
- In-line optical surface inspection for defects, scratches, or discoloration
- Automated dimensional measurement (OD, wall thickness, roundness) at multiple points along the coil
- Hardness testing (Rockwell B or Vickers) on each heat lot
- Tensile testing per ASTM E8/E8M on representative samples
- Visual surface inspection under standardized lighting conditions
- Spectral analysis (PMI) for alloy composition verification
Unique Selling Points
| Advantage | Detail |
|---|---|
| Industry-Standard Process | Horizontal continuous BA furnace — the globally recognized mainstream method for conventional BA tube, ensuring proven quality and process maturity |
| High Production Capacity | Continuous furnace operation delivers high throughput rates, enabling large-volume order fulfillment and short lead times |
| Competitive Pricing | Energy-efficient continuous process reduces manufacturing cost per unit, providing best-in-class value without compromising quality |
| Uniform Surface Quality | Isothermal horizontal furnace conditions ensure consistent bright finish from coil head to tail — no edge effects, no thermal gradients |
| Full Traceability | Complete material traceability from raw steel mill through final product with EN 10204 3.1 certificates on every shipment |
| Wide Specification Range | OD from 6.0 mm to 114.3 mm, multiple grades, flexible coil lengths — accommodating diverse customer requirements |
Ordering Information
Wenzhou Jixing Metal Materials Co., Ltd. offers flexible ordering options including standard catalog sizes and custom specifications. Minimum order quantities, lead times, and special requirements (such as custom coil weights, specific packaging, or additional testing) should be discussed with our technical sales team. All products are manufactured to the highest standards of quality and delivered with complete documentation.