Stainless Steel Coil Tube — BA (Bright Annealed) Surface Finish
Product Overview
The Stainless Steel Coil Tube with BA (Bright Annealed) surface finish is a precision-engineered tubular product manufactured by Wenzhou Jixing Metal Materials Co., Ltd. This product features the original metallic luster achieved through a controlled bright annealing process, delivering a smooth, reflective outer surface with a surface roughness of Ra ≤ 0.4 μm. The BA finish eliminates the need for additional polishing or mechanical finishing operations, making it an ideal choice for applications demanding both aesthetic appeal and functional performance in decorative and general industrial settings.
The Bright Annealed (BA) treatment is performed in a controlled atmosphere furnace, typically using a reducing or dissociated ammonia atmosphere, which prevents oxide scale formation while simultaneously relieving internal stresses induced during cold forming. The result is a clean, bright, and uniform surface that retains the inherent metallic appearance of the stainless steel substrate.
Material & Properties
BA-finished stainless steel coil tubes are typically produced from austenitic stainless steel grades, offering an excellent combination of corrosion resistance, formability, and surface quality. The following are the primary material characteristics:
- Material Grades: SUS304, SUS316, SUS321, SUS304L, and equivalent ASTM/EN grades
- Microstructure: Fully austenitic, stress-relieved condition
- Corrosion Resistance: Superior resistance to atmospheric corrosion, acidic environments, and chlorides (particularly in 316-grade alloys)
- Mechanical Properties: Maintains full ductility and toughness after annealing; no work-hardening present
- Surface Integrity: Free from scale, decarburization, or contamination; suitable for direct decorative use
- Hygienic Compliance: Smooth surface minimizes bacterial adhesion, suitable for food-grade and pharmaceutical applications
Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Surface Finish | BA (Bright Annealed) — Annealed-state original luster | ASTM A580 / GB/T 12771 |
| Surface Roughness (Ra) | ≤ 0.4 μm | ISO 4287 |
| Product Form | Coil Tube (Continuous Coiled Length) | — |
| Outer Diameter Range | 3.0 mm – 159.0 mm (typical) | ASTM A554 / GB/T 12771 |
| Wall Thickness Range | 0.3 mm – 6.0 mm (typical) | — |
| Heat Treatment Condition | Bright Annealed (Atmosphere Annealed) | — |
| Annealing Atmosphere | Controlled reducing atmosphere (dissociated ammonia / endothermic gas) | — |
| Surface Appearance | Mirror-like metallic luster; no visible scale or discoloration | — |
| Primary Application Grade | Decorative and General Industrial Appearance | — |
| Material Standards | ASTM A213, ASTM A269, GB/T 12771, EN 10217 | — |
| Coil Weight | Customized per order (typically 500 – 2,000 kg) | — |
Manufacturing Process
The production of BA-finished stainless steel coil tubes involves a precisely controlled sequence of manufacturing steps, each critical to achieving the specified surface quality and dimensional accuracy:
- Raw Material Preparation: High-purity stainless steel strip or seamless tube blanks are sourced from certified mills, with strict control over chemical composition and initial surface condition.
- Forming / Drawing: The tube is cold-formed through rolling, extrusion, or cold-drawing processes to achieve the target outer diameter and wall thickness. This step introduces residual stresses and work hardening.
- Coiling: The formed tube is wound into a continuous coil configuration for efficient handling and subsequent processing.
-
Bright Annealing (BA Process): The coiled tube is passed through a continuous annealing furnace operating under a tightly controlled reducing atmosphere. Key process parameters include:
- Annealing temperature: 1050 °C – 1150 °C (grade-dependent)
- Atmosphere: Dissociated ammonia (NH₃ → H₂ + N₂) or endothermic gas with dew point control
- Atmosphere purity: O₂ + H₂O ≤ 5 ppm
- Controlled cooling rate to prevent re-oxidation
- Stress Relief & Scale Prevention: The reducing atmosphere ensures no chromium oxide scale forms on the surface during heating and cooling, preserving the bright metallic luster.
- Surface Inspection: Finished tubes undergo visual inspection and surface roughness measurement to verify Ra ≤ 0.4 μm compliance and absence of surface defects.
- Coiling & Packaging: The BA-finished coil is wound onto a protective core, wrapped in moisture-proof film or paper, and secured for shipment.
Applications
The BA (Bright Annealed) surface finish with Ra ≤ 0.4 μm smoothness makes this product suitable for a wide range of decorative and industrial applications:
- Architectural & Decorative: Building facades, interior architectural features, handrails, balustrades, and decorative trim where a clean metallic appearance is desired without additional polishing.
- Automotive Industry: Exhaust system components, decorative trim pieces, and structural tubing requiring corrosion resistance and aesthetic surface quality.
- Appliance Manufacturing: Range hoods, refrigerator components, washing machine parts, and kitchen appliance housings.
- Food Processing & Beverage: Conveying tubing, sanitary fittings, and structural components where hygienic surface standards are required.
- General Industrial: Fluid transfer systems, instrumentation tubing, and mechanical assemblies where surface quality affects functionality or appearance.
- Consumer Goods: Furniture frames, lighting fixtures, and premium consumer products requiring a polished metallic finish.
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. adheres to internationally recognized quality management systems and industry standards to ensure consistent product performance:
- ISO 9001:2015 — Quality Management System certification ensuring systematic quality control throughout the manufacturing process.
- ISO 14001 — Environmental Management System certification for environmentally responsible production practices.
- Material Certification: Each batch is accompanied by a Mill Test Certificate (MTC) / EN 10204 3.1 Certificate documenting chemical composition, mechanical properties, and heat treatment condition.
- Surface Quality Verification: Surface roughness is measured in accordance with ISO 4287 using profilometric methods; results are documented per lot.
- Product Standards Compliance: Tubes conform to ASTM A213, ASTM A269, GB/T 12771, and EN 10217 dimensional and material requirements.
- Non-Destructive Testing (NDT): Available upon request, including ultrasonic testing (UT) for wall thickness verification and eddy current testing for surface defect detection.
Unique Selling Points
The BA (Bright Annealed) surface finish delivered by Wenzhou Jixing Metal Materials Co., Ltd. provides a one-step surface solution that eliminates the need for secondary grinding, polishing, or passivation operations. With a guaranteed surface roughness of Ra ≤ 0.4 μm, this product achieves a factory-ready decorative appearance directly from the annealing furnace, reducing total manufacturing cost, lead time, and the risk of surface damage during post-processing. The continuous coil format further enhances production efficiency for downstream users, enabling automated cutting and fabrication without handling discontinuities.
- Cost Efficiency: Eliminates secondary surface treatment steps, reducing overall processing costs by up to 30% compared to pickled-and-passivated (2B) tubes requiring subsequent polishing.
- Surface Superiority: Ra ≤ 0.4 μm provides a near-mirror finish achievable only through controlled atmosphere processing — not through mechanical polishing alone.
- Dimensional Stability: Full annealing ensures stress-free condition with maximum formability for subsequent bending, welding, and deep drawing operations.
- Consistency: Continuous furnace processing ensures uniform surface quality across the entire coil length, eliminating batch-to-batch variation.
- Customization: Available in multiple grades, diameters, and wall thicknesses to meet specific project requirements.