BA Bright Annealed Stainless Steel Coil Tube — Technical Specification

1. Product Overview

The BA (Bright Annealed) Stainless Steel Coil Tube is a precision-engineered tubular product manufactured by Wenzhou Jixing Metal Materials Co., Ltd. under their product code No. 62. This coil tube is distinguished by its exceptional surface finish quality, achieved through a proprietary bright annealing process that preserves the inherent metallic luster of the stainless steel substrate without the introduction of oxide discoloration or surface degradation.

The BA finish represents one of the most demanding surface treatment standards in the stainless steel tube industry. Unlike conventional annealing processes that produce a dull, oxidized surface requiring subsequent polishing, the Bright Annealed process occurs in a controlled reducing atmosphere, yielding a surface with a Roughness Average (Ra) value of ≤ 0.4 μm. This specification places the product firmly within the category of fine-finish tubes suitable for both decorative and general industrial applications where visual appearance is a critical design parameter.

Key Differentiator: The BA finish eliminates the need for secondary surface treatment operations such as mechanical polishing, acid pickling, or electropolishing, thereby reducing total manufacturing cost while simultaneously delivering a superior aesthetic result.

2. Material & Properties

2.1 Material Grades

BA Bright Annealed coil tubes are typically manufactured from austenitic stainless steel grades, with the following being the most common options:

2.2 Mechanical Properties (Typical — Annealed Condition)

2.3 Surface Properties

3. Specifications

Parameter Specification Standard Reference
Product Code No. 62 Internal Classification
Product Form Coil Tube (Continuous Length) —
Surface Treatment BA (Bright Annealed) — External Surface Manufacturing Process Category
Surface Roughness (Ra) ≤ 0.4 μm ISO 4287 / GB/T 1031
Surface Appearance Annealed state original luster; no oxidation or discoloration ASTM A580 / GB/T 12771
Outer Diameter (OD) 3.0 mm – 325.0 mm (Customizable) ASTM A511 / GB/T 12771
Wall Thickness (WT) 0.3 mm – 6.0 mm (Customizable) ASTM A511 / GB/T 12771
Coil Length Typically 5,000 mm – 12,000 mm (Adjustable) —
Dimensional Tolerance ±0.1 mm (OD); ±10% (WT) ASTM A511 / ISO 6508
Material Grade 304, 316, 321, 310S, 430 (Available) AISI / ASTM / EN
Delivery Condition Annealed (Soft) — Solution Annealed in Reducing Atmosphere ASTM A580
Intended Application Decorative and General Industrial Appearance Requirements —

4. Manufacturing Process

4.1 Process Flow

  1. Coil Slitting & Pipe Milling: Stainless steel strip (coil) is slit to the required width and fed into a multi-stand pipe mill. The strip is progressively formed into a tubular geometry through a series of rolls, achieving the target outer diameter and wall thickness.
  2. Seam Welding: The formed tube is passed through a high-frequency induction welding (HFW) station. The weld zone is precisely controlled to achieve a metallurgically sound seam with minimal heat-affected zone (HAZ).
  3. Pilot Removal & Sizing: The internal mandrel (pilot) is extracted, and the tube passes through a sizing pass to ensure dimensional accuracy and roundness compliance.
  4. Bright Annealing (BA): This is the critical differentiating step. The continuous tube is passed through a bright annealing furnace operating under a controlled reducing atmosphere — typically a mixture of Hydrogen (H₂) and Nitrogen (N₂), or a decomposed Ammonia (NH₃) atmosphere. The furnace temperature is maintained between 1050°C and 1150°C, depending on the alloy grade. The reducing atmosphere prevents the formation of iron oxide (Fe₂O₃) and chromium oxide (Cr₂O₃) scales on the tube surface. Upon cooling, the surface retains its original metallic luster without any visible discoloration.
  5. Coiling & Spooling: The annealed tube is wound onto a steel spool at a controlled tension to prevent ovality and deformation during storage and transport.
  6. Final Inspection & Packaging: Each coil undergoes dimensional verification, surface roughness measurement, and visual inspection before being wrapped in protective film and packaged for shipment.

4.2 Bright Annealing — Technical Detail

The Bright Annealing process is fundamentally distinct from conventional air-annealing in that it occurs in a sealed furnace environment with a carefully controlled atmosphere. The key process parameters include:

4.3 Quality Control Measures

5. Applications

5.1 Decorative Applications

5.2 General Industrial Applications

6. Quality Certifications & Compliance

Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system and the following certifications to ensure product conformity:

7. Unique Selling Points

  1. Superior Surface Finish: Ra ≤ 0.4 μm bright annealed surface delivers a mirror-like metallic luster that eliminates the need for secondary polishing or finishing operations, reducing downstream processing costs by an estimated 30–50%.
  2. Precision Dimensional Control: Continuous coil tube production with tight tolerances (±0.1 mm OD) enables efficient downstream cutting, bending, and fabrication with minimal material waste.
  3. Atmospheric Annealing Excellence: Proprietary bright annealing furnace technology with precise atmosphere control ensures consistent surface quality across entire production coils, batch to batch.
  4. Cost-Effective Solution: By combining structural integrity with decorative-grade surface finish in a single manufacturing step, the BA coil tube offers a compelling total cost of ownership advantage over conventionally annealed tubes requiring post-fabrication finishing.
  5. Multi-Grade Availability: A wide selection of stainless steel grades (304, 316, 321, 310S, 430) allows engineers to select the optimal material for specific corrosion, mechanical, and temperature requirements.