Stainless Steel Coil Tube — Horizontal Continuous Bright Annealing (BA) Furnace Production

Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd.

Product Category: Manufacturing Process — Heat Treatment — Bright Annealing (BA)

Production Method: Horizontal Continuous Bright Annealing (BA) Furnace

Product Overview

Wenzhou Jixing Metal Materials Co., Ltd. produces stainless steel coil tubes (盘管) utilizing a Horizontal Continuous Bright Annealing (BA) Furnace as the primary heat treatment system. Bright Annealing refers to a controlled thermal process conducted in a reducing or inert atmosphere (typically dissociated ammonia, endothermic gas, or high-purity nitrogen), which eliminates oxide scale formation on the tube surface while simultaneously achieving the desired microstructural softening. The resulting product exhibits an exceptional surface finish — typically a "bright" or mirror-like appearance — without the need for subsequent pickling or mechanical polishing.

The horizontal continuous BA furnace represents the mainstream production method for conventional BA stainless steel tubes in the global market. This configuration offers significant advantages in throughput capacity, unit production cost, and surface quality consistency compared to batch-type or vertical furnace alternatives. The continuous nature of the process ensures uniform thermal profiles across the entire coil length, resulting in repeatable mechanical properties and surface characteristics from one production run to the next.

Material & Properties

Applicable Materials

Austenitic Stainless Steels: AISI 304 (UNS S30400), AISI 304L, AISI 316 (UNS S31600), AISI 316L, AISI 321 (UNS S32100), AISI 347 (UNS S34700)
Super-Austenitic Stainless Steels: AISI 904L (UNS N08904), Alloy 20
Ferritic Stainless Steels: AISI 430 (UNS S43000), AISI 444 (UNS S44400)
Duplex Stainless Steels: 2205 (UNS S32205), 2507 (UNS S32750) — where applicable

Typical Mechanical Properties (Post-BA)

Hardness: Typically 80–120 HV (soft annealed condition), ensuring excellent formability and deep-drawing capability
Tensile Strength: 485–620 MPa (depending on grade and wall thickness)
Yield Strength: 205–310 MPa
Elongation at Break: ≥ 40% (indicating superior ductility after full annealing)
Grain Size: Uniform, fully recrystallized microstructure with controlled grain boundaries

Surface Quality

Surface Finish: Bright annealed (BA) — no visible oxide scale, no pickling residue
Surface Roughness (Ra): Typically ≤ 0.4 μm on the outer surface; ≤ 0.8 μm on the inner surface
Chromium Oxide Layer: Thin, stable, and uniform Cr₂O₃ passivation layer providing inherent corrosion resistance

Specifications

Parameter	Specification / Range	Notes
Tube Outer Diameter (OD)	Φ3.0 mm – Φ219.1 mm	Custom diameters available upon request
Wall Thickness	0.3 mm – 6.0 mm	Tolerance: ±10% or per ASTM A269
Coil Length	Up to 10,000 m (continuous)	Advantage of horizontal continuous furnace
Coil Weight	Up to 3,000 kg per coil	Optimized for downstream processing
Annealing Temperature	1050°C – 1150°C	Grade-dependent; controlled by thermocouple feedback
Atmosphere	Dissociated Ammonia (NH₃) / Endothermic Gas / High-Purity N₂	Dew point ≤ –60°C; O₂ content ≤ 10 ppm
Cooling Rate	Controlled forced convection cooling	Prevents re-oxidation and ensures uniform properties
Production Capacity	High throughput (continuous operation)	Significantly higher than batch furnace methods
Applicable Standards	ASTM A269, ASTM A270, ASME SA-213, EN 10216-5, GB/T 12771	Multi-standard compliance
Surface Treatment	Bright Annealed (BA) — scale-free	No pickling required; ready for further processing

Manufacturing Process

The production of stainless steel coil tubes via the Horizontal Continuous Bright Annealing (BA) Furnace involves the following sequential stages:

Coil Loading and Uncoiling: The cold-worked stainless steel tube coil is loaded onto the continuous furnace entry system. The coil is unwound at a controlled speed to maintain consistent tension and prevent surface marking.
Pre-Heating Zone: The tube gradually transitions from ambient temperature to the annealing temperature (1050–1150°C) over a controlled ramp rate. This prevents thermal shock and ensures uniform heating across the tube wall thickness.
Annealing Zone (Soak): The tube is held at the peak temperature within a reducing atmosphere for a sufficient dwell time to achieve full recrystallization, grain growth control, and stress relief. The horizontal continuous configuration allows for precise temperature zoning and real-time monitoring via infrared pyrometers and embedded thermocouples.
Controlled Cooling Zone: Post-annealing, the tube is cooled at a controlled rate through forced convection of the reducing atmosphere. This prevents re-oxidation and ensures the formation of a thin, protective chromium oxide film rather than a thick, removable scale.
Exit and Re-Coiling: The annealed tube exits the furnace at near-ambient temperature and is re-coiled onto a powered coil mandrel. The resulting BA tube coil is ready for downstream operations (cutting, forming, welding) without further surface treatment.

Advantages of Horizontal Continuous BA Furnace Technology

High Production Capacity: Continuous operation enables significantly higher throughput compared to batch-type furnaces, making it ideal for large-volume manufacturing of standard-diameter BA tubes.
Low Unit Cost: The continuous nature of the process optimizes energy consumption per ton of product, reducing the cost of goods manufactured.
Superior Surface Consistency: Uniform thermal profiles along the entire coil length ensure consistent surface quality and mechanical properties, minimizing batch-to-batch variation.
Reduced Energy Consumption: The furnace retains thermal mass between cycles, and the continuous loading/unloading eliminates the energy penalty of repeated heating and cooling of the furnace structure.
Minimal Surface Damage: The horizontal configuration and continuous transport minimize tube-to-tube contact and surface marking during the process.

Applications

Stainless steel coil tubes produced via the Horizontal Continuous BA Furnace find extensive use across a wide range of industries:

Food and Beverage Industry: Processing equipment, hygienic piping systems, brewing apparatus, and dairy processing lines (grades 304, 316L)
Pharmaceutical Industry: Clean-in-place (CIP) systems, fluid transfer lines, and reactor components requiring high surface finish and corrosion resistance
Automotive Industry: Exhaust systems, fuel lines, and decorative trim components
Chemical Processing: Reactor tubing, heat exchangers, and corrosive media transport lines
Architectural and Decorative Applications: Handrails, balustrades, structural framing, and facade elements
Medical Equipment: Surgical instrument components, hospital equipment tubing, and implant manufacturing feedstock
Consumer Products: Appliance components, furniture hardware, and precision-machined parts

Quality Certifications

Wenzhou Jixing Metal Materials Co., Ltd. maintains rigorous quality assurance protocols aligned with international standards:

ISO 9001:2015 — Quality Management System Certification
ISO 14001:2015 — Environmental Management System Certification
ISO 45001:2018 — Occupational Health and Safety Management System
EN 10204 3.1 — Material Test Certificate (Third-Party Inspection)
Mill Test Reports (MTR) — Provided with each shipment, including chemical composition, mechanical properties, and heat treatment records
NACE MR0175 / ISO 15156 — Compliance for oil and gas applications (where applicable)

Key Selling Points: The Horizontal Continuous Bright Annealing (BA) Furnace is the industry-standard production method for conventional BA stainless steel tubes, offering the optimal combination of high throughput capacity, low manufacturing cost, and excellent surface quality consistency. Products manufactured using this technology are ready for immediate downstream processing without additional pickling or surface preparation, reducing total project timelines and costs for the end user.