Mesh Belt Continuous Aluminum Brazing Furnace Process | Full Step-by-Step Guide

In the manufacture of heat exchangers for sectors such as the automotive and new energy industries, the continuous mesh-belt aluminium brazing furnace is the core equipment for achieving high-quality, large-scale welding of aluminium alloy components. As a specialist manufacturer with over twenty years’ experience in the brazing furnace industry, Changxing Hengda Furnace Industry draws on three generations of technological advancements to provide a detailed explanation of the entire process of this precision technique.

1. Preliminary Preparation: Laying a Solid Foundation for Flawless Welding

Surface Cleaning and Treatment

Before entering the brazing production line, workpieces must undergo multiple cleaning processes:

1.1 Trichloroethylene degreasing – to remove surface oil and grease

1.2 Alkaline etching – to dissolve the natural oxide layer

1.3 Ultrasonic cleaning – to eliminate residual impurities

This process ensures that the flux adheres evenly in subsequent stages, preventing welding defects caused by oil or oxide layers.

Precise Flux Application

An automatic spraying system is used to apply a non-corrosive potassium fluoroaluminate-based flux evenly across the workpiece surface, with the flux concentration strictly controlled within the range of 5%–25%. Following spraying, an air-blowing device removes excess flux, ensuring sufficient flux at the joints whilst preventing residue formation from excess flux at high temperatures.

Low-Temperature Drying and Setting

The coated workpieces enter a drying oven to remove moisture from the flux at a temperature of ≤110°C. Strict temperature control is required during this stage to prevent premature decomposition and failure of the flux, whilst preparing the workpieces for subsequent high-temperature brazing.

2. Core Brazing: Precise Temperature Control under Nitrogen Shielding

Workpieces, having undergone multi-zone temperature-controlled heating, enter a brazing furnace measuring 20–30 metres in length via a 316L stainless steel mesh belt, sequentially passing through three key stages:

The entire heating process employs a 7-zone independent temperature control system, combined with PID intelligent regulation, to achieve a temperature control accuracy of ±0.2°C, ensuring a temperature difference within the furnace of ≤±3°C.

High-Purity Nitrogen Protection

High-purity nitrogen with a purity of ≥99.9995% is introduced into the furnace throughout the process, with the dew point controlled at ≤-40°C, completely isolating oxygen to prevent oxidation of the workpieces at high temperatures. The nitrogen circulation system employs multi-stage filtration to ensure a stable furnace atmosphere.

3. Cooling and Solidification: Scientific Cooling Ensures Brazing Quality

Workpieces that have undergone brazing pass sequentially through a three-stage cooling system:

1.Water-cooling stage
Water-cooled walls rapidly reduce the workpiece temperature to 400°C, inhibiting excessive grain growth

2.Gas-cooling stage
Forced nitrogen cooling uniformly reduces the temperature to 200°C

3.Air-cooling stage
Natural cooling to room temperature allows the weld microstructure to stabilise fully

This staged cooling strategy effectively controls the cooling rate, preventing thermal stress deformation caused by rapid cooling whilst ensuring the mechanical properties of the weld.

4. Post-Processing and Quality Inspection: Triple Verification to Ensure Quality

Cleaning and Drying

After cooling, the workpieces are blown with compressed air to remove any residual flux powder from the surface, ensuring a clean appearance.

Multi-Dimensional Quality Inspection

5. Technical Advantages of Changxing Hengda Furnace Industry

As one of the earliest enterprises in China to develop continuous aluminium brazing furnaces, Changxing Hengda’s mesh belt-type continuous aluminium brazing furnace offers three core advantages:

1.Energy-saving design
Fully fibrous furnace lining structure, improving thermal efficiency by over 30% compared to traditional furnace models

2.Intelligent control
Equipped with an Industry 4.0 control system, enabling precise storage and traceability of process curves

3.Customised services
Parameters such as furnace length and mesh belt width can be tailored to workpiece dimensions and production volume requirements, catering to diverse production scenarios

From the launch of the first-generation NB series in 2008 to today’s third-generation energy-efficient brazing furnaces, Changxing Hengda has consistently focused on the innovation and upgrading of aluminium brazing technology, providing reliable thermal processing solutions to customers worldwide.