4343/3003 aluminum brazing sheet is a layered metal composite material commonly used in heat exchangers such as evaporator fin and radiator fin. It is made of 4343 aluminum alloy and 3003 aluminum alloy through a specific process. 3003 aluminum alloy is typically used as the core layer or matrix material, possessing good processing performance and formability. 4343 aluminum alloy, as the brazing layer or functional layer, belongs to the Al-Si brazing filler aluminum alloy system, and its core characteristic is a high silicon content of 4.5%-6.0%.

Material composition of 4343/3003 aluminum brazing sheet:
1. Brazing layer (4343 aluminum alloy)
- Core chemical composition (mass fraction):
Aluminum (Al) is the matrix element, Silicon (Si) 4.5%~6.0% (key brazing element), Iron (Fe) ≤0.8%, Copper (Cu) ≤0.3%, Manganese (Mn) ≤0.05%, Magnesium (Mg) ≤0.05%, Zinc (Zn) ≤0.1%. Precise control of silicon content is crucial for brazing performance; excessive silicon reduces weld toughness, while insufficient silicon affects fluidity.
- Physical properties:
Solidus 577℃, liquidus 588℃, solidification range only 11℃, classifying it as a narrow solidification range alloy. This results in strong feeding capacity during brazing, effectively reducing weld porosity and cracks. Density 2.7 g/cm³, thermal conductivity 180 W/(m・K), combining lightweight and high thermal conductivity.
2. Core layer (3003 aluminum alloy)
- Core chemical composition:
Aluminum (Al) as the base element, Manganese (Mn) 1.0%~1.5% (strengthening core element), Silicon (Si) ≤0.6%, Iron (Fe) ≤0.7%, Copper (Cu) 0.05%~0.20%. Manganese enhances material strength through solid solution strengthening without significantly reducing processing plasticity.
- Physical properties:
Melting point 650~660℃, forming a melting point difference of over 60℃ with the 4343 brazing layer, providing a safe temperature window for brazing processes; density 2.73g/cm³, thermal conductivity 160W/(m・K), tensile strength 110~220MPa, yield strength 45~160MPa, elongation ≥0.5%~25%, balancing structural support and processing requirements.
3. Structural type:
- Two-layer structure (4343/3003):
Single-sided brazing layer design, suitable for components requiring only single-sided brazing (such as single-sided heat exchange plates, simple pipe joints). The brazing layer is concentrated on the working contact surface, while the core layer provides structural support.
- Three-layer structure (4343/3003/4343):
A double-sided symmetrical brazing layer design, this is the mainstream structure for heat exchangers. It is suitable for applications requiring double-sided brazing, such as fins and manifolds, and multi-channel heat exchange cores. This ensures uniform joint strength on both sides, and the symmetrical structure reduces processing deformation.

Performance characteristics of 4343/3003 aluminum brazing sheet:
- Excellent brazing performance:
The solidus of 4343 aluminum alloy is 577℃, and the liquidus is 588℃. This is more than 60℃ lower than the melting point of 3003 aluminum alloy (melting point 650-660℃). This allows for complete brazing without melting the 3003 aluminum alloy, preventing deformation of the base material and quickly filling weld gaps of 0.1-0.3mm, reducing incomplete penetration defects.
- High corrosion resistance:
The welded joints of the 4343/3003 aluminum brazing sheet showed no significant pitting corrosion after 1000 hours of 3.5% NaCl salt spray testing, exhibiting 15%-20% higher corrosion resistance than 4047 aluminum alloy joints. It passed the test with an intergranular corrosion depth ≤0.05mm.
- Good thermal conductivity:
4343 aluminum alloy possesses excellent thermal conductivity. When combined with 3003 aluminum alloy, it effectively transfers heat from the heat source to the cooling medium, meeting the heat dissipation requirements of the heat exchanger.
- Balancing strength and processability:
The 3003 aluminum alloy provides the composite plate with a certain degree of strength and rigidity. Simultaneously, the high plasticity of aluminum alloys allows for easy fabrication into various complex shapes through stamping, stretching, and other processes, providing significant flexibility in the manufacturing of heat exchangers.

Application areas of 4343/3003 aluminum brazing sheet:
- Automotive heat exchange systems:
Used in automotive radiators and intercoolers to achieve a tight connection between fins and manifolds, with joints resistant to coolant corrosion. In new energy vehicle battery cooling plates, it ensures close contact with the battery pack, improving heat dissipation efficiency.
- Air conditioning and refrigeration equipment:
Used in air conditioner condensers, evaporators, and refrigerator evaporators. The solder has good flowability and uniform filling, improving heat exchange efficiency, reducing leakage rates, and adapting to the "thin" design of refrigerators.
- Other applications:
Widely used in electronic radiators, industrial inverter radiators, marine engineering heat exchangers, and domestic gas water heater heat exchangers.