The mainstream material for B-Tubes for Folded Radiator is aluminum alloy composite brazed plate (mostly 4343/3003/4343 three-layer composite), with a small amount of pure aluminum, aluminum alloy or stainless steel used. Its material characteristics are designed around the five core requirements of forming, brazing, heat dissipation, pressure bearing, anti-corrosion and lightweight.
1、 Mainstream materials and grades
Core substrate: 3003 aluminum alloy (Al Mn series), with balanced strength, formability, and thermal conductivity, is the main material of B-tube.
Brazing layer: 4343 aluminum alloy (Al Si system), with a low melting point (about 577 ℃), melts and fills the gaps during brazing, achieving a firm connection between the pipe body, heat dissipation belt, and main plate.
Composite structure: 4343/3003/4343 three-layer composite plate, with 4343 brazed layers on the inside and outside, and 3003 structural layer in the middle, balancing brazed properties and structural strength.
Thickness: commonly used 0.20-0.30 mm, ultra-thin models can reach up to 0.18 mm, balancing lightweight and pressure resistance.
2、 Core characteristics of material
1. Molding processability (compatible with folding technology)
High ductility: 3003 aluminum alloy has an elongation rate of ≥ 20% and can be formed into a B-type double cavity structure through multiple passes of rolling, with no cracks and minimal rebound.
Cold work hardening is controllable: the strength is improved after roll forming, without the need for subsequent heat treatment, simplifying the process.
High dimensional accuracy: The thickness of the composite board is uniform, and the dimensional tolerance of the B-pipe section after forming is small, ensuring assembly consistency.
2. Brazing adaptability (key process characteristics)
Low melting point brazing layer: The 4343 brazing layer melts at 577-590 ℃ and forms a brazing temperature window with the 3003 substrate (melting point 643 ℃) to avoid melting and deformation of the pipe body.
Good capillary filling performance: The melted 4343 brazing material fills the B-tube folding seam, tube fin, and tube main sheet gaps through capillary action, forming a continuous and dense brazed joint.
Anti brazing defects: The composite layer has strong bonding strength, and there is no delamination or peeling during brazing; The flowability of the brazing material is moderate, reducing solder leakage and virtual soldering.
3. Heat exchange performance (heat dissipation core)
High thermal conductivity: 3003 aluminum alloy has a thermal conductivity of approximately 190 W/(m · K), close to pure aluminum, with fast heat transfer and low thermal resistance.
Thin walled and efficient: With a wall thickness of only 0.2-0.3mm, the heat conduction path is short, and the heat transfer efficiency is 15-20% higher than traditional extruded tubes.
Dual cavity structure: B-type folding forms two independent flow channels, increasing the heat transfer area and improving heat dissipation uniformity.
4. Mechanics and compressive performance
High strength: 3003 aluminum alloy has a tensile strength of ≥ 140 MPa and a yield strength of ≥ 70 MPa, meeting the internal pressure requirements of the radiator (0.2-0.5 MPa).
High resistance to explosion pressure: B-pipe folding joints are brazed to form structural reinforcement bars, and the explosion pressure is 20-30% higher than that of welded pipes with the same wall thickness.
Anti vibration fatigue: Aluminum alloy has good toughness and is suitable for vibration conditions such as automobiles and construction machinery. It can be used for a long time without cracking.
5. Corrosion resistance and durability
Corrosion resistance of substrate: 3003 contains Mn, forming a dense oxide film, resistant to atmospheric and coolant corrosion.
Composite anti-corrosion: Some high-end products use MULTICLAD ® Multi layer composite technology, built-in anti-corrosion layer, SWAAT salt spray test can achieve 100 days without leakage, and the service life is increased by more than 30%.
No additional coating: The composite structure comes with anti-corrosion properties and does not require galvanizing, reducing costs and improving thermal efficiency.
6. Lightweight and Economic Efficiency
Significant weight reduction: 60-70% lighter than traditional steel pipes and 15-20% lighter than extruded aluminum pipes, helping to reduce the weight of the entire vehicle/equipment.
Cost optimization: Composite board roll forming replaces extrusion and welding, with high material utilization, fewer processes, and a total cost reduction of 5-20%.
Recyclable: Aluminum alloy is 100% recyclable and meets environmental requirements.
3、 Comparison of other materials (limited application)
Pure aluminum (1050/1060): has better thermal conductivity and excellent formability, but low strength, only used for low-pressure, small-sized heat sinks.
Stainless steel (304/316): corrosion-resistant, high temperature resistant, extremely high pressure bearing, but poor thermal conductivity, heavy weight, high cost, only used for special working conditions (such as high temperature, strong corrosion).
Copper alloy: It has the best thermal conductivity, but it is heavy, expensive, and prone to oxidation, and has been basically replaced by aluminum alloy.
4、 Key considerations for material selection
Working pressure: For medium and high pressure (>0.3 MPa), 3003+4343 composite plates are preferred to ensure brazing strength and pressure resistance.
Heat dissipation efficiency: Prioritize thin-walled 3003 aluminum alloy, balancing thermal conductivity and lightweight.
Corrosion environment: Choose multi-layer composite anti-corrosion materials for coolant/salt spray environment to extend the service life.
Cost and batch size: Choose standard 4343/3003/4343 composite boards for large quantities and general scenarios, with the highest cost-effectiveness.
