CuproBraze Technology
CuproBraze heat exchangers are made using special anneal-resistant alloys of copper and brass. Tubes are fabricated from brass strip and coated with a brazing filler material. The coated tubes and copper fins are fitted together into a core assembly, which is then brazed in a furnace.
For CuproBraze to be successful in the marketplace, it has to succeed on the factory floor. The CuproBraze process is simple and has been proven to be a cost-effective manufacturing technology. Already many small, mid-size and high-volume production facilities are making CuproBraze heat exchangers for OEMs and the aftermarket.
CuproBraze technology is flexible and scalable. The International Copper Association licenses CuproBraze technology free of charge to manufacturers. Technical experts will assist you in transferring the technology to your production line anywhere in the world.More Information about the Technology:
Tubes
Fins
Core Assembly
Brazing Furnace
Flexible and Scalable
Start with the Tubes
A high-volume production facility requires the assembly of hundreds of heat exchanger cores per day which, in turn, requires the fabrication of tons of brass tubes and copper fins.
In a radiator, engine coolant passes through the tubes; in a charge air cooler, hot compressed gas from the turbo-compressor passes through the tubes. Advanced heat exchangers use flat tubes, which maximize the contact between the fluid and the tube walls.
Tubes are made from a special anneal-resistant brass alloy that retains its strength after brazing.
Using a variety of techniques, brass strip can be fabricated into tubes. One method for making tubes is high-frequency induction heating (or HF-welding) which can make tubes with a wall thickness of 110 µm or more. HF tubes have no irregularities at the seam, which can be advantageous when assembling the tubes into cores.
Special machinery forms the strip into tubes, which are then cut to length in the same machine. The brazing alloy is applied as a foil, or sprayed onto the external surface of the tubes using a tube-spray application machine that ensures process uniformity. Alternatively, the brazing alloy can be applied to the fin tips instead of the tubes.
Once the tubes are sprayed, they are put together into cores prior to brazing.
Bring in the Fins
Copper fins are essential to the operation of advanced heat exchangers. Their high thermal conductivity and great strength allow for the fabrication of much thinner fins than aluminum. A variety of fin designs can be fabricated depending on the application. The fins are cut to length and collected for assembly.
Next Step Is Core Assembly
Typically, a heat-exchanger core is made from fins, tubes, side supports and header plates. Folded fins are inserted between the tubes. This step can be accomplished manually or with the assistance of semi-automated assembly equipment.
The tube ends of the tube-fin assemblies must be inserted into holes in the header plates. These plates hold the entire assembly together. A crucial step in the entire manufacturing process is the application of the brazing paste around the holes in the header plates, which hold the tubes. The quality of the tube-to-header joint plays a pivotal role in the longevity of the heat exchangers.
A long service life depends on uniform coverage of the joint on the header plate with the paste that contains the brazing alloy. Header slurry application machines are dedicated to one purpose: ensuring the uniformity of coatings around the header holes.Brazing in the Furnace
The heart of the CuproBraze production line is the furnace. This is where heat-exchanger cores are brazed in a nitrogen or other inert gas atmosphere. A continuous belt furnace allows for very high rates of production.
There are several sizes of furnaces available, depending on the volume of production. A single chamber batch furnace meets the needs of a small production line. A three-chamber furnace with a double in-out operating mode is ideal for a medium-size production line and increases productivity because it allows for more efficient use of the middle (brazing) chamber, where the holding time is the shortest.
For high-volume production, the best choice is a continuous furnace, in which heat exchangers are loaded onto a moving belt. A typical high-volume production furnace is sized for brazing at rates of 1500 kilograms per hour with a 1200-millimeter wide belt and a 350-millimeter pass height throughout the furnace. An automated control system allows for flexibility when brazing parts of different configuration and mass.
Given the loading and speed, the high-volume production furnace’s four zones of temperature control are preset to give fast heating to a peak temperature within the core of 650°C. Holding the temperature above 600°C allows the brazing paste and slurry to melt.
A CuproBraze brazing furnace can be fitted with a nitrogen convection-cooling section to cool the parts to 150°C. Nitrogen convection cooling gives the product a bright appearance and allows the overall length of the furnace to be shorter.CuproBraze is Flexible and Scalable
A major advantage of the CuproBraze process is its flexibility when compared to the aluminum brazing process. A wide variety of products can be processed on the same high-volume production line. This flexibility, plus high capacity, is especially important to the makers of trucks and off-road vehicles.
A worldwide network of materials suppliers and equipment makers stands ready to guide you, whether you plan to build a high-volume CuproBraze production facility or purchase CuproBraze heat exchangers from an Alliance member. For more detailed information about the CuproBraze process, please download the CuproBraze Brazing handbook.