Heat exchanger manufacturers enjoying environmental benefits with precoated aluminum tubes

Aluminum heat exchangers are commonly used in air conditioning systems, automotive engine cooling systems and also in automotive turbocharger systems. In addition to automotive applications, aluminum heat exchangers are being used increasingly for non-automotive applications in industrial and residential segments. In other words, the market for HYBRAZ precoated tubes is expanding, says the company. 

Pre-coated aluminum components ensure that assemblers are no longer exposed to harmful chemicals in producing the tubes. Manufacturers are then in compliance with new REACH and Globally Harmonized System of Classification and Labelling of Chemicals (GHS) regulations. REACH was adopted by the European Union to improve the protection of human health and the environment from the risks that can be posed by chemicals, while enhancing the competitiveness of the EU chemicals industry. It also promotes alternative methods for the hazard assessment of substances in order to reduce the number of tests on animals. The risks concerning the use of flux powder relate primarily related to the inhalation of the powder and dust. The risk of inhaling the powder is heavily reduced when flux powder has been covered in a coating layer. 

Heat exchangers are traditionally brazed together in a metal joining process whereby a filler metal is heated above melting point and distributed between two or more close-fitting parts. Controlled Atmosphere Brazing (CAB) has been considered stateof- the art in brazing aluminum heat exchangers, and is now the most conventional brazing process used by manufacturers. Introduced in 2002HYBRAZ pre-coated aluminum tubes are one of a range of product solutions that Sapa has developed for the heat exchanger (HX) market. 

These pre-coated tubes provide companies with a safer way to manufacture heat exchangers without the risk of being exposed to potentially harmful residue. This makes the tubes attractive in terms of environment, health and safety, with regard to the new regulations concerning handling of potentially harmful chemicals. When producing an all-aluminum heat exchanger, the main supporting materials needed are flux powder and filler material. The introduction of REACH regulation by the European Union, and the world-wide implementation of the GHS regulations have resulted in a stricter classification of flux, says the company. A safe work environment HYBRAZ pre-coated tubes are aluminum tubes coated with a layer of flux in an organic binder developed by Sapa Precision Tubing. 

The high performance HYBRAZ aluminum tube eliminates the need for a separate fluxing operation in the manufacturing of heat exchangers. The coated layer provides both flux and the necessary filler material needed in the brazing process, making it safer to use. According to Sapa HYBRAZ tubes allow manufacturers to safely develop heat exchangers without handling flux. This provides them with an efficient way around the new regulations concerning handling of potentially harmful chemicals. 

Furthermore, HYBRAZ eliminates wet fluxing operations along with the effluents and hazardous material that these are known to generate. Less flux residue build-up leads to less oven downtime and maintenance, thereby improving the process and making it more friendly in environmental terms. 

Keeping control of costs Implementing the use of HYBRAZ pre-coated tubes does not require major investments from the manufacturing company. The braze cycles and technologies from the conventional CAB process are essentially the same when using the HYBRAZ products. The slight modifications come in terms of the acquired heat temperatures in a standard CAB oven. 

Whereas a normal CAB procedure operates with pre-heating to around 250°C, HYBRAZ requires a pre-heating of 320 – 400°C. This modification is necessary to remove the binder from the coating and furthermore ensures no contamination of the brazing furnace atmosphere. Using pre-coated tubes also eliminates the need for a fluxing station in the brazing line during the manufacturing process, effectively streamlining the production of heat exchangers. By reducing flux usage HYBRAZ tubes are saving time and costs for manufacturers. Implementing the use of pre-coated tubes in the manufacturing process also results in a more reliable joining and brazing process. 

HYBRAZ tubes eliminate the need for cladding/filler material, as this is already provided and is reactive in the coating of the tubes. Pre-coated tubes are designed to improve corrosion resistance, which again reduces warranty costs and increases customer satisfaction run. 

Performance The traditional pre-flux coatings consist of a combination of flux and filler material. Flux as a chemical is required to clean the surfaces of the aluminum parts from the oxides and the filler metal is required from the process of bonding the metallic. The additional components used in the HYBRAZ coating improve the overall corrosion performance of the heat exchangers. The added zinc (Zn) layer in the HYBRAZ coating functions as a sacrificial layer and protects the tubes from leaking, thus improving the corrosion performances of HYBRAZ tubes. 

The HYBRAZ invention relates to a pre-flux coating that is used in the manufacturing of components by brazing, and in particular the manufacturing of heat exchangers which use aluminum components.