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The paper describes the interactions between the filler material and the copper fin in the joint in the CuproBraze® process. Due to the influence of the filler metal, part of the copper fin is alloyed. The influence of the time above the melting point of the filler material and of the maximum process-temperature were investigated. It was found that the time has the strongest influence. After laboratory tests and production scale tests a brazing window for the process has been established. That can be used to set up brazing cycles for different kind of furnaces. From a number of wind tunnel tests it has been confirmed that when the brazing is done within this window the alloying of the fin is limited that it does not have practical influence on the thermal performance of the heat exchanger.

Outokumpu Copper Strip AB has developed Copper alloys for use in heat exchanger applications where high temperature joining is employed. The alloys are basically low alloyed Copper and Brass. These alloys are particularly suitable for the brazing of Copper and Brass heat exchangers. For joining purposes an alloy has been developed as brazing filler material. That alloy has properties that give high strength at comparatively low brazing temperatures. All these alloys are being used in the CuproBraze process of manufacturing copper and brass heat exchangers. This paper will explain the properties of these materials and their use.

This is a short presentation over the differences between soft soldering and the brazing, CuproBraze®, manufacturing techniques. Additional process equipment is described and production principles are explained.

External corrosion of automotive heat exchangers, mainly radiators, has in recent years become a problem in some cases. The reasons for the corrosion attacks are a combination of air pollution on one side and road salting or tropical marine climate on the other. This paper deals with actions taken to improve the corrosion resistance of copper/brass radiators. Rapid corrosion of the tubes due to dezincification which gave early radiator leakages was solved by introducing arsenic and phosphorous containing brass qualities (1). Corrosion of fins and solder has been tackled by different types of coatings (2, 3). Copper strips that are zinc coated before the fin production are a new product for large scale application (4). Solder coated strips have been used since many years but are expensive and heavy. Organic coatings applied on complete radiators have been tested for a couple of years. The black painting that is normally used on radiators does not give any corrosion prevention.

The demands for longer lifetimes of cars have meant that the durability of radiators has also become more important, particularly with regard to the resistance to external corrosion due to environmental pollution. In this paper corrosion mechanisms, as well as some preventive measures for copper/brass radiators, are discussed. The radiator is constructed basically of solder–coated flat brass tubes and copper fins. The tubes and fins are joined together with tinllead solder. Bimetallic contact points in joints and also pores and scratches are exposed to corrosive chloride and sulfur compounds. This can initiatiate corrosion damage, if corrosion prevention measures have not been taken into consideration. Experiments have been made to evaluate the risks of bimetallic corrosion between copper, some brass alloys and soldering alloys on radiators. Experiments are based on electrochemical methods.