Significance of the brazing gap in the brazing of aluminium heat exchangers for automotive industry

Abstract

The paper presents the influence of the brazing gap width on the structure of bonded joints during the production of aluminum heat exchangers, using brazing technology, in tunnel furnaces with controlled atmosphere. Based on the wedge test, an analysis and qualitative assessment of brazed joints was made for the changing width of the brazing gap and the filler metal used. For the received brazed joints, metallographic tests were carried out using light and electron microscopy (SEM) and microhardness measurements in the characteristic areas of brazed joints. Based on the results obtained, the recommended width of the brazing gap was determined.

A new approach to flux deposition for brazing aluminium by low pressure cold spraying

“…A large field of application of flux brazing is the production of aluminium heat exchangers [3]. The process contains many parts, such as heater core, condenser, evaporator, transmission oil cooler, engine oil cooler, charge air cooler, fuel cooler and so on [4]. These components are usually made of EN AW-3003 and EN AW-3005 alloys containing manganese [5], which increases the mechanical properties and resistance to corrosion [6].…”

“…The process contains many parts, such as heater core, condenser, evaporator, transmission oil cooler, engine oil cooler, charge air cooler, fuel cooler and so on [4]. These components are usually made of EN AW-3003 and EN AW-3005 alloys containing manganese [5], which increases the mechanical properties and resistance to corrosion [6]. Additionally, the alloys show good formability, for example, by stamping and rolling, and can be applied at elevated temperatures [7].…”

“…The dominant technology in these industries is controlled atmosphere brazing (CAB) performed in continuous furnaces [8]. In the case of brazing of aluminium alloys, the most used shielding gas against air access is high-purity nitrogen [2][3][4]. However, it is not sufficient for high-quality * E-mail: tomasz.wojdat@pwr.edu.pl brazing of Al alloys, and therefore non-corrosive flux should be used as an additional material [9].…”

“…The brazeability of aluminium alloys is influenced by their physicochemical properties, that is, high thermal expansion and thermal conductivity. However, a very high affinity of aluminium to oxygen results in the formation of chemically stable aluminium oxides with a high melting point of 2,037 • C [10]. Al 2 O 3 significantly decreases the wettability of the alloy by the filler metal.…”

“…The basic factor influencing the brazing efficiency and joint quality is the flux application method. There are several methods of flux application, and the most popular are the following: (i) spraying an aqueous flux suspension, (ii) spraying flux in the form of paint (called Paint-Flux), (iii) application of a flux paste and (iv) electrostatic ap-plication of flux with the use of a mixture of flux and air [4]. The final choice depends on the production volume, geometry of the covered elements, efficiency, economic considerations and so on [4].…”