Aluminium brazing is now the preferred process for the production of automotive heat exchangers such as radiators, condensers, evaporators and heater cores. Good corrosion resistance in standard applications, formability and high thermal conductivity make aluminium an ideal material for the construction of these heat exchangers.
Aluminium brazing involves joining of components with a brazing alloy, that is an aluminium alloy (Al-Si) whose melting point is appreciably lower than that of the components. This brazing alloy is usually placed adjacent to or in between the components to be joined and the assembly is then heated to a temperature where the brazing alloy melts but not the components. Upon cooling, the brazing alloy forms a metallurgical bond between the joining surfaces of the components.
In automotive heat exchanger applications, this filler metal is supplied via a thin sheet or clad on a core alloy. The core provides structural integrity while the low melting point Al-Si cladding alloy melts and flows during the brazing process, to provide upon cooling a metallic bond between the components.