Author:Frank Time:2022-09-27Complex assemblies can be turned into single unit by just one pass through a brazing furnace. Aluminium brazing facilitates the joining of parts with a near-eutectic Ai-Si filler alloy, the liquid temperature which is about 50 ℃ lower than that of the core. In serial heat exchanger production the filler alloy is supplied via a thin clad on a core alloy.
Aluminium brazing sheet material is a sophisticated multi-layer compound consisting of a core alloy which provides the stength and life cycle requirements of the heat exchanger and a clad brazing filler. A one-sided protection layer can also be clad, in order to prevent water-side radiator corrosion.
During brazing, only the clad brazing alloy melts, while the core alloys remain solid. The design and the applied materials of the heat exchanger are adjusted to optimize the brazing result regarding the required post braze mechanical properties as well as the corrosion resistance.
Today, two basic cladding techniques, roll bonding and cast cladding, have become established industrially. Roll cladding is a solid-state welding process, which is used to join similar and dissimilar aluminium alloys, and represents the primary method of manufacturing fuselage skin sheet for aircraft, bright products and brazing sheet for automotive applications. The cladding layers are attached to the core slab by welding and metallurgical bonding using hot rolling. The cast cladding technique is based on a conventional direct chill mould modified in order to allow multiple metal streams to be casted into one single ingot.
Signi’s well established, roll bonding process guarantees tight cladding thickness tolerances, which are essential for ensuring stable brazing results. Rather thin clad layers of 5% can be manufactured, as well as brazing materials also with a cladding thickness of 20%.