In our manufacturing process of porous aluminium, the liquid aluminium is cast together with crystal salt, and after mechanical finishing the salt is washed out. The salt grains and their contact points are thus replaced by pores. In the case of sintered metals, the metal grains will agglomerate. The voidage between the granules defines the pores. Therefore, the principle is just the opposite. Where sintered metals have a metal grains, porous aluminium has pores. In our porous aluminium the pores are formed in place of the salt crystals and the empty space in the crystal salt is filled with metal.
Porous metals play an important role in modern technology. Filters and filter elements, journal bearings, silencers, fire breaks etc. of various metal powders are manufactured according to the method of powder metallurgy (powder metallurgy materials), the so-called sintering technology (sintered metal). Permeable materials with high stability and high volume porosity produced by sintering technology are usually made of bronze, copper and steel.
Aluminium has equally high heat conductivity and electrical conductivity properties but also low density and good corrosion resistance, thereby offering several advantages over bronze, copper and steel. However, it is difficult to produce porous materials from aluminium using sintering technology.
The following problem arises in the production of sintered aaluminium: Aluminium powder reacts quickly and oxidizes the aluminium grains with non-melting oxide Al2O3. The temperature, at which the oxide wrapping dissolves, is somewhat higher than the melting temperature of aaluminium. This temperature also depends on the size of the aluminium grains and the thickness of the oxide layer. Although in theory there are several methods for solving this problem, it is not yet possible to produce aluminium products with high volume porosity and adequate strength by the technology of sintering. We provide a solution – porous aluminium.
Advantages over sintered metals:
– Sintered aluminium is difficult to produce
– Volume porosity of porous aluminium is about 55%. Sintered metals have volume porosity level of 30-35%
– Thanks to cast stucture, porous aluminium has a high mechanical strength and is free of crumbling. Sintered metals are relatively fragile.