Porous aluminum is a porous material that is permeable throughout the whole volume. The manufacturing technology of porous aluminum is unique and differs from the production technologies of other porous metals such as sintered metals or metal foams. The manufacturing process of porous aluminum can be briefly described in three main steps:
Production technology of porous aluminum
1. Aluminium casting with salt
For the manufacturing of porous aluminium we do not use any cost-intensive pressing moulds as sinter technology needs, but conventional casting moulds. The mold will be filled up with crystal salt, molten aluminum is poured on it and goes through the salt particles. To obtain products with different pore sizes we use salt crystals of different particle sizes. Each salt particle has many contact points with other salt particles. Therefore, all salt particles and then all the pores are connected to each other. All pores are open, so porous aluminum is permeable throughout the whole volume and in all directions.
2. Mechanical post-processing
Mechanical finishing is an important phase in the manufacturing process of the porous aluminum products. With the help of the band saw, blocks and plates are produced in various dimensions and wall thicknesses. The cylindrical products are obtained by turning of the porous aluminium blanks. By the mechanical processing on a milling machine products of any shape and complexity according to customers requests will be realized.
3. Salt washing out
Salt washing out is the last major step before the product leaves our production facility. Instead of the salt particles, the pores appear. All pores have open structure, all are connected to each other and thus the product is completely permeable to liquid and gaseous media.
You get the product without salt, but can continue to process it mechanically as needed. Please contact us, we will gladly inform you about the recommendations for mechanical treatment after the salt washing out.
More about the technology and advantages of porous aluminum
Not only the salt qualities influence the manufacturing technology of porous aluminum and thus the material properties. There are several casting parameters that can be varied to adjust the quality of the final product. Depending on the application or customer request, it makes sense to use one or the other aluminum alloy for the production of porous aluminum. Mostly the AlSi7Mg alloy fits perfectly. There are special cases where e.g. pure aluminum is desired because of the higher heat conductivity. We are happy to meet customer requests and manufacture products made of porous aluminum in very different qualities.
It is important to mention that no bonding agent is used in the production of porous aluminum. Porous metals can be produced in various ways. According to one manufacturing method the metal powder is mixed together with a bounding agent e.g. mixed with resin. Thanks to the binder, the metal powder sticks together. This reduces the thermal conductivity of the product. In the structure of porous aluminum no binder is present, the thermal conductivity is high.
For cellular metals obtained by the sintering technology the individual metal particles are sintered together. The contact points between single metal spheres create resistance points for the thermal conductivity. Porous aluminum, unlike sintered metals, does not consist of individual particles but has a cast structure. The thermal conductivity and strength of porous aluminum products are significantly higher compared to sintered materials.
Mechanical processing is a necessary, indispensable step in the production of porous aluminum. The casting moulds for this process always have a simple shape, either rectangular or cylindrical. After the blank leaves the casting mould, it has a solid aluminium layer on the surface. This layer is removed by the mechanical processing and the salt can be washed out. Therefore it is not possible to cast porous aluminum in a mould having a complex geometry (equal to the final shape of the product) such as e.g. in the injection moulding process.
In the manufacturing of porous aluminum products, it is possible to incorporate other metals into the matrix of porous aluminum. This can be interesting for such applications as e.g. heat exchange.
As a manufacturer of products made of porous aluminum, we have the necessary knowledge to be able to reduce the mechanical processing and thus to optimize the production costs. This is doable with the help of certain mould inserts. In series production we develop moulds with specific dimensions and special construction. These measures have a direct influence on the final price of the product.
With us you get the necessary technical advice, which combines your requirements for the product and our production possibilities. Our engineers assist you in product development and communicate directly with the production management. This approach allows us to develop continuously the manufacturing technology of porous aluminum. The development is based on customer wishes or market requirements and thus always remains up to date.
The innovative and relatively simple manufacturing technology allows us to offer an attractive price / performance ratio for prototypes, single parts and large series.
For more information about the properties of porous aluminum, please click here.