Dimensionally Stable Aluminum Components For Almost All Geometries

2023 Author: Hannah Pearcy | [email protected]. Last modified: 2023-05-24 11:12

Aluminum components are used in more and more fields of application: in packaging machines and automation systems, in electrical engineering, in vehicle and aircraft construction or in the field of high vacuum applications in the solar and semiconductor industries. The reasons for this are obvious: aluminum has a low weight with high stability, very good heat and electrical conductivity as well as the best recycling properties. In addition, there are optimal surface properties, yield limits and machinability, especially in the cast plate process

For applications in construction, the strength and the yield strength of the material used are of great importance. Since aluminum in its pure form is very soft and ductile, its mechanical properties are changed by alloying, thus optimizing it for use. The alloys AlMgMn or AlZnMg are often used for constructions. AlZnMg has a strength comparable to steel, but a significantly lower density (1/3 of steel).

Seminar tip

The seminar on lightweight materials in construction teaches methods, design principles and construction methods for lightweight structures. The participants get an overview of different lightweight materials, learn about criteria for the selection of materials and learn about the advantages, disadvantages and risks of the different materials.

Block thicknesses up to 1100 mm available

The casting alloy EN AW 5083 (AlMg4.5Mn) is most frequently used in practical applications. This alloy is available in all common to very large dimensions. Block thicknesses of up to 1100 mm as well as sheets in widths of up to 2800 mm and lengths of up to 6000 mm are available. Experienced designers are happy to use these dimensions as the basis for their design in order to save handling, machining and thus costs later. But also block cuts sawn on all sides for complete machining are preferably processed in mold and tool making.

The cast alloy EN AW-7021 (Al Zn5.5Mg1.5) is characterized by a tensile strength of up to 410 MPa and an elastic limit of up to 360 MPa. This material is used in applications with high demands on mechanical properties in combination with excellent machining properties and material stability.

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Ensure dimensional stability

The mechanical properties of cast plates are optimized by the heat treatment of the raw material, i.e. the aluminum ingot. Alimex reduces the stresses in the bars through the thermal treatment. As a result, they have constant mechanical properties. This is particularly important for applications that place high demands on dimensional stability and compliance with tight dimensional tolerances on components. Alimex GmbH, based in Willich, is the leader in annealing technology. She treats the starting material in her own annealing hall and then uses it to produce cast aluminum plates and block cuts. In contrast to rolled plates, these are manufactured by band and circular saws.

Rolled plates and cast plates are suitable for production

Both types of plates are suitable for the production of aluminum components: Rolled plates usually have higher strengths and better deformation properties due to the introduced forming energy, while cast platesoffer better dimensional stability during machining as well as thicker and larger dimensions, which is advantageous, among other things, when manufacturing components from solid material. This means that welding work and, accordingly, welding seams can be prevented. Aluminum components, regardless of which plate they are made of, offer further advantages such as food compatibility, high thermal and electrical conductivity and, after appropriate treatment, a pronounced corrosion resistance. Most cast alloys can also be polished very well and are suitable for structural etching.

Controlled protective layer improves the aluminum character

Aluminum has a natural protective layer (up to 0.5 µm), which is created by oxidation in the normal atmosphere, but is attacked by acidic and alkaline solutions. This oxide layer has a low conductivity and thus inhibits corrosion processes. The prerequisites are sufficient in many standard applications in machine and fixture construction. By anodizing (protective anodizing) Alimex creates a controlled protective layer (50 to 5000 times the thickness of the natural oxidation layer), which improves the aluminum character and protects the material. This layer is transparent, but can be colored using printing processes or dye baths.

A distinction is made between soft and hard anodized. Soft-Eloxal makes the surface more wear-resistant, more resistant to chemical agents and serves to protect against corrosion. It is often used for decorative purposes, since other colors can be achieved using organic or electrolytic coloring.

Hard anodizing is used for technical surfaces when the function of the surface is less important and the components are to be protected against sliding friction, for example.

Aluminum can also be hardened and protected by coatings, such as electroplating, chromating, dispersion, powder coating and liquid coating or thermal spraying. The surface of aluminum components can also be refined by grinding, brushing or polishing. These processes are often used as a preliminary stage of the protective layer processes described.

Functional protective layers

Aluminum components are used in the construction of modules, systems and machines for automation when weight needs to be saved. For example, the transport industry is replacing steel. This can lead to less moving masses and therefore lower drive power or higher speeds.

In mechanical engineering, plants are made more energy-efficient through substitution , thus increasing the clock frequency and reducing unit costs. Movable or rotating machine parts made of aluminum can be driven faster and easier in their systems. With mechanical machining / production of aluminum components, the processing times are significantly shorter than with other materials. This shortens the manufacturing time of the machine. In addition, the wear and tear on tools is lower, which also saves costs.

In medical technology, aluminum is used not only because of its low weight, but also because of the easy-to-protect surfaces, for example through chemical nickel plating. Machining and the cooling or heating capacity of the material also play a role. In numerous applications in the medical industry, a visually perfect surface of the machines or measuring devices is also important. These requirements can be met with two cast alloys from the EN-AW 5083 and EN-AW 5754 series. We have succeeded in creating top quality for optical anodizing requirements. Aluminum components are also often used in the solar display and semiconductor industries.

* * Dipl.-Ing. Annedore Bose-Munde, specialist journalist for business and technology