Alufast®

magnesium components with threaded fasteners. The Alufast®

A

fasteners facilitate lightweight construction Arnold Umformtechnik says that its Alufast® aluminium screws are

especially advantageous for joining magnesium components, especially with material pairs exposed to thermal stress, where they significantly enhance the security of threaded fastener joints.

rnold underlines that the type 6056 aluminium alloy used for Alufast®

entire operating life. “Relaxation processes, in particular

fasteners has a proven

track record of durability for joining product line has

good characteristics for thermal expansion, corrosion resistance and recycling. At the same time, Alufast®

products fulfil stringent

requirements for retention of clamping force, thermal stability and weight reduction. Unlike steel screws, which require

over dimensioned head bearing areas for joining magnesium components, standard dimensions are sufficient with Alufast® fasteners. Furthermore, Alufast®

aluminium

screws weigh only one-third as much as equivalent steel screws. Particularly with large volumes the weight savings can amount to the equivalent of several metric tonnes of steel per year. Alufast®

fasteners also exhibit good

corrosion characteristics in contact with magnesium. The relatively small difference in electromotive force significantly reduces the risk of corrosion compared with steel fasteners. The mechanical properties of the screws are practically stable under long-term stress at temperatures up to approximately 150°C. Brief temperature excursions up to approximately 180°C do not pose a risk. Alufast®

screws can be used

untreated in combination with commonly used magnesium casting alloys, such as Az91 HP. They do not need any additional surface coating. The corrosion resistance of the components remains stable over their

180°C. In joints with steel screws, the high temperatures initially cause additional stress on the threaded fastener joint due to thermal expansion, which usually leads to relaxation or even plastification of the magnesium. These relaxation effects in magnesium lead directly to reduced clamping force at elevated operating temperatures. With a thermal expansion coefficient similar to that of magnesium, Alufast®

screws exhibit

significantly less loss of clamping force with temperature cycling than conventional steel screws.”

Combining the benefits

Rotor Clip Company Inc is helping designers of fluid power assemblies cut costs and save space in their designs by combining the benefits of wave springs and traditional retaining rings.

R

otor Clip, a manufacturer of retaining rings, hose clamps, and related products, explains that the retaining ring fixes the cover element and eliminates the need to weld or screw

down the components, making the assembly easy to repair/service in the field. The wave spring between one cover element

and the inner tube pre-loads the inner components against each other; meaning that possible axial tolerances are always balanced so no axial play occurs.

in the joined magnesium components, can lead to reduced clamping forces, especially in joints exposed to thermal stress. Particularly in applications such as engines and transmissions, the component temperature range of -30°C to 150°C leads to temperature differences of up to