Aluminium Rheinfelden provides with Unifont-90, AlZn10Si8Mg, and Castadur-50, AlZn5Mg, a wide range of cost-effective self-hardening aluminium alloys. Unifont-90 is used for sand and permanent mould casting parts, which are characterized by high mechanical strength without any heat-treatment. This allows also the economic production of large-sized castings. Unifont-94 is suitable for high-pressure die-castings which recover by self-hardening their original hardness, mechanical properties and stability to compression stress after a thermal treatment, as e.g. during vulcanization.
The sand casting alloy Castadur-50, AlZn5Mg, was developed in order to achieve good yield strength values along with elongation after self-hardening.
The open question up to now was concerning the development of a self-hardening alloy still combining good castability and ductile behaviour. Such an alloy does not fulfill normally car manufacturers’ needs, as the corrosion resistance plays a critical role.
Castadur®-50 // Castadur®-30
Within an international fruitful cooperation, the Aluminium Rheinfelden Tech Center has developed a new chemical composition AlZn3Mg3Cr, called Castadur-30. Castadur-30, AlZn3Mg3Cr, proves itself to be an excellent alloy for permanent mould castings. Elongation exceeds 10% along with over 120 MPa yield strength and a low stress corrosion cracking sensitivity.
This Letter to the Foundrymen has the aim to introduce and compare our self-hardening alloys of the Castadur family. We are gladly at disposal to discuss with you and your customer about your needs, suggesting the most suitable alloy for your application. Do not hesitate to contact Aluminium Rheinfelden’s technical assistants!
Castadur-50 is a self-hardening alloy, particularly suitable for sand castings. The corrosion resistance to atmosphere and on the road is similar to that of a standard AlSi7Mg0,3-type alloy. Moreover, stress corrosion cracking susceptibility has to be taken into account, especially for parts under highly alternating loads ( i.e. stress values over 60% or even 70% of UTS), which should be protected by a surface treatment.
The particular chemical composition of Castadur-30 leads to a very low hot tearing sensitivity, without side effects on castability. A comparison between such an alloy and standard casting alloys like AlSi7 or AlSi11 clearly shows that Castadur-30 reaches, after self-hardening, the same values in elongation, but twice as high yield strengths. A further heat treatment with subsequent water quenching after solutionizing is thus unnecessary.
The steel mould design has to be accurately done in close cooperation with the foundrymen, taking into account the significant solidification and volumetric shrinkage as well as the higher casting temperature. Reference values are given in the leaflet with the processing instructions of Castadur-30. In addition, the increased solidification rate implies a faster casting sequence and a consequent higher production rate.
Main applications of Castadur-30:
• Thin-walled castings, surface machined
• Optical instruments, lenses holders
• Machine tool parts with high deformation requirements
• Impact- or explosion- proof castings
• Decorative parts