In Zanardi Fonderie’s paper, the demonstration that better mechanical performances can be obtained for the final component
In the field of welding, technical and scientific literature does not provide significant contributions on the fatigue properties of dissimilar arc-welded joints. For this reason, Zanardi Fonderie S.p.a., in partnership with the University of Padova and the Italian Institute of Welding, has taken part in an important research project and the drafting of a document which scientifically demonstrates the excellent fatigue performance of austempered ductile iron-to-steel dissimilar arc-welded joints redressing the lack of information in this field.
The mechanical design of structural components is now increasingly focused on multi-material systems where the different properties of each material are combined to obtain high performance, thus increasing the number of functions. Unfortunately, due to the nature of material obtained through heat treatment (Austempering), ADI tends to be considered unsuitable for welding.
The purpose of this document is to demonstrate that, with the right parameters, this process can be efficiently managed, without compromising the quality and performance of the final component (correctly welded), but rather producing austempered ductile iron-to-steel dissimilar arc-welded joints with better mechanical performances for the final component.
The document provides an analysis of the microstructure at the post-weld junction point (metallographic analysis and microhardness testing); the results of the fatigue tests and, lastly, a comparison of the fatigue behaviour of the dissimilar joint with standardised and recommended welded steel joints.
Through this research activity, we have, therefore, attempted to respond to the needs of a market that is increasingly focused on solutions with a better performance, with a view to weight reduction, saving fuel, the possibility of creating complex casting shapes which are more suitable for the final application, an increase in useful scope, and much more.
Austempered ductile iron-to-steel dissimilar joints, in fact, increase the performance of the end component by combining weight reduction with net-to-shape geometry which is a key feature of austempered ductile iron. The possibility for iron castings to be designed with complex shapes and low thickness, together with the excellent static, impact, fatigue performances and moderate wear resistance offered by ADI, allows the optimisation of mass distribution and the use of steel can be limited to where needed.