The “progetto 2 millimetri” is funded by the Lombardy Region for the development of a process of gravity and low pressure casting which is able to realize 2 mm thick components.

The automotive industry is constantly looking for the best performances in terms of vehicle safety, but, also and mainly,for the reduction of emissions and fuel consumption obtainable through a process of weight reduction of the various components. For reasons of economy, these reductions are not currently compatible with the adoption of innovative lightweight materials, especially as regards the production of low-range and high volumes.

In order to obtain relevant results with the materials currently available it is necessary to try to reduce the thickness of heavier components, ensuring at the same time the current mechanical and resistance characteristics.

In the construction of a vehicle,the chassis and the suspension group represent a significant percentage of the total weight. The search for weight reduction of these components, with the use of light alloys commercially compatible with the field costs, has always confronted with a series of problems such as:

  • Need to oversize the product in order to obtain results similar to those of the components in cast iron, steel or iron sheet;
  • Limits on reliability, because the project rules have not been developed for the part regarding the fatigue, as done for steel;
  • Limits on the capabilities of casting processes in gravity and low pressure casting, not yet fully regulated and controlled by automatic systems and presenting early wears such as to affect the quality of the results;
  • Limits on the tolerances required to use the castings in automatic assembly and manufacturing plants;
  • Weldability is often incompatible with obtainable dimensional tolerances and mechanical properties;
  • Heat treatment with processes and parameters which are not defined in detail by the existing technical literature for light alloys.

In the last decade, richer applications of the automotive sector have turned to the vacuum die-casting processes in order to overcome some of the described problems. These applications have led to a monopoly of technology and of process parameters which prevented, due to the high investment needed, the development of applications in the field of medium volume or of industrial vehicles.

The desire to extend to other areas the results obtained in vacuum die-casting, through the use of casting processes in gravity and low-pressure casting which are able to realize solutions applicable to vehicles for the reduction of weight of the components economically compatible with the costs of standard vehicle production, is the motivation at the basis of the “progetto 2 mm”.

The path for the achievement of this result provides for the optimization of four aspects considered fundamental: alloys, thermal management of the process, the use of a depressurization system of the dies and the adoption of systems of control and monitoring of the process which allow to manage with repeatability and precision the parameters of mould filling.

The achievement of the technical objective requires a series of validations, ranging from mechanical characterization of the obtained castings to the validation of process simulation systems and design methods. For this purpose, it is provided for carrying out a complete mechanical, microstructural and defectological characterization, both on specimens taken from the castings in different positions and on different thicknesses, and on complete castings to verify that the mechanical, microstructures and modalities of failure of the component properties are aligned with those required by the designers and provided by set of filling, solidification and structural simulations that, at the same time, will be made on the same components. In this way, we want to define a complete set of data and planning tools that allow component designers an heightened optimization both in terms of final weight and performance.

 

OBJECTIVES OF THE R & D PROJECT: ACHIEVED LEVEL OF INNOVATION

Compared to the reference market, namely the automotive, the project has a strong level of innovation. Indeed, the technology of gravity casting, whether gravity or low pressure casting, represents excellence for the process of structural component production in the automotive and aeronautical industries as it ensures mechanical performance and a casting integrity higher than any other foundry technique for the industrial-scale production.

This technique, by virtue of the developments in metallurgy and technology fields in recent years, now, makes it possible to produce castings of complex geometry, but hardly with wall thicknesses of less than 3,0 – 3,5 mm. This limits considerably the chances of developing optimized components from the point of view of the ratio weight / mechanical performance. At the current state of technology, the average thickness of the components for structural applications in gravity casting is about 4mm, while lower thicknesses are used only for reinforcing ribs of small size because of the difficulty of filling the thin and extended walls.

From the point of view of design and optimization of the components, the possibility of realizing castings of reduced thickness would allow a considerable saving of weight on all aluminium products already currently obtained by casting. Moreover,this would pave the way to all products which today are still realized through folded and assembled plates, with evident advantages in economic terms making possible the use of aluminium components, also on cars of medium - high production. Currently, in fact, the use of structural castings for the provisioning of large scale deployment vehicles is only justified by economic matters. Instead,in the field of production of sports cars or high-end segment and low numbers, the amplification of performances justifies the high costs.

The gravity casting, on the other hand, in the traditional sense, does not allow such thickness limitations on components of significant size and past attempts have obtained only partial results which haven’t allowed the industrialization and the employment in the structural field because of the poor quality relative to the completeness of the obtained castings.

The main objective of this project is, therefore, to be able to produce castings with thin wall with dimensions of interest for structural applications through an heightened improvement of current technologies of gravity and low pressure casting.

The achievement of such results would allow a significant differentiation compared to what is currently available on the market, allowing on the one hand to extend these results to the sectors of medium volumes and industrial vehicles, on the other hand to achieve important results, such as:

  • 15% increase of mechanical yielding and breaking, compared to what is achievable with the current processes of casting and heat treatment in gravity and low pressure.
  • Ensuring% of extension values before breakage of 10%.
  • Drastically reduction of the presence of inclusions - oxides - micro cavities due to shrinkages which may influence the duration to fatigue tests and can’t be found in process control with X-ray examination.
  • Reduction of the micro cavity size due to shrinkages present in castings lower than 50 microns - estimated limit of influence of the triggering to the breaking - evaluating the shape through the use of innovative softwares applied to the simulation.
  • Reduction of the uncertainty area relating to the fatigue tests performed on light alloy castings.

 

POTENTIAL IMPACT OF THE R & D PROJECT IN RESPECT TO THE REGIONAL PRIORITIES OF INTERVENTION AND TO THE REFERENCE MARKETS

The achievement of the project objectives would give a strong impulse to the production of castings in low pressure and gravity casting and could provide impetus to small foundries of gravity and low pressure casting of which the Lombardy region is particularly rich and that, at this time, suffer for a shortage of labour. In addition, it would be possible to convert these companies by making them produce components with high technological content and, consequently, with high value added. This is because the production of components with low value added and low technological content is gradually shifting towards countries with low labour costs ( mainly Eastern Europe).

 

ROLE OF PARTNERS

In order to achieve these objectives we decided to create a network of companies belonging to the automotive industry which can generate cross-functional expertise to the entire project.

The partnership has all the skills necessary for the implementation of the project activities, except for the skills related to the casting simulation. For this activity will be used, as specified, an external consultancy of the EcoTre company, for their competences in the field of foundry with the integrated use of casting simulation software and FONDAREX vacuum technology.

 

The skills possessed and brought by each partner are complementary to each other and allow to complete the project successfully.