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A new approach to strengthening technology for metallic strips used in the electro industry

This project focuses on studying and taking a new approach to the strengthening technology for silver and copper strips used in electro fusing elements

The technological difficulties of the project are presented by a new approach of the strengthening technology for metallic strips used for the electro industry. The aim is to produce the properties required for all kinds of metallic strips using technological procedures. The most important will be the thermo-mechanical treatment of metallic casting which, using a proper combination of mechanical and heat treatment, fulfils the demanded dimensions and physical properties of Ag and/or Cu strips. Such technology has to be investigated. Although a lot of technologies for metal strip manufacturing are known about nowadays, i.e. the fundamentals of manufacturing techniques differentiated partly or completely by their feasibility for producing various shapes, a solution for correct sequence technological phases, especially when producing Ag and Cu metal strips with different thicknesses and widths, is unknown. In individual manufacturing phases, there are no solutions for controlled thermo-mechanical treatment for both kinds of strips to produce quality physical properties at various strip dimensions. The specific electrical conductivity and hardness demanded are the most important properties and could be using inappropriate technology in an inverse relationship. This means that if the strip has demanded electric conductivity, the hardness is too low (< 70 HV) and vice versa; if the hardness is high enough, the electrical conduction is too low. This is why the research activities also include the study of a technological parameter's influence on the crystal microstructure and on the physical properties of metallic strips. Detailed knowledge of material properties' changes during the manufacturing process of the present thermo-mechanical treatment has to be known in order to already plan the physical properties during the process of manufacturing. Because of superficial knowledge of changes during the thermo-mechanical process, the results of simulations are significantly different from the real behaviour of the strips, resulting in poor physical properties. With the study and, consequently, analysis of technological parameters in individual phases of the complete process of manufacturing, especially the thermo-mechanical treatment (the temperature, atmosphere and duration of annealing, the circular velocity of cylinders, the ratio of cylinder diameter versus the degree of contraction, bite angle, slitting, trimming, etc.) on the microstructure and final physical properties of the strips, their influence will be given exactly. The detailed analyses of each technological parameter on the final properties will be investigated. In this manner, new models will be established for detecting any changes in the properties of metallic strips at each phase and thermo mechanical treatment. Using these models, an accurate view of the changes in physical properties during and after manufacturing the industrial production will begin. Apart from well-known technology of thin metallic strip manufacturing, the international consortium will try to introduce alternative technological possibilities, which could be significantly cheaper and result in much better physical properties. These technologies are: continuous casting, powder metallurgy, melt spinning, internal oxidation, double roll quenching, planar flow casting, melt drag, melt extraction etc. These are techniques that could enable appropriate or even new mechanical properties of the strips in an easier way or at a lower cost. All the mentioned procedures represent, in most cases, a new generation of technology and ecology-friendly procedures. Continuous casting offers several advantages over conventional casting of semi-finished metal products including lower production costs and higher production rates as well as better surface quality and excellent internal integrity of the products. Continuous casting experiments will be carried out using a laboratory scale set-up consisting of a vacuum induction melting furnace and a vertical continuous caster. The most important parameters of this process will be: the type of nozzle, nozzle diameter, drawing mode, resting time, the length of the reverse drawing stroke, casting speed, cooling, etc. The macro and microstructure of casting strips will be monitored according to the local solidification conditions, applied nozzle/mould set-up and the selected withdrawal mode. The other possible alternative manufacturing process in producing thin metallic strips is the melt spinning technique. Using a classical casting procedure, a large macro-segregation of alloying elements, grained microstructure and segregation of inter-metallic phases can be formed. This defect results in poor mechanical, corrosive and other properties of pre-form casting. In additional manufacturing phases, these properties can not be improved, in many cases the properties get worse. The rapid solidification conditions are totally different. The velocity of cooling is very high and is in the range of 10-10(exp+8) K/s, while the solidification boundary is moving very fast (vsf > 1cm/s). Under these conditions the atoms' diffusive paths become too short in liquid to have the thermodynamic equilibrium in the solidification boundary. Such in-equilibrium solidification in the microstructure sees crystal and quasi-crystal. The aim of this research is to find a possibility for producing metallic strips without thermo-mechanical treatment. Keywords: production.
Acronym: 
MET-STRI
Project ID: 
3 863
Start date: 
01-01-2006
Project Duration: 
41months
Project costs: 
2 380 000.00€
Technological Area: 
Forming (rolling, forging, pressing, drawing)
Market Area: 
Other electronics related equipment

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