The modern high voltage power overhead lines operate with high temperature low sag (HTLS) conductors due to possibility of the current capacity increase. HTLS conductors are material and technological advanced solutions. The main advantage of HTLS conductors is a special designed operation conditions which cause the transformation of tensile stresses from the external aluminium base layers to the core. The conditions of this transformation are called “knee point” because a rapid change of the conductor sag - temperature relationship is observed. Prediction of conditions of the “knee point” temperature (KPT) is a key problem during overhead line design. The KPT is a function of different factors like conductor materials properties, conductor design, span parameters, sagging procedures and overhead line exploitation conditions. The paper presents an original theoretical model for HTLS conductors KPT calculations and shows some examples and comparisons of the different conductor designs and parameters.

Modern manufacturing technologies of flat cold-rolled products made of aluminium and its alloys are based on raw materials produced with the use of continuous casting technology. One of the most frequently used integrated production processes, based on continuous casting of metal, is twin roll casting method (TRC). In TRC method liquid metal flows into the area formed by two water-cooled rolls, solidifies and next is deformed (rolled) which allows to obtain strip with several millimetres thickness. Thanks to this, it is possible to eliminate hot rolling stage from the typical production technology, and directly subject obtained sheets to cold rolling process.This paper presents results of cold rolling strain dependency on the mechanical properties of tested aluminium alloys from 1XXX, 3XXX and 8XXX series, produced in the laboratory conditions with the use of TRC method. Furthermore the rolling loads and basic mechanical properties, determined in an uniaxial tensile, were examined.

Modern industry expects aluminum products with new, unusual, and well-defined functional properties. Last years we are able to notice constant development of aluminium alloys. In food industry, power engineering, electrical engineering and building engineering, flat rolled products of 1XXX series aluminium alloys are used.8XXX series alloys registered in Aluminium Association during last 20 years may be used as an alternative. These alloys have very good thermal and electrical conductivity and perfect technological formability. Moreover, these materials are able to obtain by aluminium scrap recycling. Fundamental alloy additives of 8XXX series are Fe, Si, Mn, Mg, Cu and Zn. Aluminium alloying with these additives makes it possible to obtain materials with different mechanical ale electrical properties. In this paper, the analysis of alloy elements content (in 8XXX series) effect on chosen properties of material in as cast and after thermal treatment tempers has been presented.Keywords: aluminium 8XXX, electrical conductivity, hardness, homogenization Współczesna gospodarka oczekuje wyrobów aluminiowych o nowych, lepszych i ściśle określonych właściwościach użyt-kowych. W ostatnich latach obserwowany jest ciągły rozwój stopów aluminium. W przemyśle spożywczym, energetyce, elektrotechnice i w budownictwie tradycyjnie stosuje sie płaskie wyroby walcowane ze stopów aluminium serii 1XXX. Alternatywą są zarejestrowane w ostatnim dwudziestoleciu w Aluminum Association stopy serii 8XXX. Stopy te mają dobrą przewodność cieplną i elektryczną oraz znakomitą podatność do odkształcenia plastycznego. Ponadto materiały te można otrzymywać na drodze recyklingu złomu aluminiowego. Podstawowymi dodatkami stopowymi serii 8XXX są Fe, Si, Mn, Mg, Cu i Zn. Stopowanie aluminium tymi dodatkami pozwala uzyskać materiały o zróżnicowanych własnościach mechanicznych i elektrycznych. W pracy przedstawiono analizę wpływu zawartości pierwiastków stopowych obecnych w serii 8XXX na wybrane własności materiału w stanach po odlewaniu oraz po obróbce cieplnej.

The paper shows a new idea of aluminium alloys. New alloys with specially selected alloying element i.e. silver have electrical conductivity similar to pure aluminium at ambient temperature and better than pure aluminium electrical conductivity at increased temperatures. Al-Ag alloys for electrical applications (mainly for electrical conductors) due to high electrical conductivity at increased temperatures at the level of the maximum conductor working temperatures give possibility of better current capacity of conductors. The experimental results of basic mechanical properties and the electric conductivity versus temperature relation are shown in the paper as well as examples of the tested material operational properties. The summary gives theoretical analysis based on examples of the potential applications of Al-Ag alloys (new conductor designs) which provide the benefits of the new solutions in comparison to traditional conductors.

Twin roll casting (TRC) technology is becoming increasingly popular because of the opportunity to receive aluminum strips which may serve as input for direct cold rolling processes. Furthermore, these strips have a favourable combination of mechanical and electric properties as well as dimensional tolerances. TRC line strips show segregation of alloying elements and structure providing a combination of casting structure and wrought alloy. As part of this study, the structure of the strips from the TRC line has been analyzed as well as the segregation of the alloying elements.