N. Ratković, Faculty of Engineering, University of Kragujevac, Kragujevac, Serbia. R. Nikolić, Faculty of Civil Engineering, University of Žilina, Žilina, Slovakia. I. Samardžić, University of Osijek, Mechanical Engineering Faculty in Slavonski Brod, Croatia. Fundamental principles of friction welding of dissimilar steels (high speed and tempering steel) from the aspect of metallurgical and che...