Association of Metallurgical Engineers of Serbia AMES Scientific paper UDC: 669.15'26'74'28-194 INFLUENCE OF Cr, Mn AND Mo ON STRUCTURE AND PROPERTIES OF V MICROALLOYED MEDIUM CARBON FORGING STEELS Nenad Radović 1 * , Ankica Koprivica 2 , Dragomir Glišić 1 , Abdunnaser Fadel 1 , Djordje Drobnjak 1 1 University of Belgrade, Faculty of Technology and Metallurgy, Department of Metallurgical Engineering, Karnegijeva 4, 11120 Belgrade, Serbia 2 Institute of Ferrous Metallurgy, Vuka Karadžića bb, 81400 Nikšić, Montenegro Received 02.12.2009 Accepted 11.01.2010. Abstract The influence of Cr, Mo and Mn on microstructure and mechanical properties of V-microalloyed medium-carbon steels has been studied by means of metallography and mechanical testing. Cr, Mn and Mo addition promotes the formation of bainitic sheaves suppressing the formation of ferrite-pearlite and acicular ferrite. The influence of Mn is somewhat masked by a low content of nitrogen. In a low nitrogen steel VN particles are not present and the nucleation of acicular ferrite is suppressed. The yield strength of Cr, Mo and Mn alloyed steels with bainite structures is lower in comparison to the base steel due to less pronounced precipitation strengthening effect. The presence of bainitic sheaves decreases the CVN 20 impact energy in comparison to ferrite-pearlite and acicular ferrite microstructures. Key words: Medium-carbon steels, Cr, Mo, Mn, bainite, acicular ferrite Introduction The main alloying element in microalloyed medium carbon forging steels is V which promotes strengthening by precipitation of V(C,N) particles which precipitate during and/or after austenite-ferrite transformation. At the same time, an increase in toughness is provided by intragranular nucleation of acicular ferrite, dominantly on VN particles [1-3]. In order to suppress the grain growth at high temperature, small amount of titanium is usually added [4]. * Corresponding author: Nenad Radović nenrad@tmf.bg.ac.rs