EN
In this study, the effect of martensite volume fraction on ductile to brittle transition of microalloyed steel joined by welding was investigated. Triple phase steel contains ferrite, perlite and martensite phases and was joined by two types of welding method as gas metal arc welding and the electric arc welding. Presence of three phases in adjacent to each other was confirmed by metallographic analysis and scanning electron microscopy studies. All welded samples were exposed to Charpy impact test at the temperature range of -30C to 30C in order to measure the fracture energies of samples having different amount of martensite volume fractions. The fracture surface micrographs of Charpy specimens, examined by scanning electron microscopy and optical microscopy, confirmed the reduction in ductility of ferrite-perlite-martensite steels with increasing martensite volume fraction.