MEDIUM-CARBON MICROALLOYED STEEL 49MNVS3 - DEVELOPMENT TOWARDS IMPROVED QUALITY

Art investigation was carried out at Tata Steel on 49MnVS3 steel in or der to achieve a combination of higher tensile strength with improved room temperature toughness. It was observed that with low oxygen conte nt and presence of stoichiometric level of titanium (with respect to i ts reaction with nitrogen) and by controlling the forging parameters, it is possible to achieve a room temperature impact values of 20-25 Jo ules (DVM, U notch) at yield and ultimate tensile strength level of 50 0 and 800 MPa respectively in this grade of steel. The transmission el ectronmicroscopy study revealed the presence of V4C3 in proeutectoid f errite along with a pearlite of fine inter lamellar spacing in microst ructure of such steel. When sulphur level of this steel was increased from 0.032 to 0.060%, keeping oxygen level low,the steel exhibited onl y a marginal improvement in machinability. This indicates the signific ant contribution by low oxygen content in this steel over the sulphur content for improving the machinability.