M. O. H. Amuda, D. E. Esezobor, G. I. Lawal, University of Lagos, Lagos, Nigeria
The level of hardness induced in heat-treatable carbon steel in a typical quenching process is dependent on operating parameters such as austenitizing temperature, quenching media, soaking time, size and shape of material, as well as condition of surface. The hardness value affects the inelastic response of material to impact loading. The paper studies the relative influence of the various quenching variables on the fracture response of 0.3C hypo eutectoid plain carbon steel. The study reveals that the fracture toughness decreases with increasing austenitizing temperature and soaking time; and rise when quenching is delayed for 30 minutes. The highest value of fracture toughness (207.37NM) is recorded when oil is used as quenching medium compared to brine solution (37.96NM). The oil and greasy surface records higher value of impact toughness (143.72NM) than clean surface. The fracture toughness of the hypo-eutectoid carbon steel can also be increased increasing plate thickness
These results are attributed to the differential distribution of the non-equilibrium phase of martensite, ferrite (pearlite) and retained austenite on the account of the incidence of different quenching variables.
Summary: The manuscript entitled “EFFECTS OF QUENCHING VARIABLES ON THE FRACTURE TOUGHNESS OF 0.3C HYPO-EUTECTOID PLAIN CARBON STEEL” is a technical paper which represents completed original work embodying the results of laboratory investigation of the relative influence of the various quenching variables on the fracture response of 0.3C hypo eutectoid plain carbon steel. It aims at establishing the pattern of relationship between some process parameters and fracture toughness of metallic materials in order to predict the properties of the material
