Ultrasonic behavior of plastically deformed and heat treated steel

Studies were made on the longitudinal ultrasonic velocity and its attenuation characteristics in medium carbon steel forging subjected to 0–60% hot upsetting followed by heat treatment. The fineness of ferrite and pearlite increased with increasing deformation and cooling rate during heat treatment. The area fraction of pearlite increased from 21% to 45% as well as the mean interlamellar spacing in pearlite decreased from 8.79 μm to 0.689 μm in the 40% deformed (upsetted) normalized sample It was observed that the ultrasonic velocity decreased with increasing degree of deformation. The velocity was found to be highest in the normalized steel acquiring a value of 5920 m/s and lowest in hardened steel acquiring a value of 4979 m/s. The attenuation decreased with increasing deformation resulting in increased back wall echo heights. The residual stresses on the surface of typical 60% deformed and annealed steel samples using x-ray diffractometry were measured to be — 39.7 MPa (compressive) and — 188.0 MPa (compressive) respectively.