Effect of Austenitizing Temperature on Pearlite Transformation of a Medium-Carbon Steel

Pearlite transformation is a necessary step in the production of ultra-high strength wires and nanostructured bainitic steels. The initial austenite grain size has an important influence on the bainite and pearlite transformation. The effect of austenitizing temperature on the austenite-to-pearlite transformation in a medium-carbon steel was investigated by using a Gleeble 1500 simulator. The initial austenite grains coarsened from 33.7 to 68.5 m when the austenitizing temperature increased from 850 degrees C to 1100 degrees C. The phase-volume percentage and interlamellar spacing of the pearlitic microstructure decreased from 86.6% to 5.2%, and from 114 nm to 110 nm, respectively, in the same austenitizing temperature range. The starting temperature of the pearlite transformation was inversely proportional to the austenitizing temperature. The pearlite-transformation temperature range (43-48 degrees C) did not change visibly with austenitizing temperature. The Vickers hardness of the transformed microstructure (pearlite + martensite) was proportional to the austenitizing temperature.