Studies on the uniformly spheroidizing of Cementite in a Plain carbon Steel

In this report, the author studied the influences of heat treatment and forging on the uniform spheroization of cementite in three kinds of commercial carbon steels with carbon 0.21,0.49 and 1.07% by means of microscopic observation and hardness measurement. The results obtained are as follows : (1) Uniformalization in form and dispersion of spheroidized cementite in low carbon steel is remarkably improved by forging at the temperature range from 550℃ to 650℃, but, spheroidized cementite in high carbon steel is coarsened by forging at the same temperature range. (2) When comparing the spheroidized cementite in forged material at the temperature range from 550℃ to 650℃ with spheroidized cementite in material as quenched, we know the former shortens spheroidizing time by 10 hours to 15 hours under the same heating temperature. (3) In order to make uniform the uniformalization in form and dispersion of spheroidized cementite in low carbon steel, it is advisable to do the forging at the first stage of tempering below A_1 transformation rather than within the austenite range (900℃&acd