Ultra-low-carbon steel spheroidization and torsion

Spheroidizing annealing and torsion testing of 0.027wt% carbon steel rod were conducted to evaluate spheroidization kinetic behavior at 943K (670 degrees C) under deformed and non-deformed states. Kinetic curves were also predicted using the Johnson-Mehl-Avrami-Kolmogorov equation, and the results agree well with the experimental ones. After spheroidization was performed twice, the spherical cementite and precipitated carbides became smaller and the distribution was more uniform. Comparison of materials subjected to single and double spheroidizing annealing indicated a difference in grain size. Torsion performance wasconsiderably improved under double spheroidization, especially the maximum torque with slight variations.