Accelerated spheroidization of cementite in high-carbon steel wires by drawing at elevated temperatures

The spheroidization of cementite lamellae in high-carbon steel wires could be achieved in a short time by drawing at elevated temperatures below the A sub 1 temperature. The rapid spheroidization was attributed mainly to shearing or fracturing of cementite plates into smaller particles. Sharp edges of the fractured particles were thought to be blunted by the diffusion of Fe and C atoms. The diffusion rate in the case of drawing at elevated temperatures was very rapid compared with that in the case of static annealing, due to continuous regeneration of dislocations and vacancies during the drawing. However, the mechanical properties of the spheroidized wires were deteriorated by internal voids formed during the drawing. Such a disadvantage could be circumvented by many cold-drawing passes followed by a final single drawing pass at an elevated temperature. 12 ref.--AA