Study of Low Tempering Temperature on Microstructure and Properties of Cold-drawn Pearlite Steel Wires

The properties and structure changes of a cold-drawn pearlite steel wire annealed at 200～300 ℃ were studied,and the strengthening and toughening mechanism during tempering was revealed by means of scanning electron microscopy,transmission electron microscopy,X-ray diffraction and conventional mechanical testing methods in this paper.The results show that the pearlite layer of cold drawn steel wire is not continuous,and the precipitation behavior of cementite nanocrystals exists during drawing and tempering.The strength and ductility of cold-drawn steel wire are improved after annealing.With the increasing of annealing temperature,the strength is increased slightly and the ductility is further improved.The change of strength is mainly due to the dislocation strengthening effect,while the improved ductility is due to the fact that the newly precipitated nanocrystalline particles can reduce the stress concentration during tension by rotation and sliding.