Drawing Behavior of Pearlitic Steel Wire Rods Controlled by Boron Addition in Medium Carbon Steel

One of the most effective methods to increase the productivity and cost down in wire manufacturing is eliminating the patenting heat treatment during drawing process. For that purpose, the ductility increase of wire rods is essential to draw wire without breakage. Dilute pearlite, i.e., pearlitic structure with low cementite volume fraction, would be optimum microstructure for increasing the drawing strain, because ferrite-pearlite interface and cementite, which act as void initiation sites, are reduced. To obtain such microstructure in production line, addition of boron was examined. As results, mechanical properties of eutectoid steel are little affected by boron addition. But, in boron added medium carbon steel, ductility is enhanced, especially large elongation at sever deformed wire after bluing. It would be due to increase the strain hardening rate by reducing of proeutectoid ferrite and cementite stabilization.