The Comprehensive Effect of Controlled Cooling and Si/Mn Elements on the Structure-Property Relationship of a Novel Wire Rod

Novel wire rods prepared for ultrafine-grained steel wire were manufactured with different cooling processes, and their tensile properties were investigated. Through process and composition improvement, the tensile strength of the wire rod was improved from 1392 to 1513 MPa. Annealed pearlites were obtained by Stelmor cooling technology, whereas fine pearlite lamellae were obtained with an isothermal organic solution bath. The average grain size was significantly refined from 3.64 to 2.05 μm with the isothermal organic solution bath. This study indicated that the enhancements in tensile strength and yield strength were accompanied by an increase in the proportion of grain boundary misorientation angles (2°-5°). The elongations of the wire rod were influenced by the length of the grain boundary misorientation angles (5°-65°). Cementite dissolution occurred in the process of steel wire drawing. Stable cementite was conducive to the drawing process and tensile properties of the wire rod. The variant composition of Si/Mn was the main factor affecting the stability of cementite. Thus, a schematic diagram of the indirect effect of Si on cementite was provided. According to the results of Thermo-Calc software, the composition design with high Mn and low Si contents effectively increased the stability of cementite.