B7 steel Φ22 mm hot-rolled rod is fractured in cold of drawing
the fractured rod is tested by chemical composition
fractography
microstructure and energy spectrum analysis. The tested results indicate that the segregation of alloy elements Mn and Cr results in that martensite exists at the center of rod caused drawing fracture. By optimizing the rolling process of reducing the coiling temperature from 905 ~915
℃ t
o 840 ~ 850 °C and extending the holding time from 285s to 420s
martensite at the center can be effectively reduced to eliminate cold drawing rod fracture phenomenon.