Abstract: 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 ℃ to 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.

摘要： B7钢Φ22 mm热轧盘条在冷拔中断裂,采用断口观察、化学成分、显微组织检验以及能谱分析测试了断裂盘条。测试结果表明:Mn、Cr偏析导致盘条中心存在马氏体组织是造成拉拔断裂的原因。通过轧制吐丝温度由905～915℃降至840～850℃以及保温时间由285 s延长至420s,可有效减少心部马氏体的产生,消除了冷拔断裂现象。

关键词: B7钢盘条, 冷拔断裂, 成分偏析, 吐丝温度