硬线盘条笔尖状断口断裂分析

采用光学金相显微镜和电子探针分析仪等测试方法对70、77MnA、82B硬线盘条在冷拉拔过程中产生笔尖状断口断裂的试样进行了分析。结果表明,硬线盘条在冷拉拔过程中断裂的断口特征为笔尖状(与之匹配的另一端为漏斗状),断裂的主要原因是盘条近中心部位存在P、Cr、Mn、S等元素的中心偏析。成分偏析的微观组织特征在纵向磨面上主要表现为偏析带、马氏体组织和网状碳化物。

Analysis on Pen-tip Shaped Fracture of Hard Wire Rod

The testing pieces of pen-tip shaped fracture occurring in the process of cold drawing the hard wire rod 70,77MnA and 82B have been analyzed by optical metalloscope and electron probe analyzer.Results show that the unique feature of the fracture of the hard wire rod generating in cold drawing is pen-tip shaped rupture (in contrast with the fracture in the opposite end,a funnel shaped rupture)and the primary cause to the fracture is found to be the central segregation of P,Cr,Mn and S etc.in the vicinity of the central area of the wire rod.The microstructures of the segregation along the longitudinal surface are mainly composed of the segregation band,martensite and web like carbonate.