1Cr18Ni9Ti棒材“裂纹”缺陷的失效分析

Analysis on the Crack in 1Cr18Ni9Ti Bar

本文通过对典型"裂纹"状缺陷进行外观检查、表面缺陷微观观察和能谱分析,以及对"裂纹"纵剖面进行光学金相观察、电子金相观察及能谱分析,确定了"裂纹"实为"面状损伤",表面可见剪切韧窝和刮擦痕迹,有颗粒镶嵌物和附着物;"面状损伤区"表面颗粒的组成主要为1Cr18Ni9Ti中Mn、Cr两种合金元素的氧化物;圆饼的正反表面缺陷之间存在两条连贯的轴向缺陷,即正反表面的缺陷实际是轴向缺陷的横截面显示。得出了1Cr18Ni9Ti棒材的次表面存在两条轴向分布的连续缺陷带,其在钢棒横向切割时被截成多节;缺陷为大量高O、Mn、Cr元素的颗粒氧化物组成,颗粒氧化物作为硬质颗粒,在机械加工中受刀具拖动刮伤金属表面,形成了"面状损伤区";缺陷颗粒物可能来源于合金冶炼过程或者由内部氧化孔洞在锻造时拉长而成的结论。

Through examining the appearance of the typical defects like crack,microscopic observation of surface defects and energy spectrum analysis,and observing the longitudinal section of crack by optical metallography,electronic metallography and energy spectrum analysis,It is confirmed that the crack is actually surface damage,with shear dimple and scratch marks,particle inlay and attachment on the surface.The composition of the surface particles in the area of surface damage is mainly the oxides of Mn and Cr in 1Cr18Ni9Ti steel;there are two consecutive axial defects between the positive and negative surface defects of the round disk,that is,the defects on the positive and negative surface are actually the cross-section display of the axial defects.The results show that there are two continuous defects on the secondary surface of 1Cr18Ni9Ti bar,which are cut into several sections when the bar is cut transversely;the defects are composed of a large number of particle oxides with high O,Mn and Cr elements,as hard particles,the particle oxides are dragged by the cutter to scratch the metal surface,forming a surface damage area;the defective particles may be from the alloy smelting process or the internal oxidation hole is elongated during forging.