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在现代的金属工艺中,为节约材料和提高材料性能,对线材或棒材等长材经常采用拉拔工艺进行加工。在这种加工艺中,会出现一种表面因拉拔而产生的白亮层,这一白亮层很薄,但硬度很高,常常引起拉拔件表面开裂,有时甚至会引起拉拔件断裂。在以往的文献记载中,常根据其硬度接近马氏体,将其归结为拉拔过程中表面异常升温而产生的马氏体。作者有幸接触到了一起因表面白亮层而导致的表面开裂,但分析结果是白亮层为极其破碎的渗碳体与铁素体的机械混合物,只是腐蚀剂由于表面张力无法进入,而使得其在金相显微镜下观察呈白色。
In modern metalworking, long materials such as wire or rod are often drawn by drawing to save material and improve material properties. In this artisanal process, there is a white bright layer on the surface due to drawing, which is very thin and white, but high in hardness, often causing the surface of the drawing element to crack, sometimes even causing the drawing element to break. In the past literature, often according to its hardness close to the martensite, attributed to the abnormal heating of the surface during drawing martensite. The authors were fortunate enough to have had surface cracking caused by a whitish surface layer, but the analysis revealed that the bright white layer was a mechanically broken mixture of cementite and ferrite, except that the etchant did not enter due to surface tension, Observe white under the microscope.