近焊缝区液化裂纹产生原因分析

为了改善工程施工过程中焊件焊缝开裂问题，采用SEM扫描电子显微镜、俄歇电子能谱仪（AES）对焊缝裂纹断口进行了微观形貌和化学成分分析，结果显示，裂纹断口属于典型的沿奥氏体晶界开裂的热裂纹形貌特征，Pb、Si、S、P元素在裂纹断口表面偏析严重。分析认为，该裂纹属于热裂纹中的近缝区液化裂纹，低熔共晶产物的存在是引起液化裂纹的主要原因。提出要尽量采用小的焊接热输入量，减少高温停留时间，从而减少低温共晶在高温下受拉应力的作用时间，有助于减少焊接热影响区裂纹的产生。

Analysis of Causes of Liquefaction Cracks in Near Weld Area

In order to improve the weld cracking of the weldment during the construction process， the microstructure and chemical composition of the weld crack fracture were analyzed by scanning electron microscope（SEM） and auger electron spectroscopy（AES）. The results show that the cracks extend along the austenite grain boundary and exhibit typical thermal crack morphology. The Pb， Si， S and P elements are segregated on the fracture surface. According to the analysis，the crack belongs to the liquefaction crack in the near-seam region in the hot crack， and the existence of the low-melting eutectic product is the main cause of the liquefaction crack. The use of small welding heat input reduces the high temperature residence time, thereby reducing the time for the low temperature eutectic to be subjected to tensile stress at high temperatures， and helps to reduce the occurrence of cracks in the heat affected zone of the weld.