我国陶瓷片密封水嘴产品质量现状分析及改进建议

Analysis on the reason of hot dip galvanized square tube＇s brittle fracture

某工程中幕墙使用的热镀锌方管在焊接时出现大规模脆性断裂的现象，对其正常使用产生了严重影响，为了分析其脆断的原因，本文以断口试样为对象，借助扫描电子显微镜、能谱仪、直读光谱仪、万能材料试验机，对其进行了一系列的试验，并深入分析。试验结果表明，方管在镀锌之前已经存在裂纹，起到了断裂源的作用；3种方管试样中均有游离渗碳体出现，级别为4．5级，且呈网状分布在晶粒边界处，这种游离渗碳体组织一般是钢材在退火过程中形成的，是导致钢材发生脆性断裂的主要原因之一。

In a curtain wall engineering, lots of hot dip galvanized square tubes occurred brittle fracture when welding, which brought serious impact on its normal use. In order to analyze the reason of the fracture, this paper did lots of research and in-depth analysis relies on scanning electron microscopy, energy dispersive spectroscopy, direct reading spectrometer and universal material test machine. The resuhs show that the square tube exist tiny fracture before hot dip galvanizes which plays a role of fracture source. 3 groups of square tubes＇ boundaries of grain all appears free cementite, distributes like a net, with level 4.5. This kind of cementite structure is generally formed during annealing of steel, which is one of the main reasons on the brittle fracture