Fracture Failure Analysis of Tapping Screw Used for Washing Machine

The fracture failure cause of the PH-INT-PC 4×14.5 tapping screw used for washing machine was analyzed by means of optical emission spectrometry,micro-hardness tester,optical microscopy,the scanning electron microscopy and energy dispersive X-ray spectrometer.The results show that the fracture of the screw was due to hydrogen embrittlement brought during manufacture process of both pickling and galvanizing of screw.In order to avoid the hydrogen embrittlement of the tapping screw,the technical parameters of the pickling and galvanizing have been modified,and hydrogen should be relieved after galvanizing as soon as possible.