Analysis on Fracture Reasons of SWRCH15A Steel Screws

The natural fracture happened to SWRCH15A steel screws after installation and use for one week. Through the methods of macroscopic examination, metallographic examination, hardness and carburized case depth testing, and fracture analysis, fracture reasons of screws were analyzed. The results show that during the process of zinc electroplating, the H+ and H2O existed in the solution caused the cathodic reaction and the precipitated hydrogen atoms gathered. It induced the stress corrosion of cathodic hydrogen embrittlement, and finally resulted in the delayed fracture of the screws.