Stress Corrosion Cracking Failure of Jackbolts for Die Casting Press

Several prematurely failed jack bolts were analyzed to determine the root causes of failure. Bolts were employed to ensure that die halves do not separate during casting of high pressure die castings of light metals. Fractography of jack bolts revealed unusual morphology consisting of both circumferential and longitudinal cracking. The basic fracture type was identified as transgranular cleavage (brittle) fracture mode. SEM / EDS analysis of the fracture surface revealed the presence of, to varying degrees, chemical species containing sulfur (S), oxygen (O) and chlorine (Cl). Material composition, heat treatment, microstructure and hardnesses of the jack bolts were found to be in agreement with the expected steel grade and properties. It was concluded that the failure of the bolts was due to a combination of inappropriately chosen mechanical properties of the bolts, operating stress, and the presence of corrosive environmental materials leading to ideal conditions that promoted stress corrosion cracking failures. Suitable remedial actions to alleviate the risk of SCC failure of the bolts are presented and discussed in the paper.