Failure analysis of large press die holder

•The failure was caused by high stress under the condition of material embrittlement.•The fracture morphology and mechanical properties were investigated.•The mechanism of material properties degeneration was studied.•The microstructure and precipitates were studied by TEM.•The thermal mechanical stress was simulated by finite element analysis.

This paper studied the cracking mode and mechanism of the large press die holder. Detailed investigations including macroscopic examination, metallographic observation, microfractography, chemical analysis and mechanical properties analysis were carried out. The investigations reveal that the failure mechanism of the die holder is fast brittle fracture caused by high stress under the condition of material embrittlement. The main crack originated from the fillet of the die holder. The serious impact toughness degeneration at the bottom of the die holder resulted in the material embrittlement. The transmission electron microscopy (TEM) investigation indicates that the material properties degeneration is related to the coarsening precipitates of M23C6 and M6C. The finite element analysis (FEA) demonstrates that the fillet suffering high stress is the weak part of the die holder.