Heat treatment process: The heat treatment process has a greater influence on the performance of the piston rod. For example, due to improper heat treatment process, reticular ferrite and Widmanstatten structure appear in the piston rod of the oil cylinder, causing embrittlement of the grain boundary. Coupled with the high content of sulfide inclusions, the ability of the piston rod to withstand alternating loads decreases, and finally brittle fracture occurs. The piston rod of the excavator undergoes multi-source fatigue fracture prematurely due to improper heat treatment process and rough machining tool marks at the transition fillet.

Machining tool marks: Rough machining tool marks will affect the performance of the piston rod. For example, the rough machining tool marks at the transition fillet of the piston rod of the excavator lead to premature multi-source fatigue fracture.