Fracture Analysis of Hammer Rod of Free Forging Electro-hydraulic Hammer

The hammer rod of a 5 t free forging electro-hydraulic hammer fractured suddenly in the course of forging. By means of macroscopic examination, chemical composition analysis, metallographic examination, mechanical properties test and so on, the fracture causes of the hammer rod were analyzed. The results showed that there were obvious machining marks at the arc transition position of hammer piston and rod because it didnt machine smoothly according to the design requirement. The machining marks induced serious stress concentration and initiation of the cracking origin at the arc transition, and at the same time the mechanical properties of the hammer rod was lower than the requirement, which resulted the hammer rod fractured with mode of low strain and high cycle early fatigue under the condition of tension-compression load.