This article deals with the construction,property and process of All sealed box type nitrocarburizing production line and the use of the BJ493Q type diesel engine crankshafts.

According to the result of comparison test,microalloy steel(49MnVS3)is choosen as a material of diesel engine crankshaft and gains huge economic benefit through its gradual application in batch production.

Throughout the course of the study,measuring the impact of nip,measurement method,common measurement of the phenomenon and solutions,are an important part of the study in the management of nip of production safety measure is also an important part,to improve the life of diesel engine crankshaft.

Based on the principle of linear clastic fracture mechanics and the method of photoelastic test, an analysis as well as experimental investigation on 3-D stress state and mechanical parameters under fracture of the crankshaft of model 6160A diesel engine have been made for the purpose of the prediction of the safety.

The reason of failure and break had been investigated for heavy diesel engine crankshaft which broke by fatigue on the basis of the physical test and chemical analysis,macrograph and microfracturegraphy(SEM、EDS) of the broke crankshaft.