| The roller is one of key parts to protect the normal operation of the valve mechanism in diesel engine for ship.For large marine diesel engines due to the bad working conditions,lubricating the difficulties,GCr15 bearing steel material are chosen by rough machining?heat treatment?grinding?dipping treatment to produce.GCr15 bearing steel with high strength and hardness,ductility and toughness characteristics,because of the heat treatmen,micro-cracks often appear in the following process easily,which wastes resources and delay production,even can cause great economic losses seriously.It is important to make analysis of crack failure mechanism which occurred during roller machining,make optimization of grinding low-stress technology.The main study content and result is listed as follows:(1)Take a certain model of roller in diesel engine for ship as object to make analysis of crack failure mechanism by measuring composition of failured roller,observing metallographic,measuring hardness of roller.It turns out that the residual stress of heat treatment and gringding does not release fully,and they superimpose each other.During the process of dipping treatment,stress corrosion occurs.(2)Make analysis of heat treatment residual stress using software SYSWELD;reaserch the process of grinding,make analysis of grinding using software ANASYS and know the distribution of grinding temperature and residual stress;use software Deform to make analysis of grinding temperature and force change.(3)Grind specimens with different grinding process parameters,ues CLSM to observe the finished surface and Surtronic to test roughness.It turns out grinding depth affects the quality and roughness of finished surface mostly.(4)Make optimization of grinding process based on above researching,verify the feasibility of the optimized grinding process by measuring composition of failured roller,observing metallographic,measuring hardness of roller with grinding process. |
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