Theoretical And Experimental Research On Creep Feed Grinding Of Narrow Deep Groove Of AISI 4340 Steel

In this paper,based on the achievements about machining mechanisms and surface qualities of high-speed and ultra-high speed grinding,after getting a good knowledge of mechanical properties and friction and wear characteristics of AISI 4340 steel,a creep feed grinding test of narrow-deep-groove of AISI 4340 steel was carried out by a monolayer electroplated CBN pattern grinding wheel.And grinding force and grinding temperature were measured at the same time.After grinding test,the surface morphology and roughness were observed and measured on the groove side-surface.Then the influence of grinding process parameters on the grinding force,grinding temperature and the quality of groove side-surface(including surface morphology and surface roughness of workpieces)were analyzed.The main research work completed are as follows:(1)Tensile experiments of AISI 4340 steel were carried out at room temperature and the mechanical properties of AISI 4340 steel were obtained.(2)Tribological behaviors of AISI 4340 steel have been investigated under dry sliding conditions at the room temperature.The morphology characteristics of the worn surface as well as the sub-surface have been observed to analyze the friction and wear behavior of AISI 4340 steel and the influence of parameters on the tribological behaviors in detail.Under the experimental conditions,the friction coefficient fluctuates irregularly with the increase of the load and decreases with the increase of the sliding speed.The volume loss presents an increase tendency with the increase of the load and the sliding speed,in which the sliding speed has a relatively slight impact on the volume loss and maintains the volume loss at a low level.The wear mechanisms gradually vary from abrasive wear to abrasive wear,adhesive wear and even oxidation with increasing the sliding speed and the load.The thickness of the friction affecting layer under the surface increases with the increase of load and decreases with the increasing sliding speed.The plastic deformation and thermal softening caused by the combination of the frictional force and frictional temperature are the main factors that affecting the topography of the surface and the subsurface.(3)A creep feed grinding test of narrow-deep-groove was performed on AISI 4340 steel by a monolayer electroplated CBN pattern grinding wheel in the MV-40 vertical computerized numerical control machining center.In order to bring to light the influence of grinding process parameters on the grinding force and grinding temperature,the grinding force and grinding temperature were measured at the same time.It was found that the grinding force and the grinding temperature both increased firstly and then decreased during the grinding process,and the maximum grinding temperature and grinding force occurred within a certain time after the length of grinding contact arc reached the maximum.For various conditions,the normal grinding force is always greater than the tangential grinding force,and both of which decrease with the increase of the grinding wheel speed and increase with the increase of the workpiece feed velocity and the cutting depth,while the highest grinding temperature in the grinding zone decreases gradually with the increasing wheel speed and increases with the increasing workpiece feed speed and depth of cut.The workpiece feed velocity has a most significant influence on the grinding temperature,followed by the depth of cut and the workpiece speed.(4)The surface morphology and roughness were observed and measured on the groove side-surface,so as to analyze the influence of grinding parameters on the surface morphology and surface roughness.It was found that scratches along the cutting direction and residual wear debris were observed on the surface under various grinding parameters,and some rough scratch areas with brittle peeling-like features were found for some parameters.The surface texture tends to be uniform and the value of surface roughness decrease significantly with the increase of the grinding wheel speed,while increasing the workpiece feed speed and depth of cut,sizes of the scratche on the grinding surface increase gradually and the surface quality deteriorates,which result in an increase in the value of surface roughness.