Influence Of Pore On Strength Of Brazed Diamond Joint And Grinding Performance Of Grinding Wheel Segment

Grinding process,as one of the most important and effective processing technologies,is the most widely used process in realizing precision machining and ultra-precision machining.As a grinding tool mostly used in the milling of difficult-to-machine materials,the superhard abrasive brazed grinding wheel is greatly distinguished from conventional bond grinding wheels.The superhard abrasive brazed grinding wheel has greater advantages than the traditional bond grinding wheel.Through the chemical metallurgical reaction during sintering,the grinding wheel brazed with superhard grits improves the holding strength between the solder metal and superhard grits.The emergence of monolayer superhard abrasive brazing wheel can improve the problem of premature shedding of abrasive particles due to insufficient strength.However,because the thickness of the grinding layer is too thin,the monolayer brazed superhard grinding wheel has the problem of finite life.Although the multi-layer brazed grinding wheel produces multi-layer distributed abrasives,it solves the limitation of single-layer brazed grinding wheel.However,due to the high holding power of multi-layer brazed grinding wheel on superhard abrasive particles,the self-sharpening performance of grinding wheel is not high,and it needs to be sharpened regularly,which affects the processing quality and production efficiency.Therefore,the porous brazed diamond grinding wheel was prepared by introducing the pore structure into the multi-layer brazed diamond grinding wheel,and the content of pore-forming agent was optimized to make it have good grinding performance in grinding work.The main contents are as follows:(1)A single grain grinding experiment was carried out.The results show that: Given the same grinding parameters,the grinding force decreases as the speed increases,and it grows in deeper depth.With the increase of grain size,the grinding forces of cone diamond and truncated octahedral diamond are increased,and the grinding forces of cone diamond are smaller overall.With the increase of wear degree,the normal grinding force of abrasive particles increases.(2)A single particle brazed joint model was established and the finite element grinding stress analysis was carried out.The results showed that the small particle size would be subjected to the concentration of grinding force,resulting in a larger stress value,and bear a greater risk of failure at the brazed joint.The bearing capacity of the larger particle size is stronger.The grinding stress of brazing joint with cone shape is greater than that of octahedron,especially the stress value of diamond abrasive has great difference.The grinding stress of brazed joint increases with the increase of abrasive wear degree.The addition of pores will increase the stress of Cu-Sn-Ti and Ti C in the brazed joint of single diamond abrasive,thus reducing the strength of the brazed joint,and it is related to the distribution of pore position.(3)Using Cu-Sn-Ti solder,diamond and NH4HCO3 pore-forming agent as the main raw materials,the multilayer brazed diamond segment with pore structure was prepared.The porosity variation law and bending strength of the segment were analyzed.It was found that the porosity was positively correlated with the content of pore-forming agent,while the bending strength was negatively correlated with the content of pore-forming agent.In the bending test,with the addition of NH4HCO3,the pores in the grinding wheel segment increase,and irregular holes appear,and the resulting stress concentration leads to the weakening of the holding strength.The pores will become the main crack source,and the cracks will expand along the pores until the diamond segment breaks,and the number of diamonds at the fracture is small.(4)In order to determine the best content of pore-forming agent with which the porous brazed diamond grinding wheel exhibits the superior self-sharpening property,experiments were carried out to grind wheel segments with different contents of pore-forming agent,and the wear morphology was observed.The results show a minimum grinding force of 1.54 and the best surface roughness of Ra=0.065 um when the content of pore-forming agent is set at8%.At the same time,there are obvious pores on the surface of the grinding wheel,and there are abrasive particle shedding pits and abrasive particle exposure phenomenon,indicating that the self-sharpening of the grinding wheel gradually gets better.