Experimental Research Of Precision Grinding And Superfinishing On Raceways Of Si₃N₄ Ceramic Bearing Outer Rings

With the strategy "Made in China 2025" being put forward and implemented,the manufacturing and development of high-quality fundamental components will be under the spotlight.Ceramic bearings,as typical mechanical components,have excellent properties and reliabilities.However,the processing of raceways on ceramic bearing rings presents a big challenge for domestic development of high-precision ceramic bearings.In the thesis,precision grinding machines,superfinishing machines,etc.were applied to carry out experimental research on raceways of ceramic bearing outer rings,with the aim to improve processing efficiency,accuracy and to provide guidance for massive production of ceramic bearings.By changing four parameters,i.e.grinding time,grinding depth,grinding wheel speed and feed rate,precision grinding experiments on raceways of Si3N4 ceramic bearing outer rings were conducted to analyze the effects of processing parameters on raceway roundness and roughness.Afterwards,an empirical formula of roundness was calculated.In the end,optimized grinding parameters were given,which were:grinding time of 30s,grinding depth of 15p,m,grinding speed of 35m/s and grinding rate of 1.5μm min-1.Experiments showed that raceway roundness and roughness,under the optimized grinding parameters,were 5.5μm and 0.242μm respectively.It was concluded that the optimized grinding parameters were able to produce better raceways and serve as groundwork for the following superfinishing step.In the superfinishing experiments,parameter effects of superfinishing time,workpiece rotating speed,oilstone pressure and oilstone oscillation frequence were studied on raceways of Si3N4 ceramic bearing outer rings.Superfinishing orthogonal experiments revealed that the optimized superfinishing parameters were:superfinishing time of 6s,workpiece rotating speed of 840m/min,oilstone pressure of 0.4N/mm2 and oilstone oscillation frequence of 300 1/min.The obtained raceway roughness under optimized superfinishing parameters was 0.0344μm,which was 0.0253μm lower than other raceway roughness.Roughness analysis showed that ceramic quality had influence on superfinishing effects.Superfinishing can decrease the raceway roundness as well.The thesis adopted the new superfinishing method,i.e.superimposed oscillation superfinishing,to study raceway roundness on Si3N4 ceramic bearing outer rings.Superfinishing parameter effects of superfinishing time,workpiece rotating speed,oilstone pressure and long-range oilstone oscillation frequence on the the raceway roundness were investigated.By carrying out contrast experiments,it was found that superimposed superfinishing method reduced raceway roundness by 1.05μm while non-superimposed superfinishing method reduced raceway roundness by only 0.80μm,indicating that superimposed superfinishing was a more efficient way to reduce raceway roundness.In conclusion,various experiments of precision grinding and superfinishing on raceways of Si3N4 ceramic bearing outer rings were conducted.Processing parameter effects on raceway roundness and roughness were studied,and optimized parameters were obtained to improve raceway quality.Results from experiments could be served as reference for efficiency processing of ceramic bearings.