Study On Surface Quality Control Of Cold Roll-beating Forming

Cold roll-beating forming is a new type of plastic forming technology,with high efficiency,low cost,high material utilization,green pollution and other characteristics,widely used in precision machine tools,automotive industry,engineering machinery,aerospace,major strategic equipment,etc.The surface quality of the cold roll-beating spline is closely related to the blending property,fatigue strength,corrosion resistance,impact resistance,service performance and fatigue life of the spline pair,and affecting the physical,chemical,and mechanical properties of spline is critical to evaluating the performance of cold roll-beating forming processes.Therefore,in order to obtain the best surface quality of the cold roll-beating spline,multi-objective decision-making is needed to determine the optimal processing parameter combination of the surface quality of the cold roll-beating spline,has important theoretical guiding significance and practical engineering application value for improving the surface quality of cold roll-beating spline.Analysis of the causes of surface roughness in the surface quality index of cold roll-beating spline,exploring the main influencing factors of spline surface roughness,carry out cold roll-beating spline surface roughness test,the two methods of grey prediction and response surface are used to construct the surface roughness prediction model of cold roll-beating spline,and the range of surface roughness processing parameters is expanded to determine the surface roughness processing parameter domain of cold roll-beating spline with different precision grades.The results show,pulling out the hit is a more rational rolling method of cold roll-beating forming technology.Choosing the right rolling wheel can reduce the impact of the hitting depth on the surface roughness.From the three aspects of fitting accuracy,difficulty of fitting and trend of fitting curve,the response surface method is better than the gray prediction method.Obtained from the surface roughness accuracy level comparison table,the surface roughness processing parameter domain of the 8,7 and 6 cold rollbeating spline.Study the causes of surface residual stress in the surface quality index of cold roll-beating spline,based on the residual stress test of the surface of the cold rollbeating spline,the relationship between the rotational speed of the rolling wheel,the workpiece feed,the depth of the residual stress layer and the residual stress of the surface layer is analyzed,using the residual stress test results of the surface of the cold roll-beating spline to construct the surface residual stress response surface prediction model.The results show,rolling stress,rolling thermal stress and rolling heat cause phase transition of the spline surface metal,these are the main causes of residual stress in the surface of the cold roll-beating spline,and spline surface layer produces residual tensile stress,and secondary surface layer produces residual compressive stress.The rotation speed of the rolling wheel is in the range of 1428~2258r/min,as the rotating speed of the rolling wheel increases gradually,the residual stress of the spline surface decreases slowly.The workpiece feed rate is in the range of 21~42mm/min,as the workpiece feed rate increases gradually,the residual stress of the spline surface decreases sharply,the processing parameters and the residual stress of the spline surface are mapped to determine the residual stress processing parameter domain of the spline surface with small impact load,certain impact load and large impact load.Analysis of the causes of work hardening in the surface quality index of cold rollbeating spline,the spline surface layer hardening test was carried out to study the variation between processing parameters and hardened layer depth,hardening degree and surface microhardness,using the test results to construct a cold roll-beating spline machining hardening prediction model,and verify the rationality and feasibility of the model.The results show,metallographic changes,rolling force,and rolling heat cause work hardening of the spline surface,the rolling heat caused by the rolling force reduces the microhardness of the surface of the spline,and the rolling heat lags behind the impact of the rolling force on the surface hardening of the spline.The rotation speed of the rolling is in the range of 1428~2258r/min,with the gradual increase of the rotation speed of the rolling,the microhardness and hardening degree of the spline surface are gradually decreasing.The feed rate of the workpiece is in the range of 21~42mm/min,with the gradual increase of the workpiece feeding amount,the microhardness and hardness of the spline surface surface increase linearly.The complex correlation coefficient is 98.56%,and the maximum relative error of the test sample is 0.903%.It is known that the constructed cold roll-beating spline machining hardening prediction model is feasible,the mapping process of the rotational speed of the rolling wheel,the workpiece feed rate and the surface hardening of the spline surface is determined to determine the processing hardening processing parameter domain of the spline surface under light load,medium load and heavy load.Based on cold roll-beating spline surface quality test results,using subjective weighted analytic hierarchy process and objective weighted entropy weight method to obtain the weight of each index of cold roll-beating spline surface quality,the subjective weight and the objective weight are linearly combined,and the combined weight ideal point method is used to determine the optimal processing parameter combination of the surface quality of the cold roll-beating spline,and the signal-tonoise ratio and gray correlation analysis method are used to verify.The results show,it can be seen from the combined weights that the importance of the surface quality of the cold roll-beating spline is in turn that the surface roughness is greater than the residual stress than the hardening degree.The optimal processing parameters of the surface quality of the cold roll-beating spline are 1428r/min for the rolling wheel rotation speed and 42mm/min for the workpiece feed rate,the optimal processing parameters combined in the decision-making are in the spline surface quality processing parameter domain,which indicates that the determined cold roll-beating spline surface quality processing parameter domain is true and reliable.