With the continuous innovation of cross wedge rolling technology,its product range is also expanding.When the stepped shaft is formed to equal diameter shaft by the cross wedge rolling,the quality of the shaft end is directly affected by its length due to the inhomogeneous flow of metal.Besides,the material utilization ratio is reduced.To obtain the better end-face quality and higher material utilization rate,it is necessary to study the influence rule in the cross wedge rolling process.The rolling-forming process was studied with numerical simulations on the DEFORM-3D finite element software and rolling experiments.Based on analysis of the distributions of the stress field,the strain field and the feature points,initially,the law of metal flow was revealed and the deformation mechanism of rolling process was clarified.Taking into account the complexity of influencing factors, the mutual orthogonal experiment was adopted to design the four process parameters of shaft-end length,step angle,step length and cross-section shrinkage ratio.The influence of these parameters on the end concave was verified,and the results showed that the concave value gradually increases as the step length and cross-section shrinkage ratio increase,while with the decrease of shaft length and step angle.Therefore,a smaller concave can be attained by reducing the shaft end length.The software SPSS 22.0 was used to analyze statistical data,and the relationship equation between the process parameters and the quality of the shaft end-face was ascertained.With the concave heart value of zero as the goal,it also determined the influence equation of the optimum shaft-end length on end-face quality.By comparative analyses of the rolling test and the simulation,shapes of the rolled piece and concave values of the end-face were basically same,so the reliability of the simulation analysis was further verified.Theoretically,these influence rules and formulas can effectively improve the end-face quality of rolled piece,and determine the optimum length of the shaft end,achieving near net forming without material head in cross wedge rolling.
