The Warm Extrusion Forming Technology Of A 40Cr Steel Long Shaft Part

In this paper, we investigated the deformation process of a 40Cr steel long shaft part in automobiles with high dimensional accuracy and complex shape. The long shaft part has a hexagonal spline on one side and a bulb on another side. It is difficult to form hexagonal spline and bulb by the traditional mechanical processing. Meanwhile, traditional forging technology possesses many shortcomings, such as, high rejection rate, low material utilization rate, low precision, and high cost. Therefore, the 40Cr steel long shaft part was formed by warm extrusion process, which enhances the material utilization rate and reduces the production cost.Warm extrusion process was investigate by analyzing the effect of processing parameters on the warm extrusion deformation ; The uniaxial compression and double-axial compression, as SPD techniques, were dedicated on 40Cr steel in order to obtain UFG materials. The effect of strain rate, strain and temperature on the microstructure of 40Cr steel was studied. The mechanism of grain refinement during uniaxial compression and double-axial compression was revealed. Finally, we obtained UFG 40Cr steel with an average grain size of about 8μm.Based on the analysis of the complex shape feature and warm extrusion principle, we investigated the warm extrusion process of the 40Cr steel long shaft part. Four warm extrusion projects and the corresponding die set-up were designed. We analyzed the advantages and disadvantages of these four projects and finally drew up the optimum project. A series of warm extrusion dies for the 40Cr steel long shaft part were designed and produced.Numerical simulation of warm extrusion process for 40Cr steel long shaft part was carried out by using FEM software DEFORM-3D. Based on the analysis of load-stroke curves, temperature distribution, equivalent stress, and damage value, we investigated the effect of processing parameters on the extrusion deformation of the 40Cr steel long shaft part. This result provide good guidance for optimizing the die structure and setting reasonable warm extrusion process parameters...