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. 2018 Jul 25;11(8):1278.
doi: 10.3390/ma11081278.

Study on Near-Net Forming Technology for Stepped Shaft by Cross-Wedge Rolling Based on Variable Cone Angle Billets

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Free PMC article

Study on Near-Net Forming Technology for Stepped Shaft by Cross-Wedge Rolling Based on Variable Cone Angle Billets

Sutao Han et al. Materials (Basel). .
Free PMC article

Abstract

Considering problems about concaves at the stepped shaft ends, this paper established the plastic flow kinetic theories about metal deforming during the cross-wedge rolling (CWR) process. By means of the DEFORM-3D finite element software and the point tracing method, the forming process of stepped shafts and the forming mechanism of concaves at shaft ends were studied. Based on the forming features of stepped shafts, rolling pieces were designed using variable cone angle billets. Single-factor tests were conducted to analyze the influence law of the shape parameters of billet with variable cone angle on end concaves, and rolling experiments were performed for verification. According to the results, during the rolling process of stepped shafts, concaves will come into being in stages, and the increasing tendency of its depth is due to the wave mode, the parameters of cone angle α, the first cone section length n. Furthermore, the total cone section length m has an increasingly weaker influence on the end concaves. Specifically, cone angle α has the most significant influence on the quality of shaft ends, which is about twice the influence of the total cone section length m. The concave depth will decrease at the beginning, and then increase with the increasing of the cone angle α and the first cone section length n, and it will decrease with the increasing of the total cone section length m. Finite element numerical analysis results are perfectly consistent with experimental results, with the error ratio being lower than 5%. The results provide a reliable theoretical basis for effectively disposing of end concave problems during CWR, rationally confirming the shape parameters of billets with a variable cone angle, improving the quality of stepped shaft ends, and realizing the near-net forming process of cross-wedge rolling without a stub bar.

Keywords: cross wedge rolling; near-net forming; plastic flow kinetic theories; stepped shaft; variable cone angle billets.

Conflict of interest statement

The authors declare no conflicts of interest.

Figures

Figure 1
Figure 1
The front view and side view of the typical cross-wedge rolling (CWR) process. 1 is the rolling piece, 2 is the roller.
Figure 2
Figure 2
Schematic diagram deformation of simple shafts under load during CWR.
Figure 3
Figure 3
Results of finite element simulation of metal crimping of simple shaft: (a) billet; (b) rolled piece.
Figure 4
Figure 4
Diagrams of traditional billets and product: (a) traditional billet; (b) rolled piece.
Figure 5
Figure 5
Finite element model.
Figure 6
Figure 6
Process of forming of end concaves of stepped shaft based on the point tracing method.
Figure 7
Figure 7
Variation of the rolling piece in the rotation period of 1.83–2.23 s.
Figure 8
Figure 8
Three views of the rolled piece when rolling time is 2.23 s: (a) Z axis direction view of rolled piece; (b) Y axis direction view of rolled piece; (c) X axis direction view of rolled piece.
Figure 9
Figure 9
Finite element simulation of a variable cone angle billet forming to be stepped shaft by cross-wedge rolling.
Figure 10
Figure 10
Shapes of billet with a variable cone angle and its product: (a) shape of billet with a variable cone angle; 1 is the first cone section, 2 is the second cone region; (b) shape of a typical rolling piece from such a billet.
Figure 11
Figure 11
Influence of total cone length m on concave depth.
Figure 12
Figure 12
Influence of the first cone section length n on concave depth.
Figure 13
Figure 13
Influence of cone angle α on concave depth.
Figure 14
Figure 14
Comparison of influence of different factors on the concave quality of the rolling end.
Figure 15
Figure 15
Diagram of the rolling site: (a) the H630 type rolling mill; (b) the cross-wedge rolling die; (c) heating device.
Figure 16
Figure 16
Billets and rolled products: (a) comparison of billets; (b) lateral comparison of rolled products; (c) axial comparison of rolled products.
Figure 17
Figure 17
Comparison of Simulation (a,c) and Experimental (b,d) rolling effects of stepped shafts: (a) simulation results of rolling by a traditional billet; (b) experiment results of rolling by traditional billet; (c) simulation results of rolling by a billet with a variable cone angle; (d) experiment results of rolling by a billet with a variable cone angle.

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