Optimization of the Hot Forging Processing Parameters for Powder Metallurgy Fe-Cu-C Connecting Rods Based on Finite Elem

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POWDER metallurgy (PM) is a promising approach to reduce production costs and improve material performance. Powder forging connecting rod technology combines the advantages of PM and precision forging in a single operation. It also provides a method of manufacturing connecting rod resulting in materials savings, and it directly prepares a near-net-shaped connecting rod with uniform density distribution and excellent mechanical properties from the sintered preform. Powder forged connecting rods not only have a non-uniform cross-section (i.e., the small end and the big end are thick compared with the central shank), but also have a complex geometric shape, as shown in Figure 1.

FENGXIAN LI and JIANHONG YI are with Kunming University of Science and Technology, Kunming 650093, China. Contact e-mail: [email protected], [email protected] JU¨RGEN ECKERT is with Erich Schmid Institute of Materials Science, Leoben 8700, Austria. Manuscript submitted March 16, 2017.

METALLURGICAL AND MATERIALS TRANSACTIONS A

During the powder forging connecting rod process, a connecting rod preform with a relative density of 0.7 to 0.8, fabricated by the conventional PM process, needs to be hot forged to its final shape with substantial densification.[1] Unfortunately, powder forged connecting rods always have challenges with poor controllability in metal flow behavior during the forming process and non-uniform density distribution. By controlling the process properly during hot forging, it is possible to control hot forging yield in the manufacturing of connecting rod with high density and excellent mechanical properties. Inspection of the available literature demonstrates that the densification behaviors of PM materials have been under great development. Some of the previous works treated the PM materials as fully dense materials, while others focused on porosity elimination of the sintered compact only considering a simple geometry.[2–4] In powder forging connecting rods, the yield function for compressible PM materials is different from that of fully dense materials. Moreover, the complex geometric shape of the connecting rod and the relative density of the connecting preform are important factors in governing the connecting rod quality, and thus, they should be considered. The dynamics of the hot forging

process presents a significant challenge for the development of meaningful models. A.D. Abdullin et al. simulated the casting and metal-forming operations with finite element method (FEM) software.[5] J.W. Qiu et al. established a constitutive equation for PM titanium alloy using isothermal compression tests and simulated the hot forming process with FEM software.[6,7] A. Rajeshkannan et al. studied the microstructures and mechanical properties of connecting rod made by powder forging process.[8] Interestingly, FEM used for mechanical behavior simulation offers the possibility to a reduction of the cost and time effectively in the optimization of processing parameters and tool design. However, in many cases, it has not been fully u