Numerical Simulation Of Iron-carbon-copper Powder Net-shape Forming

With the rapid development of powder metallurgy industry, the powder metallurgy parts have been widely used in various fields, while the parts are required to achieve higher quality. The density distribution has significant effects on the final mechanical properties of the parts. The numerical simulation technology is employed to simulate the metal powder forming process and predict the compact density distribution, which greatly reduces the design cost and shortens the development cycle. In this paper, intense studies were made on the mechanism of plastic forming, the establishment of material model, the numerical simulation of powder forming process as well as the relationship between mechanical properties and the relative density. The research contents are summarized as follows.:1. Powder material model for the Fe-lwt.%C-2wt.%Cu alloy was acquired based on experiments. Simulation of powder compaction was carried out for the cylinder model and the cam-shaped model on the basis of the ellipsoidal yield criterion and the plasticity flowing rule. The model was then validated by comparing density distribution of simulation and experiment.2. Based on the cylinder model and the cam-shaped model, finite elements analysis was made to optimize the compaction process. For the cylinder model, the influence of temperature, friction, compacting style, speed and time of dwell on the relative density distribution during compaction was studied, attempting to achieve the optimum compaction route. For the cam-shaped model a tube model was employed to carry out the numerical simulation on the density distribution of the compacts under different compacting styles including single compaction, double compaction, floating compaction and friction compaction. Moreover, the numerical simulation analysis of the density distribution of the sintered compacts under different combinations of five primary parameters for hot forging process was conducted using finite element method.where the five parameters are speed, friction, heating temperature of compact, preheating temperature of mold and initial relative density of compact.3. In this paper, numerical simulations were carried out on the compaction process of a three-dimensional spur gear and oil-quantity-controlling sleeve based on the optimum route and Fe-1 wt.%C-2wt.%Cu powder material model. For optimization of the spur gear structure, the tube was studied to determine the size of the hole in the center of the spur gear. For the oil-quantity-controlling sleeve, the density distribution after the compaction process using different design of molds was investigated by finite elements method. The molds mentioned above are different in the following aspects, including shapes of core rod, approaches of dividing upper floating punch, designs of powder leakage hole and local fill factor.4. This paper also focused on mechanical properties of Fe-1wt.%C-2wt.%Cu. Thus, compaction curve, transverse rupture, tensile strength and hardness of the sintered compacts were examined and analyzed. In addition, the morphology and microstructure of the sintered samples were also analyzed. Based on experimental data, the relation between relative density and mechanical properties was studied and one model was put forward. According to these models, mechanical properties of the parts and production process could be predicted.