Numerical Simulation Of Iron-carbon-copper Powder Net-forming Process

With the rapid development of powder metallurgy industry,it's imperative to achieve P/M parts with complex shape,high density and high performance.Applying simulation method into powder net-forming process is an effective way to predict the quality of compacts,shorten the production cycle and greatly reduce the cost.The density distribution of compacts can significantly influence the quality of P/M parts.Hence,the compaction principles of iron-carbon-copper powder are studied in this paper.The main research contents are summarized as follows:1.The material parameter models for the Fe-2%Cu-0.8%C powder mix were established based on experiments.Combined with the elliptical yield criteria and modified Coulomb friction model,the finite element model for compaction of Fe-2%Cu-0.8%C powder mix was established.The model was then validated by comparing the density distribution results of experiment with that of simulation.Afterwards,the technological parameters(including compaction method,compaction velocity,friction coefficient as well as dwelling time)were optimized based on orthogonal test.2.The compaction process of cylinder model was simulated.Also,the influence of compaction method,aspect ratio and friction coefficient on density distribution was studied.Through qualitative and quantitative analysis,the linear relationship between density range"??"' and aspect ratio "AR" was put forward.Also,the effect of bidirectional pressing in improving density uniformity is limited and it is related to aspect ratio.Besides,the study on spring back showed a linear relationship between aspect ratio"AR"and nodal density decrease"?'.Moreover,the nonsynchronous bidirectional pressing method was also studied and the results showed that the density uniformity under such compaction method depends on the reduction of the two punches.If the reduction of the first moving punch is close to the total reduction and a slight reverse pressing is then performed by another punch until the final size of compact is achieved,then the density uniformity can be greatly improved.3.For compaction of stepped part which is "convex" shaped,the 3D simulation was performed.To study how to guarantee the density uniformity and reduce the crack tendency in compacting stepped part,various compaction schemes are compared with respect to mold design and punches action design.Finally,the compaction principle for such stepped part was proposed.4.The design and optimization of powder forging process for stepped mechanical disk part were carried out in this paper.By comparing various schemes from different respects such as metal flow,formability,density uniformity,damage and punch load,an improved powder forging scheme for this kind of part was proposed.In addition,the influences of four factors,including initial density,forging temperature,mold temperature and friction coefficient,on the powder forging process were analyzed in detail.Finally,the technological parameters were optimized.