Papers by Keyword: Die Pressing

Abstract: This paper presents the experimental results of the effects of the pressing speed on the press ability of the cementite powders alloyed with iron powders, in order to obtain sintered steels. Cementite or iron carbide is a chemical compound with Fe₃C formula having orthorhombic crystal structure. Regarding mechanical properties, cementite is hard and brittle being important in the metallurgical processes. For the research process was used a mixture consists by cementite and iron powders (6,75%Fe₃C+93.25%Fe) which was obtained by mechanical alloying technique for 30 hours. The cementite powders were produced by direct carburizing of Fe powders. The mixture was unilateral die pressing at three pressures 200, 400 and 600 MPa respectively 5 pressing speeds 10 up to 50 mm/min. The green billets were sintered in argon atmosphere and were studied by microstructural point of view. The evolution of microhardness function the pressing parameters was studied too.

Abstract: The processing of nanocrystalline yttria doped zirconia powder via dry forming routes has been investigated via the granulation of the powder using spray freeze drying (SFD). Free-flowing and crushable powders suitable for either die or isosatic pressing have been achieved via the combination of SFD with additions of up to 2 vol% of Freon 11; the latter reducing the strength of the granules whilst not affecting the powder flowability into the die. The approach has allowed relic-free green bodies of up to 55% of theoretical density to be produced using pressures as low as 250 MPa.

Abstract: A method for combining the FEA softwares, I-DEAS and MSC.Marc, with the iSIGHT design platform is presented to optimize die –pressing (DP) process. In the optimization design, two kinds of optimization algorithms, genetic algorithm (GA) and sequential quadratic programming (SQP), are employed. The result reveals that the residual stress is minimum under conditions that die rake angel equals to 48.50, dieing depth1.9, and friction factor 0.065. The above results give preference to design dieing form tools and process parameters.

Abstract: The 3D finite element simulations are conducted for the cold working of a fastener hole in a low carbon steel plate. The simulation models the actual cold working process where the hole edge is chamfered with die-press. The agreement of finite element method and experimental results is good enough. The residual stresses are analyzed under the different die-press parameters and contact conditions i.e. die-pressing depth, friction factor, the die taper. The main results in this work are as follows: With increasing in chamfer depth the maximum compressive residual stress shows an increasing within the chamfer range of C1.5; the compressive residual stress is decrease with increasing friction; with increase in die taper the maximum compressive residual stress shows the slow increase. The efficiency for enhancing the load-carrying capacity of structural components with cylindrical holes subjected to bending load has been proved by means of FE simulation. The study shows that the simulations of cold working are necessary for if predicted residual stresses are to be used to assess fatigue life and for design die-pressing tool, improvement of parameters of the process of DP working.

Abstract: The yield criterion describing asymmetric behavior of powdered metal compacts in tension and compression is introduced by modifying that used for sintered powdered metals. The plasticity theory related to the modified yield criterion is reviewed and summarized for a powdered metal compact. The constitutive equation is applied to the variational principle and its discritization is also introduced. Axisymmetric die pressings with copper powders were performed to see the deformation mechanics of hollow three-level parts. The simulation includes two different types of multiple-motion tooling compaction of a Class IV part of hollow three-level component. Predictions are made for density distributions, load-stroke relationships, average density as function of height, pressure distributions along the die-walls and punches, average compact densities at each level, and energy consumption for each pressing. The information from simulation can be used to synthesize the various punch motions in a multiple action tooling system.