Flavia de Paula Vitoretti

Densification Behaviour Modelling for Metallic Powders

Powder forming involves fabrication of a preform by conventional press-and-sinter processing, followed by various forming processes, citing as examples, rolling, compaction, forging, extrusion, among others, of the porous preform into a final shape through substantial densification. This work makes a finite element analysis for porous metals. The finite element model was applied to simulating the case of compaction of nanocristalline copper under uniaxial compression conditions in order investigate the densification behavior. The model was simulated using explicit integration method as applied to the evolution variation of the relative density and the dislocation density of the compact. Finite element analysis program used was Abaqus. Finite element calculations were compared with literature data. The agreements between finite element model and literature results for densification of nanocristalline copper were good.

Kinetic of Self-Reducing Mixtures of Iron Ore and Biomass of Elephant Grass

In this work, kinetic runs of self-reducing mixtures composed by pellet feed, BOF dust and biomass of elephant grass were performed using TGA-DSC method, for the temperatures, 900, 950, 1000, 1050 and 1100°C, and carbon percentages (15, 20 and 30% of carbon). The converted fraction versus time was calculated, and the different regions of the reactions progress were selected to analyze the reactions kinetics that occur in the mixture (devolatilization of biomass, Boudouard and sequence of reduction reactions). The kinetic behavior for the different steps showed good agreement with the first-order kinetic law. Using Arrhenius plot, was possible to estimate the apparent activation energy values obtained for the reaction mechanisms corresponding to Fe3O4→FeO and FeO→Fe. The kinetic constants for the 1100°C temperature and mixture containing 30% of carbon were the higher values: 0.0037 s-1 for the reaction Fe3O4 → FeO and 0.0258 s-1 for the mechanism FeO →Fe.

Microstructural Characterization of a High Copper (Nd0.75Pr0.25)2Fe14B Magnet

A commercial magnet following the N 48 specification was submitted to a detailed microstructural characterization. The magnet presents 10 kOe of coercivity and good 2nd quadrant squareness. The grain size is around 10 micrometers. Scanning electron microscope (SEM) EDAX analysis shows that it is a high copper NdPrFeB alloy following the 3Nd:1Pr proportion, with some aluminum. The magnet was covered by a 15 micrometers layer, with nickel and copper. The microstructural data allow a better understanding of the effect of the alloying elements.

Deformations Limits Analysis of Sheet Metal Manufatured through the Incremental Forming Process

The present study is primarily engaged in the implementation of the incremental stamping process in a computerized numeric control This paper presents two different approaches to this forming process, an experimental and other numerical. Experimental used by the computer numerical control to perform the printing process and performs numerical simulations of the process using the finite element method. Some parameters are analyzed in both approaches, such as product geometry effects, tool geometry, tool speed, tool path, contact conditions and mechanical properties of the materials.

A Finite Element Analysis for an Iron Ore Pellet Compression Test

The increasing global demand for iron ore pellets has made the pelletizing companies to step up their investments. The mechanical strength of the pellets, as well as its wear resistance are important factors to characterize the mechanical behavior. These properties are influenced by the type and nature of the ore or concentrate, the additives and the subsequent heat treatment used. This paper develops a numerical finite element model in order to characterize the mechanical behavior of iron ore pellets. The main objective of this study was to establish a valid finite element model that is able to simulate the mechanical behavior of iron ore pellets. The uniaxial compression test was made to evaluate the mechanical properties of the pellets. Furthermore, modeling and simulations are done using the software ABAQUS CAE® for uniaxial compression using the material properties obtained by the test. Lastly, in order to validate the model, the experimental data is crossed with the simulation results to discuss its correlation and particularities.

Analysis of the Iron Ore Pellet Mechanical Behavior under Biaxial Compression

The increasing global demand for iron ore pellets has made the pelletizing companies to step up their investments. The mechanical strength of the pellets, as well as its wear resistance are important factors to characterize the mechanical behavior. These properties are influenced by the type and nature of the ore or concentrate, the additives and the subsequent heat treatment used. This paper develops a numerical finite element model in order to characterize the mechanical behavior of iron ore pellets. The biaxial compressive stress was analyzed in this study. The results show that the pellet subjected to biaxial stress supports higher levels of stress and strain when compared to uniaxial efforts. Accuracy increase of the simulation results can be obtained with the implementation of a failure criterion for brittle materials in the numerical model. Finally, could be seen that the pellet had higher levels of deformation under biaxial symmetric strain, when compared with the uniaxial compression results.

Evolution of Sintering of Particles that Compose Iron Ore Agglomerates

The increasing demand for new technologies in the ironmaking/steelmaking field has been motivating several studies towards pelletizing process improvement. Within this context, evaluate the reduction of iron ore pellets using the dilatometer technique constitutes a promising approach for optimizing this process. This paper aims the metallurgical characterization through the sintering of particles in iron ore pellets. With this purpose, some experimental procedures are of concern as follows. Firstly, the kinetic densification of the iron ore pellets is measured using a dilatometer, which heats the samples up at 30 K/min until high temperatures about 1473 K and an isotherm at 10 minutes have been done. Then, the sample is cooled back to room temperature and undergoes a microstructural characterization, with the aid of a scanning electron microscope. At last, the density of the pellets is evaluated, using an Arquimedes Principle and consequently the porosity of the agglomerates. The results indicate the sintering progress of the particles that comprise the pellets as well as reduction the porosity. This behavior is due to the fact that the heat arising from gas induces the partial liquid phase formation and involves the agglomerate particles aiding in the sintering process.