Technologic Center

Manresa, Spain

Technologic Center

Manresa, Spain
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Mostafa K.M.,Ghent University | Cmara F.G.,Ghent University | Petrov R.,Ghent University | Petrov R.,Technical University of Delft | And 5 more authors.
Journal of Applied Physics | Year: 2011

High silicon steel is widely used in electrical appliances. Alloying iron with silicon improves its magnetic performance. A silicon content up to 6.5 wt. gives excellent magnetic properties such as high saturation magnetization, near zero magnetostriction and low iron loss in high frequencies. Their workability is greatly reduced by the appearance of ordered structures, namely B2 and D03, as soon as the Si content becomes higher than 3.5 wt. %. This limits the mass production by conventional rolling to this maximum percentage of Si. In this work a series of FeSi (7.5 wt.% Si) samples with different degrees of deformation are investigated with positron annihilation spectroscopy and optical microscopy (OM). The influence of annealing on the concentration of defects of different deformed FeSi alloys has been investigated by positron annihilation lifetime spectroscopy and Doppler broadening of the annihilation radiation. OM is used to investigate the microstructure of deformed samples before and after annealing. The values of the S parameter present a decrease for all studied FeSi alloys with the increase of the annealing temperature, being attributed to a decrease of the concentration of defects. A sudden increase of the S-parameter value at 600 C was observed for all samples, which could be related to the change of the ordering of the FeSi alloys at that temperature. At 700 C, the values of the S parameter decreased drastically and starting from 900 C, they became constant. The microstructures of the alloys, investigated by OM, show that recrystallization is completed at 900 C and the samples are mainly free of defects, which is in agreement with the positron annihilation lifetime data. © 2011 American Institute of Physics.

Camara F.G.,Ghent University | Mostafa K.M.,Ghent University | Petrov R.,Ghent University | Petrov R.,Technical University of Delft | And 5 more authors.
International Journal of Materials Research | Year: 2012

FeSi samples with 7.5 mass.% Si were cold deformed with a thickness reduction of 16% and isochronally annealed for one hour at different temperatures. Their microstructure was characterised using positron annihilation lifetime spectroscopy and electron backscatter diffraction. Positron annihilation mean lifetime values (τmean) decreased slightly with the increase in annealing temperature (20 to 600°C), a process related to recovery. In addition, τmean decreased significantly in the 700-900°C temperature range. The measured value of τmean is 106 ps, which is similar to the pure undeformed Fe after annealing at 900°C. Thus, the material is virtually free of defects at 900°C. Microscopy and diffraction studies showed a high amount of shear bands for the deformed sample. In the temperature range of 20 - 600°C, no recrystallisation was observed. According to the electron backscatter diffraction data, the recrystallisation starts after 700°C, and it is completed at 900°C. © 2012 Carl Hanser Verlag GmbH & Co. KG.

Rodriguez-Calvillo P.,Technologic Center | Rodriguez-Calvillo P.,University of Barcelona | Houbaert Y.,Ghent University | Petrov R.,Ghent University | And 2 more authors.
Materials Chemistry and Physics | Year: 2012

The microstructure and texture development during high temperature plane strain compression of 2% in weight silicon steel was studied. The tests were carried out at a constant strain rate of 5 s -1 with reductions of 25, 35 and 75% at temperatures varying from 800 to 1100 °C. The changes in microstructure and texture were studied by means of scanning electron microscopy and electron backscattered diffraction. The microstructure close to the surface of the samples was equiaxed, which is attributed to the shear caused by friction, whereas that at the centre of the specimens was made of a mixture of elongated and fine equiaxed grains, the last ones attributed to the action of dynamic recovery followed by recrystallization. It was found that the volume fraction of these equiaxed grains augmented as reduction and temperature increased; a 0.7 volume fraction was accomplished with a 75% reduction at 1100 °C. The texture of the equiaxed and elongated grains was found to vary with the increase of deformation and temperature, as the γ-fibre tends to disappear and the α-fibre to increase towards the higher temperature range. © 2012 Elsevier B.V. All rights reserved.

Suarez L.,Technologic Center | Rodriguez-Calvillo P.,Technologic Center | Houbaert Y.,Ghent University | Colas R.,Autonomous University of Nuevo León
Corrosion Science | Year: 2010

Oxidation tests were carried out in samples from an ultra low carbon and two silicon bearing steels to determine the distribution and morphology of the oxide species present. The ultra low carbon steel was oxidized for short periods of time within a chamber designed to obtain thin oxide layers by controlling the atmosphere, and for longer times in an electric furnace; the silicon steels were reheated only in the electric furnace. The chamber was constructed to study the behaviour encountered during the short period of time between descaling and rolling in modern continuous mills. It was found that the oxide layers formed on the samples reheated in the electric furnace were made of different oxide species. The specimens treated in the chamber had layers made almost exclusively of wustite. Selected oxide samples were studied by scanning electron microscopy to obtain electron backscattered diffraction patterns, which were used to identify the oxide species in the layer. © 2010.

Suarez L.,Technologic Center | Warichet D.,Galva Power Group NV | Houbaert Y.,Ghent University
Defect and Diffusion Forum | Year: 2010

Hot dip galvanizing has proven to provide excellent protection against corrosion of steel for a wide range of applications. Coatings of Zn-Al alloys on steel sheet give a high corrosion resistance due to the corrosion prevention by zinc and the passivation by Al. Many important industrial processing steps require a reliable procedure for process verification. Verification on production or pilot lines is neither economical nor efficient. Simulators for the HDP (Hot Dip Process) allow laboratory scale simulations of the (hot dip) coating and of the consequent annealing processes occurring in industrial production lines, serving for process and product improvement and development. To improve and further develop the production and the final coating properties, hot dipping experiments are performed in a HDP simulator using different substrates, bath compositions and hot dipping parameters. The results obtained by these simulations are transferable to the production process of real continuous galvanizing lines. Important industrial steps of the process can be simulated in the HDPS with a high variability of parameters. © (2010) Trans Tech Publications.

Calvillo P.R.,Technologic Center | Suarez L.,Technologic Center | Houbaert Y.,Ghent University
Defect and Diffusion Forum | Year: 2010

Steels alloyed with Si and Al are used as core material in flux carrying machines, they are commonly called electrical steels, divided into grain oriented and non-oriented when a material without magnetic anisotropy or not is desired and used in transformer and electrical motors, respectively. The appearance of brittle ordered structures when Si+Al content in steel is above 4 m.- % does not always make its industrial production easy. Therefore hot dipping in a Al-Si bath followed by a diffusion annealing was found to be a productive way of steels with high Si and/or Al concentration and to overcome the creation of fragile structures during deformation processes, such as rolling. The formation of different layered Al-(Si)-Fe intermetallics on the steel substrate depends on diverse processing parameters such as bath temperature and composition, immersion time, preheating of the steel substrate and its composition and cooling down to room temperature. This contribution reports the diffusion kinetics of Fe2Al5 products obtained during the hot dipping process in an Al iron saturated and a hypoeutectic Al - 5 m.-% Si baths of ultra low carbon steel and Fe-substrates with 3 m.-% Si, annealed and cold rolled to different thicknesses. The preheating of the samples and bath temperatures were varied between 670 to750°C. Dipping times between 1 to 600 sec. were applied. The different layers and compounds formed were characterized by Scanning Electron Microscopy (SEM), using Back Scattered Electron (BSE) detector and Energy Dispersive Spectroscopy (EDS). The influence of the substrate and bath chemical composition on the growth kinetics of the Fe 2Al5 intermetallics was investigated assuming a parabolic law. Si addition retards the growth kinetics and, as result, raises the activation energy from 71.3 to 159.8 kJmol-1, the obtained results are in agreement with the literature. © (2010) Trans Tech Publications.

Mostafa K.M.,Ghent University | Gonzalez Camara F.,Ghent University | Petrov R.,Ghent University | Rodriguez Calvillo P.,Technologic Center | And 4 more authors.
Solid State Communications | Year: 2011

A series of FeSi samples were deformed to a thickness reduction of 16%. They were isochronally annealed for one hour at different temperatures and characterized by the Doppler broadening of the annihilation radiation (DBAR) measured at room temperature. Optical microscopy (OM) is used to investigate the microstructure of the deformed samples before and after annealing. The S parameter data show a decrease with the increase of the annealing temperature. At 973 K a significant decrease sets in. The microstructures of the alloys, investigated by OM, show that recrystallization is completed at 1173 K. © 2011 Elsevier B.V. All rights reserved.

Suarez L.,Technologic Center | Suarez L.,University of Barcelona | Rodriguez-Calvillo P.,Technologic Center | Rodriguez-Calvillo P.,University of Barcelona | And 3 more authors.
Oxidation of Metals | Year: 2011

The deformation of the oxide layer grown in ultra low carbon steel was studied by means of electron backscattered diffraction analyses. Samples of the steel were reheated for shorts periods of time at 1050 °C in a chamber designed to obtain thin scale layers before deforming them by plane strain compression at temperatures ranging from 650 to 1050 °C. Microstructural analyses showed that the oxide layer was made almost exclusively of wustite that is ductile when deformed above 900 °C. It is found that wustite develops texture components of the cube and rotated cube type while growing; these components rotate towards 〈201〉 {100} components once a certain degree of deformation is achieved. Undeformed ferrite close to the oxide layer shows weak 〈201〉 {100} components that rotate into weak rotated cube components when the substrate is deformed in the austenite range and to strong 〈554〉 {225} components when deformed in ferrite. Rolling trials carried out in an experimental mill showed similar trends. © 2011 Springer Science+Business Media, LLC.

Colavizza E.,Technologic Center | Puliga F.,Technologic Center | Escudero E.,Technologic Center
Annual Technical Conference - ANTEC, Conference Proceedings | Year: 2010

Injection molding although widely extended as one of the main replication technologies has shown important limitations when applied to the manufacture of plastic parts in the micro and mini scale. The present work describes a new moulding process based on the fusion of thermoplastics materials via ultrasounds that has been developed in the Sonoplast European project. First experimental achievements led to an innovative concept of mould and ultrasound moulding machine for the production of plastic parts (micro and mini). In addition the molding process management is simplified and directed by few machine parameters differing from conventional injection molding. The ultrasound molding process is extremely fast and with reduced filling pressures achieves a very good reproduction of the mould micro details. Besides it has been possible to obtain reductions about 50% on sprue volumes (around 0, 16 g of plastic per shot) comparing with a conventional microinjection machine. Moreover, process energy consumption and power requirements are between 500 and 1200J and 200 and 500W, respectively. Finally, rheological analysis showed that no noticeable degradation process occurred after processing; equally, tensile testing gave better mechanical performance retention, comparing with traditional microinjection processes.

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