45 research outputs found
Produzione di spugne di acciaio tramite metallurgia delle polveri
I materiali cellulari sono caratterizzati da un’interessante combinazione di proprietà fisiche e meccaniche. Inquesto contesto, le schiume metalliche in acciaio possono essere impiegate come alternativa alle leghe leggerein tutte quelle applicazioni dove si necessita un buon compromesso tra leggerezza e resistenza meccanica. Inquesto studio viene presentato un nuovo approccio per la realizzazione di spugne in acciaio tramite metallurgiadelle polveri utilizzando sfere di SiC come riempitivo. Terminato il processo produttivo le particelle ceramichesono state rimosse tramite lisciviazione e le spugne sono state caratterizzate dal punto di vista morfologico,microstrutturale e meccanico. Il risultato della caratterizzazione ha dimostrato la fattibilità del processoproduttivo per l’ottenimento di spugne metalliche in acciaio
New perspective in steelmaking activity to increase competitiveness and reduce enviromental impact
The competitiveness of the European steel industry is strictly related to the introduction of high performanceproducts and to the increase in process efficiency and to the reduction in environmental impact. Thesechallenges can be faced to ensure a future to the area’s important industrial assets and some actions need to beidentified. Several aspects about steelmaking plants, processes and steel products have been highlighted andnowadays, they may become the object of innovative action and efforts in order to achieve and maintain a highlevel of competitiveness and to solve this serious industrial crisis
Study on the microstructure influence in ultrasonic test in duplex forged components
Ultrasonic tests are fundamental to grant the integrity of the metal products, especially after forgingoperations. Due to the high attenuation of duplex stainless steel (DSS), the efficiency of ultrasonic test (UT)performed on DSS components could decrease and make the inspection difficult.The interaction between the ultrasonic acoustic radiation and the microstructure of 2205 duplex stainlesssteel was studied. The specimens were treated at 780 °C for different soacking times to promote theprecipitation of intermetallic phases. The UT response of each specimen was measured and associated to thecorresponding microstructural features.Electron Back Scatter Diffraction (EBSD) was performed to analyze the grains orientation and to relate therevealed crystallographic texture with the acoustic signal attenuation.Tensile test were performed to determine the variation of the main mechanical parameters (yield strength,ultimate tensile strength, elongation and Young modulus) induced by the presence of the secondary phases.The variation of ultrasound velocity can be associated to the modification of the volume fraction of theprecipitated intermetallic phases (sigma (s) and chi (?) phases) and to the morphology of the structuralconstituents observed within the material
Scaling of Star Polymers with one to 80 Arms
We present large statistics simulations of 3-dimensional star polymers with
up to arms, and with up to 4000 monomers per arm for small values of
. They were done for the Domb-Joyce model on the simple cubic lattice. This
is a model with soft core exclusion which allows multiple occupancy of sites
but punishes each same-site pair of monomers with a Boltzmann factor . We
use this to allow all arms to be attached at the central site, and we use the
`magic' value to minimize corrections to scaling. The simulations are
made with a very efficient chain growth algorithm with resampling, PERM,
modified to allow simultaneous growth of all arms. This allows us to measure
not only the swelling (as observed from the center-to-end distances), but also
the partition sum. The latter gives very precise estimates of the critical
exponents . For completeness we made also extensive simulations of
linear (unbranched) polymers which give the best estimates for the exponent
.Comment: 7 pages, 7 figure
A review of Monte Carlo simulations of polymers with PERM
In this review, we describe applications of the pruned-enriched Rosenbluth
method (PERM), a sequential Monte Carlo algorithm with resampling, to various
problems in polymer physics. PERM produces samples according to any given
prescribed weight distribution, by growing configurations step by step with
controlled bias, and correcting "bad" configurations by "population control".
The latter is implemented, in contrast to other population based algorithms
like e.g. genetic algorithms, by depth-first recursion which avoids storing all
members of the population at the same time in computer memory. The problems we
discuss all concern single polymers (with one exception), but under various
conditions: Homopolymers in good solvents and at the point, semi-stiff
polymers, polymers in confining geometries, stretched polymers undergoing a
forced globule-linear transition, star polymers, bottle brushes, lattice
animals as a model for randomly branched polymers, DNA melting, and finally --
as the only system at low temperatures, lattice heteropolymers as simple models
for protein folding. PERM is for some of these problems the method of choice,
but it can also fail. We discuss how to recognize when a result is reliable,
and we discuss also some types of bias that can be crucial in guiding the
growth into the right directions.Comment: 29 pages, 26 figures, to be published in J. Stat. Phys. (2011
Study about the augmented reality adoption in the maintenance in steelmaking area
In this work a study about the application of the augmented reality in steelmaking area is presented. Augmented reality systems add virtual computer-generated material to the surrounding physical world. The augmented reality systems use see-through headworn displays to overlay graphics and sounds on a person's natural vision and hearing. As the person moves about, the position and orientation of the head is tracked, allowing the overlaid material to remain tied to the physical world. An application and description of prototypes to the training and maintenance of continuous casting machine is described
Pig Iron – Direct Reduced Iron high temperature microstructural interaction
A steelmaking facility (for making products with low residual levels) is forced to use high-quality high-cost prompt scrap. The alternative is to use a combination of the polluted obsolete scrap along with what is generally referred to as clean iron units, such as Pig Iron (PI) or Direct Reduced Iron (DRI). These are raw materials containing little or no residual elements. Indeed, during the usual practice EAF-based producers use DRI, which is produced by the reaction between iron ore and reducing agents, typically from 20 up to 30 % of the charge weight, to improve the metallic charge by diluting impurities introduced by scrap. Due to this, the world’s direct reduction industry continued its solid growth setting a new record each year and it is expected to grow quite considerably over the next few decades.
Since its high carbon content, the charge of PI, typically from 5% up to 60%, results in a significant increase of the carbon content of the resultant steel. Its consequent decarburization, if adequate, allows a maximum recovery energy from CO, since it is an exothermic reaction. This could result as a very important source of chemical energy within the EAF, granting power savings. Moreover, due to the still oxidized 7% volume of DRI, the carburizing environment generated by PI would grant beneficial effects on DRI yield.
After the characterization of both pig iron and DRI, testing trials have been performed in order to evaluate their interaction at high temperatures, simulating their behavior within EAF
STUDY ON YIELD OF HOT BRIQUETTED IRON CHARGE INSIDE ELECTRIC ARC FURNACE
The EAF steel production process currently provides very stringent limits on emissions but the environmental impact appears to be minor, if compared to blast furnace cycle. The electric arc furnace operates as a batch process. The scrap yard operators classify and prepare buckets of scrap according to the chemical and production needs of the Electric Arc Furnace. The study about the preparation of the charge bucket is becoming an important operation, in order to ensure proper melt chemistry and good melting conditions. Actually, most of charging operations are based on buckets, where different kind of scrap is charged inside. The addition of high quantity of shredded scrap can increase the concentration of unwanted alloy elements inside the metal bath. The use of HBI can be considered a good operational practice both for increasing the melt yield and for decreasing the high quality scrap fraction used in the EAF cycle. This implies a decrease of the environmental impact, without affecting the production and it avoids the high concentration of undesired elements (e.g. Sulphur, Copper, Tin), due to the charge of low quality scrap
Application of virtual/augmented reality in steelmaking plants layout planning and logistics
In the past years, Virtual or immersive Reality (VR), Augmented Reality (AR) and Mixed Reality (MR) technologies have largely been developed for the military, although it has been used for commercial purposes as well, especially for the development of virtual museums, exhibitions, games, and other cultural and amusement projects. Moreover, as realistic and productive visual simulation continues to develop, coupled with a drop in prices for image generators, the market for architectural design systems based on AR is expected to rapidly grow. Nowadays, the human-computer interaction, due to its long-established approach, can show drawbacks and limitations of traditional interfaces. Promising alternatives are offered by Virtual or immersive Reality (VR) and by Augmented Reality (AR), enabling humans to behave in a nearly natural way. Natural interaction means human actions in the real world with other humans and/or with real world objects. In order to achieve these results, prototype tools, build on video-based interaction, support construction and plant layout planning. The exploitation of Virtual Reality (VR) and Augmented Reality (AR) has already been studied and used in architecture, construction and logistics, application fields with many common duties to the steelmaking industry. In detail, the best possible configuration and arrangement of all production units and transport systems are necessary prerequisites to maximize productivity. Furthermore, also the rationalization of the logistics is a crucial point in order to achieve both the lowest operating costs and a seamless material flow without bottlenecks. These reasons grant to Facility Layout Planning (FLP) and logistics a very promising scenario for VR/AR employment in steel industry. Consequently, possible on-field applications in a near future have been investigated. Indeed, although the metal industry is still conservative, the need for more efficiency and an overall optimization of whole plants would lead to the integration of these new technologies in the daily practice
Experimental analysis on the use of BF-sludge for the reduction of BOF-powders to direct reduced iron (DRI) production
Approximately 25 Mt/year of sludge and dust are obtained from the treatment of the exhaust gases produced during the manufacturing of cast iron and steel from blast furnace, converter and continuous casting machines. This waste contains a large amount of valuable elements that could be recycled in the steelmaking process itself. Unfortunately, sludge and dust are difficult to recycle and so most of them are disposed in landfills. In this work, a feasibility study on the use of blast furnace sludge as a reducing agent to produce direct reduced iron from BOF-dust is presented. Self-reducing briquettes containing a mixture of BOF-dust, BOF-sludge and BF-sludge were produced. Thermo-gravimetric and roasting tests were performed in non-isotherm conditions from room temperature to 1170 °C in both argon and air atmospheres. The XRD and SEM analysis performed highlighted the metallization ratio of about 50-60% for air reduced briquette and 60-80% for argon reduced briquette. These results foster the technical feasibility of the use of BF sludge as a reducing agent to produce direct reduced iron (DRI). The use of BF-sludge as C-source for BOF dusts reduction lead to a cost saving estimated to 1500 M€/year worldwide