Browsing by Author "Martínez, S."
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Item Fours rotatifs à oxy-combustion: Optimisation de la fusion de la fonte(2004-03) Carnicer, P.; Meléndez, A.; Rezabal, X.; Gutierrez, A. M.; De Ulzurrun, J. A.Díez; Martínez, S.; Visús, J.; Aranda, I.; Etxebarria, G.; Tecnalia Research & InnovationSystematic tests aimed at optimizing the iron smelting process in oxy-combustion rotary furnaces from the aspects of the energy, metallurgical, and the environmental. The oxy-combustion rotary furnaces were substituted with clear success for coke cupola and in some cases by induction furnaces. The knowledge collected about oxy-combustion rotary furnaces promoted the creation of new actions in the search for energy, metallurgical, and environmental efficiencies through a double burner system in the design of the burner, using a unit with two independent flame burners. The decrease of gases obtained by means of the double burner system involves a positive environmental impact, with a particular focus on lesser consumption of raw materials and reduction of the CO2 emissions. The step to automated control will greatly simplify the conduction tasks of equipment, which at the same time will save time for the personnel responsible for the maintenance and operation of the furnace.Item An industrial approach of laser polishing with different laser sources: Industrielle Methode zum Laserpolieren mit verschiedenen Laserstrahlquellen(2015-07-01) Ukar, E.; Lamikiz, A.; Liébana, F.; Martínez, S.; Tabernero, I.; COMPOSITESurface finishing of dies and molds is one of the most interesting applications of laser polishing process. Because of the variety of materials used in die and mold manufacturing, as well as the different surface topographies, in each case, it is necessary to use appropriate process parameters. The presented work focuses on the study of laser polishing process on three commonly used materials in the manufacture of dies and molds, such as tool steels AISI D2 and AISI P20, ductile cast iron GGG70L and LaserForm ST-100, a specific material developed for plastic injection mold making. Experimental studies were carried out determining the influence of the energy density on the roughness reduction rate. A key point that has a direct impact on the resulting surface roughness is the initial surface finishing of the material before laser polishing. In order to determine the degree of influence, experimental studies were conducted on two steels, AISI H13 and AISI P20, which are typically used in mold making industry. The experimental tests showed that a random distribution of peaks and valleys allows more homogenous material melting and gives as result a smoother surface after laser polishing.Item Laser hardening prediction tool based on a solid state transformations numerical model(2010) Martínez, S.; Ukar, E.; Lamikiz, A.; Liebana, F.; COMPOSITEThis paper presents a tool to predict hardening layer in selective laser hardening processes where laser beam heats the part locally while the bulk acts as a heat sink. The tool to predict accurately the temperature field in the workpiece is a numerical model that combines a three dimensional transient numerical solution for heating where is possible to introduce different laser sources. The thermal field was modeled using a kinetic model based on Johnson-Mehl-Avrami equation. Considering this equation, an experimental adjustment of transformation parameters was carried out to get the heating transformation diagrams (CHT). With the temperature field and CHT diagrams the model predicts the percentage of base material converted into austenite. These two parameters are used as first step to estimate the depth of hardened layer in the part. The model has been adjusted and validated with experimental data for DIN 1.2379, cold work tool steel typically used in mold and die making industry. This steel presents solid state diffusive transformations at relative low temperature. These transformations must be considered in order to get good accuracy of temperature field prediction during heating phase. For model validation, surface temperature measured by pyrometry, thermal field as well as the hardened layer obtained from metallographic study, were compared with the model data showing a good adjustment.Item Nouveau modèle de brûleur au gaz naturel pour améliorer l'efficacité des fours rotatifs à oxygaz(2001) Gutiérrez, A. M.; Díez De Ulzurrun, J. A.; Meléndez, A.; González, J. J.; Martínez, S.; Tecnalia Research & InnovationA new natural gas burner design to improve efficiency in oxygas rotary furnaces was presented. The optimum energy savings obtained, with respect to the referential heat, were 10-12% depending on the charge protection. In parallel, operational cost savings were 18-22%. When the furnace was tested with the new burner design, both the oxidation level of the molten metal and the slag analysis values remained similar to those obtained with the conventional burner. From an environmental perspective, the new oxygas burner design represented a decrease in total atmospheric exhaust gas emission of ∼ 20%. CO2 reduction figures were ≤ 10%. Unburnt gases were eliminated by controlling stoichiometric combustion parameters. Refractory wear was unaffected by the new burner design.