Gonzalez-Ojeda, Roberto

Main Affiliation

Facultad de Ingeniería - CampCM

Preferred name

Official Name

Gonzalez Ojeda, Roberto

ORCID

0000-0003-2319-1631

Researcher ID

DTL-2716-2022

Scopus Author ID

56314856300

Now showing 1 - 10 of 38

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Effect of pressure in the microstructure of die cast Al-8.5Si-3.5cu alloys
(2014)
Barbés Fernández, Miguel Ángel
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Verdeja González, José Ignacio
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Quintana, María José
;
Verdeja González, Luis Felipe
;
Gonzalez-Ojeda, Roberto
The microstructure of Pressure Die Casting of an Al-8.5 Si-3.5 Cu alloy used for clean room tiles shows amount of constituents (eutectic and Si phases) that do not correspond to the ones indicated by the phase diagram. Furthermore, there are differences in amount of constituents between the core and the surface zones of parts produced by this process. The work presents quantitative microstructural analysis of this type of industrially produced part, and as a possible cause for these differences, simulations of the effect of pressure on the eutectic (temperature and chemical composition) in the Al-Si system. As the production rate of these parts is very high, and solidification is very fast, microstructural heterogeneity may be related to local entrapment of gasses unable to escape during casting.
2 9
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Material wear in blast furnace crucibles
(1998-05)
Verdeja González, Luis Felipe
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Alonso, A.
;
Gonzalez-Ojeda, Roberto
5 11
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Warm-stamping mechanical behavior and microstructural characterization of Al-Si metal sheets using water refrigerated tooling
(IEEE, 2026)
Estrada-Warn, Paola
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Garcia-Santibañez, G. J.
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Jauregui-Pablos, M.
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Vazquez-Gomez-Orduña, Sebastián
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Gonzalez-Ojeda, Roberto
The use of water refrigerated tooling in a laboratory scale was used to simulate conditions of warm (500°C) stamping of aluminum plates with 0.8 mm in thickness. The work presents load-displacement curves of room temperature and heat treated samples during stamping at 120 and 240 mm/min, effect of the treatment in the anisotropic characteristics of the rolled sheet plate and electron microscopy analysis along with element detection, as this alloy contains small amounts of silicon. The processes resembles a solution treatment and, thus, also an aging treatment at 120°C for 12 h was carried out in order to understand the application possibilities of the manufacturing process in the automotive or aero-space industry. © The authors © IEEE.
13 2
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Ultrafine-grain Steels: Mechanical Behavior
(2016)
Quintana Hernández, María José
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Gonzalez-Ojeda, Roberto
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MARÍA JOSÉ QUINTANA HERNÁNDEZ;576914
In recent years, both the steelmaking industry and laboratories in different parts of the world, have shown an increasing interest in reaching an industrial-level production of ultrafine grained steels (also known as ultrafine ferrite), which have a grain size d lower than 5 μm, and enhanced mechanical resistance and fracture toughness. At room temperature, the capacity of the material to be deformed during bending or drawing operations (typical of requirements for automotive parts applications) depends on the interaction of a hard and a soft phase in the microstructure. On the other hand, at high temperatures, these steels may show superplastic behavior if deformed at a precise combination of temperature and strain rate.
31
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Presintering of TiCN-TiC-WC-Cr 3 C 2 -Ni cermets under N 2 -H 2 atmospheres
(2017)
López-Ezquerra, Belén
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Gonzalez-Ojeda, Roberto
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Iparraguirre, I.
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Rodríguez, N.
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Sánchez-Moreno, José Manuel
C/N ratios in TiCN-TiC-WC-Cr3C2-Ni cermets can be intentionally modified by changing the composition of the presintering atmosphere. This affects not only the sinterability but also the final microstructure of these materials. Melting occurs at lower temperatures as the nitrogen content of the presintering atmosphere rises. However, the final densities are lower due to the precipitation of free carbon. Grain growth of the carbonitride phase is accelerated in samples presintered in N2 due to the activation of solution reprecipitation kinetics. Finally, the precipitation of the Cr-rich M7C3 carbide can also be controlled by the appropriate selection of the presintering atmosphere up to 7.8 wt.% Cr contents. © 2016 Elsevier Ltd
Scopus© Citations 14 1 17
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Using FEM to determine temperature distribution in a blast furnace crucible
(2000)
Verdeja, Luis Felipe
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Gonzalez-Ojeda, Roberto
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Ordóñez, Alejandro
Temperature distribution in the crucible of a blast furnace is an important operation variable that is a function of the materials used in its construction, temperatures reached in the pig iron-refractory interface, and cooling-system performance. Defining the crucible zones where high shear and tensile stresses are reached is an important step in developing a tribological model to understand and predict high wear zones and crucible life. In this work, temperature distribution was simulated using the finite-element method for a blast furnace built following the ceramic solution (oxide and nitride ceramics in contact with the pig iron and carbon and microporous graphite blocks in contact with the refrigeration system).
Scopus© Citations 8 1 1
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Microstructures of a pressure die cast Al-8.5%Si-3.5%Cu alloy
(2017)
Barbés Fernández, Miguel Ángel
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Quintana, María José
;
Verdeja González, José Ignacio
;
Gonzalez-Ojeda, Roberto
Quantitative microstructural measurements of constituents of an Al-Si-Cu alloy, used to manufacture a part with thin sections by Pressure Die Casting (PDC), do not correspond to phase diagram calculations. A simulation of the liquid velocity when filling the mold was made in order to understand the relation between this parameter and pressure, cooling rate and the eutectic amount and morphology. Also, the microstructures of the same alloy solidified in a ceramic crucible (low cooling rate) and in a metal flask (high cooling rate) were compared to those obtained by PDC to analyze the role of pressure on the displacement of eutectic composition and formation of different eutectic morphologies. The amount of constituents varies with distance from the mold walls, producing higher or lower pressure zones, which may be estimated from the Al-Si phase diagram simulation at different pressures. As these pressures must be very high (∼ 2 GPa), a possible explanation for the displacement of the eutectic point is the combination of high cooling rate of the manufacturing process, entrapment of gases during solidification and influence of the alloying elements.
1 8
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High temperature mechanical behavior and microstructural evolution of 304 stainless steel
(2010-05)
Quintana Hernández, María José
;
Gonzalez-Ojeda, Roberto
The use of stainless steel at very high temperatures requires a detailed study of stress-strain and microstructure relationships. The tests made with a 304 type stainless steel are presented in order to study tensile properties at both 700 and 850oC, as well as microstructure characteristic such as austenite grain size (predominant phase in this steel), twinning and carbide M23C6 precipitates distribution and size, comparing them also to room temperature data. Though the resistance is reduced in considerable amount, the results indicate that the time the samples are maintained at the test temperature is a critical factor in the stress-strain curve, which is related to the presence of twins and its different concentration at the core or exterior part of the sample, as well as the amount of carbide precipitates at the interior or borders of the austenite crystals.
1 18
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The Nodal Wear Model (NWM) as an Alternative to Understand the Mechanisms of Flow and Wear in the Blast Furnace Crucible
(2010)
Barbés Fernández, Miguel Ángel
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Verdeja González, Luis Felipe
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Ruiz Bustinza, Íñigo Eloy
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Mochón Muñoz, Javier
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Duarte, Ramón Martín
The presence of thermocouples in the lining of crucibles has become a general practice in the new construction of blast furnaces. The Nodal Wear Model (NWM) has also emerged as an instrument that, while using experimental data, obtains nodal variables whose experimental measurement is not possible: global coefficient of pig-iron/refractory heat transfer h pig−iron/lining g−i and nodal temperature Ti . Starting from these nodal properties, the wear of the lining or the growth of scabs may be controlled, independently of the mechanisms responsible for them. In the same way, the properties and influence zone of the dead man in the hearth of the blast furnace may be calculated, along with those regions where the fluid is allowed to move without any other restrictions than the ones of the corresponding viscous flow (raceway hearth region).
Scopus© Citations 1 1 4
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New binder phases for the consolidation of TiB2 hardmetals
(1996)
Gonzalez-Ojeda, Roberto
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Barandika, M.G.
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Oña, D.
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Sánchez, J.M.
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Villellas, A.
New TiB2-based cermets have been consolidated by hot isostatic pressing of powder mixtures of TiB2 and metallic alloys based on Fe, Ni and Co additions. Relevant thermodynamic aspects of the systems B-Ti-Ni, B-Ti-Fe and B-Ti-Co, essential for avoiding the formation of extremely brittle secondary borides, especially the secondary boride M23B6, are discussed in this work. The role of contaminants like oxygen, carbon and nitrogen, which can also lead to the formation of these compounds is also explained. The hardness, toughness and cutting behaviour of the cermets produced with these new binder phases are comparable with the highest commercial WC-Co grades.
Scopus© Citations 49 1 7

Gonzalez-Ojeda, Roberto

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