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Cooling efficiency in furnace design
(Universidad Nacional de Colombia, Facultad de Minas, 2013-12)
Gonzalez-Ojeda, Roberto
;
Quintana Hernández, María José
;
Ruiz Bustinza, Iñigo
;
García Carcedo, Fernando
;
Barbés, Miguel Ángel
During melting, reduction or thermal treatment of a steel charge, the input of energy (either chemical or electrical) is indispensable to guarantee the viability of the process. Under these circumstances, it will be reasonable to design the furnace lining in such a way that heat loss through the walls is minimized. Nevertheless, it can be proved that, for some situations, it is more efficient to withdraw as much heat as possible from the walls than trying to thermally isolate the system. The work presents recommendations for the design of walls and cooling systems in furnaces obtained by quantitative analysis of temperatures reached in specific locations of the furnace using the nodal wear model. The analysis indicates that the wear process of the lining may be controlled if all the elements that intervene in the process are known.
10 2
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Correction to: Texture Analysis of Additively Manufactured Ti-6Al-4V Deposited Using Different Scanning Strategies
(2020)
Quintana Hernández, María José
;
Kenney, Matthew J.
;
Agrawal, Priyanka
;
Collins, Peter C.
The following is missing from the Acknowledgments in the original article:
9 2
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Spherical pores as ‘microstructural informants’: Understanding compositional, thermal, and mechanical gyrations in additively manufactured Ti-6Al-4V
(2021)
Kenney, Matthew J.
;
O'Donnell, Katie
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Quintana Hernández, María José
;
Collins, Peter C.
Detailed analysis of defects such as spherical porosity can act as informants, providing some information regarding the complex and often hidden physics associated with additive manufacturing. Variation in the presence and nature of these defects can shed new insights into the AM process. In this paper, the compositional, crystallographic, microstructural, and morphological characteristics surrounding gas pores in Electron Beam Melted Ti-6Al-4V have been assessed and correlated with different scanning strategies (raster and two point melting ones, Dehoff and random). The large spherical pores (>25μm), exclusively present in raster scan, exhibit perturbations normal to the vertical sidewalls of the pores that are likely the result of elastic instabilities resulting from chemical and crystallographic variations and initiated by vertical compression caused by thermal stresses related to the cyclic process – effectively a form of microbuckling. Electron backscatter diffraction maps support the theory that these perturbations occur at elevated temperatures and prior to the final solid-solid phase transformation. © 2021
Scopus© Citations 8 11 1
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Grain Size Distribution on a Forged Ni-Cr-Mo Low-Alloy Steel
(2018)
Quintana Hernández, María José
;
Ales, T.
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Gonzalez-Ojeda, Roberto
;
Collins, P.
;
Kenney, M.
Microalloyed Ni-Cr-Mo steel (8620) combines good characteristics of formability during forging at 1100°C with the capacity to transform into martensite, while distributing residual stresses and allowing surface treatments and modifications in mechanical parts such as gears and cams. The work presents grain size measurements at different locations of a hot forged gear analyzing it by quantitative metallography techniques and simulating deformation by finite element modeling to estimate local strain and strain rate. Dynamic recrystallization mathematical models for the austenitic initial grain size before forging were applied to calculate theoretical final grain size and correlate the results with microstructural observations, taking also into account the role of precipitation of Cr and Mo carbides. Copyright © 2018 MS&T18®
11 1
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Texture Analysis of Additively Manufactured Ti-6Al-4V Deposited Using Different Scanning Strategies
(2020)
Quintana Hernández, María José
;
Kenney, Matthew J.
;
Agrawal, Priyanka
;
Collins, Peter C.
A limited number of features that comprise the more wholistic materials state of electron beam, powder bed additively manufactured Ti-6Al-4V have been investigated. Coupling scanning electron microscopy and orientation microscopy, the microstructure and texture of samples produced using different AM scan strategies have been studied at various positions along the build height of the samples. Both the qualitative and quantitative results, including parent beta grain orientation, alpha lath texture, and predominant type of microstructure (colony vs basketweave), and their length scales are included. Both the scan strategy used for the build and the time between proximal molten pool passes have been shown to significantly influence the resulting microstructure and texture. © 2020, The Minerals, Metals & Materials Society and ASM International.
Scopus© Citations 9 15 1
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Microstructure Characterization and Mechanical Properties in Individual Zones of Linear Friction Welded Ti-6Al-4V Alloy
(2020)
Mendoza, Michael Y.
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Quintana Hernández, María José
;
Collins, Peter C.
Linear friction welding (LFW) offers a new approach to manufacture aerospace components while improving the buy-to-fly ratio. However, the fundamental knowledge associated with the LFW process, including the attendant microstructural evolution and corresponding mechanical behavior is still rather limited. In this research effort, subscale tensile coupons were prepared and tested to determine the properties of each discrete zone of the linear friction welded specimen, namely the welded zone, thermomechanically affected zone, and parent material. The results show that the yield strength of the welded zone is 20 pct higher than the parent material and the thermomechanically affected zone is 13 pct higher than the parent material. Materials characterization, including optical microscopy, scanning electron microscopy, electron backscattered diffraction-based orientation microscopy and transmission electron microscopy, was conducted to develop an understanding of the microstructure–property relationships. The highly refined nature of the microstructure makes final interpretations challenging, but the evidence suggests that the mechanical behavior is dominated by phenomenon that operate at the 1 to 50 nm length scale, including strain hardening and highly refined features that hinder slip. © 2020, The Minerals, Metals & Materials Society and ASM International.
Scopus© Citations 1 3 2
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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.
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