Sebastián F. Medina
Spanish National Research Council
Ferrite (iron)Isothermal processKineticsStrain rateRecrystallization (metallurgy)Dynamic recrystallizationMetallurgyGrain sizeMaterials scienceMicroalloyed steelTorsion (mechanics)VanadiumNiobiumNucleationPrecipitation (chemistry)MicrostructureActivation energyAusteniteThermodynamics
113Publications
25H-index
1,906Citations
Publications 111
Newest
#1David M. Bastidas (University of Akron)H-Index: 22
Last. Sebastián F. Medina (CSIC: Spanish National Research Council)H-Index: 25
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Abstract null null The premature causes of failure of ball joint heads attached to the weight bearing bar used on high speed trains, which were continuously under traction, have been studied, with an average load of 47.5 kN plus a cyclical load of ± 7.5 kN. Ball joint heads made of C45 (AISI 1045) carbon steel show a pearlite microstructure (80–90 %) with ferrite surrounding the prior-austenite grain boundaries. Two different external elliptical-shaped fatigue cracks of 14.5 mm and 7.7 mm nuclea...
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#1David M. Bastidas (University of Akron)H-Index: 22
Last. Sebastián F. Medina (CSIC: Spanish National Research Council)H-Index: 25
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Abstract Herein, a premature failure analysis of structural tempered high-strength boron steel 27MnCrB5–2 bolts (0.0006 wt. B), used for railcar wheel-axle assembly, is presented. Fractographic analysis revealed a moderate ductile fracture. The applied torque produced elongation of the bolt until final fracture. A scarce presence of precipitates was observed, mainly of Ti(C,N), TiC, and inclusions such as Al2O3 and MnS. The mechanical properties of the boron steel 27MnCrB5–2 bolts were 1112 and ...
1 CitationsSource
#1David M. Bastidas (University of Akron)H-Index: 22
#2Sebastián F. Medina (CSIC: Spanish National Research Council)H-Index: 25
Last. J. M. Bastidas (CSIC: Spanish National Research Council)H-Index: 32
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D.M.B. and J.R. acknowledge funding from The University of Akron, Fellowship Program FRC‐207367.
3 CitationsSource
#1Ana Pastor (National Institute of Aerospace)H-Index: 3
#2P. Valles (National Institute of Aerospace)H-Index: 7
Last. Sebastián F. Medina (CSIC: Spanish National Research Council)H-Index: 25
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Microstructural characterisation has been carried out on X38CrMoV5-1 steel parts manufactured by gravity investment casting. Optimal heat treatment was applied to the parts: annealing at 780 °C (1 h) and cooling in the furnace; heating at 1020 °C (1 h), cooling in oil and double tempering at 580 °C (2 h). Hillert and Stefansson thermodynamic principles were used to calculate the fraction precipitated of V(C, N) and AlN and the percentages in solution of elements (V, Al, C, N). Calculations showe...
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#2P. Valles (National Institute of Aerospace)H-Index: 7
Last. José-María CabreraH-Index: 32
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Using a theoretical model, the nucleus number and nucleation time were determined for a V-microalloyed steel. The calculated data has made it possible to plot the nucleus number vs. temperature, nucleation critical time vs. temperature, and precipitate critical radius vs. temperature. The nucleus number was calculated by integration of the nucleation rate expression. On the other hand, an experimental study was performed and the nucleation time vs. temperature was plotted (PTT diagram), thus all...
2 CitationsSource
#1Iván Díaz (CSIC: Spanish National Research Council)H-Index: 10
#2H. CanoH-Index: 10
Last. Manuel Morcillo (CSIC: Spanish National Research Council)H-Index: 39
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Abstract This work considers fourteen weathering steels manufactured by adding Cu, Cr and Ni alloying elements to extra mild steel. The steels were exposed for up to 5 years in different atmospheres. The atmospheric corrosion resistance of the steels was evaluated and the rust layers formed were characterised by X-ray diffraction, optical microscopy and scanning electron microscopy. The addition of Ni, particularly at 3.0 wt%, leads to a notable increase in corrosion resistance. The rusts formed...
37 CitationsSource
#1Ana Pastor (National Institute of Aerospace)H-Index: 3
#2P. Valles (National Institute of Aerospace)H-Index: 7
Last. Sebastián F. Medina (CSIC: Spanish National Research Council)H-Index: 25
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Abstract X38CrMoV5-1 (AISI H11-1) steel parts are often manufactured by die-casting followed by quenching and tempering and the microstructure is highly process-sensitive. In order to eliminate the presence of pores in the parts, a different though more expensive manufacturing process has been implemented, involving the hot rolling of a plate and machining of samples in parallel and perpendicular to the rolling direction. Heat treatment of the samples was optimised and the mechanical tensile pro...
4 CitationsSource
#1Ana Pastor (National Institute of Aerospace)H-Index: 3
#2P. Valles (National Institute of Aerospace)H-Index: 7
Last. Sebastián F. Medina (CSIC: Spanish National Research Council)H-Index: 25
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The phase transformations of the X38CrMoV5-1 (AISI H11-1) steel are studied in the present work. Parts are usually manufactured by die-casting followed by a heat treatment, and the resulting microstructure as well as the mechanical properties are highly sensitive to the heat treatment conditions. The heat treatment consists on a quenching and tempering and it is not able to remove the casting dendritic microstructure or porosity but anyway, it is carried out to achieve an acceptable ductility, g...
3 CitationsSource
#2P. VallesH-Index: 7
Last. I. AmurrioH-Index: 1
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#1Sebastián F. Medina (CSIC: Spanish National Research Council)H-Index: 25
#2Alberto QuispeH-Index: 14
Last. Manuel Gómez (CSIC: Spanish National Research Council)H-Index: 18
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Niobium and vanadium precipitates (nitrides and carbides) can inhibit the static recrystallization of austenite but this does not happen for Ti, which form nitrides at high temperatures. RPTT diagrams show the interaction between recrystallization and precipitation allowing study the strain induced precipitation kinetics and precipitate coarsening. Based on Dutta and Sellars’s expression for the start of strain-induced precipitation in microalloyed steels, a new model has been constructed which ...
2 CitationsSource