Uranga-Zuaznabar, P. (Peio)
- Publications
- item.page.relationships.isContributorAdvisorOfPublication
- item.page.relationships.isContributorOfPublication
14 results
Search Results
Now showing 1 - 10 of 14
- Effect of Nb and Mo on austenite microstructural evolution during hot deformation in boron High strength steels(Springer, 2022) Mohrbacher, H. (Hardy); Isasti-Gordobil, N. (Nerea); Uranga-Zuaznabar, P. (Peio); Detemple, E. (Eric); Zurutuza, I. (Irati); Schwinn, V. (Volker)This work has focused on the study of hot working behavior of boron high strength steels microalloyed with different combinations of Nb and/or Mo. The role of Nb and Mo during the hot deformation of low carbon steels is well known: both mainly retard austenite recrystallization, leading to pancaked austenite microstructures before phase transformation and to refined room temperature microstructures. However, the design of rolling schedules resulting in properly conditioned microstructures, requires microstructural evolution models that take into account the effect of the different alloying elements. In this specific case, the effect that high levels of molybdenum (0.5 pct) have in the recrystallization delay was evaluated. In that respect, hot torsion tests were performed in this work to investigate the microstructural evolution during hot deformation of four boron steels, with different Nb (0.025 pct) and Mo (0.5 pct) combinations. The retardation in recrystallization kinetics was modeled in all cases and measured kinetics agree with those predicted by equations previously developed for Nb–Mo microalloyed steels with lower Mo concentrations (< 0.3 pct). The strain-induced precipitation in the Nb and Nb–Mo bearing steels was also characterized. Finally, the fractional softening evolution during multipass rolling simulations was compared with MicroSim® model predictions, showing a good agreement with experimental results.
- Effect of intercritical deformation on final microstructure in low carbon grades.(2017) Isasti-Gordobil, N. (Nerea); Rodriguez-Ibabe, J.M. (José María); Uranga-Zuaznabar, P. (Peio); Mayo-Ijurra, U. (Unai)Heavy gauge line pipe and structural steel plate materials are often rolled in the two-phase region for strength reasons. However, strength and toughness show opposite trends and the exact effect of each rolling process parameter remains unclear. Even though intercritical rolling has been widely studied, further understanding of the evolution of the microstructure under intercritical conditions and the effect of different austenite-ferrite phase contents at high temperature is needed to define stable processing windows. For that purpose, laboratory thermomechanical simulations reproducing intercritical rolling conditions have been performed in low carbon steels. A methodology able to distinguish deformed ferrite from non-deformed ferrite was developed using Electron Backscattered Diffraction (EBSD) technique. The effect of chemical composition, austenite-ferrite balance and deformation on the final microstructure was evaluated. This analysis is intended to deepen the knowledge of the effect that intercritical rolling has on the microstructural evolution and, by extension, on the mechanical properties.
- Relation between microstructure and mechanical properties on intercritically deformed low carbon steels.(Elsevier, 2020) Isasti-Gordobil, N. (Nerea); Rodriguez-Ibabe, J.M. (José María); Uranga-Zuaznabar, P. (Peio); Mayo-Ijurra, U. (Unai)Intercritical rolling is often applied in order to improve the mechanical properties of heavy gauge structural steel plates. However, these products have large temperature and deformation gradients both over thickness and width, being the control of the process very complex. Considering this issue, it is important to analyze the microstructural evolution under intercritical conditions and how the different process parameters like deformation temperature, chemical composition etc. influence on the final mechanical properties. For that purpose, plane strain compression tests simulating intercritical rolling conditions were carried out for a CMn and a NbV microalloyed steel. Tensile tests perfomed for various austeniteferrite contents prior to the last deformation, show that the reduction of deformation temperature increases strength properties. However, ferrite fractions higher than 25% prior to the last deformation, reduce significantly the ductility. These analyses give the necessary background for the definition of stable process windows that optimize the strength-ductility property balance of intercritically rolled products. Similarly, the estimation of the contribution of different strengthening mechanisms such as, solid solution, grain size and dislocation density, allows the prediction of the yield strength of an intercritically deformed microstructure.
- Interaction between microalloying additions and phase transformation during intercritical deformation in low carbon steels(MDPI AG, 2019) Isasti-Gordobil, N. (Nerea); Rodriguez-Ibabe, J.M. (José María); Uranga-Zuaznabar, P. (Peio); Mayo-Ijurra, U. (Unai)Heavy gauge line pipe and structural steel plate materials are often rolled in the two-phase region for strength reasons. However, strength and toughness show opposite trends, and the exact effect of each rolling process parameter remains unclear. Even though intercritical rolling has been widely studied, the specific mechanisms that act when different microalloying elements are added remain unclear. To investigate this further, laboratory thermomechanical simulations reproducing intercritical rolling conditions were performed in plain low carbon and NbV-microalloyed steels. Based on a previously developed procedure using electron backscattered diffraction (EBSD), the discretization between intercritically deformed ferrite and new ferrite grains formed after deformation was extended to microalloyed steels. The austenite conditioning before intercritical deformation in the Nb-bearing steel affects the balance of final precipitates by modifying the size distributions and origin of the Nb (C, N). This fact could modify the substructure in the intercritically deformed grains. A simple transformation model is proposed to predict average grain sizes under intercritical deformation conditions.
- Production of a non-stoichiometric Nb-Ti HSLA steel by thermomechanical processing on a steckel mill(2023) De-Souza, A.L. (Altair Lucio); Isasti-Gordobil, N. (Nerea); Rodriguez-Ibabe, J.M. (José María); Rebellato, M.O. (Marcelo Orantes); Uranga-Zuaznabar, P. (Peio); Gorni, A.A. (Antoni Augusto); De-Faria, G.L. (Gerardo Lucio); Martins, C.A. (Cleiton Arlindo); Cohn, J.A.C. (Jorge Adam Cleto); Mayo-Ijurra, U. (Unai)Obtaining high levels of mechanical properties in steels is directly linked to the use of special mechanical forming processes and the addition of alloying elements during their manufacture. This work presents a study of a hot-rolled steel strip produced to achieve a yield strength above 600 MPa, using a niobium microalloyed HSLA steel with non-stoichiometric titanium (titanium/nitrogen ratio above 3.42), and rolled on a Steckel mill. A major challenge imposed by rolling on a Steckel mill is that the process is reversible, resulting in long interpass times, which facilitates recrystallization and grain growth kinetics. Rolling parameters whose aim was to obtain the maximum degree of microstructural refinement were determined by considering microstructural evolution simulations performed in MicroSim-SM (R) software and studying the alloy through physical simulations to obtain critical temperatures and determine the CCT diagram. Four ranges of coiling temperatures (525-550 degrees C/550-600 degrees C/600-650 degrees C/650-700 degrees C) were applied to evaluate their impact on microstructure, precipitation hardening, and mechanical properties, with the results showing a very refined microstructure, with the highest yield strength observed at coiling temperatures of 600-650 degrees C. This scenario is explained by the maximum precipitation of titanium carbide observed at this temperature, leading to a greater contribution of precipitation hardening provided by the presence of a large volume of small-sized precipitates. This paper shows that the combination of optimized industrial parameters based on metallurgical mechanisms and advanced modeling techniques opens up new possibilities for a robust production of high-strength steels using a Steckel mill. The microstructural base for a stable production of high-strength hot-rolled products relies on a consistent grain size refinement provided mainly by the effect of Nb together with appropriate rolling parameters, and the fine precipitation of TiC during cooling provides the additional increase to reach the requested yield strength values.
- Molybdenum alloying in high-performance flat-rolled steel grades(2020) Mohrbacher, H. (Hardy); Yang, J.R. (Jer-Ren); Uranga-Zuaznabar, P. (Peio); Guo, A.M. (Ai-Min); Shang, C.J. (Cheng-Jia); Senuma, T. (Takehide)Considerable progress in developing flat-rolled steel grades has been made by the Chinese steel industry over the recent two decades. The increasing demand for high-performance products to be used in infrastructural projects as well as in production of consumer and capital goods has been driving this development until today. The installation of state-of-the-art steel making and rolling facilities has provided the possibility of processing the most advanced steel grades. The production of high-performance steel grades relies on specific alloying elements of which molybdenum is one of the most powerful. China is nearly self-sufficient in molybdenum supplies. This paper highlights the potential and advantages of molybdenum alloying over the entire range of flat-rolled steel products. Specific aspects of steel property improvement with respect to particular applications are indicated.
- Effect of quenching strategy and Nb-Mo sdditions on phase transformations and quenchability of high-strength boron steels(2021) Mohrbacher, H. (Hardy); Isasti-Gordobil, N. (Nerea); Uranga-Zuaznabar, P. (Peio); Detemple, E. (Eric); Zurutuza, I. (Irati); Schwinn, V. (Volker)The application of direct quenching after hot rolling of plates is being employed in the production of ultra-high-strength hot rolled plates. When heavy gauge plates are produced, the complexity involve in achieving high cooling rates in the plate core is increased and the formation of undesirable soft phases within martensite is common. In the current paper, both direct quenching and conventional quenching (DQ and CQ) processing routes were reproduced by dilatometry tests and continuous cooling transformation (CCT) diagrams were built for four different high-strength boron steels. The results indicate that the addition of Mo and Nb-Mo suppresses the ferritic region and considerably shifts the CCT diagram to lower transformation temperatures. The combination of DQ strategy and the Mo-alloying concept provides the best option to ensure hardenability and the formation of a fully martensitic microstructure, and to avoid the presence of soft phases in the center of thick plates.
- Thermomechanical processing of steels(MDPI AG, 2020) Rodriguez-Ibabe, J.M. (José María); Uranga-Zuaznabar, P. (Peio)The combination of hot working technologies with a thermal path, under controlled conditions (i.e., thermomechanical processing) provides opportunities to achieve required mechanical properties at lower costs. The replacement of conventional rolling plus post-rolling heat treatments by integrated controlled forming and cooling strategies implies important reductions in energy consumption, increases in productivity and more compact facilities in the steel industry. The metallurgical challenges that this integration implies, though, are relevant and impressive developments that have been achieved over the last 40 years. The development of new steel grades and processing technologies devoted to thermomechanically-processed products is increasing and their implementation is being expended to higher value added products and applications.
- Effect of microstructure on post-rolling Induction treatment in a low C Ti-Mo microalloyed steel(MDPI AG, 2018) Isasti-Gordobil, N. (Nerea); Rodriguez-Ibabe, J.M. (José María); Uranga-Zuaznabar, P. (Peio); Larzabal-Primo, G.(Gorka)Cost-effective advanced design concepts are becoming more common in the production of thick plates in order to meet demanding market requirements. Accordingly, precipitation strengthening mechanisms are extensively employed in thin strip products, because they enhance the final properties by using a coiling optimization strategy. Nevertheless, and specifically for thick plate production, the formation of effective precipitation during continuous cooling after hot rolling is more challenging. With the aim of gaining further knowledge about this strengthening mechanism, plate hot rolling conditions were reproduced in low carbon Ti-Mo microalloyed steel through laboratory simulation tests to generate different hot-rolled microstructures. Subsequently, a rapid heating process was applied in order to simulate induction heat treatment conditions. The results indicated that the nature of the matrix microstructure (i.e., ferrite, bainite) affects the achieved precipitation hardening, while the balance between strength and toughness depends on the hot-rolled microstructure.
- Impact of two-phase region rolling on the microstructure and properties distribution in heavy gauge structural steel plate (INCROHSS).(Publications Office of the European Union, 2020) Isasti-Gordobil, N. (Nerea); Caruso, M. (M.); Lorenz, U. (U); Nguyen, M.T. (Minh); Sietsma, J. (J.); Akbary, F.H.(F.H.); Uranga-Zuaznabar, P. (Peio); Duprez, L. (L.); Petrov, R. (R.); Tolleneer, I. (I.); Mayo-Ijurra, U. (Unai)Heavy gauge line-pipe and structural steel plates are often rolled in the two-phase region for strength reasons. However, strength and toughness show opposite trends and the exact effect of each rolling process parameter remains unclear. A stable process window can only be achieved by a more profound understanding of the microstructure development during the intercritical rolling and its relationship with final microstructures and mechanical properties. By means of recently developed microstructure investigation techniques and modeling, the relationship between the temperature gradient, α-γ phase balance at high temperature, strain partitioning between phases and subsequent transformation was studied in detail to allow for wider process windows.