Browsing by Author "Arribas, Maribel"
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Item Austenite Reverse Transformation in a Q&P Route of Mn and Ni Added Steels(MDPI, 2020-06) Arribas, Maribel; Gutiérrez, Teresa; Del Molino, Eider; Arlazarov, Artem; De Diego-Calderón, Irene; Martin, David; De Caro, Daniele; Ayenampudi, Sudhindra; Santofimia, Maria J.In this work, four low carbon steels with different contents of Mn and Ni were heat treated by quenching and partitioning (Q&P) cycles where high partitioning temperatures, in the range of 550 °C-650 °C, were applied. In order to elucidate the effect of applying these high partitioning temperatures with respect to more common Q&P cycles, the materials were also heat treated considering a partitioning temperature of 400 °C. The microstructure evolution during the Q&P cycles was studied by means of dilatometry tests. The microstructural characterization of the treated materials revealed that austenite retention strongly depended on the alloy content and partitioning conditions. It was shown that the occurrence of austenite reverse transformation (ART) in the partitioning stage in some of the alloys and conditions was a very effective mechanism to increase the austenite content in the final microstructure. However, the enhancement of tensile properties achieved by the application of high partitioning temperature cycles was not significant.Item Characterization of a Medium Mn-Ni Steel Q&P Treated by a High Partitioning Temperature Cycle(2022-03-13) Arribas, Maribel; Del Molino, Eider; Gutiérrez, Teresa; Arlazarov, Artem; Martin, David; De Caro, Daniele; Ayenampudi, Sudhindra; Santofimia, Maria J.; CIRMETAL; PROMETALIn this work, a medium Mn-Ni steel was treated through Quenching and Partitioning (Q&P) with a partitioning temperature (PT) of 650 °C, which corresponded to the start of the austenite reverse transformation (ART) phenomenon. The influence of the quenching temperature (QT) and partitioning time (Pt) on austenite stabilization and mechanical properties was investigated. A strong influence of the quenching temperature was observed. Results were compared with those obtained after a Q&P treatment with 400 °C partitioning temperature. The Q&P cycle with quenching to room temperature and a high partitioning temperature produced a steel with a high retained austenite (RA) volume fraction and exceptional strength–ductility balance. The analysis of the mechanical stability of the retained austenite revealed a significant stress-induced transformation. Nevertheless, the austenite, which was stable at stresses above the yield stress, provided significant TRIP-assisted ductility. Bending, hole expansion and post-stamping properties were also evaluated for the most promising conditions.Item Impact of Si on Microstructure and Mechanical Properties of 22MnB5 Hot Stamping Steel Treated by Quenching & Partitioning (Q&P)(2017-11-21) Linke, Bernd M.; Gerber, Thomas; Hatscher, Ansgar; Salvatori, Ilaria; Aranguren, Iñigo; Arribas, Maribel; CCAM; CIRMETALBased on 22MnB5 hot stamping steel, three model alloys containing 0.5, 0.8, and 1.5 wt pct Si were produced, heat treated by quenching and partitioning (Q&P), and characterized. Aided by DICTRA calculations, the thermal Q&P cycles were designed to fit into industrial hot stamping by keeping partitioning times £ 30 seconds. As expected, Si increased the amount of retained austenite (RA) stabilized after final cooling. However, for the intermediate Si alloy the heat treatment exerted a particularly pronounced influence with an RA content three times as high for the one-step process compared to the two-step process. It appeared that 0.8 wt pct Si sufficed to suppress direct cementite formation from within martensite laths but did not sufficiently stabilize carbon-soaked RA at higher temperatures. Tensile and bending tests showed strongly diverging effects of austenite on ductility. Total elongation improved consistently with increasing RA content independently from its carbon content. In contrast, the bending angle was not impacted by high-carbon RA but deteriorated almost linearly with the amount of low-carbon RA.Item Influence of Mn and Ni on Austenite Stabilization during a High Temperature Q&P Treatment(Trans Tech Publications, 2021-01) Del Molino, Eider; Gutierrez, Teresa; Serna-Ruiz, Mónica; Arribas, Maribel; Arlazarov, Artem; Ionescu, Mihail; Sommitsch, Christof; Poletti, Cecilia; Kozeschnik, Ernst; Chandra, Tara; Tecnalia Research & Innovation; PROMETAL; CIRMETAL; SGThe aim of this work was to study the influence of quenching and partitioning temperatures combined with various levels of Mn and Ni contents on the austenite stabilization along the quenching and partitioning (Q&P) cycle. Three steels with 2 wt.%, 4 wt.% and 6 wt.% manganese and one steel with 2 wt.% nickel content were investigated. Phase transformation temperatures and critical cooling rates were obtained experimentally using dilatometer for each alloy. Q&P cycles with different quenching and partitioning temperatures were also done in dilatometer, thus, allowing monitoring of the expansion/contraction during the whole Q&P cycle. Microstructure characterization was performed by means of a Scanning Electron Microscope and X-Ray Diffraction to measure retained austenite content. It was found that, strongly depending on the Q&P conditions, austenite stabilization or decomposition occurs during partitioning and final cooling. In case of high partitioning temperature cycles, austenite reverse transformation was observed. Certain cycles resulted in a very effective austenite stabilization and interesting microstructure.Item New Multiphase CP and DP 1000 MPa strength level grades for improved performance after hot forming(2019-11-26) Lahaije, C T W; Rana, R; Sunderkoetter, C; Pérez, Iñaki; Arribas, Maribel; Aranguren, Iñigo; Caro, Daniele De; Pérez, Iaki; Aranguren, Iigo; CIRMETAL; CCAMPure martensitic steels have after hot forming limited performance in terms of rest ductility which limits the application in crash relevant parts. New steel grades were designed in the EU project HOTFORM including the corresponding process routes. These steel grades have ferritic-martensitic dual phase (DP) and martensitic-bainitic complex phase (CP) microstructures after hot forming process. The laboratory tests show an improved formability after hot forming. The basic concepts of the new alloys are explained. Furthermore, for validation of upscaling purposes a semi-industrial test is carried out and the results are discussed. The main application is for vehicle safety. This is evaluated by comparing the crash performance of these hot formed grades with cold rolled DP1000 and CP1000 for crash cans in a drop tower test.