Browsing by Author "Gutierrez, Teresa"
Now showing 1 - 4 of 4
Results Per Page
Sort Options
Item Data Driven Performance Prediction in Steel Making(2022-01-18) Boto, Fernando; Murua, Maialen; Gutierrez, Teresa; Casado, Sara; Carrillo, Ana; Arteaga, Asier; Tecnalia Research & Innovation; FACTORY; CIRMETAL; PROMETALThis work presents three data-driven models based on process data, to estimate different indicators related to process performance in a steel production process. The generated models allow the optimization of the process parameters to achieve optimal performance and quality levels. A new approach based on ensembles has been developed with feature selection methods and four state-of-the-art regression approximations (random forest, gradient boosting, xgboost and neural networks). The results show that the proposed approach makes the prediction more stable reducing the variance for all cases, even in one case, slightly reducing the bias. Furthermore, from the four machine learning paradigms presented, random forest is the one with the best results in a quantitative way, obtaining a coefficient of determination of 0.98 as a maximum, depending on the target sub-process.Item Evolution of Microstructure during Isothermal Treatments of a Duplex-Austenitic 0.66C11.4Mn.9.9Al Low-Density Forging Steel and Effect on the Mechanical Properties(Multidisciplinary Digital Publishing Institute (MDPI), 2021-01-26) Kaltzakorta, Idurre; Gutierrez, Teresa; Elvira, Roberto; Jimbert, Pello; Guraya, TeresaIn the last decades, low-density steels for forging have increasing interest in the automotive industry, and good mechanical properties are required for their real application. This paper describes the results obtained for a 0.66C11.4Mn9.9Al duplex austenitic low-density steel after applying a set of isothermal treatments at different combinations of time and temperature, aimed to promote kappa carbide precipitation, and improve the mechanical properties obtained with a water quenching treatment. The effects of the different isothermal treatments on the microstructure and on the mechanical properties have been analyzed and compared to those obtained from a quenching heat treatment. We found that isothermal treatments in the range temperature between 550–750 °C promoted the profuse precipitation of coarse kappa carbides at grain boundaries, which dramatically reduced the ductility of the alloy, whereas a traditional quenching treatment resulted in a better combination of ductility and mechanical strength.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 Manufacturing and forging issues encountered while upscaling 1.3C30Mn10Al-austenitic and 0.65C12Mn-duplex low-density steels(2021-07) Kaltzakorta, Idurre; Gutierrez, Teresa; Elvira, Roberto; Jimbert, Pello; Guraya, Teresa; CIRMETALDifficulties found when manufacturing and forging two low density steels in different scales are described in this work. Austenitic and duplex low-density steels have attracted a lot of interest due to their good combination of mechanical properties and density reduction. In this work, the fabrication of 1.3 C30Mn10Al austenitic low-density steel and 0.65 C12Mn10Al duplex low-density steel have been studied. The scaling up of the manufacturing process from 1 Kg to 35 Kg ingots of both materials and the subsequent hot forging of the ingots is described, showing the difficulties encountered during the production and transformation of these steels. Only the small ingots were successfully forged, but not the larger ones, showing the important differences in the forging properties depending on the geometry and dimensions of the final part to be forged, and the homogenization temperatures. The possible causes of this scale dependence are proposed from the experimental results obtained, as well as from the hot axial compression tests and the thermodynamic simulations carried out.