Desarrollo de utillajes de nueva generación para la mejora de las características mecánicas y dimensionales de piezas estampadas en caliente

El contenido de los capítulos IV y V está sujeto a confidencialidad. 180 p.Con el fin de aumentar la resistencia de las actuales herramientas empleadas en la estampación en caliente se proponen soluciones basadas en las tecnologías de deposición como alternativa a la construcción de herramientas bi-metálicas.Para ello se trabaja sobre tres aceros convencionales de trabajo en caliente empleados en la construcción de herramientas de estampación en caliente y se analiza el comportamiento a desgaste de las mismas a temperatura ambiente y elevada temperatura. De estos estudios se selecciona el metal base a utilizar en la construcción de herramientas bi-metálicas. Tras la selección del acero base, se desarrollan materiales capaces de aumentar la resistencia a desgaste y que puedan fabricarse mediante tecnologías de deposición. Tras la selección de distintas soluciones se fabrican muestras estas se caracterizan metalúrgicamente. Los resultados de la caracterización realizados permiten identificar la mejor solución capaz de mejorar la resistencia al desgaste de las actuales herramientas. Finalmente, se llevan a cabo ensayos de desgaste a escala de laboratorio mediante ensayos tribológicos, con el fin de realizar una primera aproximación y comparación entre el acero de referencia y el material de aportación desarrollado a temperatura ambiente y elevada temperatura.IK4 Azterla

Desarrollo de utillajes de nueva generación para la mejora de las características mecánicas y dimensionales de piezas estampadas en caliente

El contenido de los capítulos IV y V está sujeto a confidencialidad. 180 p.Con el fin de aumentar la resistencia de las actuales herramientas empleadas en la estampación en caliente se proponen soluciones basadas en las tecnologías de deposición como alternativa a la construcción de herramientas bi-metálicas.Para ello se trabaja sobre tres aceros convencionales de trabajo en caliente empleados en la construcción de herramientas de estampación en caliente y se analiza el comportamiento a desgaste de las mismas a temperatura ambiente y elevada temperatura. De estos estudios se selecciona el metal base a utilizar en la construcción de herramientas bi-metálicas. Tras la selección del acero base, se desarrollan materiales capaces de aumentar la resistencia a desgaste y que puedan fabricarse mediante tecnologías de deposición. Tras la selección de distintas soluciones se fabrican muestras estas se caracterizan metalúrgicamente. Los resultados de la caracterización realizados permiten identificar la mejor solución capaz de mejorar la resistencia al desgaste de las actuales herramientas. Finalmente, se llevan a cabo ensayos de desgaste a escala de laboratorio mediante ensayos tribológicos, con el fin de realizar una primera aproximación y comparación entre el acero de referencia y el material de aportación desarrollado a temperatura ambiente y elevada temperatura.IK4 Azterla

Effect of the Martensitic Transformation on the Stamping Force and Cycle Time of Hot Stamping Parts

Stamping dies perform two functions in the hot stamping process of body-in-white components. Firstly, they form the steel sheet into the desired shape and, secondly, they quench the steel at a cooling rate that leads to hardening by means of the austenite-gamma to martensite transformation. This microstructural change implies a volume expansion that should lead to a force peak in the press, which has yet to be detected in industrial practice. In this study, a set of hot stamping laboratory tests were performed on instrumented Al-Si-coated 22MnB5 steel flat formats to analyze the effect of the stamping pressure on the detection of the expected peak. Plotting the sheet temperature and pressure curves against time allowed us to identify and understand the conditions in which the force peak can be detected. These conditions occurred most favorably when the stamping pressure is below 5 MPa. It is thus possible to determine the exact moment at which the complete hardening transformation occurs by monitoring the local pressing force of the tool in areas where the pressure exerted on the metal format is below 5 MPa. This information can be applied to optimize the time needed to open the dies in terms of the complete martensitic transformation.The authors gratefully acknowledge the funding provided by the Department of Research and Universities of the Basque Government under Grant No. IT947-16 and the University of the Basque Country UPV/EHU under Program No. UFI 11/29

Wear And Friction Evaluation Of Different Tool Steels For Hot Stamping

The aim of this work is to investigate the durability of tool steels for hot stamping by comparing the wear resistance of three hot work tool steels. Friction and wear behaviours of different tool steels sliding against a 22MnB5 uncoated steel at elevated temperatures were investigated using a high-temperature version of the Optimol SRV reciprocating friction and wear tester at temperatures of 40 and 200°C. Our results show that friction decreased with increasing temperature, whereas wear of the tool steel increased with temperature for the second and the third tested tool steels. The slightly better wear behaviour of steel specimen 1 comes from the hardness of the carbides in the martensitic microstructure, which are rich in vanadium.The authors gratefully acknowledge the funding provided by the Department of Research and Universities of the Basque Government under Grant no. IT947-16 and the University of the Basque Country UPV/EHU under Program no. UFI 11/29

Retained Austenite Control for the Soft Machining of High-Hardness Tool Steels

Most high-hardness tool steels comprising forming dies require expensive finish machining operations to compensate for the dimensional distortion and surface oxidation caused by the die heat treatment. Precipitation-hardening (PH) tool steels allow for soft finish machining followed by an aging treatment without major deformation or oxidation in the die, but exhibit poor wear performance owing to the lack of carbides in their structure. This drawback can be overcome by combining laser cladding technology, austenite retention, and cryogenic treatments. Hence, an alternative die manufacturing route based on laser cladding was explored. The forming surface of a modified chemistry tool steel die was subjected to cladding. The martensite finish (M-f) temperature of the steel was tuned to enhance austenite retention at room temperature. The cladded surface was then machined in a reduced-hardness condition resulting from retained austenite formation. Subsequent deep cryogenic treatment of the die favoured the retained-austenite-to-martensite transformation, thereby increasing the die hardness without major distortion or oxidation. This process combined the advantages of high-carbide-bearing tool steels and PH steels, allowing for a die with hardness exceeding 58 HRC to be finish machined at <52 HRC. Controlling the occurrence of retained austenite represents an effective strategy for achieving new manufacturing scenarios.The authors gratefully acknowledge the funding provided by the Department of Research and Universities of the Basque Government under Grant No. IT947-16 and the University of the Basque Country UPV/EHU under Program No. UFI 11/29

Effect of the Martensitic Transformation on the Stamping Force and Cycle Time of Hot Stamping Parts

Stamping dies perform two functions in the hot stamping process of body-in-white components. Firstly, they form the steel sheet into the desired shape and, secondly, they quench the steel at a cooling rate that leads to hardening by means of the austenite-&gamma; to martensite transformation. This microstructural change implies a volume expansion that should lead to a force peak in the press, which has yet to be detected in industrial practice. In this study, a set of hot stamping laboratory tests were performed on instrumented Al&ndash;Si-coated 22MnB5 steel flat formats to analyze the effect of the stamping pressure on the detection of the expected peak. Plotting the sheet temperature and pressure curves against time allowed us to identify and understand the conditions in which the force peak can be detected. These conditions occurred most favorably when the stamping pressure is below 5 MPa. It is thus possible to determine the exact moment at which the complete hardening transformation occurs by monitoring the local pressing force of the tool in areas where the pressure exerted on the metal format is below 5 MPa. This information can be applied to optimize the time needed to open the dies in terms of the complete martensitic transformation

Desarrollo de utillajes de nueva generación para la mejora de las características mecánicas y dimensionales de piezas estampadas en caliente

El contenido de los capítulos IV y V está sujeto a confidencialidad. 180 p.Con el fin de aumentar la resistencia de las actuales herramientas empleadas en la estampación en caliente se proponen soluciones basadas en las tecnologías de deposición como alternativa a la construcción de herramientas bi-metálicas.Para ello se trabaja sobre tres aceros convencionales de trabajo en caliente empleados en la construcción de herramientas de estampación en caliente y se analiza el comportamiento a desgaste de las mismas a temperatura ambiente y elevada temperatura. De estos estudios se selecciona el metal base a utilizar en la construcción de herramientas bi-metálicas. Tras la selección del acero base, se desarrollan materiales capaces de aumentar la resistencia a desgaste y que puedan fabricarse mediante tecnologías de deposición. Tras la selección de distintas soluciones se fabrican muestras estas se caracterizan metalúrgicamente. Los resultados de la caracterización realizados permiten identificar la mejor solución capaz de mejorar la resistencia al desgaste de las actuales herramientas. Finalmente, se llevan a cabo ensayos de desgaste a escala de laboratorio mediante ensayos tribológicos, con el fin de realizar una primera aproximación y comparación entre el acero de referencia y el material de aportación desarrollado a temperatura ambiente y elevada temperatura.IK4 Azterla

Microstructural Tuning of a Laser-Cladding Layer by Means of a Mix of Commercial Inconel 625 and AISI H13 Powders

The aim of this work is to evaluate the microstructural evolutions developed by mixing a corrosion-resistant and high-performance material with a high-hardness material in a coating obtained by laser-cladding technology. In this paper, five different mixtures of Inconel 625 alloy and AISI H13 steel powders have been deposited on a plate of 42CrMo4 steel using a 2.2 kW diode pumped Nd:YAG laser. The effect of adding tool steel to a Ni-based superalloy has been analyzed by the characterization of each cladded sample using optical microscopy and scanning electron microscopy (SEM). The precipitates observed in the samples have been analyzed by energy dispersive X-ray spectroscopy (EDS X-ray). SEM micrographs and EDS analysis indicate the existence of Laves phase. It has been observed that the presence of these precipitates is stabilized in a certain range of AISI H13 addition

L-DED numerical model for sensor embedding

[EN] Sensor integration is one of the drivers in modern industry for obtaining real-time data and enabling transition to Industry 4.0. Sensor integration on production systems and tooling is one of the key points for data acquisition. Although several techniques can be applied for sensor integration, Laser Directed Energy Deposition (L-DED) is becoming one of the most relevant, since the sensor can be placed into the manufactured layer-by-layer structure. However, the thermal nature of the L-DED poses a challenge when heat-sensitive parts, such as thermocouples, are to be embedded. In order to ease parametrization and anticipate the behavior of the L-DED process, modeling is an interesting tool that has attracted the attention of academia in the last years. Nevertheless, most models are highly complex and focused on a very local scale or include symmetry assumptions that restrict their use for real applications. In view of this need, in the present research work a thermal model that considers material addition and determines the clad geometry is developed. The model includes an automatic meshing algorithm that adapts the element size by refining the mesh where required. Besides, the model enables 5 axis L-DED, in-process variation of the machine feed rate, and allows to switch on and offthe laser to simulate not only the material deposition, but also the idle movements. The model is validated in two steps: single clad deposition on a flat surface and single clads on a 0.3 mm thick thermocouple sheath. Finally, the validated model is used for defining the maximum laser power for embedding virtually a 3 mm diameter K-type thermocouple with a 0.3 mm thick sheath. The results of the simulation are also corroborated by experimental integra- tion of the same thermocouple, which functionality is tested afterwards. Therefore, the L-DED modeling is proven to be an effective tool for manufacturing complex parts on the first try.This work was supported by the Basque Government (Eusko Jaurlaritza) through the ELKARTEK program , grant numbers KK- 2022/0 0 080 and KK-2021/00120 and the Spanish Ministry of Econ- omy and Competitiveness under the PID2019-109220RB-I00 ALA- SURF project