O desenvolvimento de métodos de simulação física e numérica tem criado novas possibilidades de otimização dos processos relacionados à estampagem com inclusão de processos industriais reais. Portanto, recorrendo à aplicação destes métodos de análise, é possível avaliar a transformação mecânica e as transformações de fase que ocorrem no material e prever as interações entre as propriedades dos materiais no processo de conformação, o comportamento constitutivo do material, as variáveis de otimização do processo, bem como a previsão das tensões e deformações a fim de estabelecer a melhor relação material-processo-desempenho. A introdução e crescente utilização de aços avançados de alta resistência (AHSS) em aplicações automotivas exige uma maior compreensão dos fenômenos físicos envolvidos no processamento termomecânico a fim de otimizar a performance da peça final fabricada. O presente trabalho teve como objetivo avaliar experimentalmente o processo de estampagem a quente, com posterior tratamento térmico de têmpera e partição e analisar as microestruturas formadas e suas propriedades mecânicas. A formação de microestruturas durante o processo de estampagem a quente e de têmpera e partição foi avaliada neste trabalho por simulação física em simulador termomecânico Gleeble, acoplado à uma linha de difração de raios X (XTMS) de feixe de luz síncrotron no Laboratório Nacional de Nanotecnologia (LNNano). Foram avaliadas a partição do carbono, a estabilidade térmica da austenita retida e a formação de microconstituintes resultantes da transformação da austenita durante resfriamento forçado (têmpera), seguido de partição de carbono em patamares isotérmicos. Foram utilizadas técnicas de caracterização com apoio de microscopia eletrônica (MEV-FEG e STEM), EBSD, tomografia de sonda atômica (APT) e avaliação de propriedades mecânicas por ensaios de tração e indentação instrumentada. A análise numérica foi realizada por meio do método dos elementos finitos (MEF) e por elementos finitos orientada a objetos (OOF, Object Oriented Finite Element Analysis) visando estabelecer correlações entre microestrutura e propriedades mecânicas, comparando com resultados experimentais. Os resultados e conclusões obtidos no projeto, além de possibilitarem a identificação dos mecanismos fundamentais de geração de microestruturas durante o processo, auxiliam no projeto de aços AHSS estampados a quente, usados principalmente na indústria automobilística, na busca pela redução do consumo de combustível, através da redução do peso, e pelo aumento da segurança dos passageiros. / The development of numerical and physical simulation methods has created new possibilities regarding the optimization of metal forming processes, taking into account real industrial forming processes. Therefore, by applying such methods of analysis it is now possible to assess the material phase transformations and predict the interactions between material properties and the forming process, the constitutive behavior of the material, and optimize process variables as well as predicting the best material-process-performance relationship. The increasing usage of Advanced High Strength Steels (AHSS) in automotive applications demands a better insight of the physical phenomena involved in the thermomechanical processing in order to optimize the performance of the final manufactured part. Thermomechanical simulation of the hot stamping, quenching and partitioning process was carried out in a Gleeble machine coupled to the XTMS Synchrotron X-ray diffraction line at the National Nanotechnology Laboratory (LNNano). Carbon partitioning, carbon contents, and amount of retained austenite, martensite, bainite and ferrite was assessed online during the experiments. In addition, characterization techniques by optical, electron microscopy (FEG-SEM and STEM), EBSD, and Atom Probe Tomography (APT) were applied. Mechanical testing of subsize specimens of the processed steels was performed by means of tensile tests and macro and nanoindentation tests. The numerical analysis was performed using the finite element method (FEM) and object-oriented finite element technique (OOF). The results were compared with the experimental results of mechanical testing of specimens used in the thermomechanical simulations and with hot stamped sheets, where quenching and partitioning were carried out. The results and conclusions obtained in this project allow the identification of the fundamental mechanisms of the process, helping the design of the hot stamping process for AHSS steels used primarily in the automotive industry, seeking weight reduction to improve fuel economy and increased passenger safety.

Die vorliegende Arbeit untersucht den Einsatz einer induktiven Längsfelderwärmung im Wärmebehandlungsprozess der direkten Warmumformung automobiler Karosserieblechbauteile. Zur Charakterisierung des Erwärmungsvorgangs werden sowohl experimentbasierte Regressionsmodelle als auch ein FEM-Simulationsmodell entwickelt. Der Einfluss der induktiven Erwärmung auf die Ausbildung der AlSi-Beschichtung, die Widerstandspunktschweißbarkeit so-wie die Korrosionsbeständigkeit gefertigter Blechbauteile wird dargelegt. Abschließend wird ein Anlagenkonzept entwickelt, das durch den Einsatz der induktiven Längsfelderwärmung eine Verringerung der Erwärmungsdauer um etwa 50 % sowie eine Verkürzung der erforderlichen Ofenlänge um etwa 37 % ermöglicht. / The present thesis investigates the usage of longitudinal induction heating in the austenitization process of direct press hardening. In order to describe the induction heating procedure, experiment-based regression models as well as a FEM model are developed. The influence of an induction heating process on the properties of press hardened parts with aluminum-silicon coating is depicted. Therefore, resistance spot welding tests, paint adhesion tests and corrosion tests are performed. Finally, a heating concept for series production including a longitudinal induction heating is developed, which allows a decrease in heating time of about 50 % and a reduction of furnace length of about 37 %.

Many automotive components are made of Al-Si coated ultra-high strength boron steel (UHSS) and are produced by hot stamping process. In this process, the workpiece is heated to an austenitizing temperature and is then formed and quenched simultaneously between the tools to achieve the desired shape and high strength. During hot stamping process, friction and wear occur which affect formability and maintenance intervals for tool replacement and repair. To repair worn tools, metal is deposited by fusion welding technique. The tribological behaviour of repair welded tool steel sliding against Al-Si coated UHSS has not been studied in detail and there is a need to investigate if the modified tool surface will affect friction and wear. Hot stamping, similar to many manufacturing processes, is affected by the global mega trend of digitalization and Industry 4.0. To monitor the process and optimize the control and operation are the main aims. In view of this, tribological condition monitoring is a promising approach that can allow measurement of physical properties such as vibrations, temperatures, and acoustic emission to be coupled to the tribological response of the system. The aim is to monitor the hot stamping process and enable early detection of changes in friction and wear which can be used for e.g. optimized maintenance and minimized scrap. The aim of this M.Sc. thesis was to improve the robustness of hot forming processes by studying the tribological behaviour of repair welded tool steel sliding against Al-Si coated UHSS under conditions relevant for hot stamping. Another aim was to obtain more predictable tool maintenance by the implementation of acoustic emission measurement system on a hot-strip tribometer and correlating condition monitoring signals to friction and wear phenomena. The tribological tests were carried out using a hot-strip tribometer in conditions representative of a hot stamping process of automotive components. Acoustic emission during sliding between hot work tool steel and different automotive component material surfaces was measured at room temperature in the same strip drawing tribometer and correlated to friction and wear of the surfaces to get more predictable maintenance intervals. Tool steel specimens were welded with the same material as the base material QRO90. Before conducting the tribological test, the repair welded tool steel pin cross-section was polished, etched, and observed under optical microscope and SEM to analyze the effect of Tungsten Inert Gas (TIG) welding process on the microstructure. The analysis was completed with EDS to study the elements in the microstructure. Microhardness was measured to obtain the microhardness profile from the repair welded tool steel pin surface to the bulk in order to study the effect of different microstructures on the mechanical properties. The weight and surface roughness of the pins were measured before the tribological test. After the test was finished, the weight of the pins was measured to calculate the weight difference. The sliding surface of the pins and the strips were photographed. The sliding surface of the pins was also observed and analyzed using SEM and EDS after the test to study wear characteristic of the repair welded tool steel at high temperatures. Acoustic emission signal from the sliding was studied using Toolox44 pins with surface roughness 300-400 nm and with lay direction parallel and perpendicular to sliding direction. Toolox44 pins were sliding against uncoated UHSS, as-delivered Al-Si coated UHSS, and heat-treated Al-Si coated UHSS strips. Acoustic emission was measured during the sliding at the same time as COF measurement. Weight of the pins was measured before and after the test and the wear damage on both surfaces was photographed. COF, AE signals in the time and frequency domain, and wear damage were compared and analyzed. It is found that repair welded tool steel has similar COF compared to the original hot work tool steel with the largest weight gain from the test at 700 ⁰C due to compaction galling mechanism with slower lump formation and the presence of wear particles, transfer layer, and formation of lumps. The weight gain is smaller from the test at 750 ⁰C due to faster lump formation. The weight loss from the test at 600 ⁰C is due to abrasive wear mechanism. SEM micrographs revealed that the repair welded tool steel surface and transfer layers can be found beneath a transfer layer. Wear particles adhered on the repair welded tool steel surface come from broken transfer layer or directly from Al-Si coated UHSS. A change in wear mechanism is indicated by acoustic emission burst signals or gradual amplitude change in the time domain. Frequency analysis of AE signals revealed a change in wear mechanism due to the formation of transferred material in the form of a lump causes AE signals with peaks at higher frequencies above 0.3 MHz to shorten.

Os projetos de carrocerias veiculares atuais procuram desenvolver estruturas leves, seja para reduzir o consumo de combustível, no caso dos motores de combustão interna, seja para maior autonomia de bateria, no caso dos veículos elétricos e híbridos. Redução no consumo de combustível significa redução na emissão de poluentes. As estruturas precisam ser leves, mas cada vez mais resistentes e rígidas a fim de proporcionar máximo conforto e segurança aos ocupantes. Estas premissas têm levado ao contínuo desenvolvimento dos materiais. No caso dos aços, um dos processos que tem permitido a melhora significativa das propriedades mecânicas é a estampagem a quente. Nos últimos anos, as peças estampadas a quente têm ocupado lugar de destaque na estrutura das carrocerias veiculares por estarem em sintonia com as demandas mencionadas. Há muitas pesquisas em curso para esta tecnologia, seja nos materiais, nos meios de produção, nos revestimentos e em aplicações. O aço mais utilizado neste processo, 22MnB5, também apresenta o chamado efeito bake hardening; a tensão de escoamento é aumentada após tratamento térmico realizado em temperaturas próximas a 200 °C. Neste trabalho, visando à melhoria nas propriedades mecânicas, amostras foram tratadas termicamente na faixa de temperatura supracitada. Após isso, dados obtidos de ensaios mecânicos foram inseridos em programas de simulação de impacto lateral cujo resultado foi a redução na intrusão na célula de sobrevivência. O efeito bake hardening também propiciou um aumento na absorção da energia de impacto em teste estático feito com barras de proteção lateral. O mecanismo metalúrgico envolvido no fenômeno, devido à difusão de intersticiais foi evidenciado no ensaio de atrito interno. / The current auto body projects seek to build light structures whose immediate impact is in the reduction in fuel consumption of internal combustion engines or in longer battery life for electric and hybrid vehicles. Reduction in fuel consumption means reduced emissions. The structures need to be lightweight, but increasingly resistant to provide maximum comfort and safety to the occupants. These demands led to the continuous development of new materials. In the case of the steels hot stamping has allowed significant improvement in the mechanical properties. In recent years, hot stamped parts took prominent place in the structure of auto bodies to be in line with the mentioned demands. There are a lot of researches lines for this technology: materials, modes of production, coatings and applications. The most commonly used steel in this process, 22MnB5, also exhibits the bake hardening effect: its yield strength is increased after thermal treatment at temperatures close to 200 °C. To verify this improvement in the mechanical properties, samples were thermally treated. After that, data obtained from mechanical tests were inserted into side-crash simulation programs that resulted in a reduction in intrusion in the passengers compartment. The bake hardening effect also provided an increase in the absorption of the impact energy in a static test done with door beam. The metallurgical mechanism involved in the phenomenon, due to the movement of interstitial was evidenced in the internal friction test.

A demanda por produtos mais econômicos, eficientes e menos poluentes faz com que a indústria automobilística invista em novos e melhores materiais e processos de produção. Assim, surgiu o processo de estampagem à quente chamado Press Hardening e seus produtos, os Press Hardened Steels. Esta classe de aços é capaz de produzir uma microestrutura totalmente martensítica durante o rápido resfriamento em prensa. Com o aumento da produção de peças por Press Hardening, evidenciou-se um grave problema: a suscetibilidade à fragilização por hidrogênio dos aços submetidos a esse processo. A ocorrência das chamadas fraturas retardadas induzidas por hidrogênio é relatada na literatura e uma pesquisa indica que microadições de nióbio ao aço 22MnB5 poderiam aumentar a resistência à fratura induzida por hidrogênio. Para estudar os efeitos do hidrogênio no aço 22MnB5, foram utilizadas seis diferentes composições A, C, CP, Ec, Ep e N (contém nióbio) em dois ensaios principais: ensaio de permeabilidade de hidrogênio e trincamento induzido por hidrogênio. A técnica de microdureza Vickers foi posteriormente utilizada para verificar possíveis efeitos do ensaio de permeabilidade de hidrogênio. Quatro das seis ligas receberam inicialmente o tratamento de press hardening e todas as seis apresentavam estruturas martensíticas nos ensaios de permeabilidade e trincamento. Por meio do método tlag, os parâmetros de difusão dos ensaios de permeabilidade foram calculados e comparados à literatura. As ligas CP e N apresentam os maiores valores de difusividade aparente de hidrogênio, menores valores de concentração máxima de hidrogênio e menores densidades de sítios de aprisionamento, sendo assim menos suscetíveis à fragilização por hidrogênio. Os ensaios de trincamento revelaram que as composições A, C e Ec apresentam trincas maiores do que as demais ligas, corroborando os resultados obtidos nos ensaios de permeabilidade (melhor resistência à fragilização por hidrogênio das ligas CP e N que contém Nb). Os ensaios de microdureza Vickers mostraram que não há redução na dureza após o ensaio de permeabilidade. Palavras-chave: A demanda por produtos mais econômicos, eficientes e menos poluentes faz com que a indústria automobilística invista em novos e melhores materiais e processos de produção. Assim, surgiu o processo de estampagem à quente chamado Press Hardening e seus produtos, os Press Hardened Steels. Esta classe de aços é capaz de produzir uma microestrutura totalmente martensítica durante o rápido resfriamento em prensa. Com o aumento da produção de peças por Press Hardening, evidenciou-se um grave problema: a suscetibilidade à fragilização por hidrogênio dos aços submetidos a esse processo. A ocorrência das chamadas fraturas retardadas induzidas por hidrogênio é relatada na literatura e uma pesquisa indica que microadições de nióbio ao aço 22MnB5 poderiam aumentar a resistência à fratura induzida por hidrogênio. Para estudar os efeitos do hidrogênio no aço 22MnB5, foram utilizadas seis diferentes composições A, C, CP, Ec, Ep e N (contém nióbio) em dois ensaios principais: ensaio de permeabilidade de hidrogênio e trincamento induzido por hidrogênio. A técnica de microdureza Vickers foi posteriormente utilizada para verificar possíveis efeitos do ensaio de permeabilidade de hidrogênio. Quatro das seis ligas receberam inicialmente o tratamento de press hardening e todas as seis apresentavam estruturas martensíticas nos ensaios de permeabilidade e trincamento. Por meio do método tlag, os parâmetros de difusão dos ensaios de permeabilidade foram calculados e comparados à literatura. As ligas CP e N apresentam os maiores valores de difusividade aparente de hidrogênio, menores valores de concentração máxima de hidrogênio e menores densidades de sítios de aprisionamento, sendo assim menos suscetíveis à fragilização por hidrogênio. Os ensaios de trincamento revelaram que as composições A, C e Ec apresentam trincas maiores do que as demais ligas, corroborando os resultados obtidos nos ensaios de permeabilidade (melhor resistência à fragilização por hidrogênio das ligas CP e N que contém Nb). Os ensaios de microdureza Vickers mostraram que não há redução na dureza após o ensaio de permeabilidade. / The demand for more economical, efficient and less polluting products makes the automobile industry invest in new and better materials and production processes. In this way, arose the hot stamping process called Press Hardening and its products, the Press Hardened Steels. This class of steels is capable of producing a fully martensitic microstructure during rapid cooling in the press. With the increase of the production of pieces by Press Hardening, a serious problem was evidenced: the susceptibility to the hydrogen embrittlement of the steels made by this process. The occurrence of the so-called hydrogen-induced delayed fractures is reported in the literature and a research indicates that micro-alloying of niobium to 22MnB5 steel may increase hydrogen-induced fracture resistance. In order to study the hydrogen effects on the 22MnB5 steel, were used six different compositions A, C, CP, Ec, Ep and N (which contains niobium) in two main tests: hydrogen permeation test and hydrogen induced cracking. The Vickers micro hardness technique was later used to verify possible effects of the hydrogen permeation test. Four of the six alloys received the press hardening processing and all six had martensitic structures in the permeability and induced cracking tests. By means of the tlag method, the diffusion parameters of the permeability tests were calculated and compared to the literature. The CP and N alloys present the highest values of hydrogen apparent diffusivity, lower values of maximum hydrogen concentration and lower densities of trapping sites, thus being less susceptible to hydrogen embrittlement. The induced cracking tests showed that compositions A, C and Ec present higher cracks than the other alloys, corroborating the results obtained in the permeability tests (better resistance to hydrogen embrittlement of the alloys CP and N containing Nb). The Vickers microhardness tests showed that there is no reduction in hardness after the permeability test.

Os projetos de carrocerias veiculares atuais procuram desenvolver estruturas leves, seja para reduzir o consumo de combustível, no caso dos motores de combustão interna, seja para maior autonomia de bateria, no caso dos veículos elétricos e híbridos. Redução no consumo de combustível significa redução na emissão de poluentes. As estruturas precisam ser leves, mas cada vez mais resistentes e rígidas a fim de proporcionar máximo conforto e segurança aos ocupantes. Estas premissas têm levado ao contínuo desenvolvimento dos materiais. No caso dos aços, um dos processos que tem permitido a melhora significativa das propriedades mecânicas é a estampagem a quente. Nos últimos anos, as peças estampadas a quente têm ocupado lugar de destaque na estrutura das carrocerias veiculares por estarem em sintonia com as demandas mencionadas. Há muitas pesquisas em curso para esta tecnologia, seja nos materiais, nos meios de produção, nos revestimentos e em aplicações. O aço mais utilizado neste processo, 22MnB5, também apresenta o chamado efeito bake hardening; a tensão de escoamento é aumentada após tratamento térmico realizado em temperaturas próximas a 200 °C. Neste trabalho, visando à melhoria nas propriedades mecânicas, amostras foram tratadas termicamente na faixa de temperatura supracitada. Após isso, dados obtidos de ensaios mecânicos foram inseridos em programas de simulação de impacto lateral cujo resultado foi a redução na intrusão na célula de sobrevivência. O efeito bake hardening também propiciou um aumento na absorção da energia de impacto em teste estático feito com barras de proteção lateral. O mecanismo metalúrgico envolvido no fenômeno, devido à difusão de intersticiais foi evidenciado no ensaio de atrito interno. / The current auto body projects seek to build light structures whose immediate impact is in the reduction in fuel consumption of internal combustion engines or in longer battery life for electric and hybrid vehicles. Reduction in fuel consumption means reduced emissions. The structures need to be lightweight, but increasingly resistant to provide maximum comfort and safety to the occupants. These demands led to the continuous development of new materials. In the case of the steels hot stamping has allowed significant improvement in the mechanical properties. In recent years, hot stamped parts took prominent place in the structure of auto bodies to be in line with the mentioned demands. There are a lot of researches lines for this technology: materials, modes of production, coatings and applications. The most commonly used steel in this process, 22MnB5, also exhibits the bake hardening effect: its yield strength is increased after thermal treatment at temperatures close to 200 °C. To verify this improvement in the mechanical properties, samples were thermally treated. After that, data obtained from mechanical tests were inserted into side-crash simulation programs that resulted in a reduction in intrusion in the passengers compartment. The bake hardening effect also provided an increase in the absorption of the impact energy in a static test done with door beam. The metallurgical mechanism involved in the phenomenon, due to the movement of interstitial was evidenced in the internal friction test.

De nombreux revêtements sont actuellement disponibles pour les aciers emboutis à chaud et trempés pour le domaine de la construction automobile. Afin d’augmenter les performances des produits actuels en termes d’aptitude à la mise en forme à chaud, de résistance contre la corrosion et de compatibilité avec les procédés de fabrication ultérieurs, les constructeurs automobiles et les sidérurgistes ont développé de nombreux types de matériaux alternatifs. Peu de produits ont trouvé une place importante dans l’utilisation industrielle. L’objectif de ce travail est de procéder à une vue d’ensemble des performances des produits actuels, d’identifier de nouveaux concepts de revêtements et d’étudier leur compatibilité pour l’application de la mise en forme à chaud. Cette étude porte sur les revêtements d’alliages de Zn-Mn. De nombreux bains électrolytiques et paramètres électriques ont été étudiés afin de déterminer des conditions de déposition optimales pour obtenir des alliages Zn-Mn avec une forte teneur en Mn. Les propriétés cristallographiques, microstructurales et anticorrosives de couches obtenues sur des plaques d’acier de grandes dimensions ont été caractérisées avec de nombreuses techniques. La compatibilité des couches protectrices pour le traitement d’austénitisation a été évaluée après des traitements thermiques à différentes températures et durées de chauffe. Une attention particulière a été portée sur l’évolution de la composition et des phases d’interdiffusion formées, ainsi que sur l’apparition de mécanismes d’oxydation et d’évaporation à haute température. Enfin, l’aptitude à la mise en forme à chaud et notamment la susceptibilité à la fissuration par métaux liquides de ces nouveaux revêtements ont été évaluées par des essais d’emboutissage / Various coatings are currently available for press-hardened steels used for the automotive construction, mainly with the aim of providing good anticorrosive properties to the body components. In order to improve performance of the coated products in terms of hot formability, corrosion protection and suitability for subsequent manufacturing processes, steelmakers and car manufacturers investigated various alternative coating materials. Only a few solutions resulted in a serial production. The aim of this study is to proceed to a screening of the performance of current coating variants, to identify new concepts for alternative coating materials and assess their suitability for the hot stamping application. The present work is focused on the study of Zn-Mn alloy coatings. Various electroplating baths and electric parameters were studied in order to determine optimal deposition conditions for obtaining Zn-Mn alloys with high Mn contents. The deposits obtained on large-scale steel plates were characterized with regards to their crystallographic, microstructural and anticorrosive properties. The behavior of the coating materials during austenitizing treatment was studied after heat treatment to different temperatures and heating durations. A particular attention was given to the evolution of the composition, the interdiffusion phases formed as well as to the presence of oxidation and evaporation mechanisms at high temperature. At last, the forming properties of the alternative coating materials and their susceptibility for liquid metal embrittlement were assessed on the basis of direct hot stamping experiments

Hot-pressed aluminium and silicon coated boron steel is used in the car industry where high tensile strength is of great importance, such as in the safety cage of a car where deformation has to be kept to a minimum in case of a collision. After hot-pressing the AlSi-boron steel shows excellent properties with high tensile strength, minimal spring back and also shows good protection against corrosion. A thickness of the AlSi coating of 150 [g/m2] for AlSi coated boron steel is typically used by the car industry today. However the coating thickness would be desirable to be minimized to 80 [g/m2]. Welding of this boron steel with 80 [g/m2]have shown difficulties; and it’s not clear why this occurs. In this report the metallurgical properties of the different coating layers will be investigated, simulations with Thermocalc module Dictra will be used, SEM/EDS will be used to characterize phases in coating layers and correlate to weldability. Resistance spot welding tests will also be performed where the welding parameters of pre-pulse, pulse time, time in between pulses and current will be varied to achieve desirable weld plug diameter without expulsion. Hardness testing in form of micro Vickers will executed. The Materials used will be USIBOR® 1500, AS80 with four different annealing times and one sample of AS150.

Over the last decade, the application of ultra-high strength steel as safety components and structural reinforcements in automobile applications has increased due to their favourable high-strength-to-weight ratio. The complex shaped components are widely produced using hot stamping. However, this process encounters problems such as galling and increased wear of the tools due to harsh operating conditions associated to the elevated temperatures. Moreover, quenching is a critical step that affects the hot formed components. Slow cooling rates results in inhomogeneous mechanical properties and increased cycle time. Therefore, fast and homogeneous quenching of the formed components in combination with reduction of wear rates during hot forming are important targets to ensure the quality and efficiency of the process. The use of additive manufacturing (AM) technologies opens up potential solutions for novel tooling concepts. The manufacturing of complex shape cooling channels and integration of high-performance alloys at the surface could benefit the tribological performance in the forming operation. However, the research into high temperature tribological behaviour of AM materials in hot forming applications is very limited. The aim of this work is to study the tribological performance of additively manufactured materials. Two steels were used – a maraging steel and modified H13 tool steel. The hot work tool steel H13 is commonly applied for dies in metal forming processes. In this thesis it was used to study additive manufacturing as the processing route instead of conventional casting. The choice of a maraging steel is motivated by a possible application of high-performance alloys as a top layer on dies. The materials were post-machined and studied in milled, ground and shot-blasted conditions. The different post-machining operations were applied to study the effect of surface finish on the tribological behaviour and also to evaluate different methods of post-machining an AM surface. As fabricated dies are usually manufactured with milled surface. During its use, the dies undergo refurbishment after certain number of cycles and the surface condition is changed to a ground surface. These surface finishes are commonly tested for hot forming applications. The shot blasted operation was chosen as alternative surface finish. The process allows to prepare large sized tools easily and the surface has beneficial compressive stresses. The tribological behaviour of AM steels was studied using a hot strip drawing tribometer during sliding against a conventional Al-Si coated 22MnB5 steel. The workpiece temperature during the tests was 600 and 700°C. The results of the tribological performance of AM materials were compared to conventionally cast tool steel QRO90.The results have shown that the friction behaviour of both maraging and H13 steels at 600°C was stable and similar whereas at 700°C the COF was more unstable and resulted in an earlier failure of the tests due to increased material transfer of Al-Si coating from the workpiece surface.The main wear mechanisms for AM materials were galling and abrasion at both temperatures. Abrasion is more severe for the AM steels in comparison to cast tool steel QRO90. The galling formation on milled and ground surfaces showed similar behaviour to cast steel and it increased with higher workpiece temperatures. The shot-blasted surfaces showed less build-up of transferred material on the surface but folding of asperities and entrapment of Al-Si particles within surface defects generated during shot-blasting.

Eine effiziente und effektive Technologieentwicklung und –optimierungen im Bereich der Umform- und Fertigungstechnik erfolgt heutzutage fast ausschließlich rechnergestützt auf Basis der Finiten Elemente Methode (FEM) oder der Finiten Differenzen Methode (FDM). Die aktuellen Umformsimulationssysteme sind in der Lage die notwendige Energie der Anlagen, den prozessbedingten Stofffluss des Umformgutes inkl. der resultierenden Temperaturen und die Spannungen des Halbzeuges bzw. Bauteiles als auch der Werkzeuge vorauszuberechnen. Allerdingssind bereits dafür die sehr sensitiven Materialdaten, wie z. B. temperatur- und umformgeschwindigkeitsabhängige Fließkurven, Wärmeleitfähigkeit usw., notwendig. Momentane Forschungsaktivitäten beschäftigen sich damit, den nächsten Schritt der FE-Simulation zu bewältigen, in dem die Gefügeentwicklung und die daraus resultierenden mechanischen Eigenschaften (Zugfestigkeit, Bruchdehnung etc.) numerisch ermittelt werden können. Auch dafür müssen sehr aufwendige und materialspezifische Materialdaten generiert und modelliert und abschließend in Simulationssysteme über Schnittstellen implementiert werden. Die Vorhersage zu Verschleiß und Versagen von Werkzeugen wird in Zukunft immer mehr in das Interesse von Anwendern von FE-Software rücken, um die kompletten Einflussgrößen der Prozesse abzubilden. Dieser Beitrag soll am Beispiel einer aushärtbaren Aluminiumlegierung (EN AW 6.xxx) verdeutlichen, wie unterschiedlich das Materialverhalten in Abhängigkeit des Ausgangszustandes (stranggepresst, stranggegossen) und der Erwärmungsmodi (konvektiv, induktiv) sein kann und wie sich diese Variationen für ein und denselben Werkstoff auf die Berechnungsgenauigkeit ausgewählter Warmmassivumformprozesse (Reckwalzen, Gesenkschmieden) auswirkt.