No description available.

Объектом исследования является технологический процесс штамповки детали болт по ГОСТ 7798-70 на предприятии ООО «Арморика». Выполнено исследование влияния температуры нагрева заготовок на технологические факторы штамповки поковок фланца на пресс КГШП, а именно усилие штамповки, анализ напряженно – деформированного состояния штамповки поковки фланца, оценка проработки структуры металла. Выполнена разработка технологического процесса штамповки болта, расчет усилия пресса, компьютерное моделирование процесса горячей объемной штамповки болта с заданной в технологическом процессе температурой, технологичного, анализ влияния нагрева заготовок на технологические факторы, литературный обзор. / The object of the study is the technological process of stamping the bolt part according to GOST 7798-70 at the Armorica LLC enterprise. The study of the effect of the heating temperature of the workpieces on the technological factors of stamping flange forgings on the KGSHP press, namely the punching force, analysis of the stress–strain state of stamping flange forgings, evaluation of the study of the metal structure. The development of the technological process of bolt stamping, calculation of the press force, computer modeling of the process of hot volumetric stamping of a bolt with a temperature set in the technological process, technological, analysis of the effect of heating workpieces on technological factors, a literary review.

Made available in DSpace on 2016-12-08T15:56:17Z (GMT). No. of bitstreams: 1 Andre Olah Neto.pdf: 11111826 bytes, checksum: 36a7c3a3c11e61f18d8a74f06d619cc0 (MD5) Previous issue date: 2015-04-10 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / In recent decades the automobile industry has made a great effort to deal with ecological and security challenges. To do so, it was necessary to develop vehicles which are lighter, more economical and have a greater intrusion resistance when subjected to a crash. This was made possible, among other actions, by the development of advanced high strength steels, associated with the use of new manufacturing processes. Inside this approach the use of the hot stamping and the emergence of 22MnB5 boron-alloyed steel, with high hardenability, stand up. The hot stamping operation has gained great importance for enabling the manufacture of strategic components of high complexity and high mechanical resistance, associated with reasonable toughness. In order to ensure its technological evolution this process has been widely studied by numerous authors, so that the phenomenon was better understood, allowing better control as well as the quality and reliability requirements involved in the stamped components. This focus led to the development of this work, whose main objective was to study the hot stamping process, evaluating the mechanical and thermal effects. To achieve this aim an experimental apparatus was developed which allowed simulating the main thermomechanical aspects involved, such as the temperature, the conformation and the cooling. The purpose was to reproduce the conditions of the process and evaluate the influence of certain variables of the cooling speed on microstructure and on the final properties of the material, in order to study and understand some phenomena involved. This apparatus was composed of a heating furnace, an aluminum cooler, water cooled, operated at low pressure of closing and a control system, assembled on a mechanical testing 12 machine to promote the desired deformation. The experimental work was carried out in three stages. Initially, the hot plastic behavior of 22MnB5 steel was studied, evaluating the effect of temperature and strain rate on the mechanical characteristics, to determine the conditions for necking formation. In the second stage, the kinetics of phase transformation was studied, seeking to understand the effect of heating and cooling conditions on the cooling rate and on the final properties after quenching. In the last step, the plastic behavior on the kinetics of phase transformation, i.e., the effect of necking on cooling, was studied. The main objective was to show that the necking, depending on its intensity and geometry, generates the formation of a clearance between the cooler and the surface material, reducing the cooling rate to the point of affecting the mechanical properties in this region. Despite being localized, it can jeopardize the stamped component performance forming a fragile region of low mechanical strength and low toughness. It was concluded that hot plastic deformation undergone during the hot-stamping has a significant influence on the phase transformation, being necessary the proper control of process conditions so that the necking is also controlled, thus ensuring the structural homogeneity of the component and its performance. / Nas últimas décadas a indústria automobilística tem realizado um grande esforço em atender os desafios ecológicos e de segurança e para isto foi necessário desenvolver veículos mais leves, econômicos e com maior resistência à intrusão quando submetidos a um acidente. Isto foi alcançado, entre outras ações, através do desenvolvimento de aços avançados de elevada resistência mecânica, associado à utilização de novos processos de fabricação. Dentro deste enfoque se destaca dois aspectos, a utilização do processo de estampagem a quente e o surgimento do aço 22MnB5 de elevada temperabilidade ligado ao boro. A operação de estampagem a quente tem ganhado uma forte importância por possibilitar a fabricação de componentes estratégicos de elevada complexidade e elevada resistência mecânica, associada à razoável resistência ao impacto. No sentido de garantir sua evolução tecnológica este processo tem sido amplamente estudado por inúmeros autores, para que os fenômenos envolvidos pudessem ser mais bem entendidos, permitindo um melhor controle bem como o atendimento dos requisitos de qualidade e a confiabilidade envolvida nos componentes estampados. Com este enfoque desenvolveu-se este trabalho, cujo principal objetivo foi estudar o processo de estampagem a quente, avaliando os efeitos mecânicos e térmicos. Para este fim foi desenvolvido um aparato experimental, que permitiu simular os principais aspectos termomecânicas envolvidos, como a temperatura, a conformação e o resfriamento. O propósito foi o de reproduzir as condições do processo e avaliar a influência de determinadas variáveis sobre a velocidade de resfriamento, sobre a microestrutura e sobre as propriedades finais do material, no sentido de estudar e entender 10 alguns fenômenos envolvidos. Este aparato foi dotado de um forno de aquecimento, de um resfriador de alumínio refrigerado a água, operado a baixa pressão de fechamento e de um sistema de controle, montados sobre uma máquina de ensaios mecânicos para promover a deformação desejada. O trabalho experimental foi realizado em três etapas. Inicialmente foi estudado o comportamento plástico a quente do aço 22MnB5, avaliando-se o efeito da temperatura e da velocidade de deformação sobre as características mecânicas, determinando-se as condições para formação da estricção. Na segunda etapa foi estudada a cinética de transformação de fase, procurando-se entender o efeito das condições de aquecimento e do resfriamento sobre a velocidade de resfriamento e sobre as propriedades finais deste aço após têmpera. Na última etapa se relacionou o comportamento plástico sobre a cinética de transformação de fase, ou seja, o efeito da estricção sobre o resfriamento. O objetivo principal foi mostrar que a estricção, dependendo de sua intensidade e geometria, gera a formação de uma folga localizada entre a superfície do resfriador e do material, reduzindo a velocidade de resfriamento a ponto de afetar as propriedades mecânicas nesta região. Apesar de localizada esta folga pode comprometer o desempenho do componente estampado formando uma região de pouca resistência mecânica. Concluiu-se que a deformação plástica a quente sofrida durante a estampagem a quente apresenta uma significativa influência sobre a transformação de fase, sendo necessário o controle adequado das condições do processo para que a estricção também seja controlada, garantindo assim a homogeneidade estrutural do componente e o seu desempenho.

Aufgrund fluiddynamischer Effekte bei der Schnellerwärmung für die Warmumformung wird die Applikation der Technologie erschwert. Die vorliegende Arbeit thematisiert diesen Effekt und evaluiert die Triebkräfte sowohl numerisch als auch im Experiment. Aufbauend darauf werden Vermeidungsstrategien aufgezeigt und experimentell validiert um eine Verschiebung der Beschichtung zu verhindern. Es können insbesondere die temperatursensitive Marangonikraft als auch die magnethydrodynamische Wirkung der Lorentzkraft bei einer induktiven Erwärmung als Haupttriebkräfte identifiziert werden, die sich aufgrund identischer Kraftvektorrichtungen überlagern und verstärken. Es hat sich gezeigt, dass für den vorliegenden Fall einer 20-30 μm dünnen AlSi-Beschichtung die Marangonikraft gegenüber der Lorentzkraft um einen Faktor von mindestens 68 überwiegt. Ein vergleichbarer Effekt ist auch bei konduktiver Erwärmung zu beobachten. Hinsichtlich möglicher Vermeidungsstrategien einer globalen Beschichtungsverschiebung bietet die Applikation von lokalen Flussbarrieren mittels Laser, Induktion oder Walztexturierung, sowie das Vermeiden einer freien Flüssigkeitsoberfläche durch Aufbringen einer Zusatzbeschichtung, das größte Potential. In der zweiten Versionierung der Dissertationsschrift wurde auf S. IV im Vorwort, sowie auf S.72, Kapitel 4.2 eine ergänzende Nennung eines Instituts und Kooperationspartners hinzugefügt. / The application of fast heating technologies for hot forming is hindered by fluiddynamic effects and a resulting coating shift. Present thesis investigates this effect to evaluate the driving forces numerically as well as experimentally. Based on this evaluation, strategies are developed and investigated to avoid a global displacement of the AlSi-coating. In case of inductive fast heating the main driving force is represented by a superposition of Lorentzian forces as well as surface tension related Marangoni forces with a force vector pointing from hot to cold regions on the blank. The numerical evaluation shows that in case of 20-30 μm thin layers of AlSi the Marangoni force is at least 68 times higher than the Lorentz force and therefore represents the main driving force. A comparable effect is observable in case of conduction heating. Local flow barriers realized by Laser, inductive heating or texturing as well as the avoidance of a free liquid-surface due to application of additional coating layers show huge potential to prevent a global coating flow.

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.:Kurzzeichenverzeichnis 1 Einleitung 2 Stand der Wissenschaft und Technik 2.1 Warmumformung 2.1.1 Begriffe und Einordnung 2.1.2 Werkstofftechnische Grundlagen der Warmumformung 2.1.3 Platinenwerkstoffe und -beschichtungen 2.1.4 Erwärmungstechnologien in der Serienproduktion 2.2 Induktive Erwärmung 2.2.1 Begriffe und Einordnung 2.2.2 Physikalische und werkstofftechnische Einflüsse 2.2.3 Induktive Erwärmung von Bandmaterial 2.2.4 Induktive Erwärmung von Formplatinen für die Warmumformung 3 Aktuelle und zukünftige technologische Anforderungen an die Erwärmungstechnik in der Warmumformung 4 Problemstellung 5 Versuchsanlage zur induktiven Erwärmung von Formplatinen 6 Entwicklung eines mathematischen, experimentbasierten Modells der induktiven Erwärmung von Rechteckplatinen 6.1 Systembeschreibung 6.2 Methode 6.3 Validierung 6.4 Charakterisierung wesentlicher Einflussgrößen in Bezug auf erreichte Platinentemperaturen und Wirkungsgrade 7 Entwicklung eines FEM-Simulationsmodells der induktiven Erwärmung von Formplatinen 60 7.1 Geometrie 7.2 Elektromagnetisches Modul 7.3 Thermisches Modul 7.4 Vernetzung 7.5 Kopplung der Module 7.6 Validierung 8 Entwicklung eines Anlagenkonzepts zum Einsatz der induktiven Erwärmung für die Serienfertigung von Warmumformbauteilen 8.1 Methoden zur Definition von Betriebsparametern 8.2 Induktive Erwärmung von Formplatinen warmumgeformter Bauteile eines PKWs in Serienfertigung 8.3 Dünnblech-Warmumformung und Tailor-Rolled-Blanks 8.4 Entwicklung eines Prozessfensters auf Basis von im automobilen Fertigungsprozess relevanten Bauteileigenschaften 8.5 Konzeptionierung einer Erwärmungslinie für die Serienproduktion von warmumgeformten Karosseriebauteilen 9 Zusammenfassung und Ausblick 10 Literaturverzeichnis 11 Anlagen / 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 %.:Kurzzeichenverzeichnis 1 Einleitung 2 Stand der Wissenschaft und Technik 2.1 Warmumformung 2.1.1 Begriffe und Einordnung 2.1.2 Werkstofftechnische Grundlagen der Warmumformung 2.1.3 Platinenwerkstoffe und -beschichtungen 2.1.4 Erwärmungstechnologien in der Serienproduktion 2.2 Induktive Erwärmung 2.2.1 Begriffe und Einordnung 2.2.2 Physikalische und werkstofftechnische Einflüsse 2.2.3 Induktive Erwärmung von Bandmaterial 2.2.4 Induktive Erwärmung von Formplatinen für die Warmumformung 3 Aktuelle und zukünftige technologische Anforderungen an die Erwärmungstechnik in der Warmumformung 4 Problemstellung 5 Versuchsanlage zur induktiven Erwärmung von Formplatinen 6 Entwicklung eines mathematischen, experimentbasierten Modells der induktiven Erwärmung von Rechteckplatinen 6.1 Systembeschreibung 6.2 Methode 6.3 Validierung 6.4 Charakterisierung wesentlicher Einflussgrößen in Bezug auf erreichte Platinentemperaturen und Wirkungsgrade 7 Entwicklung eines FEM-Simulationsmodells der induktiven Erwärmung von Formplatinen 60 7.1 Geometrie 7.2 Elektromagnetisches Modul 7.3 Thermisches Modul 7.4 Vernetzung 7.5 Kopplung der Module 7.6 Validierung 8 Entwicklung eines Anlagenkonzepts zum Einsatz der induktiven Erwärmung für die Serienfertigung von Warmumformbauteilen 8.1 Methoden zur Definition von Betriebsparametern 8.2 Induktive Erwärmung von Formplatinen warmumgeformter Bauteile eines PKWs in Serienfertigung 8.3 Dünnblech-Warmumformung und Tailor-Rolled-Blanks 8.4 Entwicklung eines Prozessfensters auf Basis von im automobilen Fertigungsprozess relevanten Bauteileigenschaften 8.5 Konzeptionierung einer Erwärmungslinie für die Serienproduktion von warmumgeformten Karosseriebauteilen 9 Zusammenfassung und Ausblick 10 Literaturverzeichnis 11 Anlagen

Aufgrund fluiddynamischer Effekte bei der Schnellerwärmung für die Warmumformung wird die Applikation der Technologie erschwert. Die vorliegende Arbeit thematisiert diesen Effekt und evaluiert die Triebkräfte sowohl numerisch als auch im Experiment. Aufbauend darauf werden Vermeidungsstrategien aufgezeigt und experimentell validiert um eine Verschiebung der Beschichtung zu verhindern. Es können insbesondere die temperatursensitive Marangonikraft als auch die magnethydrodynamische Wirkung der Lorentzkraft bei einer induktiven Erwärmung als Haupttriebkräfte identifiziert werden, die sich aufgrund identischer Kraftvektorrichtungen überlagern und verstärken. Es hat sich gezeigt, dass für den vorliegenden Fall einer 20-30 μm dünnen AlSi-Beschichtung die Marangonikraft gegenüber der Lorentzkraft um einen Faktor von mindestens 68 überwiegt. Ein vergleichbarer Effekt ist auch bei konduktiver Erwärmung zu beobachten. Hinsichtlich möglicher Vermeidungsstrategien einer globalen Beschichtungsverschiebung bietet die Applikation von lokalen Flussbarrieren mittels Laser, Induktion oder Walztexturierung, sowie das Vermeiden einer freien Flüssigkeitsoberfläche durch Aufbringen einer Zusatzbeschichtung, das größte Potential. / The application of fast heating technologies for hot forming is hindered by fluiddynamic effects and a resulting coating shift. Present thesis investigates this effect to evaluate the driving forces numerically as well as experimentally. Based on this evaluation, strategies are developed and investigated to avoid a global displacement of the AlSi-coating. In case of inductive fast heating the main driving force is represented by a superposition of Lorentzian forces as well as surface tension related Marangoni forces with a force vector pointing from hot to cold regions on the blank. The numerical evaluation shows that in case of 20-30 μm thin layers of AlSi the Marangoni force is at least 68 times higher than the Lorentz force and therefore represents the main driving force. A comparable effect is observable in case of conduction heating. Local flow barriers realized by Laser, inductive heating or texturing as well as the avoidance of a free liquid-surface due to application of additional coating layers show huge potential to prevent a global coating flow.

Hot stamping of aluminium alloys allows for increased formability, decreased springback and the possibility of integrating age-hardening heat treatments into the process. However, it can be challenging due to the occurrence of material transfer of aluminium onto the tool, as aluminium is prone to adhesion even at low temperatures. Hence, lubrication is always necessary when forming aluminium, but lubricants can still fail, leading to direct interaction between tool and workpiece and thus material transfer. This phenomenon reduces the efficiency of the process, as interruptions are necessary for the refurbishment of the tools. Understanding of how material transfer takes place is important in order to find new or improved solutions, in terms of lubrication and surface engineering, to prevent adhesion. Nevertheless, current research in high temperature tribology of aluminium, mainly in terms of material transfer mechanisms, is very limited, as many of the works focus on lubricated conditions and do not look into the fundamental interactions between aluminium alloys and tool steels. In this context, the aim of this work is to investigate the mechanisms behind the occurrence of aluminium alloy transfer onto tool steel during sliding at high temperature and in dry conditions. A hot-strip drawing tribometer was used to perform tests at room temperature, 300°C, 400°C, and 500°C, directly after solubilizing the aluminium alloy at 520°C. Two different topographies for the tool steel were used: ground and polished. Material transfer characterization was performed mainly through scanning electron microscopy. It was found that grinding marks (ground tool steel) and carbides (polished tool steel) act as initiation sites for the transfer to occur. Temperature plays a role on the growth mechanisms of the transfer films during sliding, as thermal softening of the aluminium alloy is the dominant factor in determining the growth direction of the transfer layers. A growth towards the trailing edge (shearing and smearing of the transferred aluminium) or a growth towards the leading edge (build-up of transferred aluminium, leading to a thicker and more localized transfer material).