P 1056 - Intelligent lightweight construction through multi-component processes

P 1055 - Development of ultra-high-strength steels for alternative heat treatments and for cold forging of automotive powertrain components The increasing demands in the passenger car sector for safety, comfort and driving performance have led to a continuous increase in vehicle weight in recent years. In order to achieve further development in the area of driving dynamics in the future while at the same time reducing CO2 emissions and fuel consumption, this trend must be countered by new lightweight construction measures. Based on the current state of the art, approaches are being pursued in the field of material and structural lightweight construction as well as lightweight production and concept construction. As part of this research project, new steels and/or an adapted heat treatment for components used in the powertrain were developed. The focus was on lightweight material construction. According to a study by the Institute for Automotive Engineering at RWTH Aachen University (ika), approx. 1/3 of lightweight construction ideas for the powertrain are based on lightweight material construction. This study also identified the problem that, in many cases, measures in the field of lightweight material construction are usually directly linked to other measures in the field of lightweight design or lightweight manufacturing. The very high costs associated with this have so far led to major obstacles to the implementation of these lightweight material construction approaches. In this research project, this problem was addressed in co-operation with other sub-projects. An initial focus here was on the development and optimisation of steels with a higher load-bearing capacity for lightweight applications in the drivetrain. To this end, the chemical composition and heat treatment of case-hardening and heat-treatable steels already used on an industrial scale were modified in such a way that the potential of their property profile is utilised to a far greater extent than before. Furthermore, with a focus on large-scale realisation, new material concepts were specifically adapted to the promising heat treatment process of carbonitriding by means of microalloying, which lead to a higher component load-bearing capacity and thus have an increased lightweight construction potential. The lightweight construction potential was assessed using the gear component in extensive experimental load-bearing capacity tests. The second focus of the research project was to increase the lightweight construction potential of drivetrain components in conjunction with lightweight manufacturing. Of particular interest here is the cold forging of steels with a high forming capacity, which are more cost-effective than lighter aluminium alloys and have the required high basic strength. In order to ensure a reduction in production costs, subsequent heat treatment should be dispensed with. Newly developed but not yet commercially available materials with higher formability for cold forging were therefore optimised in terms of their property profile and manufacturing process. Publication: February 2020 Participating companies: ArcelorMittal Hochfeld GmbH, Bharat Forge CDP GmbH, Bodycote Wärmebehandlung GmbH, BorTec GmbH, Daimler AG, Deutsche Edelstahlwerke GmbH, EZM Edelstahlzieherei Mark GmbH, Felss Systems GmbH, fischerwerke GmbH & Co. KG, Georgsmarienhütte GmbH, GKN Driveline Trier GmbH, HAMMERWERK FRIDINGEN GmbH, Hanomag Lohnhärterei GmbH, Härterei Tandler GmbH & Co. KG, Heess GmbH & Co. & Co. KG, Hirschvogel Umformtechnik GmbH, Johann Hay GmbH & Co .KG, LechStahlwerke GmbH, Mannesmann Precision Tubes GmbH, Opel Automobile GmbH, Räuchle GmbH + Co. KG, RENK Aktiengesellschaft, Robert Bosch GmbH, Rohde Schutzgasöfen GmbH, Rohrwerk Maxhütte GmbH, Saarstahl AG, Salzgitter Mannesmann Forschung GmbH, Schaeffler Technologies AG & Co. KG, Sidenor SA, SKF GmbH, Swiss Steel AG, Vallourec Deutschland GmbH, Vestas Nacelles Deutschland GmbH, voestalpine BÖHLER Edelstahl, Volkswagen AG, ZF Friedrichshafen AG Research institutes: Institute of Ferrous Metallurgy, RWTH Aachen University Leibniz Institute for Materials-Oriented Technologies - IWT, Bremen FZG - Research Centre for Gears and Transmission Engineering, TU Munich

P 1057 - Lightweight construction through targeted adjustment of local component properties with optimised forming and machining processes The project aims to close the existing gap between the definition of requirements for local component properties, in particular with regard to work hardening, residual stresses and stress-appropriate fibre flow, and the assurance of these properties through optimised forming and machining processes. The development of steel materials with process-appropriate properties (cold formability, yield stress, hardening, machinability) is also considered. A further aim of this sub-project was the development of an efficient efficient methodology for the virtual design of robust forming and machining processes to achieve optimum local component properties. Usually, only a homogenised increase in material strength as a result of cold forming is assumed with sufficient certainty and lightweight construction potential is exploited from this. Local strength properties of cold-formed workpieces as well as residual stresses and, in particular, the fibre orientation are often insufficiently taken into account in component and forming process design and subsequent machining processes. In this sub-project, lightweight construction potentials for cold-formed components were investigated through the targeted adjustment of local component properties with optimised forming and machining processes. To this end, a methodology was developed for the efficient CAE-based design of optimised and robust cold extrusion and downstream machining processes for the economical production of lightweight components. In the cold extrusion of steel components, an improved prediction of the mechanical material properties as a result of work hardening and residual stresses can be achieved. Due to the more precise property determination and adjustment, lighter components can be designed. Similar deficits exist in the development of steel materials. Following the process chain, the local component properties were first modelled during cold extrusion using FEM forming simulations and then during subsequent machining. The previous results were recorded in a structural-mechanical FEM simulation and the load direction-dependent component properties were determined. The findings of these three simulation packages were subsequently used for the integration into a CAE-based design of optimised and robust process chains. Two demonstrator components (gear hub and piston pin) were developed using this methodology to demonstrate the lightweight construction potential. A mould was constructed for the gear hub and a gear was manufactured based on TP2. Finally, the results obtained were used to carry out economic analyses with regard to machining as well as technological component tests to determine the lightweight construction potential and lightweight construction costs. Publication: February 2020 Participating companies: CARL BECHEM GmbH, Daimler AG, Deutsche Edelstahlwerke, DYNARDO GmbH, EZM Edelstahlzieherei Mark GmbH, Fastenrath Befestigungstechnik GmbH, Felss Systems GmbH, fischerwerke GmbH & Co. KG, Georgsmarienhütte GmbH, GKN Driveline Trier GmbH, Gühring KG, HAMMERWERK FRIDINGEN GmbH, Hermann Bilz GmbH, Mahle GmbH, Max Aicher Stiftung, Metal Improvement Company Inc. Surface Technologie, Opel Automobile GmbH, Räuchle GmbH + Co KG, Robert Bosch GmbH, Rohrwerk Maxhütte GmbH, Saarstahl AG, Schaeffler Technologies AG & Co KG, Seco Tools GmbH, SEISSENSCHMIDT GmbH, Sidenor SA, SMS Group GmbH, Swiss Steel AG, SynOpt GmbH, thyssenkrupp Presta AG, Vestas Nacelles Deutschland GmbH, Volkswagen AG

P 1054 - Joining high-strength steel grades in lightweight structures by means of self-piercing resistance element welding on conventional resistance spot welding systems The aim of the research project is to develop a new type of resistance element welding process (WES) for joining ultra-high-strength steels in combination with dissimilar materials. In contrast to the current state of the art, a single-stage process and thus the use of conventional resistance welding technology is planned for both the insertion and welding of the auxiliary joining parts. The realisation of the results obtained will make an important contribution to the further development of resistance element welding and the economic production of future steel-intensive lightweight structures in mixed construction. The kmU user group includes, in particular, system manufacturers of element and feeding technology, suppliers of connecting elements and suppliers of resistance welding technology and automation technology. The high probability of short-term integration of the process into existing production processes due to low investment costs opens up numerous new business and application areas for these SMEs. Overall, this creates a direct benefit for SMEs by offering flexible and innovative joining solutions, which helps their customers to manufacture mixed structures cost-efficiently. In the research project, process principles were developed that characterise the mechanical and technological properties of single-stage joined WES joints and the joining process. The development of punchable, cold-formable and simultaneously weldable auxiliary joining part geometries and the definition of process parameters for optimal joint formation are milestones in this regard. Another milestone is the derivation of application guidelines as well as design and production instructions based on a preceding parameter influence analysis to determine systematic influencing and disturbance variables on the joining process. The research results achieved contribute to the process expansion of resistance welding technology and demonstrate a possibility that enables the joining of steel-intensive sheet metal structures in combination with thin aluminium sheets and adhesives. The assemblies can be produced economically, in line with cycle times and with relatively low investment costs. The efficiency of resistance welding technology combined with the outstanding properties of ultra-high-strength and ultra-high-strength steels allows the production of weight-optimised and rigid passenger cells in mass production, as both the choice of material and the choice of joining technology are economically advantageous. The advancing development of ultra-high-strength high-performance steels (3rd generation steels) and the increasing trend towards mixed construction emphasise the need for cost-efficient joining solutions. Publication date: November 2020 Authors: Prof. Dr.-Ing. G. Meschut, M. Sc. H. Günter

P 1058 - Extending the technological limits of forging in different temperature ranges As an element of the lightweight solid construction research network, three demonstrator components were investigated in sub-project 4 "Extension of technological limits in solid forming in different temperature ranges", which were produced in different temperature ranges using fundamentally different solid forming processes. This sub-project is further divided into four work packages, which deal with different processes and demonstrator components. The content of the first work package consisted of investigating the manufacturability of a piston pin by stretch forming and the stiffness-related optimisation of a spiral-shaped inner contour with regard to its lightweight construction potential compared to a conventional cylindrical inner contour. In the second work package of the sub-project, the focus was on the production of a scaled gear shaft, also using a cold forging process, full forward extrusion. The aim here was to optimise the surface properties of hardness, roughness and residual stresses with regard to possible downsizing or the elimination of downstream heat treatment steps. With the aim of possibly substituting conventional hardening processes, extruded components were also deep rolled. The required parameter sets were determined on the basis of investigations on the starting materials. It was shown that already hardened components can be further strengthened by deep rolling. However, deep rolling of cold-formed components led to surface failure in the form of cracks in both the piston pin and the gear shafts. surface failure in the form of cracks and spalling. In the field of hot forging, multi-stage precision forging was successfully used to adjust local microstructural properties. A fine-grained microstructure with a typically good strength-to-toughness ratio was achieved on a gear rim through targeted thermomechanical treatment during individual part production. The results of the sub-project show impressively on the basis of the investigated demonstrator components that the processes of massive forming have numerous hidden potentials with regard to lightweight construction, which is increasingly taking centre stage. These processes in all temperature ranges allow the production of ever new component shapes with increasingly more efficient production sequences. In addition, it is generally possible to adjust local component properties in a targeted manner. To achieve this, the means of numerical process simulation must be utilised and further developed, and conventional forming processes must also be rethought. Although these points always entail new challenges, these can be overcome, as the results of the sub-project show, within the framework of joint research projects such as the research alliance for solid lightweight construction. FOSTA - Research Association for Steel Application e. V. February 2020 Participating companies: A. + E. Keller GmbH & Co. KG, BAUBLIES AG, CARL BECHEM GmbH, Cotarko GmbH, Daimler AG, ECOROLL AG, EZM Edelstahlzieherei Mark GmbH, Felss Systems GmbH, fischerwerke GmbH & Co. KG, Georgsmarienhütte GmbH, GKN Driveline Trier GmbH, HAMMERWERK FRIDINGEN GmbH, HOERBIGER Antriebstechnik GmbH, Houghton Deutschland GmbH, Johann Hay GmbH & Co .KG, LEIBER Group GmbH & Co. KG, Mahle GmbH, Mannesmann Precision Tubes GmbH, Max Aicher Stiftung, Muhr und Bender KG, Opel Automobile GmbH, Räuchle GmbH + Co. KG, Rohrwerk Maxhütte GmbH, Schaeffler Technologies AG & Co. KG, SEISSENSCHMIDT Components Processing GmbH + Co. KG, Sidenor SA, Simufact Engineering GmbH, SMS Group GmbH, Stelter Zahnradfabrik GmbH, Swiss Steel AG, SynOpt G Research institutes: Institute for Forming Technology and Forming Machines, Leibniz Universität Hannover Institute for Forming Technology and Lightweight Construction, Dortmund University of Technology Institute for Forming Technology, University of Stuttgart