P 611 - Electron beam welding of surface-finished, high-strength thin sheets to atmosphere

P612 - Development and design of a new modular antenna support structure For the new mobile phone networks, there is a very high demand for antenna support structures that can be erected quickly and economically. The aim of this research project was to develop a simple, type-tested system that can be used in series. The required features were a modular, unobtrusive design with shielding, which ensures that the radio radiation is well below the legally required limits. In its decision of 5 March 2003, the Münster Higher Administrative Court (OVG) already demanded higher requirements with regard to both the optical effects of the transmitters and radiation emissions. Against this background, the research results presented here gain additional topicality. A support structure system was developed that allows different construction heights with an otherwise identical design. It consists of standardised modules with identical connecting flanges for all system lengths. By installing one or two shielding modules, even stricter limits for radio radiation can be safely complied with. The antenna support structure can be brought to the construction site as a complete, finished delivery unit and attached directly to a pre-assembled substructure using a crane. The same support tube cross-section was selected for all planned construction heights when determining the load and dimensioning the antenna support structure. The verification against vortex-excited transverse vibrations is important. These can reach high numbers of load cycles transverse to the wind direction. The supporting structure must therefore be designed to be fatigue-resistant. The structural analysis was designed for wind load assumptions in accordance with E DIN 1055-4 and DIN 4131 or 4133 and already for the new E DIN 1055-4, whereby the decisive aerodynamic coefficients were determined in extensive wind tunnel tests. The system has been type-tested by the North Rhine-Westphalia Structural Testing Office. The tests have shown that the dynamic behaviour as a result of wind impact is largely determined by the substructure in addition to the antenna design. In order for the above-mentioned statics to be valid, a minimum rigidity of the existing substructure must therefore be ensured. This must also be verified by the site planner. The antenna system can be installed on almost all roof locations and any roof shape. The respective internal forces required on site for the substructure can be read from a simple table. This speeds up the production and assembly of the system considerably thanks to the possibility of prefabricating the modules and also makes it more cost-effective. STUDIENGESELLSCHAFT STAHLANWENDUNG e. V. Publication: 2003 Authors: Dr.-Ing. M. Hortmanns, Dipl.-Ing. S. Stark

P 613 - Laser-MSG hybrid welding of innovative steel materials The aim of the research project was to provide the crane, vehicle and plant construction industry with a tool that can be used to weld high-strength fine-grain structural steels economically and safely using the laser-MSG hybrid process. To this end, suitable welding consumables and the corresponding temperature cycles were qualified together with the process for these steels. The process is particularly interesting for the steel S1300QL, which has only recently been trialled and represents the current upper limit of water-quenched and tempered fine-grain structural steels suitable for welding in terms of strength. Its suitability for hybrid welding was demonstrated for the first time in this project. With the only representative of thermomechanically rolled steels analysed, the steel S700MC (1.8974), joints were produced together with a MoNi-type welding wire that met the requirements in terms of strength and toughness. In the tensile test, fracture occurred in the weld metal as the hardness of the weld metal was lower than that of the base material. The water-quenched and tempered fine-grained structural steels S690QL (1.8928) and S960QL (1.8933) proved to be comparable in terms of the behaviour of the welded joint. As the hardness of the heat-affected zone and weld metal was significantly higher than that of the base material, the fracture occurred in the unaffected sheet. A "hardness sag" in the heat-affected zone could not be observed either with extremely short or longer cooling times. The values for the impact energy required in the delivery conditions were also met at low temperatures down to -40°C. It was demonstrated that laser MAG hybrid welding is suitable for welding high-strength fine-grain structural steels in the sheet thickness range between 5 and 7 mm for vehicle and crane construction with nominal yield strengths of 690 MPa up to 1300 MPa. The solid and metal powder wires developed for MAG welding can be processed with the laser hybrid welding process without any problems. Authors: H. Haferkamp, O. Meier, B. Boese, R. Mittelstädt, G. Kuscher Publication: 2007

P 614 - Semi-hot precision forging of a connecting rod with open web The research objective of this project was to investigate the precision forging of a connecting rod double piece as a residue-minimised component production and weight reduction in the field of warm forging. Two different materials were selected, C70S6 as a typical crackable material for connecting rod production and an AFP steel 38MnVS6. As a result, material and component analyses were to be carried out. The material properties were determined in the laboratory. The connecting rods were forged using a complex tool specially developed for precision forging with integrated hydraulic volume compensation. The tool can be used in the nominal temperature range of 950 °C to 1200 °C. An essential part of the project was the development of an optimum intermediate mould for precision forging. This development was carried out on two tracks in direct combination with practical testing and simulation. Once the exact geometry of the intermediate mould had been determined, it was produced by conventional die forging (rough/finish forging and trimming) with very tight tolerances. For forging in the area of warm forging, the die inserts and the active parts in the complex mould must be heated to an operating temperature above 200 °C and kept at this temperature for the duration of forging. The forging tests for precision forging were carried out at three different forming temperatures: 950 °C, 1050 °C and 1200 °C. An electric chamber furnace was used to heat the intermediate moulds for precision forging. During the "precision forging" forging process, the forces occurring on the active parts in the die were measured. These forces were used to precisely dimension the hydraulic volume compensation. A chemical analysis of the base material was carried out as part of the evaluation of the material-related investigations and the material-specific characteristic values of yield strength, tensile strength, elongation at break and constriction at break were determined. These characteristic values formed the basis for the fatigue strength tests on the service life of the precision-forged connecting rod doubles. The material analyses also included a structural analysis of the material in the web area of the connecting rod. The evaluation for the C70S6 was based on the practice-relevant values from MAHLE Brockhaus GmbH. The individual connecting rods are tested by a certified test laboratory on the basis of the VW standard "VW 500 30". The evaluation for the material 38MnVS6 was not carried out in comparison with C70S6, as both materials are not comparable due to their The evaluation for the material 38MnVS6 was not carried out comparatively with C70S6, as both materials have very different characteristics due to their composition of their microstructure and the resulting properties. Authors: R. Neugebauer, H. Hartwig, A. Wagner, R. Salomon Publication: 2008

P 615 - Innovative steel construction solutions for primary and secondary structures of multi-purpose buildings in the public sector Particularly in the area of public construction projects, reservations about economical and innovative realisations in the steel sector are noticeable. This is due in particular to unfounded prejudices and a lack of knowledge among users about the current state of the art. Frequently discussed topics originate from the areas of building physics and corrosion protection. However, where steel structures are used, the results of the latest research and development work in the construction industry are rarely or only very inadequately taken into account during realisation. In order to facilitate the decision in favour of the use of steel as early as the preliminary planning stage, this documentation uses a potential specific construction task as an example to illustrate the structural and economic advantages associated with the extensive use of steel for such buildings. The aim here is to demonstrate a sensible use of steel in a concrete realisation. Authors: K. Luig, V. Lenze Publication: 2003