P 614 - Semi-hot precision forging of a connecting rod with open web

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 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

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 611 - Electron beam welding of surface-finished, high-strength thin sheets to atmosphere With regard to the weight reduction of car bodies, various lightweight construction concepts are gaining importance. For lightweight construction, this requires the use of new, higher-strength sheet steel materials. These require joining processes that are metallurgically suitable as well as highly reliable and economical. Electron beam welding in an atmosphere (non-vacuum electron beam welding, NVEBW) is a suitable beam welding process for sheet metal processing due to the high welding speeds that can be achieved and the good gap-bridging capability. As part of the research project, the suitability of this joining process for welding surface-coated high-strength and ultra-high-strength sheet steel was investigated. The galvanised and hot-dip aluminised steel sheet materials investigated cover a wide range of materials currently used in car body construction in terms of their carbon equivalent as well as their strength and elongation properties. The NVEBW of galvanised steel sheet materials at welding speeds of at least 8 m/min demonstrated large process tolerances with regard to gap bridging, sheet thickness jumps, edge offset and positioning inaccuracies. Welding parameters were identified for all seam geometries analysed that ensure sufficient zinc degassing and therefore flawless seams. While no special measures for zinc degassing are required for I-seams, tailored blanks and end fillet welds, a joint gap is absolutely necessary for the NVEBW of flanged seams and lap seams. The NVEBW of hot-dip aluminised sheet steel is also possible in all seam geometries examined and can be carried out without a welding gap. The increased alloying element content of the high-strength and ultra-high-strength steels and the microstructure resulting from the welding process lead to weld hardening. Weld seam hardening reduces the formability of all investigated sheet steel grades, but in most cases does not reduce the strength of the welded joints. In addition to pore formation, which can result from the evaporation of the zinc coating, edge notches, bonding defects and humping were identified as possible weld defects and measures to prevent them were presented. Application-oriented investigations of the behaviour under crash load and corrosion tests were also carried out on selected weld seams. The investigations show the potential of the NVEBW of coated steel sheet for car body construction. This was also demonstrated with an NVEB-welded component example and with component-like welded Z-profiles. Authors: F. W. Bach, G. Kremer, K. Lau Publication: 2006