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Power stations and plants for the generation, supply and conversion of energy require qualified structural steel materials. The further development not only of these materials but also of the quality of their welded …
Power stations and plants for the generation, supply and conversion of energy require qualified structural steel materials. The further development not only of these materials but also of the quality of their welded joints is of particular importance for immediate technical progress. Improved steel grades or new and optimised welding processes as well as increased requirements regarding the wall thicknesses to be welded require precise knowledge of the failure mechanisms due to creep rupture stress in order to ensure unrestricted operational safety over long periods of time. The investigations carried out as part of the present research project concerned fractured creep rupture specimens from welded joints of CrMo and CrMo alloyed creep-resistant steels, mainly subjected to long-term stress.
Metallurgographic and electron microscopic investigations were carried out to characterise the damage state of creep-tested welded joints. They were supplemented by analyses of the precipitation state and the chemical composition of the diffusion zones of the welded joints. In this way, the risk area for failure due to creep rupture was localised on similar and dissimilar welded joints. As a result of the work carried out as part of this research project, a large number of metallurgic and microscopic investigations have been documented. The microstructures of the base materials and weld metal as well as the fracture process and damage state in the respective areas, including the heat-affected zone, are illustrated. Furthermore, hardness values and hardness curves are shown over the failure point. The stress, service life, chemical analysis, heat treatment and other factors can be assigned to the analysed samples. For users in the field, especially in power plant and plant engineering, this documentation provides the basic material for comparative analyses to assess cases of damage and their future avoidance. STUDIENGESELLSCHAFT STAHLANWENDUNG e.V.
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P 100 - Development of characteristic values for the production of cold rolled profiles from the point of view of economical production of dimensionally accurate profiles Cold profiling using the roll forming process is a forming process that has been used industrially for over half a century. It allows the production of cold-formed profiles with consistent and high dimensional accuracy, some with sharp-edged bends, many curved sections, complicated double folds, with - if desired - targeted work hardening of the starting material and finally the combination of profile shaping with further processing steps such as punching, beading and bending. Although the diverse requirements and the general technical development of mechanical engineering have led to a wide variety of roll forming systems over the course of time, the technology of roll forming is still largely based on practical experience. This applies both to the dimensioning of production facilities and to the design of forming tools. This unsatisfactory situation can probably be explained essentially by the fact that the entire process - in addition to the rather difficult geometric relationships of forming - is governed by numerous working conditions which influence each other. For this reason, the Technical Committee of the German Cold Forming Association has been working closely with a well-known plant manufacturer for several years on the development and dimensioning of a machine and drive concept for research purposes. A machine and control technology solution was developed and realised which for the first time makes it possible to empirically investigate the interactions between the parameters of the production process and the properties of the product in a reproducible manner. This research work was carried out on behalf of the Studiengesellschaft für Anwendungstechnik von Eisen und Stahl e.V. by Prof. Dr.-Ing. D. Schmoeckel, Institute for Forming Technology at Darmstadt Technical University. In addition to confirming some of the results of earlier investigations, new findings of practical relevance were obtained. This applies in particular to the experiments on slip reduction, which resulted in a drastic saving in the energy used, and on the relationship between the quality of the finished product and the selected forming strategy. These results represent a step towards a better understanding of the complex manufacturing process, but at the same time demonstrate the need for further intensive efforts to conduct in-depth research into roll forming technology. The research project was funded by the Federal Ministry of Research and Technology (BMFT) and was supervised by Kernforschungsanlage Jülich GmbH (KFA) as the project sponsor for the raw materials research programme. STUDIENGESELLSCHAFT FÜR ANWENDUNGSTECHNIK VON EISEN UND STAHL e.V. Publication: 1986 Authors: Prof. Dr.-Ing. D. Schmoeckel, Dipl.-Wirtsch.-Ing. U. Eichler
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