Load-appropriate arc brazed joint of high-strength sheet steels under metallurgical and geometrical aspects (joint proposal)

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There is a great divergence between the principle application possibilities and the real applications of arc brazed joints. This is ascribed to the fact that, currently, the knowledge about the failure of arc-brazed sheet steel joints under static and cyclic load is not advanced enough for carrying out the load-appropriate design of the joined components.This fundamental comprehension of the connections between the geometrical design of the brazed seam on lap joint as well as its local metallurgical composition and the joint properties shall be worked out within the scope of the research project. It has, so far, not been possible to give a precise specification of the exact local processes and failure mechanisms which lead to the failure of the brazed seam. Therefore, the objective of the planned research project is the detailed investigation of the main factors which exert influence on the static and cyclic joint strength, such as braze material strength, adhesion, diffusion, wetting, geometry/force flow and the changes of the base material properties; another reason is to make references to the basic failure mechanisms. Thus, a more reliable statement about the failure reasons is possible and the way for the load-appropriate application of arc brazed joints is paved. This objective shall be achieved by means of a numerical simulation model and also by metallurgical model tests. The arc brazed joint is, under consideration of the above-mentioned influential factors, separated into strength-relevant geometrical and metallurgical individual aspects (e.g. gap filling, etc.) which can be examined separately. Subsequently, the individual results are consolidated again in order to determine thus the effects of the individual factors on the strength (static, cyclic) of the entire brazed joint. During consolidation, also interactions of the examined influential factors on the joint properties are taken into consideration.The objective of the research project is subdivided into two sub-ordinate objectives. Objective 1 stands for the achievement of a brazed joint which is characterised by a high static strength on base material level with, at the same time, good cyclic strength. Objective 2 stands for the production of a joint which is characterised by a very good cyclic strength, clearly higher than the hitherto possible 25% of the load of the base material with, at the same time, still sufficiently good static strength. Here, the integrative target requirement to both objectives is the high reliability and reproducibility of the results with low scattering. It is, in this manner, possible to achieve a more reliable and stronger joint with regard to the predominant type of load.