Residual stresses in brazed hybrid steel joints

In many cases, e. g. in vehicle or plant construction, heating or energy technology, manufacturing processes based on brazing technique are applied. In this context many components made of high-alloy steels are produced which are brazed in vacuum or protective gas furnaces at temperatures above 900°C. Often joining of ferritic and austenitic steels is desiderable or even necessary. Due to different thermo-mechanical properties of the materials and the solder used, high amounts of residual stresses can occur, which considerably reduce strength in comparison with joints made of similar steel types. In this project residual stress states are analyzed and assessed in detail depending on material combinations, geometries of the joints and the process parameters applied furnace brazing operations. From the results, strategies will be derived and validated to achieve minimum residual stress amounts in brazed dissimilar joints. The main objective of the project is to develop appropriate constructions and brazing processes adapted to the steel combinations used for dissimilar joints to achieve minimum residual stress amounts. As a result, manufacturers should be able to produce reliable high-strength hybrid components made of different stainless steel qualities by appropriate brazing processes applying reliable and process routes.One can expect that especially ferritic stainless steel qualities, which up to now are hardly used in practice will gain increasing importance as construction materials.