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To extend the possibilities of innovative lightweight construction, increasingly stronger steel sheet materials are being developed by steel manufacturers and increasingly used by the sheet metal processing industries. Typical representatives of this group are the so-called multiphase steels. Due to their higher strength compared with non-alloyed or low-alloyed steels, they allow the implementation of new design and safety-relevant aspects. Major applications are components made from cold-formed sheet metal, i.e. in automotive engineering for door impact beams or for strengthening the B-pillar as well as in the design of cranes or for wear-stressed components, for example in transport vehicles or agricultural equipment. This means that the sheet metal is subjected to a forming process before welding for virtually all applications, i.e. by bending or deep drawing. The changed material properties as a result of cold forming and stretching, such as increased springback behaviour and local changes in structural/stress conditions and hardness, may impair the suitability for welding or soldering. As part of a research project [1] at the Welding Training and Research Institute SLV Munich, investigations were therefore conducted into the laser welding and soldering of non-deformed and specifically deformed highstrength steel sheet and analysed with regard to changes in process and materials behaviour and bonding properties in terms of the fields of application. The effects on the suitability for laser welding are presented in the following. [ABSTRACT FROM AUTHOR]

Welding simulation offers the metal-processing industry a great potential for reducing the development times and costs. In this respect, a stress-free initial condition is generally assumed for simplification purposes. Since this assumption does not apply to the welding of deep-drawn sheet parts, it may be necessary to define the component condition from a forming simulation as the initial condition. Moreover, accuracy losses may occur during that transfer of results from the forming simulation to the welding simulation which is required to this end because, in both simulations, different models are used, for example, for the material behaviour. The accuracy losses are expressed, for instance, in the falsification of the geometry and of the stress condition. The objective of the presented investigations was to answer the questions: not only "On what influences do these accuracy losses depend?" but also "When is it necessary to take account of forming results in a welding simulation as the initial condition?" [ABSTRACT FROM AUTHOR]

In series and mass fabrication, resistance projection welding is a very economically viable joining process because of its short fabrication times. One decisive advantage of the process technology lies in the fact that several joints can be manufactured in one operation [1...5]. However, the resistance projection welding on the advanced high-strength to ultrahigh-strength sheets which have been introduced into fabrication in the meantime [6] is leading to great difficulties at the moment, amongst other reasons, because the projection geometry is not optimum. The strength of the joints is frequently lower than in the case of conventional soft deep-drawing steels and also exhibits a wide scatter. Moreover, fractures in the joining plane (shear fracture) occur very frequently. In the research project entitled "Optimisation of the geometry of embossed projections for the resistance projection welding on advanced high-strength to ultrahigh-strength steel materials" which is being promoted by AiF, investigations into the optimised designing of the projection geometries were conducted at SLV München and werecompared with the projections according to DIN EN 28167. Results with the HCT690TD and HCT780TD TRIP steels, with the HCT780CD complex-phase steel as well as with the DX54D+Z100 soft deep-drawing steel (all sheet thicknesses: 1.5 mm) are presented within the framework of this publication. The welding was carried out with identical materials and in various mixed combinations. The welds were executed on a medium-frequency projection welding machine from Dalex, model: PMS 32-5 MF. [ABSTRACT FROM AUTHOR]

Rotational friction welding is the most widespread friction welding process for metals. The joints exhibit outstanding properties - not only when materials with the same or similar compositions are joined but also in the case of materials with restricted fabrication weldability (cast materials or materials manufactured by means of powder metallurgy) and of dissimilar material joints, e.g. steel/titanium and steel/aluminium. However, the rotating relative movement causes the weldable geometries to be restricted to quasi-rotationally symmetrical cross-sections. Orbital friction welding in particular offers good process engineering prerequisites for joining also non rotationally symmetrically cross sections. [ABSTRACT FROM AUTHOR]