The joining of components with as few weld layers as possible is an important aspect of weld seam design due to the resulting reduced manufacturing effort and reduced influence of thermal cycles on the base material as well as reduced distortion. For materials with good thermal conductivity, this is not easily possible. The energy density of the arc has been found to be the core parameter for determining the penetration. In the present work, it is shown how the use of a hyperbaric process environment (2 to 16 bar) allows an increase of the energy density of the arc and thus an increase of the penetration depth for selected aluminium and copper alloys. Furthermore, the effects of this novel approach on weld metal metallurgy are presented. It is shown that the penetration depth can be doubled by increasing the ambient pressure. Furthermore, a statistical model for the prediction of the penetration depth depending on the welding parameters will be presented.
Due to the increased demands for reducing CO2 emissions, improving fuel efficiency of modern vehicles has been continuously monitored. The body of a typical compact car design has a weight share of approx. 40%. In addition to increasing torsional stiffness and crash safety of the body, the aim is also to reduce the overall weight at the same time. In order to achieve these individual requirements, the use of three-sheet steel stack-ups with adhesive applications for car body construction is one of the current strategies used in automobile manufacturing. Adhesive applications lead to a change in process behavior of resistance spot welding. The effective weldability lobe is reduced and an adjusted preheat current is necessary to reconstitute the weldability of a component. Depending on squeeze time and electrode force the adhesive will be displaced. For an asymmetric sheet stack-up, the electrical resistance for every faying surface is highly differentiated. During welding, a specific characteristic of the electrical resistance is created for each individual material combination. These characteristics can be analyzed by using an online measurement device. In this manuscript, different sheet stack-ups are examined with regard to their weldability lobes and their process behavior. The individual three-sheet steel stack-ups used are made of low carbon steel (DX51), HSLA-steel (HX340) and UHS-steel (22MnB5). The corresponding characteristics of electrical resistance will be recorded by using an online measurement device. In addition, the process of adhesive displacement during the squeeze time and the initial welding current are discussed on the basis of the electrical energy generated in the component to be welded. The obtained results contribute to a direct verification of the welding process and an automatic detection of possible imperfect welds.
Hyperbaric welding is used for different steels in many underwater applications as a repair welding process. A difference between wet and dry welding processes can be made. Due to the increased ambient pressure, these processes have special features inherent in the process that influence the cooling and penetration behaviour. The positive use of these effects outside underwater applications is currently rarely addressed in science and application. The presented work establishes these advantages on the basis of a higher strength structural steel and characterizes the effects on the microstructure of a joined S700MC steel and on the mechanical properties of the joint. It will be shown that a hyperbaric environment can be used to orient the weld more towards the depth of the sheet. Furthermore, it will be shown that this change leads to modified cooling, which in itself influences the mechanical properties of the weld seam.
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