So-called heat-reduced arc welding processes dominate the joining technology in the automotive sector today. They offer the advantage to reduce deformation of thin walled plates. Also, metallurgy and material properties are affected decisively. Based on the present state of the art in power-controlled gas metal arc welding (GMAW) this paper present the developing of a welding process, that allows a quasi-decoupling of the energy input between filler metal and base material. This is being realized by a polarity reversal. In conjunction with pulse control and the specific adjustment of the pulse a significant improvement of the arc stability can be achieved. This applies particularly to non-ferrous materials tending to concentrate oxygen on its surface like aluminum, magnesium and their combinations, respectively. Especially it is possible to control the deposition rate, welding formation and bonding conditions between base material and filler metal. Furthermore spatter can be reduced and manufacturing time can be saved. The present investigation includes the comparison between various modern GMAW processes, such as ColdMIG®, CMT® and short arc, with the pulsed GMAW using alternating current (AC) for welding aluminum. Thereby, mainly the penetration depending on the heat input is taken into account. It can be noted that the AC pulsed GMAW process produces weld seams of the same quality as well-known processes in matters of height and width of the joint. The generated welds have low notches at the edge of the seam and a uniform weld scaling. Visual imperfections on the surface have not been detected.
To increase productivity when joining galvanised sheet metal, metal inert gas (MIG) and tungsten inert gas (TIG) arc brazing are combined in a hybrid process. This coupling of two arc processes increases brazing speed and reduces weld reinforcement and the tendency to spatter. Because the arcs are 6 mm apart, they influence each other. Therefore, the blowing action is a major challenge in hybrid arc brazing. A current modulation and the optimal relative position of the arcs to each other are compulsory conditions. Selected brazing parameters are tested in order to verify the hybrid arc brazing. Overlap joints are brazed on galvanised sheets. The mechanical-technological properties of the brazed joints are determined. It has been shown that hybrid brazing can achieve significantly higher brazing speed with the same or better brazing quality compared to standard arc brazing. For the realisation of the hybrid arc brazing process, software-controlled welding machines are used, which will replace conventional power sources in the future.
The modulated direct current of pulsed arcs can be used to influence heat input and drop size in a process reliable and reproducible manner. Modern power sources possess arc controls due to the development in the area of computer engineering, which enable thermal spraying with pulsed current due to their dynamics and efficiency. In order to use this technology in the area of arc spraying (AS), investigations are required on the process behavior depending on the electrical parameters. A plant prototype was available for this investigation. The experiments were conducted using a wire-shaped spraying consumable of an iron-base alloy with a diameter of 1.6 mm. Parameters relevant for the process such as background current Iground, pulsed current Ipulse, pulse duration tpulse etc. were varied and measured using appropriate measuring technology. The objective was to develop an understanding of the process and to determine suitable parameters. Using high speed imaging, the arc was monitored and the melting of the consumables was analyzed. The influence of the pulsed current on the coating was determined by evaluating the porosity and the oxidic phase fractions by using a light microscope. Furthermore, the particle sizes were determined. Layers generated with conventional processes served as a comparison. The investigations on pulsed AS were able to prove stable process characteristics and improved coating results compared to conventional AS.
The atomizing gas dynamics and the applied process energy have a significant influence on the produced particles. The melting process of the two wires can be influenced by current modulation. As for arc welding processes, more and more electronic and software-controlled machines are being used for arc spraying and will have replaced conventional power sources in the future. Due to the highly dynamic, fast regulating computing technology in the latest energy source, technology arcs can be operated with different current forms and types. The modern machines allow process-stable, reproducible variation of the particles and heat input into the substrate. Constant and pulsed current can be used as current forms. Usable current types are direct current (DC) and alternating current (AC). The electrical parameters must be analyzed to evaluate the process behavior. The consumable used is a wire-shaped iron-based alloy with a diameter of 1.6 mm. Relevant process parameters such as basic current Iground, pulse current Ipulse, pulse duration tpulse, impulse frequency fpulse, and alternating current frequency, fAC, are varied and recorded using appropriate measurement technology. The aim is to change the process performance and thereby the particle formation in a broad band. High-speed images are used to observe the arc and the deposition process. In addition, particle sizes are determined.
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