Mechanised plasma-powder-arc-welding (PPAW) of aluminium sheets. - In: Sheet metal 2005, (2005), S. 225-232
The use of aluminium alloys rose in the last decade, as its specific mechanical properties allow a reduction of mass as for example in automotive. Moreover aluminium, due to its high corrosion resistance, is a very important material class in plant construction, where it is used for pipes or container till 250 C. Aluminium can be welded with different technologies. Nowadays TIG and MIG are mainly used for example in plant construction or in mechanical engineering. Laser beam welding is a widely established technology in automotive. The advantage is the high energy concentration, which leads to a high welding speed and a narrow heat affected zone. Plasma welding is applied when joining aluminium with alternating current, as an easy removal of the oxide layer in the surface of the weld pool is possible. Plasma-Powder-Arc-Welding (PPAW) method has been developed from Plasma Transferred Arc (PTA) weld surfacing and Plasma Arc Welding (PAW) methods by combining a small PAW torch (PAW is traditionally performed with wire as filler material) with powder filler material feeding as used in PTA-equipment. The coupling leads to a better mechanisation of the welding process as the consumable is fed directly through the welding torch. In this paper investigations on aluminium sheets (< 2 mm) AA5xxx and AA6xxx using different powder materials are reported. The influence of the processing parameters and conditions on the process reliability, when welding with industrial robots butt and corner welds is investigated. Conventional PPAW of aluminium is performed with AlSi12 filler material. A post processing of the joint, as for example anodising in order to improve corrosion resistance, leads to a very different optical aspect, as the colouration of the weld seam after anodising differs from the base material. Thanks to a correct choice of filler material it is possible to reduce the colour differences between base materials/heat affected zone and bead, so that the weldment can be set for high quality optical applications, too.
Use of zinc-alloys for low temperature soldering of zinc coated steels. - In: Sheet metal 2005, (2005), S. 127-134
Due to the boiling temperature of zinc (907 deg C), which is lower than the steel melting point, the welding of zinc coated steel sheets presents many difficulties. As a result of the violent evaporation of zinc, pores in the weld seam are present after solidification and the zinc coating near the weld is damaged. ZnAl-alloys are characterized through low melting temperature, which are comparable to the melting point of zinc, so that the damaging of the zinc coating can be reduced. Investigations carried out with ZnAl-materials for joining zinc coated steel sheets as DC04ZE75/75 and DX56Z are reported. The process reliability of laser soldering with ZnAl-alloys and a Nd:YAG as well as a diode laser is reported. The low surface tension leads to a wide bearing section. The edge welds were evaluated through tensile tests. Soldering with ZnAl-wires reduces the damaging of zinc coatings. Due to the low melting point of these alloys, which is lower than the boiling point of pure zinc, it is possible to process zinc coated steels. The best results were achieved for Nd:YAG-laser with a power of about 1500 W to 1800 W and a ratio of wire-/process-velocity of 2:1 to 1:1. For the use of diode lasers the results are similar, but a higher laser power and a smaller ratio of wire-/process velocity are needed. The optimization of the process parameters, especially a higher ratio of wire-/process velocity, allowed a better filling of the soldering gap. If the ratio is too high the soldering material is only partly molten and results in an incomplete bonding.The damage of the zinc layer was reduced to a very small region of about 100 micrometer or was avoided completely. The high capillary pressure and the low viscosity of the zinc melt leads to an extreme wide bonding area, which can reach values up to 4 mm. The transition from the soldering material to the steel sheet is very uniform, thus the notch effect is reduced.
Mechanical behaviour of overlap joints of titanium. - In: Science and technology of welding and joining, ISSN 1743-2936, Bd. 10 (2005), 1, S. 50-60
https://doi.org/10.1179/174329305X24334
Herstellung metallischer Mikrobauteile durch Mikrozerspanung und Thermal Spray Moulding. - In: Mikro-System-Technik Chemnitz '05, (2005), S. 84-87
Beschichten, Fügen, Zerspanen : 1. Fertigungstechnisches Kolloquium, 17./18. März 2005 in Ilmenau. - Ilmenau : Techn. Univ., 2005. - 1 CD-ROM
Design of thermal spray processes. - In: Handbook of metallurgical process and design, (2004), S. 833-856
Entwicklung und Bewertung eines diffusionsgeschweißten Werkzeuges für den Mikrospritzguss. - In: Tagungsband, (2004), S. 271-278
Vollmechanisiertes PTA-Auftragschweißen in Zwangslage an Bauteilen komplexer Geometrie. - In: Verschleißschutz von Bauteilen durch Auftragschweißen, (2004), S. 26-32
Das PTA-Schweißen zeichnet sich durch die geringe Wärmeeinbringung, die geringe Aufmischung und hohe Schichtqualität aus. Hierfür begründet sich sein zunehmender Einsatz an Bauteilen, die bisher mittels Flammpulverauftragscheißen beschichtet wurden. Ein hohes Kosteneinsparungspotential kann erschlossen werden, wenn es gelingt, den PTA-Prozess für Kleinserien automatisiert auch in Zwangslage durchzuführen. In diesem Beitrag werden Automatisierungs- und Prozessführungsstrategien für 3-D Konturen in Zwangslage dargestellt. Die Beschichtungsqualität wird auf der Basis von Feldversuchen mit konventionell geschweißten Bauteilen verglichen.
Influence of process parameters on the plasma powder cladding in constraint position. - In: Proceedings, (2004), S. 435-444
Influence of the current generator characteristic on the quality and properties of arc sprayed coatings. - In: Proceedings, (2004), S. 277-286
Due to the low running costs, high spray rates and efficiency wire arc spraying has gained nowadays great attention, especially as a tool for coating large areas with high deposition rates. The main applications are for corrosion and wear protection of large structures, such as coating with zinc for anodic protection or with high alloyed chromium steel for longer surface service time. Innovative applications with high quality tailored materials are possible with cored wires. Disadvantages of the arc spraying process are on the one hand that only electrically conductive materials can be processed and on the other hand that the particle velocity is low compared to other thermal spray processes such as HVOF or APS. - Innovative and flexible power supply systems were developed for arc welding technologies in the last decade. Today power supply devices with new features for arc wire spraying technologies are present at the market, too. The coating properties such as the particle size and morphology can be optimized by changing the current generator characteristic and modulating the energy input for example by pulsing up to 500 Hz. As a consequence of the power modulation and of further process tailoring possibilities, the oxidation of particles can be reduced by a lower heat input based on lower spray voltage. Investigations in order to influence the droplet behavior and the coating microstructure using dynamic generators were performed for zinc, copper, aluminum and steel and are reported in this paper. Besides an enhancement of the layer's microstructure a higher process stability and reliability were achieved.