Influence of the voltage modulation frequency on voltage trace and coatings properties. - In: Conference proceedings, (2005), S. 393-398
Effective laser-cladding through the application of magnetic induced forces. - In: Conference proceedings, (2005), S. 1264-1269
In the last years laser beam cladding was recognised as a high quality coating process. Low thermal influence, high cooling rates, metallic bonding, minimal surface roughness are only some of the positive aspects. On the other hand the process efficiency is very low and the running costs in comparison with PTA or Thermal Spraying are high. Attempts to improve the productivity, aim to enhance the efficiency of the beam source itself or to optimize the energy management. This is for example possible through a higher coating speed or through hybrid setups, which allow the use of an additional preheat source (e. g. plasma-assisted laser cladding). Regarding flexibility, defined as the capability of a process to answer in a short time to application requests, the effectiveness of laser cladding can be widely increased through free forming (shaping) of coatings without additional clamping devices. The geometric shape of the coating seam is mainly defined by gravity and surface tension of the melt. An additional force, as for example Lorentz force, can optimize the geometry and improve the process conditions. Wide seams allow for example a low number of overlapping layers when coating large areas and rise the specific area deposition rate. Slim coatings on the contrary are advantageous when generating 3&Ohaak;dimensional structures. The induced force depends from the applied magnetic field and the flow of an electric current. The presented investigations clarify the physical background, the interaction of the magnetic force and the geometric shape of the coating and the possibility to apply them for technical coatings. The application of an external force made it possible to increase the efficiency of the laser cladding process and to gain more interest of the industry.
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.