Praezisionsbearbeitung mit Festkoerperlasern: Fuegen. Hartloeten von Blechformteilen mit dem Nd:YAG-Laser Abschlussbericht

Manual brazing, as it is used today in the manufacture of automobile bodywork, can be of variable quality and may be responsible for thermal damage to both base material and filler metal. Reworking is often necessary, but the need for this expensive and time-consuming process can be minimised by the automation of the brazing procedure. If Nd:YAG-lasers are used as heat sorce for brazing, the laser energy can be controlled with ease and specific temperature fields can be set up. Fibre-optic laser routing also makes it easy to integrate the technology into manufacturing systems. The goal of this project was the systematic development and optimisation of process controls and associated systems technology for automated flux-free brazing using double-beam laser technology. The system developed in the project was designed to handle modern bodywork materials (DC04; DC04+ZE) and materials for lightweight construction (AlMg0,4Sil,2; AlMg5W17) as well as aluminium alloys in combination with construction steels. The highest brazing quality was achieved with L-CuZn40 and L-Ag55Sn filler metals. The use of 95 % N_2 and 5 % H_2 as a protection gas allowed flux-free brazing. If allowances are made for capillary action and gravity, it is possible to produce high quality joints using laser brazing and spacial seam-orientation. It is advantageous to use on-line process controls for the processing of critical contours. In flux-free laser brazing of aluminium alloys, an additional pulsed Nd:YAG-laser is used to modify the surface activity, making the surface more wettable to the filler metal. The different heat dispersal coefficients of aluminium and its oxide coat lead to disruption of this oxide layer and enable the filler metal to wet the surface. Combinations of construction steel and aluminium alloy can be brazed without flux by using the reducing gas and a zinc-based solder which is capable of wetting both materials. (orig.)SIGLEAvailable from TIB Hannover: F96B1218+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman

Trennen mit Festkoerperlasern. Feinschneiden mit Festkoerperlasern Abschlussbericht

Solid state lasers have been mainly used for spot welding up to now. Recently some work around the cooperation project 'To separate the solid state lasers' is proving the readiness for use of Nd:YAG-lasers for cutting of steels, Al- and Ti-alloys, hardmagnetic and ceramic materials. A description itself when cutting with pulsed Nd:YAG-laser by capturing the signals that are emitted by the process couldn't be found in literature. Therefore examinations are made to find out a better understanding of the ongoing interaction process and to find out signals that enable a process supervision. This is done by using different diagnostic abilities like short time camera, photodiode, spectrometer and pyrometer. Corresponding technology experiments on cutting of steels and non-ferrous-metals that show the dependence of the working result on the different parameters verify the statements of the experiments on process diagnostics. Also they allow the classification of the separation method 'cutting with pulsed ND:YAG-lasers' with regard to different production technologies. The process and therefore within certain limits the working quality could be supervised by the signals that are emitted out of the interaction zone. These are especially the laser radiation that is transmitted through the cut kerf, the intensity of the process glowing and the temperature radiation. The working quality is good to very good with the thermophysical material properties influencing the cutting result. This final report offers many data for the conversion of the results to a user-specific applicatication. (orig.)SIGLEAvailable from TIB Hannover: F95B231+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Forschung und Technologie (BMFT), Bonn (Germany)DEGerman

Oberflaechenbearbeitung mit CO_2-Lasern. Teilvorhaben: Erhoehung der Absorption beim Laserhaerten durch Einspiegeln eines TEA-CO_2-Impulslasers in den Strahlengang eines cw-CO_2-Lasers Abschlussbericht

The efficiency of CO_2-laser material hardening could be improved by combining a cw-CO_2-laser and a TEA-CO_2-pulsed laser. The developed dual-beam technique has been successfully tested in the martensitic laser hardening of different steels for hardening and tempering (C 45, C 60, 42 CrMo 4, 90 MnCrV 8). By this technique an increased absorption is achieved without additional coating or intensified oxidation of the sample surface. Results obtained with a 1 kW-cw-CO_2-laser could be scaled up to a 4 kW and to a 18 kW cw-CO_2-laser. (WEN)Available from TIB Hannover: F94B848+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Forschung und Technologie (BMFT), Bonn (Germany)DEGerman

Abtragen und Bohren mit dem Festkoerperlaser. Praezisionsbohren mit dem Nd:YAG-Laser Abschlussbericht

Precision drill-holes with diameters between 100 and 200 #mu#m, commonly used for spraying and injection nozzles, are manufactured for mass productions in metals up to now only with mechanical and electroerosive drilling processes. In comparison to these manufacturing methods laser beam drilling has the advantage of extremely high processing speeds. Therefore it was the target of this project to examine the potential of suitability of laser beam drilling for the named applications with regard to their high demands on drill-hole geometry and reproducibility. Investigating this topic many parameter studies have been made varying laser beam characteristics and process conditions for a stainless steel (X5 CrNi 18 10). Drill-hole geometry has been determined by diameter, conicity and roundness, for statements about reproducibility the mass flow through the drill-hole has been chosen. It was possible to manufacture drill-holes with diameters down to 25 #mu#m, but it was not possible to keep roundness and conicity in the demanded tolerances. The reproducibility however could be improved by a factor of 10 compared to conventional drilling methods with the realization of a closed loop control by measuring the amount of gas flowing through the drill-hole. (orig.)Available from TIB Hannover: F95B1024+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Forschung und Technologie (BMFT), Bonn (Germany)DEGerman

Eurolaser: Safety in the Industrial Applications of Lasers (INDAL). Teilprojekt: Schadstoffbildung bei Laserschweissen und Vergleich der Schadstoffmengen beim Laser- und Plasmaschneiden Abschlussbericht

Comprehensive investigations of emissions were carried out using a special experimental set-up (see chapter 5) during laser cutting with oxygen and with nitrogen as well as during plasma cutting with compressed air and with argon/hydrogen, especially for high-alloyed steels with thicknesses ranging between 3 and 8 mm. The emission behaviour during laser welding of zinc-coated sheet with approximately 1 mm thickness and of high-alloyed materials with 3 mm thickness was investigated as well. Variing the process parameters, the emissions of toxic gases were determined and the particulate emission products were quantitatively recorded (see chapter 6) and analyzed regarding substances harmful to health (see annex A). From the results of the investigations the dependence of the process parameters on the emission behaviour was determined. On this basis, possibilities of minimizing the toxic substances during cutting and welding of the selected materials were found and generalized by a processes optimization (see chapter 7). Further investigations of the emissions have shown that with suitable measures of exhaustion and ventilation the MAK- and TRK-values at the workplace are not exceeded. By that, the health hazard of the operating personnel will be reduced (see chapter 8 and 9). Any general comperative statements on the emission behaviour between the laser and the plasma process cannot be made as it is dependent on the respective process variant. The results will be worked in to standards and directives on safety at work. (orig.)Available from TIB Hannover: F98B872+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany); European Union (Euro), Brussels (Belgium)DEGerman

Oberflaechenbehandlung von Metallen mit Excimerlasern Abschlussbericht

The in-air treatment of large ceramic and metallic material surfaces of low roughness with high power density and over a material depth of only a view #mu#m can be currently realized only by application of excimer lasers. Spectral resolution and time-integrated characterization of plasma luminescence can be used for on-line quality control of excimer laser treatment. In simple off-line cases efficient quality control can be achieved by spectroscopically dispersed difference reflectometry. Technical feasibility and a pronounced improvement of material properties is demonstrated with contact materials and with components for the automotive industry. For technical aluminium alloys a considerable increase in corrosion resistance as a result of the laser treatment has been demonstrated. (WEN)SIGLEAvailable from TIB Hannover: F95B904+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Forschung und Technologie (BMFT), Bonn (Germany)DEGerman

Proceedings of the EUREKA 205 international workshop 'Excimer laser applications

SIGLEAvailable from TIB Hannover: RR 4033(2) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman