A welding process that combined plasma arc welding with laser welding was used to make autogenous bead on plate welds on a sheet stock of a carbon steel. A wide range of welding parameters (arc current, laser power, weld speed) was employed. The experimental weld pool shapes were analysed and the data were used to train a neural network to predict weld pool shape as a function of process conditions. The predictions of the neural network model showed excellent agreement with the experimental results, indicating that a neural network model is a viable means for predicting weld pool shape. Using the model, a parametric study was carried out to examine the influence of process conditions on the final weld pool profile.
The objective of this work was to assess techniques for joining NZP ceramics, a new family of ceramic materials that have low coefficient of thermal expansion, low thermal conductivity, and excellent thermal-shock resistance. Initially, the authors evaluated laser-beam welding over volatile fluxing agents (ferric oxide, copper oxide, boric acid, and boron nitride). They also examined other laser, arc-welding, brazing, and cold joining techniques. The NZP materials were capable of sustaining the thermal stresses associated with these joining processes without substantial cracking. Of the volatile fluxes, only the copper oxide promoted weld fusion. Efforts to accomplish fusion by laser-beam welding over copper, titanium, stainless steel, yttrium barium copper oxide, fused silica glass, and mullitdalumina were unsuccessful. Gas-tungsten arc welding accompanied by porosity, irregularities, and cracking was achieved on copper sheet sandwiched between NZP tiles. Attempts at conventional oq-acetylene welding and torch brazing were unproductive. Silica-based oxide mixtures and copper oxide-based materials show potential for development into filler materials for firnace brazing, and phosphate-based cements show promise as a means of cold joining.
An evaluation was made of the Photolytic Iodine Laser (PIL) being developed by Advanced Optical Equipment and Services Corporation for metalworking applications. This laser operates in the infrared region of the spectrum and was anticipated to have a very small focal spot size and very low divergence. With these properties, it would be very effective at making small welds and narrow slots in metals. The program was of limited success due to low power output from the laser as well as power and positional instability. Some narrow slots were made and evaluated. The PIL may have applications in the electronics industry, even at low power, if the instability in the beam power and position can be solved.
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