AWS C7.2M:2010 pdf free download

AWS C7.2M:2010 pdf free download.Recommended Practices for Laser Beam Welding , Cutting , and Allied Processes.
5.4.1 Temporal. Nd:YAG lasers may be operated in either pulsed or continuous wave (CW) modes. Pulsed Nd:YAG lasers have flashlamps or diodes, while CW Nd:YAG lasers use continuous arc lamps. Nd:YAG lasers cannot be switched from pulsed to CW operation because the excitation equipment (lamps and power supplies) is distinct and significantly different for each type. Pulse repetition rates are generally below 200 Hz. Control of the power going into the lamps allows tailoring of the laser-pulse shape and duration. The solid laser medium has a high concentration of light-emitting atoms, so the peak power can be very high. Material removal is usually accomplished with short, high-power pulses, while joining is done with longer pulses of lower peak power or with a continuous beam.
5.4.2 Spatial. Laser rods accumulate heat in the center as they are cooled along their outside surface. Therefore, there will be a temperature gradient across the rod’s diameter whenever substantial power is produced. This gradient induces changes in the rod’s refractive index, which degrades the optical performance of the laser. High-power Nd:YAG lasers have multimode outputs with high divergence. This limits the ability of optics to focus the beam to a small spot, and requires the resonator to be near the work area.
The total internal reflection face pumped laser (TIR-FPL), also called the “slab” laser, reduces this problem by bouncing the beam from side to side within a rectangular crystal, compensating for thermal gradients in the material (see Figure 5.10). The thermal stresses in the YAG medium, which distort the laser light, are canceled-out as the light crisscrosses the long axis between slabsurface reflections.
5.5.1 Nd:glass. Nd:glass lasers are very similar to Nd:YAG lasers. The laser rod is made of neodymium-doped glass rather than garnet. When glass rather than YAG is used as a matrix, a higher concentration of neodymium atoms can he incorporated in the laser rod. This allows glass lasers to produce stronger pulses than Nd:YAG lasers, which makes them more appropriate for deep drilling. Because the poor thermal conductivity of glass limits the pulse frequency to about one pulse per second, this type of laser is not used for contour cutting.AWS C7.2M:2010 pdf free download.