LASER WELDING

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Abstract
Technological improvements in welding have proceeded at a slow pace usually brought about by incremental advances in techniques or materials. An opportunity is now being afforded the Navy to increase its welding technology by giant steps by utilizing the emerging technology of laser welding. Welding with a laser is no longer a research curiosity; it is a viable manufacturing process that is used in large industries. Laser welding is no longer confined to trimming resistors or pulsed welding of microelectronic components. Deep penetration welds have been made by utilizing and focusing high power, continuous carbon dioxide laser beams onto a wide variety of metal and alloys. These welds have been made at speeds up to 70 inches per minute in one half inch thick aluminum alloys at power levels of 8 kilowatts. High strength, low alloy steels have been welded at speeds of 40 inches per minute in one half inch plates at power levels of 12 kilowatts. Recently, it has been demonstrated that quenched and tempered steels can be welded in thicknesses up to three quarters of an inch at speeds in excess of 25 inches per minute at power levels of 14 kilowatts. Many of these improvements have taken place because of refinements in techniques, gas shielding, power stability and a decrease in spot size.Not only does the laser weld faster but the properties of laser welds are significantly better than the normal arc welding techniques and even better than another esoteric welding technique, electron beam welding. This improvement in properties is manifested both in mechanical properties and fracture resistance values. Typically autogeneous laser welds of quenched and tempered steels have yield strengths exceeding those of the base plate. At the same time, there is no significant reduction in the ductility of these welds. On the other hand, the fracture toughness values of laser beam welds approach the values obtained for the base plate and are significantly higher than the values obtained by conventional arc welding processes.Laser beam welding has the capability of making very narrow welds and has an unprecedented ability to lend itself to automation through numerical controlled procedures.