FORMATION MECHANISM OF PROCESS INSTABILITIES AND STRATEGIES TO IMPROVE WELDING QUALITY

摘要

The deep penetration welding process with CO_2 lasershas been employed successfully for many years inindustry. It generates little spatter on the work piecesurface and therefore produces excellent seam qualityat high process speed with good process reliabilityover a wide range of parameters. With a wavelengtharound 1 μm, solid-state lasers are being increasinglyused in industrial production thanks to simple beamguidance by means of laser light cable and their highelectrical efficiency. Disk and fiber lasers haveadvanced into the domain of CO_2 lasers by way ofpower and beam parameter product. However the seamquality is highly dependent on the focusing conditionsused, whereby the mechanisms that cause processinstabilities are still not properly understood. Also, athigh intensities with high feed rates, considerablespatter is generated on the work piece surface,reducing productivity in applications where thedemands on surface quality are high. In thispublication, based on online X-ray observation andhigh-speed imaging, the suitability for welding and theformation mechanism of process instabilities likespattering and humping were compared at differentfeed rates. Based on a better process understandingstrategies which can improve welding quality arepresented.