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Usability Research Of High Power Laser Welding Of Thick Ship Plates

Posted on:2009-11-15Degree:MasterType:Thesis
Country:ChinaCandidate:Z TangFull Text:PDF
GTID:2132360242977025Subject:Materials Processing Engineering
Abstract/Summary:PDF Full Text Request
The laser welding technology is a high speed and efficient welding method, which can achieve high quality weld formation with little weld distortion. As a result of fact, it has a bright future for its application in the ship building industry. For domestic shipyards planning to apply this welding technology, a primary issue which they have to face is the adaptation of domestic-made ship steel to the high power laser welding process. In this paper, high power CO2 laser welding with coldwire and laser-MIG hybrid welding processes of home-made marine HSLA steel were studied, covering the real-time process, weld formation, joint microstructure and mechanical properties.First, the real time process of laser welding with cold wire of HSLA has been observed and analyzed by means of the high speed photography. In this part, the effects of size fluctuation of the laser-induced plasma on the welding process and weld formation have been studied. Second, the relations between weld formation and the prime parameters of coldwire welding including laser power, welding speed, wire feeding rate, gaps etc. have been represented based on the experimental analysis. The experiment results of 12mm thick HSLA steel butt welding shows that, high power laser welding with cold wire can produce a weld with high quality formation and little distortion. The joint was found to have a"Y"shaped cross-section and that most are quenched structures in terms of metallographic analysis. Then tensile, bend and impact tests have been done to determine the mechanical properties of the weld according to the CCS rules for welding.Third, the interaction between laser induced plasma and arc during laser-MIG hybrid welding has been studied based on the high speed photography system. It has been found that this interaction behavior mostly represents as the way that the arc being attracted to the laser induced plasma. Furthermore, experiments have been conducted to find out how this combination of laser and arc played its role on the welding process and weld formation.Fourth, the hybrid welding process and the corresponding weld formation results under the conditions of different sizes of grooves have been analyzed in this paper and then the conclusion helped to determine the optimized size of groove for hybrid butt welding of 16mm thick steel. According to the feathers of the combination between laser and arc, an efficient way has been given to simplify the work of finding suitable parameters of the hybrid welding experiments. In addition, mechanical properties tests have been conducted as well for the hybrid welded joints and came out very good results.At the end of this paper, the comparative analysis has been made on weld formation, joint microstructures and mechanical properties between laser coldwire welding and laser-MIG hybrid welding processes. The results showed that, comparing to hybrid welding of the plates of the same thickness, the coldwire welding process required a lower heat input and therefore had a higher cooling rate in the joint resulting in a smaller grain size and higher quench hardening tendency.
Keywords/Search Tags:High power laser, coldwire welding, hybrid welding, HSLA Steel, Joint structures, mechanical properties
PDF Full Text Request
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