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Experimental and numerical study on the influence of the laser hybrid parameters in partial penetration welding on the solidification cracking in the weld root
摘要： The aim of the present study is to investigate the influence of the laser hybrid welding parameters on the solidification cracks in the weld root for partial penetration welding. Welding trials were performed on thick-walled high-strength steels of grade S690QL under the same critical restraint intensity, with a variation of the welding velocity, wire feeding rate, and the focal position of the laser beam. It was ascertained that the welding velocity has a high impact on the solidification cracking phenomenon. A decrease in the welding speed leads to a reduction of the number of cracks in the weld root. The arc power has also a slight influence on the solidification cracking, while the change of the focal position of the laser beam shows also a remarkable effect. Besides, numerical simulation was performed to understand the thermomechanical behavior of the welds for different welding parameters to assist the interpretation of the experimental results.
关键词： Thick-walled steels,Solidification cracking,High-power laser beam,Partial penetration,Laser hybrid welding
更新于2025-09-16 10:30:52
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Avoidance of end crater imperfections at high-power laser beam welding of closed circumferential welds
摘要： The present work deals with the development of a strategy for the prevention of end crater defects in high-power laser welding of thick-walled circumferential welds. A series of experiments were performed to understand the influence of the welding parameters on the formation of end crater defects such as pores, cracks, root excess weld metal and shrinkage cavities in the overlap area. An abrupt switch-off of the laser power while closing the circumferential weld leads to a formation of a hole which passes through the whole welded material thickness. A laser power ramp-down causes solidification cracks which are initiated on the transition from full-penetration mode to partial penetration. Defocusing the laser beam led to promising results in terms of avoiding end crater defects. Cracks and pores in the overlap area could be effectively avoided by using defocusing techniques. A strategy for avoiding of end crater imperfections was tested on flat specimens of steel grade S355 J2 with a wall thickness of between 8 and 10 mm and then transferred on the 10 mm thick pipe sections made of high-strength pipeline steel API5L-X100Q.
关键词： Thick-walled pipes,End crater,Circumferential weld,High-power laser beam,Laser beam welding
更新于2025-09-12 10:27:22
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Weld pool shape observation in high power laser beam welding
摘要： The geometry of the melt pool in laser beam welding plays a major role to understand the dynamics of the melt and its solidification behavior. In this study, a butt configuration of 15 mm thick structural steel and transparent quartz glass was used to observe the weld pool geometry by means of high-speed camera and an infrared camera recording. The observations show that the dimensions of the weld pool vary depending on the depth. The areas close to the weld pool surface take a teardrop-shape. A bulge-region and its temporal evolution were observed approximately in the middle of the depth of the weld pool. Additionally, a 3D transient thermal-fluid numerical simulation was performed to obtain the weld pool shape and to understand the formation mechanism of the observed bulging effect. The model takes into account the local temperature field, the effects of phase transition, thermo-capillary convection, natural convection and temperature-dependent material properties up to evaporation temperature. The numerical results showed good accordance and were furthermore used to improve the understanding of the experimentally observed bulging effect.
关键词： high power laser beam welding,transient weld pool shape,bulging,numerical process simulation
更新于2025-09-12 10:27:22