Evaluation criterion and closed-loop control of penetration status during laser-MIG hybrid welding J. Laser Appl. 22, 92 (2010); 10.2351/1.3492616 Studies on characteristics of CO 2 laser-GTAW hybrid welding of austenitic stainless steel J. Laser Appl. 22, 79 (2010); 10.2351/1.3455995The effect of shielding gas composition on welding performance and weld properties in hybrid CO 2 laser-gas metal arc welding of carbon manganese steel Hybrid processes have been established for the joining of thick plates. The presented approach enables single side welding of thick metal plates by combining a laser beam and two gas metal arc (GMA) welding torches in one setup. By using this hybrid process for joining high material thicknesses, manufacturing time can be significantly reduced in comparison to conventional multilayer arc welding processes. Additionally, new joint designs can be used to reduce filler metal consumption. In order to benefit from these economic advantages, and to make use of brilliant high power lasers in pipeline manufacturing, this hybrid process needs to run robustly for common gap and tolerance ranges. The process time, compared to conventional methods, will be significantly decreased, due to the use of disk lasers with a maximum output power of 16 kW combined with two high power GMA subprocesses. For process development, American Petroleum Institute (API) 5L X70 pipeline steel plates with a thickness of 23 mm have already been joined in a flat position using a single weld pass. Based on these parameter studies, the process limitations have been determined with regard to energy input, gap bridgeability, vertical edge offset, and a lateral offset of the energy sources from the weld joint. The robustness of the hybrid process developed has been demonstrated in experiments representative of the pipeline application. V C 2014 Laser Institute of America.
The industrial use of GMA-laser hybrid welding has increased in the last 10 years, due to the brilliant quality of the laser beam radiation, and higher laser output powers. GMA-laser hybrid welding processes operate in a common molten pool. The combination of the laser beam and the arc results in improved welding speed, penetration depth, heat affected zone and gap bridgeability. Single-layer, GMA-laser hybrid welding processes have been developed for high-strength fine-grain structural steels with a grade of S690QL and a thickness of 15 mm and 20 mm. In addition, the welding process is assisted by an integrated, inductive preheating process to improve the mechanical properties of the welding seam. By using the determined parameters regarding the energy per unit length, and the preheating temperature, welding seams with high quality can be achieved.
Lightweight construction is currently of high interest, not only for the automotive sector, but also for the maritime industry, due to various benefits. On the one hand, CO2 emissions can be reduced as a result of lower fuel consumption, and on the other hand a higher speed can be achieved, especially for yachts. Hence, hybrid joints of steel and aluminum parts are in great demand for yachts. Presently, these parts are joined using explosive welding adapters, which are complex, time-consuming, and costly to manufacture. For efficient manufacturing of such adapters, a high-power laser welding process is predestined. Aluminum alloy EN AW-6082 (t = 8 mm) and steel S355 (t = 5 mm) are welded in a lap joint configuration using a diode laser with a laser beam power of 10.4 kW. The challenge of welding this dissimilar material combination is the formation of hard and brittle intermetallic compounds within the weld seam, which may lead to cracks and negative effects on mechanical properties of the joint. To meet the required mechanical properties, the mixing ratio of the intermetallic compounds can be limited, as determined in the context of the presented welding process development. Using suitable mixing ratios, the weld seam quality can be increased as shown in metallography analysis, hardness tests, and tensile shear tests. Among other things, the welded samples provide a shear force of approximately 9 kN.
Over the last few decades, the demand for lightweight constructions has been increased continuously for several industrial applications, like automotive and ship building, to reduce the weight of vessels in order to minimize the CO2 emissions as a result of a lower fuel consumption. Lightweight construction is almost applied for ship applications, especially for yachts, which are designed by using aluminum for the deck constructions and steel for the ship hull. For joining these parts, a high-power laser welding process shall be developed. However, the welding of these dissimilar materials is associated with great challenges, due to the different physical properties and the formation of hard and brittle intermetallic phases, which may influence negatively the properties of the weld seam. The quality of dissimilar joints depends strongly on the mixture ratio between the molten amount of steel and aluminum. However, the mixture ratio varies over the weld seam length due to a high dynamic of the keyhole resulted by welding of this material combination. Furthermore, different batches of materials and varied sheet thicknesses t may influence the mixture ratio. In this study, a high-power laser welding process is developed with in-process control of the penetration depth tP by analyzing the spectral process emissions for dissimilar lap joints of aluminum alloy EN AW-6082 (t = 8 mm) and steel S355 (t = 5–7 mm). In the context of these investigations, an increase of occurring cracks within the weld seam and ejections of molten material with increasing penetration depth tP can be observed. To achieve a relative high joint strength, the penetration depth tP must be kept constant at a value of 1.4 mm. In case of varied batch of material, thickness t of the used sheets, welding speed vS, and leap of the steel sheet thickness t, the penetration depth tP requested cannot be achieved. Using the in-process control of the penetration depth tP, the weld seam quality remains almost constantly over the weld seam length, as shown in visual inspections, metallographic analyses, profiles of the penetration depth tP, and tensile shear testing. Among other things, the appearance of ejections of molten material can be avoided by using the in-process control of the penetration depth tP.
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