METALLURGICAL STUDY ON LASER-MAG HYBRID WELDING OF HSLA-590 STEEL

摘要

The Laser-Arc hybrid welding of HSLA-590 steelhas been studied using 2.4kW CO2 laser and 350AMAG welding machine. In this paper, the leadingprocess, MAG current, welding speeds wereinvestigated. The results show that arc leading hybridwelding is better than laser leading hybrid weldingfrom the result of experiments. MAG welding currentof 120~180 ampere is the effective arc parameter to getbetter welds in 2kW CO2 laser hybrid welding. Theacceptable distance DLA LA between Laser and Arc is alsoimportant parameter that is decided by observing thewelding process and the cross section of welds. Gaptolerance and groove angle are also investigated in theexperiments.Microstructure, cooling curve of HAZ and Hardness ofwelds under different hybrid welding conditions werestudied. The cooling curve of HAZ was measured. Thecooling time (cooling from 800oC to 500oC) affectsmicrostructure of welds and grain size in HAZ. Theaverage grain size in HAZ was measured. The resultsshowed the hybrid welding was useful to increase thetough microstructure, such as ferrite and bainite,comparing with Laser welding and MAG weldingindividually under the same welding speed. The SEM(Scanning Electron Microscope) and DAS (DendriteArm Spacing) of base metal and weld metal werestudied. The hardness of welds was measured, whichshowed the weld metal hardness of hybrid welds waslower than that of Laser welds and MAG welds.Key words: Laser-Arc hybrid welding, High strengthsteel, Process parameter, Microstructure, Hardness.