Study On The Characteristics Of Laser Filler Wire Multi-narrow Gap Welding For GH3535Alloy Medium/Thick Plate

Narrow gap filler wire laser welding technology which recently developedin recent years is a high efficiency thick plate connection method, which couldexpand laser welding application fields to large welded structures by using lowerlaser power. The traditional welding manner can not get good quality of weldingjoint, because of many reasons, such as low welding speed, wide heat affectedzone, apparent welding deformation and welding process inflexibility impreciseand so on. The laser welding beam energy is easy to control, and energy densityis generally distributed in a Gaussian mode, with a high collimation and highdirectivity, making laser welding has obvious advantages in the narrow gapwelding medium and heavy plate.The technology experiments of laser filler wire multi-narrow gap weldingwas carried out with thickness of4mm and22mm high GH3535in this paper.Firstly studied the backing weld on4mm thin plate, and analyzed laser weldingorganization characteristics and mechanical properties of GH3535alloy.Secondly designed groove shapes and groove dimensions, and ultimatelydetermined the most appropriate narrow gap groove form by process experiments.Finally, studied the filling the welding process in22mm thick plate, controllingthe laser beam energy density distribution in order to optimal weld appearance byvarying the defocus amount. The positive defocus amount can improve thestability of narrow gap higher power laser filler wirewelding. The experimentalresults show that the use of+18mm~+20mm defocus amount is the mostappropriate, toincrease the laser seam effective utilization and filling height innarrow gap groove,and inhibit the sidewall incomplete fusion, and reduceporosity defects.This test has researched the backing weld on4mm thick GH3535alloy, anddeeply analysised the GH3535alloy laser welding characteristics. In the aspectof weld organizational, through series of observation and analysis, such asmetallography, SEM (EDS), XRD, TEM, the experimental results found thatweld metal is the single austenite, and the carbide of base metal has dissolved toaustenitic matrix under the laser energy. In the aspect of weld performance,experiments performed normal temperature/high temperature tensile propertiestesting, bending performance testing, corrosion resistance performance test, andthe performance is close to the base material.By optimizing the narrow gap groove dimensions and laser narrow gap filler wire welding process, the22mm thick GH3535alloy achieved reliableconnection, getting a excellent weld cross-section morphology. Further, theorganization was observed between the filling layers, and vicker hardness and thehigh-temperature tensile strength was tested hierarchically. Some small fillinglayer overlap regions exist equiaxed grains, probably laser repeated action playsa role of normalizing heat treatment. There are softening in weld overlappingregion, and hardness values have significantly decreased compared with bothsides of the weld.