Laser Welding Technology And Properties Of 2205 Duplex Stainless Steel

The main microstructure of 2205 Duplex Stainless Steel is ferrite and austenite,with excellent corrosion resistance and good weldability.It has high significance and application value for welding 2205 DSS with laser processing technology because of its high flexibility.Many experts and scholars have researched on the welding 2205 DSS much more,but most are based on conventional methods(such as GTAW)for processing.The welding research for 1mm sheet has not been reported.The paper has important reference value for 2205 duplex stainless steel sheet laser welding study of 1mm.The main process parameters,welding speed,input current,pulse width,pulse frequency,defocus distance and protective gas were focused studied in this paper.To take.tensile test,roughness test,surface hardness test and microstructure observation for weldments which were obtained from single factor experiment and orthogonal experiment under different levels of factors,then studied and analyzed the relationship between different welding parameters and weldments'welding performance,and the changes in morphology and microstructure of the weld.Finally,having get a processing program with a set of optimal welding parameters.The main conclusions are as follows:1.Maintaining the welding speed unchanged,the pulse frequency and width and input current increases,the energy absorbed of metal artifacts joint increases,and the weld is less prone to insufficient solder and other welding defects,and not only improving the joint strength,but a significant welding performance workpieces enhanced through single factor experimental study,and vice versa.Through the experimental results analysis,ultimately determine the value of each factor's levels are as follow:V=500/600/700 mm/min,Z=-1 mm;I=150/160/170 A;T=4/5/6 ms;f=15/24/25 Hz;2.It found that the area close to proximity of welding fusion line keeping the maximum hardness due to its higher alloy content than other regions through the results of welding surface vickers hardness test.The area close to the weld center is affected by the welding thermal cycling that its grain size is smaller than the base metal's led to its hardness is larger than the base metel's.3.After conducting four factors and three levels orthogonal experimental design and performing orthogonal range analysis of L9(34),it claimed that frequency had the most significant effect on the workpieces' welding capabilities,followed by the pulse width and current,but the feed speed is the most inapparent.From the result of calculation and analysis shows the values of P is less than 0.05 and the correlation coefficients are greater than 0.9 which indicates that the difference between the groups is significant.4.As the welding surface microstructure observations show:Due to the moderate welding speed and higher input current,pulse width and pulse frequency that metal weld joints absorb adequate laser heat brought about dry joint don't appear and surface finish is higher,minimum roughness value and no spatter,dross and undercut.The welding performance of weldments are the best and the overlap rate of spot is more than 78%under the condition of I=160A,T=5ms,f=25Hz,V=500mm/min and Z=-1mm.On the contrary,there is a large number of incomplete penetration and dry joints on the back of the weld,and the overlap rate of spot is less than 10%.Meanwhile,there is numbers of obvious spatter and dross and severe undercut on weldments'surface,and weld has a more severe subsidence trend all of that leds to weldments a serious decline in the weldability.5.From the results of microstructure observations of the three sets of weldments in the orthogonal experiment can be seen that grain shape is slender,and the grain shape in the weld central area increases affected by high temperature.The ferrite and austenite content of weld region is roughly the same overall in conditions of I=160A,T=5ms,f=25Hz,V=500mm/min and Z=-1mm.The grain size in the central weld is larger but the overall size is more uniform which is the reason makes the weldment obtain better welding performance.6.All welded microstructure showed the grain size is the smallest both sides of the direction perpendicular to the weld and along both sides of the welding direction the grain size is the maximum due to the different impact of the heat and thermal conductivity.Then this paper proposed preheat and soldering process "heat treatment" optimization scheme.With different temperature gradient and the cooling and solidification rate,metal flow like "ripple"emerged on front and back of weld spots surface and obvious around the weld.