Effect Of Highfrequency Micro-vibration On Microstruction And Fatigue Fracture Behavour Of Laser Welding

Usually in the conventional laser welding,the introduction of vibration technology to give weldments of exciting force exerting process is referred to as"vibration welding".Its purpose is to reduce the welding residual stress,improving welding joint forming,optimizing the joint purpose,such as organization and refine the grain size and a welding method to improve the performance of welded joint,which is based on the development of a new vibration aging technology.Laser welding with high energy density,heat affected zone more narrow,fast welding speed and deep wide characteristics such as widely used in welding process.Material life of the important measures is based on the fatigue performance,through the analysis of the fatigue life of welded joint can reduce joint fracture accident caused economic losses.This paper chooses 316 stainless steel welding,applying mechanical vibration in conventional laser welding process,analyzes the different welding process parameters on the joint forming and the influence of microstructure,through electronic microscope and scanning electron microscope the weld appearance,using micro hardness tester,analysis of mechanical vibration on the influence of the microhardness of 316 stainless steel,316 stainless steel to make use of drawing machine tensile experiments,through fatigue testing machine for the study of the fatigue fracture behavior of 316 stainless steel,using scanning electron microscopy(SEM)observation on fatigue fracture morphology analysis,find best when welding process parameters through experiments.The resarch have shown that chooses with the increase of vibration frequency,macro welding defects can effectively improve,316 laser applying high-frequency welded joint of micro vibration can increase the weld penetration;Weld with the improvement of mechanical vibration frequency,the grain refinement trend more significantly,when compared with no vibration microhardness in the weld zone decreased by 58%,the average grain size decreases with the reduce of grain refinement with vibration acceleration,in laser welding power is 3000 w,from coke for 5-10 mm,vibration frequency is 923 hz,vibration acceleration of 49.6 m/s2,when the welding speed of 1.2 m/min,can get good weld mechanical properties,grain refinement is most obvious,can be greatly improved.The conventional laser welded joint with high frequency of micro vibration of laser welded joint fatigue experiment,compared with vibration of laser welded joint is no vibration of laser welded joint fatigue performance improved significantly with life,when the vibration frequency and inherent frequency of materials to achieve resonance,the volume of the fatigue life of laser welded joint.In 10~7 cycle number of load cases,316stainless steel material and the condition of laser welded joint fatigue strength 297.32 Mpa,287.49 Mpa,286.69 Mpa,287.49 Mpa,respectively for their tensile strength of 57.2%,55.3%,55.1%,55.85%.316 stainless steel laser welding joint fatigue material and the macroscopic fracture mainly by fatigue crack source area,crack spreading area and transient breaking area of three phase.Fatigue source area and joint specimens were observed by scanning electron microscopy(SEM)surface is mixed with loose surface,etc.,and the fatigue crack propagation region appeared strip secondary cracks,transient fault appeared toughening nest nest,shear lips and tenacity,typical morphology characteristics,such as the base of fatigue fracture of the source is basically caused by the existence of surface gap or inclusions,fatigue crack propagation region appears to understand from the steps and secondary cracks,dissociative steps is a typical brittle fracture characteristics of the spreading area of second phase particles has effect on the fatigue crack propagation.Specimens under the action of cyclic load will be affected by the effect of squash and stretch,will make the fatigue fracture of slip line,sliding process can produce many micro cracks in the grain boundary,gathered many micro cracks of fatigue crack extension.Combining 316 stainless steel organization and fatigue performance,analysis of mechanical vibration on can promote the fatigue life of laser welded joint,but is not very big influence on fatigue fracture morphology.