A Research On Thin Plate Stainless Steel Welding Technology Using Fiber Laser

Welding by nanosecond fiber laser is a new welding method.Compared with other welding methods,its main advantages are: the heat affected zone is small,so the deformation of the weldment is small;the size of the welding points can be controlled flexibly,so can get small size welding points;the fusion area between the two weldments is large,so the pulling force of the welding points will be strong.The thin metals usually weld by this method.Welding by nanosecond fiber laser is mainly in the application stage now,few studies have been done,nowhere can find reference to the temperature field simulation.The goal of this paper is to study the heat transfer method and theoretical mechanism of thin stainless-steel sheets welding by nanosecond pulsed fiber laser,providing the theoretical basis for selecting the most appropriate parameters of laser welding process.In order to achieve the goal,this paper analyzes the relevant mechanisms of welding stainless steels by nanosecond fiber laser from two aspects: obtaining the effect of welding by different parameters of laser process by doing experiments and obtaining the temperature field of welding by Finite element simulation,analyzing the related mechanism and heat transfer method of welding stainless steel by nanosecond fiber laser.Weld two pieces of 316 L stainless steels with thicknesses of 100 um and 300 um of seam weld and spot weld by different parameters of laser welding.Obtain the surface size and section shape of molten pool by the experiment of seam weld.Obtain the pulling force of welding spot by spot weld.Based on the results of the experiment,discussing the relation between the welding spot geometry and pulling force and parameters of laser welding process: power,frequency,pulse width,defocus and welding speed.In order to better understand the welding process of welding stainless steel by nanosecond fiber laser and improve the reliability of welding spot,in this paper,established suitable heat source model for welding of stainless steel by nanosecond laser,used ANSYS finite element analysis software to simulate the welding temperature field distribution of the welding process.For simulating the accurately process of welding by nanosecond fiber laser,in this paper,staring from the whole welding process,do not analyzing the process of hole forming.According to the actual cross section shape of weld seam,established a suitable heat source model that it can reflect the influence of the hole to the geometry shape of the weld seam.Based on the analysis of the characteristics of the existing heat source model,a heat flow peak index decrement column and an ellipsoid combination heat source model are proposed in this paper.The simulation results show that the temperature field distribution and the shape of the welding seam can be simulated by the combined heat source model of the heat flow peak index and the ellipsoid combined heat source model that proposed in this paper.After analyzing the laws of each parameter of laser process on the welding effect,some optimization methods are proposed for the problems encountered in the welding: By adding 99.999% argon gas during the welding process,metal splashing will be avoided during welding,a beautiful molten pool and a large welding spot pull force can be obtained;In the case of no protective gas,can avoid metal splashing by using positive defocus;Optimize the beam quality of the laser,can obtain a large depth ratio of the molten pool.