| Laser welding belongs to the category of special processing,and is widely used in modern welding,especially for difficult welding material because of its high precision,high energy and high flexibility.Laser welding has an unparalleled advantage.2205 duplex stainless steel has good corrosion resistance,high toughness and welding performance.It plays an important role in the Marine pipeline transportation,petrochemical,natural gas and other industries.During the traditional welding of 1mm thick duplex stainless steel,it can generate wide weld seam,large deformation,stress,splash,over burning and other welding defects,so as to affect the strength and morphology of the weld seam.With the use of laser welding,it can give full play to the advantages of laser welding.Both the strength and precision of the welding seam can be guaranteed.In this study,laser butt weld and lap welding experiment of 1 mm thick business 2205 duplex stainless steel were conducted with the pulse laser machine.Also laser butt welding experiment of 1 mm and 2 mm thickness was performed.By comparing the experiment to study the effect of shielding gas on the welding joint performance and to analyze the effect of laser processing parameters on mechanical properties,microstructure and morphology of the welding joint during the laser welding of 2205 duplex stainless steel.An attempt was made to measure the force acting on the surface of the workpiece during laser welding.The formation of molten pool,flow and solidification process periodically in the laser welding was studied by means of high speed photography.The thermal field distribution and change of laser welding duplex stainless steel were studied by infrared thermal imaging technology.The content of chemical elements was also measured with the help of energy spectrum analysis instrument.Above all,to explain the complex optical,thermal and chemical phenomena in laser welding process.In addition,the welding model of 2205 duplex stainless steel was established,and the thermal field,thermal stress and thermal deformation were simulated and studied.In this study,the influence of various laser processing parameters on the mechanical properties of the welded joint and joint morphology was analyzed and the forming mechanism of weld duplex stainless steel during pulsed laser welding has been expanded.This paper presented a scheme to monitor the thermal field change and the simulation of laser welding with infrared thermal imaging system,and enriched research method of the thermal field distribution in laser welding of stainless steel.It has important theoretical value and application guiding significance to the development of laser welding technology.The main conclusions are as follows:1.In contrast,the welding joint mechanical performance of the laser lap welding of 2205 duplex stainless steel is better than the other two kinds of situations.The tensile strength(maximum reached 919.71 MPa)and bending properties are excellent,and the formed weld seam appearance is more beautiful.The fracture of laser butt welding weldment is mainly happened in the welding joint,and the fracture is made up of from solder joint edge on the surface to the center of solder joint to fracture.The fracture mode is dimple fracture mechanism.The fracture of laser lap welding weldment mainly occurs in the base metal,and its fracture mode is intergranular dimple fracture mechanism.2.The greater the input current,the greater the depth of the molten pool.The welding width on lower surface is greatly influenced by the laser pulse width.With the increase of pulse width,welding width on lower surface increases.The increase of laser frequency makes the distance between adjacent solder joints become smaller,and the phenomenon of incomplete penetration is more likely to occur,but it can reduce the occurrence of concavity.The protective gas can protect the weld seam from being oxidized to obtain a relatively smooth surface.There is no protective gas will produce air holes,and both will cause incomplete penetration welding faults.3.In the laser butt welding,the thermal field is parabolic move forward.The welding temperature is uniform,and the temperature of the weld center is higher.The temperature field distribution of laser lap welding is similar with that of laser butt welding with unequal thickness.A second heat field was formed from the molten metal gas except the thermal field around the weld seam.4.The energy of the laser beam was absorbed by weldment only in the pulse time,during which a tiny solder joint weld pool formed,then constantly absorbing the energy,and the molten pool was expanding rapidly,the metal vaporization occurred,generating white smoke and dazzling light and lots of plasma until the end of the pulse.It's solder solidification time once the pulse is ended.Weld seam formed with the process goes round. |
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