Study On Non-penetration TIG Lap Spot Welding Process And Numerical Simulation Of EGR Cooler Bracket

With the increasing emission standards of motor vehicles,the application of EGR technology has been paid attention to.EGR cooler is the core component of EGR technology,and its manufacturing process is a key factor affecting product quality.The EGR cooler is subject to long-term vibration fatigue load and exposed to high temperature and highly corrosive gas during work,so it is particularly important to control the welding quality of the EGR cooler.This paper studies the quality control of argon arc welding non-penetration lap joint spot welding of 304 stainless steel EGR cooler.The range of non-penetration spot welding process parameters suitable for EGR cooler brackets was studied by single factor control variable test,numerical simulation and orthogonal test.The main research content of this paper is as follows:(1)Taking the four welding parameters of welding current,electrode height,welding angle and current mode as the object,the spot welding process of 304 stainless steel argon arc welding was studied.After welding,the macroscopic morphology,microstructure and mechanical properties of spot welded joints were characterized,and the influence of different process parameters on the appearance size of solder joints,weld size,metal structure formation,microhardness and maximum tensile force were investigated.The results show that the non-penetration welding spot can be obtained when the constant current is below 140 A in the spot welding process;the control of welding angle and electrode height is conducive to obtaining a uniform welding spot;under the action of pulse current,the appearance size of the welding spot increase,the depth of penetration and the width of the weld leg decrease;under different welding parameters,the metal structure in the weld zone is dominated by ferrite structure,and gradually changes from lath-like ferrite structure according to the speed of temperature drop in the weld zone The body structure changes to a skeleton ferrite structure.(2)In terms of mechanical properties,the microhardness distribution of the base metal zone,heat-affected zone and weld zone under different process parameters all show that the microhardness of the heat-affected zone is the highest,followed by the base metal zone,and the microhardness of the weld zone is the highest.The characteristics of the lowest microhardness.When the penetration depth of the solder joint is smaller than the thickness of the lapped plate,the higher the penetration depth,the greater the tensile force that the solder joint can provide;when the solder joint is fully penetrated,the change in the hardness of the weld zone caused by different process parameters is the cause of the maximum tensile force The main factor of the force change;since the microhardness of the weld zone is always the lowest in the three regions,the location of the tensile fracture is near the center of the weld.(3)Through numerical simulation,the temperature field distribution centered on the solder joint under different welding parameters is studied.The results show that the increase of welding current makes the overall temperature field of the solder joint area rise greatly;the welding angle and electrode height have a great influence on the distribution position of the temperature field;the pulse frequency has little effect on the temperature field,and the decrease of the maximum temperature is not obvious;The simulation of the pool morphology shows that the Gaussian model is more accurate for the simulation of the lap welded lower plate,and the maximum error of the penetration depth and width is 9.5%.(4)Taking the EGR cooler bracket as the object,an orthogonal test with welding current,electrode height and welding angle as the parameters is designed,and the numerical simulation model of the EGR cooler bracket is established,and the rationality of the selection of the orthogonal test parameters is verified by simulation;analysis The influence of different process parameters on the morphology of solder joints,weld size and microstructure.The results show that in the range of welding current 110 A-130 A,electrode height 2 mm-2.5 mm,and welding angle 45 °-75 °,non-penetrating EGR cooler bracket welding spots with good shape can be obtained.