Study On The Welding Process Of Dissimilar Materials 304 Stainless Steel And Polyethylene Terephthalate (PET)

With the rapid development of modern industry,the performance of materials and structures are being concerned more and more.Many engineering structures and high-end products are required possess the advantage of a wide variety of materials,this requires several types of materials to achieve these multi-components,and this the problem of the connection of dissimilar materials.As the most widely used materials in industry and life,metal and plastics have their own unique excellent properties,and the connection of them can obtain the structure with comprehensive performance.Therefore,the research on the connection between metal and plastic has great value and broad application prospect.This paper use 304 stainless steel and polyethylene terephthalate(PET)as the research object to explore the new method of metal and plastic connection,and make the reference for the future development.This paper use 6KW fiber laser for the lap welding of 304 stainless steel and PET,the experiments were carried out under certain conditions and welding parameters,and with two welding methods: metal-side laser-irradiation welding and laser transmission welding(LTW).Due to the overload input power of the laser,the experiment failed to achieve the LTW of two dissimilar materials.The joint with good appearance and high connection strength was successfully obtained by metal-side laser-irradiation welding,and the tensile strength of the joint obtained under optimum process parameters can reach 79% of PET.The effects of laser power,welding speed and defocusing distance on the tensile strength of the joint were analyzed by comparing the welding results obtained through tensile test.The morphology of the joint was observed by optical microscope and scanning electron microscope(SEM).The elements and groups were detected by X ray energy spectrum analysis(EDS)and Fourier infrared Spectrometer.Based on the analysis of the results,it is inferred that the reason for obtained high strength laser welding joint of 304 stainless steel and PET is the combined action of riveting and chemical bonding.In the process of welding,on the one hand,the grooves were filled with plastic to form the riveting;on the other hand,the metal element may react with the CO group in the PET and then made the chemical bonding.And then study on the TIG welding instead of laser.The lap welding of 304 stainless steel and PET was successfully achieved under the certain process parameters.The tensile strength of the welded joints obtained by the optimum process parameters could reach 100% of PET.The joint have good appearance and with no defects of burning loss etc.The tensile tests of welding joints were carried out under different parameters,and the effect of welding current,welding speed and the height of tungsten electrode on the tensile strength of the joint were summarized through the comparative and analysis of the result.The morphology of the joint was observed by optical microscope and scanning electron microscope(SEM).The elements and groups were detected by X ray energy spectrum analysis(EDS)and Fourier infrared Spectrometer.Based on the analysis of the results,it is inferred that the reason for high joint strength of the 304 stainless steel and PET is the combination of riveting and chemical bonding.In the welding process,the first is that the grooves on the steel plate was filled with molten plastic then form the riveting mechanism;the second is that the chemical reaction was happened between the metal element in the stainless steel and the CO group of PET to form a chemical bond.Compared with the results of laser welding,the higher lap shear strength of the joints was obtained by TIG welding.The reason is that the laser welding energy is too large and highly concentrated to reduce the joint strength.