Laser Oscillating Welding Of 304 Stainless Steel To Plastic

Plastics and metals have good complementarity in performance.Connecting plastics to metals can reduce the weight of the structure and bring high economic benefits to industrial production.However,traditional mechanical connections and chemical cementing have problems such as poor sealing and environmental pollution.Laser joining is gradually attracting attention from plastics and metal connection research due to its high efficiency,no contact,and accurate energy control.In this paper,the oscillating scanning laser joining process?circular scanning method?was introduced to improve the quality of plastic and metal dissimilar join.The process characteristics and bonding mechanism were studied based on 304 stainless steel and PA66/PET plastics.The main findings are as follows:First,the influence of different process parameters on the shear strength of 304 stainless steel/PA66 plastic laser oscillating heat conduction joints was investigated based on orthogonal test and analysis of variance.The results show that the joint interface can be divided into three regions:the completely melted zone?CMZ?,the partially melted zone?PMZ?,and the softened zone?SZ?.The area ratio of PMZ to the entire joint is the main factor determining the shear strength of the joint.When the PMZ area ratio increases from35.9%to 52%,the corresponding joint shear strength increases from 2.9 MPa to 7.75 MPa.It has been found that the binding force dominated by C-O-Cr chemical bonds is the main force of interfacial bonding.The relative content of C-O-Cr chemical bonds in PMZ is twice that of CMZ,and therefore has a higher bonding strength.The orthogonal experiment shows that increasing the laser beam oscillation frequency is beneficial to increase the PMZ area ratio,which has the most significant effect on the joint shear strength.The contribution percentage is 63.07%.In addition,the scan radius has the least influence,and the contribution percentage is only 5.49%.Secondly,the process characteristics of 304 stainless steel/PET plastic laser transmission joining were studied.It was found that the joint morphology can be divided into two types:one is that the pores in the center of the joint are significantly larger than the non-uniform joints on both sides;the other is uniform welds with similar pore sizes in each area.On the premise that the laser spot energy distribution is uniform,the energy distribution discipline in a single circular sweep period under different scanning radius is established.It is found that when the scanning radius?r?and the spot radius?r₀?satisfy the relationship of r₀?r?1.25r₀,The weld behaves as a uniform joint.The optimum process parameters of laser scanning transmission joining obtained by the experiment are:laser power 300 W,joining speed 50 cm/min,positive defocusing 20 mm,beam scanning radius 2 mm,oscillation frequency 300 Hz.Under these conditions,the joint is well formed with a shear tensile force of 1036 N,which is 78.1%of the strength of the PET base metal.Finally,the characteristics of 304 stainless steel/PET plastic heat conduction joining and transmission joining process were compared.Porosity formation of heat conduction joining and transmission joining were found to be mainly different.The thermally conductive joint proes is subjected to the pressing force in the up and down direction during the expansion process,and is easily discharged from the gap of the substrate,and the pores in the transmission joint are only subjected to the one-way upward reaction force.The decrease of the porosity of the heat conduction joint is beneficial to increase the effective joint area,and it is easier to form the chemical bond strengthening interface of C-M and C-O-Cr.Therefore,the heat conduction joining shear performance is better than the transmission joining.Under the same process parameters,The shear tension of the 304stainless steel/PET heat conduction joint is 1283 N,reaching 96.7%of the base metal,which the transmission joint is only 1036 N.