Numerical Simulation And Experimental Research Of Laser Sealing Vacuum Flat Glass

Vacuum glazing has the characteristics of low heat transfer coefficient,high anti-condensation factor,high sound insulation performance,long life and light structure.It has become an important energy-saving insulation material in construction,agriculture and other fields such as solar water heaters,holding cabinets and so on,and the reliable edge sealing of vacuum glazing is the first and necessary prerequisite for its successful application.The traditional method of heating furnace edge-sealing takes a long time,consumes a large amount of energy,has poor adaptability to glass size,and can not meet the dependence of vacuum glazing on tempering,limits the development of vacuum glazing industrialization,and seeks a "no heating furnace"sealing technology has become a frontier research hotspot in this field.Laser welding has the advantages of good connection quality,high degree of automation,environmental protection and cleanliness,high economic efficiency,etc.,which can effectively compensate for the shortage of heating furnace edge sealing technology.Therefore,this paper uses a combination of theory-simulation-experimental method to systematically study the mechanism of laser sealing vacuum glazing.Firstly,according to the theory of laser welding heat transfer and thermoelastic theory,the vacuum heat transfer process,temperature distribution and thermal stress distribution of vacuum glaszing are analyzed to find out the key process parameters affecting laser sealing quality;vacuum slab is established by ANSYS.The three-dimensional finite element model of glass was used to study the influence of laser average power and welding speed on the temperature field and thermal stress field of the welding process.The average temperature of the laser sealing and the ultimate stress of the glass are used as indicators to obtain the average laser power.The range of variation is 45?75W,and the welding speed varies from 1 to 2mm/s.Secondly,the type of PbO-TiO2-SiO2-RxOy glass solder and ordinary nano-calcium glass with high transparency are selected as the main materials for welding.Due to different material properties,it is necessary to consider the thermal expansion coefficient matching between materials.The thermal expansion coefficient of the solder measured by the thermal expansion analyzer is 9.1×10-6K-1,which is similar to the thermal expansion coefficient of ordinary soda lime glass(CTE:9?10×10-6K-1),which satisfies the matching sealing requirements of solder and glass.The sealing is essentially a surface wetting problem.Therefore,the wettability study of solder and glass was carried out before the welding experiment.The influence of heating temperature on the macroscopic morphology and wetting angle of the wet sample was analyzed,and the solder was determined.The liquidus temperature is 450?,and the sealing temperature is 475 to 510?.Finally,the pulse current,pulse width,pulse frequency and welding speed are selected as the main research parameters.The laser sealing process parameters are designed according to the numerical simulation results,and the laser sealing vacuum glazing process experiment is carried out to study the various parameters of the process.The influence of parameters on the micro-morphology and mechanical properties of the edge seal are studied.The results show that at the interface of the welded joint,the interface between the sealing layer and the glass substrate is clear,the bonding is tight,and the joint interface is good.The joint is mainly composed of a molten layer,an interface reactive wetting layer with a certain thickness and continuously distributed outside the sealing layer.And the glass matrix composition;appropriately increasing the pulse current helps to improve the micro-morphology of the sealing layer and improve the mechanical properties.Excessive pulse width will cause "spheroidization" of the molten layer,and cracks will occur in the sealing layer.If the pulse frequency is too low,the pores of the sealing layer will increase,but too high a pulse frequency will cause cracks in the sealing layer.Too low welding speed will cause the solder to burn and generate a large number of connected cracks in the sealing layer,.Too high welding speed will cause the solder to melt unevenly and the sealing layer pores will increase;When the pulse current I=160A,pulse width r=2ms,pulse frequency f=18Hz,welding speed v=90mm/min,the molten layer The morphology is good,the porosity of the sealing layer is low,the thickness of the interface reactive layer is large,the mechanical properties are good.The quality of the sealing layer is an optimal set of process parameters.