| TIG short for tungsten inert gas shielded arc welding is one of the commonly used welding processes at present,which has been widely used in aerospace,petrochemical and other fields that weld quality was higher,because of its stable arc,no splash,good weld forming,good mechanics performance characteristics.However the problems of low energy density and low production efficiency exists simultaneously.At this point,scholars at home and abroad have reformed and innovated on the basis of traditional TIG,for instance,active agent TIG,hot wire TIG,ultrasonic TIG and so on and so forth.Based on the previous experiments and reading a large number of literature,the dissertation analyzed the arc characteristics and the results showed that the magnetic field can constrain the energy density of the arc and achieve high efficiency,thus further research on the external magnetic field of TIG welding was carried out.The dissertation focused on the following aspects of the research experiment.Coordinate with the magnetic head structure,the dissertation put forward a high-low frequency pulse magnetic field generator with independent research and development.The basic parameters as following:the rated voltage of the device:220V;frequency of exciting current:0-10KHz;welding current:5-200A;the rated output current:10A;the duty ratio is50%,which has the output function of DC and alternating square wave and equipped with the magnetic head structure matching the TIG welding torch.The inverter TIG welding machine was used as welding power source.The structure of the self developed magnetic head and welding gun was installed on the test stand stably.The high and low frequency magnetic field was generated by the self designed high frequency and low frequency pulsed magnetic field generator.Magnetic pulse frequency from1KHz-10KHz was tested separately.After finding the magnetic pulse frequency with obvious effect,the group test was carried out.FASTCAN Mini UX50 high-speed camera was adopted to shoot arc images.The measurement of arc heat distribution coefficient by concentric anode device with upper and lower cavity.HR200+CG-UV-NIR multi-channel high resolution transient spectral diagnostic instrument was used to measure arc temperature.Probe method was used to measure the arc current density.The pressure sensor was used to measure the arc pressure continuously.The arc shapes were observed and the weld depth,the weld width and the residual height were measured.By preparing the specimen,the shape of the weld was observed and the weld depth and width of the weld were measured.Experimental results show that,the rotating arc was compressed from the bell type to the cylinder,when the welding magnetic field parameters were 70A,30mT and 1.5KHz,the voltaic arc was compressed at its best.Arc pressure at the center increased from 0.32KPa to0.45KPa;the heat distribution coefficient increased from 38.79%to 50.78%;the current density increased from 17.87A/mm~2 to 49.80A/mm~2;the highest arc temperature was14072.86K;while the magnetic field makes good weld forming,the penetration depth was increased from 1.36mm to 1.98mm,the weld width decreased from 4.22mm to 4.08mm,the depth to width ratio was significantly increased.And when the frequency was up to 2KHz,the effect of the arc compression was weak. |
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