| Inert gas shielded tungsten arc welding（TIG welding for short）,as an important weldingtechnology, has stable welding arc without any spatter and high quality which is in commonuse on kinds of metal connection. It belongs to gas metal arc welding, but the low welding arcenergy concentration makes low welding penetration (usually used only in thin plates welding)and and the low welding efficiency, which has not yet been satisfactorily resolved. Weldingworkers made many improvements, such as active flux TIG welding, hot wire TIG welding,ultrasonic frequency TIG welding and so on, but they have respective limitations. For example,the pollution problems of active flux TIG welding, hot wire TIG welding can’t be used incopper or aluminum wire, the welding current of ultrasonic frequency TIG welding is smallwith high device cost. Under the basis of many documents and large numbers of experiments,in this paper, the characteristics of TIG welding arc was analyzed, then imposed externalhigh-frequency longitudinal magnetic field on welding arc to produce “pinch effects”, whichcombined with high frequency current welding equipment could improve the welding arcenergy and increase welding penetration as an innovative processes. This technology withadditional device has low cost, small size, convenient use and can improve arc shape and arcbehavior. The paper around this new technology contains following works:The paper developed a electricity magnetism double-pulsed TIG welding controlequipment with electrical and magnetic pulse work together in range of adjustable parameters.The basic parameters as following: welding current:0~500A;welding current frequency:0~500Hz；magnetizing current adjustment range:0~15A; frequency of exciting current0~8kHz; duty ratio:50％,which has the function of direct and alternating square-wave output,equipped with a TIG welding torch head structure.A high-speed camera was used to obtain the changes of arc shape under the control ofhigh frequency electric pulse and magnetic pulse.A spectra measurement was used to measurearc temperature under high-frequency electro-magnetic pulse. Homemade ring concentriccracking device was used to measure arc heat distribution under high-frequencyelectro-magnetic pulse and the probe method was used to measure arc current density radialdistribution under high-frequency electro-magnetic pulse. Experimental results showed thatarc turning radius significantly reduced under high frequency Magnetic pulse, the arc shape changed from the cone-shaped to compressed columnar, the arc was compressed more withinhigh frequency current pulse. When the effective welding current was80A, current pulsefrequency was500Hz, the magnetic flux density was30mT, magnetic pulse frequency was1500Hz, arc temperature raised from13402.21K in free arc up to14958.3K, heat distributioncoefficient increased from39.52%to66.07%, the arc current pressure and density wereunimodal distributions, central pressure increased from0.35KPa to0.54KPa, current densityincreased from20A/mm2to30.9A/mm2.The welding experimental results under the effect of high-frequency electric andmagnetic double pulse showed that, the weld formation was well under high frequencyelectro-magnetic pulse, when melt width decreased, penetration increased significantly, andthe greater of current pulse frequency, the greater of the effect, and there was an optimumrange of parameters of magnetic field.It was the first time to analysis TIG welding arc behavior under high frequencyelectro-magnetic pulse, using a three dimensional mathematical model calculate arctemperature field and flow field distribution under vertical magnetic field. Then thecompressed arc mathematical model of high frequency magnetic field was constructed tosystemly explain arc air pressure variation law under high frequency magnetic field(from acircle bimodal distribution to a column-shaped distribution),and provided new research ideason TIG welding process within high-frequency electric and magnetic fields. |
