| The magnesium alloy which is perceived and developed broadly domestically and abroad widely is a sort of lightweight material for the moment. It has huge potential applications, and it takes on spacious application prospects in aviation, astronautics, metallurgy, machinery and so on. Welding technology applied in electromagnetic field is the welding technology which is emerging in the last few years. The arc welding of technology in the electromagnetic field affection has obtained fast development. Furthermore, the technology is applied increasingly broadly. The numerical simulation methods as a type of software which bases on finite element method has been created vigorous condition for weld technological development. ANSYS can do disciplinary research including thermal, sound, fluid as well as electromagnetic field and so on. What is more, it can simulate magnetic field configuration, magnetic field intensity, magnetic field force and other coherent parameters accurately. Above all, ANSYS supplies first-phase preparations for welding experiments in external magnetic field, and it achieves that either computer technology or engineering method in modern times can be combined perfectly as well.In this thesis, the GTAW welding of AZ31 magnesium under the double inversion pulse magnetic field is investigated. Through the analogue of magnetic field, studies are taken on the cross and lengthwise proportion of magnetic coil. At last, we find the better magnetic coil which cross extent is 80mm and longitudinal length is 37.5mm. The effects of corrosion resistant plate and iron core to magnetic field being studied, the result indicates magnetic intensity of welding arc zone decreases to some extent, joining iron core increases magnetic density, but makes magnetic field non-homogeneous, moreover, compared with the magnetic field of permanent magnet and electric coil, the former one is more powerful.On stage of the experiment, adjusting the magnetic current and frequency, the hardness test, tension test and SEM are used to the effect of magnetic field on the forming ability, mechanical property and microstructure. The acting mechanism of magnetic field on the solidification process of welded joint is explored. The relationship between the shape, numbers and distribution and mechanical properties of welded joint is discussed. When the magnetic field current fixed, the mechanical properties of welded joint change with the magnetic field frequency, and optimally properties were obtained when I=2A, f=25Hz,σ_b=219.3Mpa,δ=7.42%,ψ=4.34%. The crystal grain of welded joint is refined by intensifying the magnetic-field strength and the electromagnetic stirring increases at the same time. Compared with 1 A, at the time of magnetic currency of 2A, magnesium has better situation in mechanical property, hardness degree and microscopic structure.
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