Study On The Magnetic Control Mechanism Of High Deposition Rates MAG Process

As the competition among welding products has become tougher and harder in the international market, it is the predominant way to increase the competitiveness of welding products by raising productivity and cuffing costs. The simplest way to meet the demand of competition of welding products is to enhance the wire deposition rates. The T.I.M.E. process, since it arose, has become one of the research focuses due to its excellent performances. The high deposition rates MAG process with nonhelium or less helium in the shielding-gas mixture are developed to avoid paying for its patent, reduce the costs of shielding-gas mixture and make the process popular. It is very difficult to acquire stable metal transfer mode in the region of high continuous current with non-helium or less helium in the shielding-gas mixture. Therefore, the welding current is limited and so is the deposition rates.Wire deposition rates consist of wire molten rates and deposition efficiency. Wire molten rates means the molten metal mass per unit time, and deposition efficiency is the ratio of deposition metal to molten metal mass. It can be done to enhance deposition rates in two ways. One is raising wire molten rates, which means melting more wire per unit time, the most common method of which is to increase welding current. The other is raising deposition efficiency, which means that the droplets are transferred into the molten pool stablely, other than lost as spatter, in simple terms, kept a stable metal transfer mode. Therefore, the most useful way to enhance deposition rates is to keep a stable metal transfer mode in the region of high continuous current.The influencing factors of wire molten rates are studied, and the critical current of rotating spray transfer mode is also studied by using high-speed motion analyzer. The results shows that the percentage of each component in the mixture has hardly effect on wire molten rates. It is the key to realizing high deposition rates MAG process with non-helium in shielding-gas mixture to acquire stable metal transfer mode in the region of high continuous current.On the basis of experimental results above and the interactivity between arc plasma and magnetic field, the way to control the metal transfer by controlling arc shape with additional magnetic field is first presented, and the stable rotating spray transfer mode without helium in shielding-gas mixture in the region of high continuous current is finally acquired.The stable state and dynamic models of magnetic control arc are established.ILJ~ it~眫4~~IIIUMAG LI~The magnetic control mechanism of arc motion and the motion of magnetic control arc are stated in detail. And the concept of preliminary stable state is given. The stable state of magnetic control arc relates to magnetic field shape but does not to magnetic induction, while the preliminary stable state relates to them all. The energy supplied by power source comes down to the lowest when the arc system comes to stable state. The kinetic energy of arc column is supplied by power source other than the additional magnetic field.According to FEA, the additional magnetic field shape is subjected to the shape of excitation coil and the distance between the coil and the pieces. The magnetic field shape and magnetic induction can be changed simultaneously by adjusting the distance between the coil and the pieces.On the basis of theory analysis and experimental results, the stable rotating spray transfer mode in the range of high continuous current is implemented by using additional magnetic field control instead of helium in shielding-gas mixture. The stabilization of metal transfer in the range of high continuous current is solved, and the high deposition rates MAG process without helium in shielding-gas mixture is realized.