The Characteristic Of TIG Arc And The Application Of Ultra-narrow Gap Welding Technology With Constricted TIG Arc By Two Pieces Of Solid

The ultra-narrow-gap welding is a high efficient welding technology in which I groove is used, because of its advantages such as high productivity and lower welding distortion. The key technology of Ultra-narrow gap welding is the problem of the sidewalls fusion. At present, arc oscillation and arc rotation are adopted to solve the problem of fusion of the sidewalls, but these methods make the control process of welding and equipments more complex. Thus, the application of the ultra-narrow-gap welding is limited in many fields.The author designed a new TIG welding torch for ultra-narrow welding with flux strips constraining arc. Adopting rotary torch that installs two ceramic pieces on two sides of tungsten electrode on submerged arc welding equipment, avoiding the arc climbing up from the narrow gap bottom, avoiding the occurrence of plasm between sidewall and tungsten electrode, which can effectively control the heating zone of arc, thus it can solving the problem of fusion of the sidewalls. For the first time,introducing shielding gas to make the ceramic pieces wheeling and protecting the welding gap from three directions.the appropriate gas flow can be made sure. The author studies arc morphology and heating characteristic of arc under different constricting conditions by observing arc morphology and masuring the sizs of ultra-narrow gap welds. In addition, the effect of arc heating base metal also has been studied with rotary ceramic. To obtain matched parameters and fusion of the sidewalls in ultra-narrow gap welding, the author analyzes width of melting and depth of melting that is influenced by welding parameters, for voltage,current and so on. So ultra-narrow-gap welding technology could be carry out under 6mm. The experiment determined the current distributing disciplinarian by adopting anode in flat. At the same time, Moving electrostatic probe made of copper wire was developed to be used for diagnosis of TIG arc. The potentials of the arc column for various probe positions were measured with low perturbation. In basis of the mechanism of interaction between electrostatic probe and plasma, the characteristics of probe potential waveform in plasma were explained. The main result of this work is that when the electrostatic probe locates the center area of arc, it alternately contacts with current carrying plasma and non-current-carrying plasma, thereby the potential on it changes between negative and zero. Oscillating current-carrying channel model of TIG arc was present in this paper. In an inner arc region, current carrying channels connecting the cathode spots and anode spots oscillate with the frequency of hundreds Hz to form the higher temperature region of the arc, and the current carrying channels carry all arc current. In the outer region where the current carrying channels do not reach, there is a negative ion region with the lower temperature.