The Hot Characteristic Of Narrow Gap Welding With The Arc Constricted By Flux Strips

Ultra-narrow gap welding is widely regarded as an important technology 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, many scientists invent many ways to solve this problem such as arc oscillation and arc circumrotation. But the complexity of these methods constrained the practicality of these methods applied in industry productivity. The thesis searched a new way to realize the ultra-narrow gap welding by using the gap of 5 mm, the flux strips that made of special aggregates are put into arc zone through the gap sidewalls. Flux strips can constrain arc to prevent it from going upside, and control the heating zone effectively to ensure good fusion of the sidewalls.The UNGW of constricting arc with flux strips(UNGWFS) is brought forward, which is based on the principle of flux bands constricting arc. The corresponding welding torch of UNGW has been designed and improved, the technology of making flux strip with silica sol has been developed by a series of experimrnts, accordingly, all of this have established a foundation for the next study of the UNGW with flux strips constricting arc.Adopting surfacing welding on the plate and adjusting welding parameters to photograph the arc and measure action length of arc and flux strip(ACL), by which analysis the effect of arc heating flux strip and the change of ACL. Thereby, theoretic gist can be provided to be convenient for understanding the mechanism of flux strips constricting arc.The flux strips constricting arc is applied in UNGW. The results shows that welds with good fusion on sidewalls can be achieved with flux strips constricting arc. Positional conditions of flux strips in the arc zone that can ensure to constrict arc effectively have been obtained, by analyzing the influence of position of flux strips in the arc zone on constricting arc. Otherwise, the matching range of voltage and velocity of feeding flux strips has also been gained. At the same time, the experiment shows that short circuiting transfer mode is the proper transfer mode of drop, and the proper range of voltage and current in UNGWFS is 20-24V and 220-270A. At last, the heating characteristic of flux strips constricting arc in UNGW is studied by analyzing the influence of welding parameters such as voltage, current and velocity of feeding flux strips on the cross sectional sizes of welds. Correlation between position of flux strip in its constricting arc and potential of flux strip has been analyzed by collecting the waveforms of flux strip and voltage. At the same time, the transfer modes of melted flux strips have been also analyzed. Furthermore, the waveforms of flux strip with good constriction and lack constriction have been analysed contrastively.