The Research Of Coupled Arc Aa-tig Welding

The A-TIG welding has some disadvantages of complex coating process, long development time for different kinds of surfactant types and uneasy control of amount of active flux although it has achieved great developmen. A novel type of activating TIG welding was proposed by changing the way of introducing surfactant to the weld pool.Recently, the research of the A-TIG welding shows that change of temperature coefficient of surface tension on the surface of weld pool is the main mechanism for the increase of weld penetration for mild steel, stainless steel due to the presence of the oxygen and other active elements.Coupled arc AA-TIG welding was proposed on the basis of Arc assisted Activating TIG Welding, namely as AA-TIG welding. In order to change traditional way of adding the active elements into the weld pool, assisting arc with Ar+CO2 mixed shielding gas was used. CO2 will contact with liquid on the surface of welding pool in the the oxidizing atmosphere and a thin oxide film will appear on the surface of the pool in place of traditional way of coating activating flux on the surface of base metal. Coupled arc is a new arc form formed by the interaction of the two arcs putted in a near distance. Two welding torches were assembed very near to each other according to certain parameters to obtain a coupled arc in the AA-TIG welding process forming a weld pool only. The welding method can obtain a significant increase in weld penetration and is a novel activating welding process Suitable for a variety of material.Experiments result show that the content of CO2 gas in mixture shielding gas of auxiliary is an important factor for increasing weld depth. With the best welding parameters, weld penetration depth of coupling arc AA-TIG can significantly increase, which amounts to 1.9times more than that of traditional TIG welding and 1.6 times of the single arc AA-TIG welding. The weld efficiency can obviously be improved.Influence of CO2 gas on AA-TIG weld was studied through analyzing the microstructure and the mechanical performance including tensile properties, corrosion resistance, hardness and impact toughness. Chemical changes as well as tensile fracture morphology of coupled arc AA-TIG welding were analyzed through SEM technique. Experimental results show that weld produced by coupled arc AA-TIG welding is not very different from that of the traditional TIG welding in mechanical properties and chemical composition except an obvious reduce in toughness. Although large increase in the weld depth, Strict control of the content of CO2 gas is very essential to reduce the bad effects of oxygen on the weld toughness.In order to clarify the main mechanism of increasing weld depth, Firstly, the characteristics of the welding arc was studied in arc shape change and arc voltage. Secondly, the form of the oxygen and carbon element in the weld was analyzed by SEM and EPMA technique. The effect of oxygen on the surface tension was also studied. Results proved the former theory that the shrinkage of arc and increase of arc voltage are not the main reason for the weld penetration increase. Active element such as oxygen can change the temperature coefficient of surface tension of weld pool is the main mechanism of increasing AA-TIG welding penetration depth.Coupled arc AA-TIG welding has extensive application.it can adopt different mixture of shielding gases and can be applied to various kind of steel products. The novel welding method can realize full automate bulk production with the advantages of higher efficiency, which is a kind of advanced welding technology for deeper development.