Babych O. Hybrid plasma-arc welding with the coaxial placement of the arc of the fusible electrode.

The paper addresses the current scientific and technical challenge of creating technological methods and equipment for hybrid plasma-arc welding steels and aluminum alloys to increase the mechanical characteristics of the obtained joints while simultaneously reducing costs by means of reducing heat input and maintaining the content of alloying elements in the seams by combining the calculated approach with experimental studies. Based on the analysis of the current state of hybrid Plasma-MIG welding, it is shown that the presence of plasma arc leads to uniform distribution of the arc with a melting electrode over the entire surface of the droplet, which is formed during mass transfer, reducing current density on its surface and significantly reducing of the temperature of the droplet surface and, as a consequence, reducing the burnout of low-melting alloying elements of the electrode wire. It is established that the influence of the arc with a fusible electrode on the plasma arc of positive electrode polarity in combination with the modification of the gas dynamics of the plasma-forming gas creates conditions for cyclic movement of the anode spot along the working end of the annular nonfusible electrode, which increases its service life. It was established, that at hybrid plasma-arc welding of steels such as Q235, AISI304 and aluminum alloys AMg6, 1561, 5083, 7075 thickness up to 10 mm with speeds of 15-60 m/h heat input (plasma+MIG) is (450...750)+(250...750) kJ/mm, which allows to minimize the burning of light alloying elements and ensure the strength of the compounds of aluminum alloys at the level of 85-95% and their relative elongation to 80% of the parameters of the base metal in combination with the residual deformations are up to 20- 40% less than those for MIG welding and residual stresses at the level of such for MIG welding. In order to improve mechanical properties while increasing the cost-effectiveness of obtaining welded joints of complex alloyed aluminum alloys, technological techniques of hybrid plasma arc welding have been created, which allow to reduce the heat input up to 40% in comparison with the MIG process and minimize the burning effect of such alloying elements as Mg (≤5%), Mn (≤15%). A mathematical model was developed. It allows to predict the dynamics of the melting of the electrode wire in the presence of the surrounding plasma arc and to determine the influence of the MIG arc on the volt-ampere characteristics of the plasma arc. Developed, manufactured, and implemented in the Guangdong Welding Institute (Guangzhou, China), as well as in the Welding Joint Stock Company "HUAHENG" (Kunshan, Jiangsu Province, China) a set of equipment for hybrid Plasma-MIG welding. Using this set of equipment a batch of elements of ship structures was manufactured which made of aluminum alloys 1561 and 7075 with a thickness of 5-8 mm and steels up to 12 mm thick in one pass without the development of edges.