K e y w o r d s : gas-shielded arc welding using consumable and non-consumable electrode, dynamic arc, mathematical model, power balance, investigations There are number of dynamic arc models at present time. Therefore, the researchers when solving the specific tasks on investigation of processes in power source-welding arc system face with the problem of selection of a model providing complete description of the main arc peculiarities in each specific case. This paper is dedicated to objective estimation and comparison of models of dynamic arc and elaboration of recommendations for model selection on this basis.Some progress in description of welding arc of constant length (non-consumable electrode) as part of electric circuit was achieved using mathematical model of dynamic arc, developed at the E.O. Paton Electric Welding Institute (PWI-MA) [1]. PWI-MA was further developed in works [2,3]. Arc column in PWI-MA has been phenomenological considered as heat inertial macroobject, for which the following power balance is valid:where Q is the internal energy of arc column; P and P θ is the input and output power, respectively. All isoenergetic identical states in PWI-MA are characterized by one parameter, i.e. arc state current i θ [1,3]. It determines such characteristics of the arc column as static resistanceand output powerwhere U col is the function defining static voltampere characteristic (SVAC) of the arc column. Input power is determined by arc column resistance as well as value of its transitional current:Voltage on the arc column in dynamic is found from expressionState current i θ for any representative point on plane, corresponding to arc column dynamic states in the coordinates of arc column voltage arc current (u col , i), is determined as x-coordinate of cross point of beam from the origin, passing through this point, with arc column SVAC. Work [3] shows that PWI-MA equation in differential form [2] corresponds to energy balance equation (1):which is electroengineering analog of equation (1). At that internal energy of arc column equalswhere θ is the time constant of arc column.Since all other models use such a value as arc column conductivity g [4], PWI-MA equation * Translation of paper from «Avtomaticheskaya Svarka» Journal, 1989, No. 2, pp. 33-36. Monitoring of references to the papers, published in this Journal, showed that paper of I.V. Pentegov and V.N. Sydorets is one of the most cited in area of welding arc modelling. It is dedicated to comparison of dynamic model of arc, being developed at the E.O. Paton Electric Welding Institute, with other models and is still of high interest up to the present moment. Unfortunately, «Avtomaticheskaya Svarka» Journal was not translated in English in 1989. However, current reality of the world scientific community necessitates publications in English. Therefore, the Editorial Board of the Journal has made a decision to publish this paper in «The Paton Welding Journal» in order to make it more accessible to wider audience of researchers, post-graduate st...

Development of new laser-arc heat sources is one of the urgent directions of modern science and engineering in the field of fusion welding of metals. Allowing for their physical features can promote increase of laser-arc welding productivity due to improvement of effective efficiency, i.e. increase of the ratio of power of the heat source applied to the metal in welding to the total power of the electric arc and laser radiation. One of the ways to improve the effective efficiency of welding is reduction of laser energy losses associated with radiation reflection from the surface being welded. The work is a study of the influence of concurrent heating, provided by the electric arc, on the change of the conditions of laser radiation absorption by aluminum alloys in their laser-arc welding. The problem of determination of temperature dependence of the coefficient of laser radiation absorption by aluminum was defined and solved within the model of almost free electrons on the base of studying vapour-gas channel behavior in hybrid welding. Comparison of obtained calculation dependencies of absorption capacity with the available experimental data showed satisfactory agreement. The respective heat conductivity equation was solved, in order to determine such parameters of laser-arc welding mode as arc component power and distance between the arc impact zone and laser beam axis. Experimental verification of the proposed approach to increase of effective efficiency of laser welding, performed on samples of aluminum alloy AMg6, confirmed the validity of the predicted results. 12 Ref., 7 Figures. K e y w o r d s : laser-arc welding, aluminum alloys, CO2-laser radiation, absorption coefficient, welding current, welding speed

Well-grounded selection of optimum modes of non-consumable pulse-arc welding requires investigation of dynamics of pulsed arc burning. Proposed earlier model of nonstationary arc with distributed parameters, due to large computing expenses, allows considering effect on arc of only single current pulse. Whereas, investigation of dynamic characteristics of the arc in supply of batches of high-frequency pulses of welding current is of practical interest. In this connection, it is interesting to develop an arc dynamic model with lumped parameters, which does not have limitations from point of view of amount of computations and allows high accuracy tracing of the dynamics of change of characteristics in arc with refractory cathode at high-frequency current modulation. The same data were received for comparison using calculation method based on the model with distributed parameters. Arc column time constant was determined based on calculation data of dynamics of arc voltage change, received employing the model with distributed parameters. In total complex of carried research and experimental investigations allowed working out an algorithms of application of the model with lumped parameters and identifying them. The results are given on expemental investigations of dynamics of change of current and arc voltage in high-frequency non-consumable pulse-arc welding, which are matched with the results of calculations using the model with lumped parameters. 14 Ref., 1 Table, 8 Figures. K e y w o r d s : pulse-arc welding, non-consumable electrode welding, high-frequency pulses, dynamic characteristics of arc, nonstationary arc, arc column, argon arc, refractory cathode

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