: 3-15
Lviv Polytechnic National University
Lviv Polytechnic National University
Lviv Polytechnic National University

Purpose. It consists in the design and technological optimization of the spot condenser welding process of planar elements from AMG-6 alloy with a thickness of 400 microns. Relevance. The need for scientific and applied research is due to the requirements for reducing the mass-dimensional parameters of welded products of precision instrument-making based on aluminum alloys of small thickness with the simultaneous strict requirement to preserve their performance indicators. This can be solved by switching to welding with capacitor energy dispensers, created on the basis of a deep modernization of the electrical part of the existing serial equipment for contact micro-welding with an AC pulse. The latter requires, besides the design study, also the study of the technological aspects of spot-capacitor welding, especially when the number of adjustable parameters of the welding mode is limited. The loss of control flexibility requires the selection of a reasonable criterion for assessing the quality of welding and the basic parameter to describe the formation of a high-quality weld point. It unambiguously allows the machine parameters to be matched with current indicators of the welding process (current, current form, welding time) for a given electrode compression force. The technique. Justification of the choice of the method of destructive testing of welded joints for assessing the quality of external indicators of the welded zone of the product Statistical analysis of the impact of the original indicators of welded parts. The choice of the basic parameter for evaluating the process of forming a high-quality welded joint is the rigidity of the regime. The calculation of the thermal state of the welding zone according to the standard model and the linear model of the heat removal to the electrodes, which allows to determine the indicators of the shape of the current pulse and their temporal distribution. Determination of the parameters of the mode of such indicators and electrical structural elements of the upgraded equipment. Experimental optimization of the combination of machine parameters to ensure the quality of welding. Analysis of models of the influence of mode parameters on the quality parameters of a welded joint. Selection of the most effective parameters that meet the requirements for a welded joint and defect-free (no splash) welding. Results. 1. The main destabilizing factors determining the initial welding conditions are the condition of the surface films on the parts. The latter can be estimated through the scatter of microhardness (HB = 79.9 16.74 kg / mm2; scatter of 21%) and the contact resistance R0 = 18.6 13.8 mΩ; scatter ± 67%; 2. The basic parameter of optimization of the welding mode is the stiffness criterion, which allows you to set the welding time = 6ms; 3. Using the standard model of the thermal state of the welding zone and the linear model of the formation of a welded core of given geometric dimensions with the prevailing heat output to the electrode mass allows calculating the energy state of the welding zone and current mode parameters (peak value of current I = 2600), as well as determining the current pulse geometry ; 4. Using the current mode parameters and similarity criteria typical for discharging capacitances to unbranched circuits, it is possible to determine the limiting values of the mode parameters (50≤Cp≤300mkF, 50≤ ≤300) and check the suitability of the structural elements of the discharge circuit of the upgraded equipment to ensure a given shape welding current parameters; 5. Submission of product quality assessment responses through the joint solution of a pair of mode parameter changes allows limiting the area of experimental search for their optimal values with a constructively imposed condition that the charging voltage remains constant over the whole range of variation of the transformation ratio and the value of the charging capacity; 6. The most influential and unambiguous direction in assessing the quality of a welded joint is the transformation ratio and the compression force of the electrodes. The latter is desirable to fix unchanged due to the impact on the initial conditions of the welding zone; 7. The size of the charging capacity has a sharply pronounced optimum, which does not allow its effective use as a regulating parameter in this design solution of the charging part of the electrical circuit of the machine; 8. There is a statistically significant correlation between the baseline indicator of the strength of a welded joint — the diameter of the cast core and the rotation angle φ0 of welded plates of parts during random torsion tests with destruction, which allows one to limit the quality assessment to one parameter that does not require additional technological operations to identify and determine characteristics welded core. Scientific novelty. It is proved that a sufficient and necessary condition for optimizing the welding mode is to establish an indicator of its rigidity. Practical significance. Simplify the calculation of welding modes and ensure, under other equal conditions, its quality indicators on the upgraded equipment.

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