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EN
This paper establishes the trends in structure formation of 4 mm thick 1561 aluminum alloy welded joints, depending on changes in the parameters of the MIG welding mode on a steel substrate (specifically, the speed and heat input of the process). Welding modes were selected based on the criterion of satisfactory seam formation, and the optimal welding mode was determined based on the criteria of minimizing porosity, grain refinement, and improved mechanical properties. Technological studies have shown that, based on the criterion of satisfactory seam formation with a quality level ranging from C to B according to ISO 10042, it is advisable to select a welding speed between 380 and 600 mm/min with a heat input between 217 and 240 J/mm. Metallographic studies have shown that increasing the MIG welding speed promotes weld grain refinement, decreases their shape factor, and simultaneously increases the number of pores while reducing their size. Mechanical tests demonstrated that increasing the welding speed enhances the mechanical properties of welded joints. Therefore, when using MIG welding of aluminum alloys in industry, it is recommended to increase the speed to 600 mm/min and higher.
EN
The paper is devoted to investigation of spectral parameters of constricted arc plasma, as a foundation for further development of basic approaches to intellectual controlling of plasma-arc technologies of material treatment and welding. The relevance of application of spectrometric analysis of the welding arc consists in obtaining the possibility of sufficiently accurate control of its temperature and energy input into the product being welded, recording initiation of weld defects (including internal pores), determination of atmospheric oxygen ingress into the weld pool, etc. The spectral composition, temperature and concentration of the constricted welding arc plasma were determined in the paper to more precisely define its physical characteristics at 80 and 100 A currents, in order to establish the further applicability of dynamic spectral analysis of a constricted plasma arc in control of welding processes. As modern spectrometers with CCD-detectors of the spectral range of 200÷1100 nm have the resolution of the order of 0.35 nm, which 2-3 times exceeds the quantization step by the measured wavelength, and may lead to considerable errors, an approach is proposed to increase the accuracy of spectrometric measurements to acceptable values. Radiation spectra of the constricted welding arc measured in the wavelength range of 650÷1000 nm allowed within the model of local thermodynamic equilibrium calculating the excitation temperature of the main spectral range components: Ar I and O I. It was established that the excitation temperature of electron levels of Ar atoms in the welding arc plasma only weakly depends on the discharge current, and it is equal to 13500 ± 500 K. Excitation temperature of O I electron levels was equal to 10000 ± 500 К at arc current of 100 A and to 7200 ± 500 К at 80 A current. Electron density of high-current welding arc plasma was measured by Stark broadening of Ar I lines (696.543; 772.4; 912.3 nm). It was found that with the rise of current of the constricted welding arc by 20%, an increase of charge concentration in the arc plasma by 1.5 times and of its temperature by 1.2 times are observed.
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