Exploratory Research of Reliability Improvement of High-duty Welded Metal Constructions Operated under the Conditions of the North

Introduction. Welding affect fundamentally on the availability of the constructions operated under the low temperatures due to a decrease in resistance to the nucleation and propagation of cracks in the heat-affected zone and weld metal. Despite the existence of a sufficiently large number of ways to improve the reliability of welded joints, some of them have now completely exhausted its capabilities, while others have not been brought to the stage of wide practical application. Therefore, the development of the necessary special welding technology in low temperature conditions remains an urgent problem. The purpose of the work: to find the ways to improve the reliability of high-duty metal constructions welded at low temperatures. The welded joints of 09G2S steel obtained by welding with direct current and pulsed low-frequency current modulation under conditions of positive (+ 20 °C) and negative (-45 °C) ambient air temperatures are investigated using three new types of welding electrodes. The methods of investigation. Mechanical tests for static tension and impact bending of welded samples, as well as spectral analysis of the chemical composition and metallurgical studies of weld metal are undertaken. Results and Discussion. It is revealed that the metal constructions operational factors depend on the choice of the welding method and welding temperature, as well as the characteristics of the welding material. It is established that to increase the impact strength of samples welded at negative temperatures by the adaptive pulse-arc welding method, an increase in heat input is required, relative to the rat of energy input, realized in the process of welding at positive temperature. The effect of the weld metal structure refinement using adaptive pulse-arc welding with coated electrodes is confirmed, including in conditions of negative ambient air temperature (down to 45 °С below zero). The presented results confirm the prospects of the developed approach aimed at obtaining new classes of materials and products, intended for operation in the conditions of the North and the Arctic.

welded joints, weld metal, pulse-arc welding, coated electrodes, low climatic temperatures, mechanical properties, structure, impact strength, rat of energy input