Problems of weld overlay of seating surfaces of pipe fitting and solutions

Abstract

Introduction. A problem of providing the necessary functions of pipe fitting for blockage, control, distribution of the working medium flows under the most adverse operating conditions of oil and gas pipelines associated with abrasive particles, mechanical impurities, hydrogen sulfide, carbon dioxide and organic acids with sulfate-reducing bacteria, is considered.Materials and Methods. High performance properties of seating surfaces of pipe fittings are provided through anticorrosive plating of alloyed and high-alloyed metals based on iron with the addition of chromium, nickel, cobalt and niobium. The basic weld overlay methods are analyzed: metalarc welding, nonconsumable and consumable-electrode weld facing in shielding gases, submerged arc surfacing. Advantages and disadvantages of surfacing methods implemented in recent years are noted: laser, plasma-powder and plasma-arc methods.Research Results. Taking into account the automation capabilities, a high-tech process of robotic anticorrosive surfacing using a consumable electrode with an additional filler metal feed to the front welding puddle for shielding the thermal effect of the arc, is proposed. Industrial application of the proposed technology requires a set of studies related to assessing the effect of technological parameters on the quality of the deposited layers to provide the required operational characteristics of the fitting.Discussion and Conclusion. It is proposed to carry out the above studies using physical and mathematical modeling of the anticorrosive surfacing, which reduces the time and number of experiments. Therefore, the primary task is to develop a mathematical model of the surfacing process with a consumable electrode with an additional filler wire and transverse vibrations of the welding burner. Such a model should virtually reproduce the surfacing process, as well as its thermal cycle followed by calculating the ratio of the structural components of the deposited metal and the substrate metal. The system of equations of the model should be solved by a special computer program. The algorithm presented for solving this class of problems will allow us to make a sound connection of the technological parameters of the surfacing process and the quality parameters of the formation of the deposited layers, to determine the program for their optimization to provide the required operational properties of pipeline fitting.