The aim of the work is experimental verification of possibility of using the thyristor frequency converter with direct connection for 37.5 Hz for power supply of two-phase flash-butt welding machine from threephase mains for its uniform loading. For experimental verification and tests the converter was designed according to the circuit with two three-phase full-wave controlled rectifiers connected in an antiparallel mode. The industrial tests were conducted in welding of steel R65 rails using continuous and pulsating flashing during two years at the rail welding enterprise. It was found that the quality of welded joints met the technical specifications. The analysis of plots of changes of effective values of phase currents showed that difference of these values did not exceed ±2 %. At the same time the phase currents were 20 % lower than the current at the load. Thus, the pilot tests of the frequency converter for 37.5 Hz showed its possibility and rationality for application for flash-butt welding, in particular, of railroad rails due to uniform loading of three-phase mains. At that the efficiency of using converter can be significantly increased by applying it in the flash-butt welding machine power transformer, designed for 37.5 Hz. 7 Ref., 3 Figures.
In the recent years the DC sources are widely applied in the equipment for flash-butt welding. At the same time there is a positive experience in AC application in such equipment. The aim of the present work consisted in comparative evaluation of power and technological characteristics of welding processes in using two power sources. The flash-butt welding of low-alloy steel plates of 25 mm thickness using continuous flashing was performed using AC and DC power sources. The influence of high-frequency pulsations of voltage in DC welding on reactance of welding circuit, conductivity of diodes of rectifier and stability of flashing process was studied. The phenomenon of overvoltages as a result of transition processes in welding circuit in flashing was explained. It was shown that at the same heating of specimens the consumption of electric power in DC welding is 15 % higher than at alternating one. The macrorelief of flashing surface in DC welding is better by its quality than that at alternating one. 4 Ref., 1 Table, 10 Figures.
Introduction. Flash-butt welding (FBW) of rails is controlled in real time based on the tolerances of the main process parameters according to the data of specifications. The operational control algorithm enables real-time detection of low quality weld and inadmissible trends in the process. Problem Statement. In addition to the existing method, in order to control the compliance of welding of new high-strength steel rails with the specifications, it is necessary to take into account the width of the heat-affected zone (HAZ). The known numerical methods for calculating the HAZ in real time cannot be implemented because of insufficient computatio¬nal capabilities of modern control systems. Purpose. To develop an algorithm for real-time monitoring of FBW with predicting the width of the HAZ, in compliance with technical specifications. Materials and Methods. A numerical method for calculating thermal fields during flash-butt welding, a regression analysis for HAZ prediction. The HAZ width is calculated based on the process parameters at the burningoff stage and on the upsetting. Results. A real-time algorithm has been developed for controlling FBW of modern high-strength steels with prediction of the HAZ width. The algorithm is based on mathematical modeling of joints formation during flashbutt welding. Conclusions. The regression equation in the form of a second-order polynomial or MLP neural network with a structure of 3 neurons in the input layer-2 neurons in the hidden layer-1 neuron in the output layer can be used for calculating the HAZ width in real time with the required accuracy for practical use. Prediction of the HAZ width during operational control expands the possibilities of its use for resistance butt-welding of high-strength rails. The developed algorithm has increased the accuracy and reliability of operational control of FBW in real time. K e y w o r d s : flash-butt welding, high-strength rails, heat-affected zone, regression model, fuzzy logic, and Sugeno classifier.
Для контактного стикового зварювання рейок із термічно зміцненої сталі проведено дослідження та розроблено режими зварювання і технічні умови на процес. Відповідно до технічних умов розроблена дворівнева система, яка дозволяє підвищити точність контролю та керування процесом зварювання. На нижньому рівні в системі прямого цифрового керування контролем якості зварних з'єднань запропоновано алгоритм на основі «нечіткої» логіки, який враховує розмитість границь припустимих відхилень, розподіл параметрів процесу всередині допуску та взаємний вплив комбінації параметрів на показник якості стику. Контроль технічного стану устаткування здійснюється за даними тестової і функціональної діагностики. Для забезпечення стабільного енерговкладання розроблено обладнання стабілізації напруги на вході зварювального трансформатора при живленні від двофазної електричної мережі та перетворювач частоти і числа фаз для живлення від трифазної мережі. На верхньому рівні в діагностичному центрі Укрзалізниці здійснюється статистична обробка протоколів зварювання рейок, які надходять із підприємств галузі, для виявлення відхилень, які складно проконтролювати прямими вимірами, наприклад, незадовільне виконання допоміжних операцій з підготовки рейок перед зварюванням, відхилення фізико-хімічних властивостей металу рейок, незадовільне дотримання технологічних операцій зварником, незадовільні умови виробництва. Розроблені алгоритми і технічні засоби автоматизації пройшли експериментальну перевірку й можуть бути рекомендовані для подальшого впровадження у виробництво. Бібліогр. 3, табл. 1, рис. 14.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.