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During designing and manufacture of aircraft structures from modern thermomechanically strengthened aluminium alloys, there is a problem of producing welded joints with satisfactory mechanical properties without post heat treatment of large-sized products. In the work the formation of joints of thermomechanically strengthened 2219-T87 alloy during flash butt welding was investigated. It was found that a low-temperature resistance heating in combination with a shortterm heating by flashing provide the formation of defect-free welded joints. Metallographic examinations showed that joints are formed through a thin layer of melt, which is a necessary condition for a high-quality welding of aluminium alloys. The influence of intense plastic deformation during upsetting with a forced formation on the morphology of θ-phase (CuAl2) particles was studied. A decrease in the values of hardness in the joint area as a result of dissolution and coagulation of a strengthening θ'-phase was established. The strength of welded joints both along and across the rolled metal lines amounts to 76 % of the strength of the base metal. 20 Ref., 2 Tables, 7 Figures. [ABSTRACT FROM AUTHOR]

The article presents a study of the accuracy of reproduction of parameters of operational control of flash butt welding of railway rails in order to increase the reliability of evaluating the compliance of the process to the Technical Specifications (TS) and improve the quality of welded joints. For the statistical analysis of protocols of welding rails at rail-welding enterprises the review of existing indices of accuracy and stability of technological processes was made. For the analysis, the coefficient of variation Kv was chosen, which is not related to the tolerance of the deviation of the process parameter. Evaluations of Kv coefficients according to the welding protocols of more than 10 thou joints and more than 100 specimens of a technological test for the stationary machine K1000 showed that the mode parameters set directly by the control system, are reproduced with an error of not more than 1.5 %. The Kv coefficients increase sharply for the rate of flashing, transition from flashing to upsetting and particularly upsetting, which are included in the TS for welding rails and an active electric power, that occurred during flashing at the input of the welding transformer. The studies of Kv coefficients with grouping of welding data by six months showed that the variation of process parameters had no trends and the process was stable over time with a sufficient accuracy. The mean values and the standard deviation of the parameters of the process of welding rails and specimens of a technological test differ within the statistical error, which indicates the possibility of approximating the results of test studies on the rail joints. Evaluation of effect of parameters of the process of rate, tolerance and energy of flashing on the heat-affected zone (HAZ) with the use of linear regression dependence showed an essential dependence of HAZ on variation of electric energy during flashing. For control of active energy, the measuring converter of average active electric power with a pulse output was developed, which is adapted to the control systems of K1000 and K922 machines with input signals of current to 1000 A and voltage to 440 V, a frequency band of these signals to 1 kHz and the resulted error of measurement to 1 %. It is recommended to include active electric power released during flashing at the input of the welding transformer in the list of control parameters to the TS, and to improve the quality of joints not only to control the parameters within tolerance, but to create the conditions of the smallest variation of parameters from obtained data. [ABSTRACT FROM AUTHOR]

Replacement of outdated technologies in the production of tubular parts is an urgent task. The paper presents the materials of carried out investigations on press welding of high-loaded steel tubular parts with a diameter of up to 120 mm and wall thickness of up to 6 mm, development of control system, metallographic and mechanical examinations on determination of the properties of welded joints. The main technological advantages of press welding of high-loaded products are shown. 7 Ref., 3 Tables, 6 Figures. [ABSTRACT FROM AUTHOR]

In most heavy-duty railways of Ukraine, flash-butt welding is the dominant process for joining rails. Welding is performed in special shops and in field conditions during the construction of new main lines and repair of existing railways. Technologies and equipment are constantly being improved in connection with the use in the railways of Ukraine and other countries of the world, of new generations of high-strength rails with an increased wear resistance, in accordance with the requirements to high-speed main lines. In the last decade, the developed countries of the world are revising the basic standards governing the quality of rail steels and requirements to mechanical properties of rail welded joints, taking into account their use on heavy-duty and high-speed main lines. One of the specified tasks is the adaptation of the Ukrainian standard TU U 24.1-40075815-002: 2016 (for stationary and mobile welding machines), which determines the requirements to the quality of welded joints of high-strength rails, to the valid European standard EN 14587-1 2007 (for stationary welding machines) and EN 14587-2 2009 (for mobile welding machines). 9 Ref., 4 Tables, 12 Figures. [ABSTRACT FROM AUTHOR]

The technical requirements to the basic elements of the control system are determined. The structural design of the control system is described. The influence of the process parameters of press welding using magnetically-impelled arc on the quality of the produced joints is investigated. The limits of fluctuations of values of the parameters and their in- fluence on quality of the produced joint are determined. The software of the system for evaluation of quality of welded joints is developed. 7 Ref., 6 Figures. [ABSTRACT FROM AUTHOR]

Materials for carrying out works in the framework of investigating weldability of parts of hydraulic cylinders with diameters from 40 to 200 m and a wall thickness of up to 10 mm, the results of performed metallographic examinations and mechanical properties of welded joints are presented. The basic conditions for forming welded joints of tubular parts of hydraulic cylinders were determined. The process of press magnetically-impelled arc welding of pipes of hydraulic cylinders with a diameter of up to 200 mm and a wall thickness of up to 10 mm was developed. 8 Ref., 4 Tables, 16 Figures. [ABSTRACT FROM AUTHOR]