Study On Constrained Arc Welding System With Flux Strips And Its Parameters Setting For Grooved Rails

In the high-speed development of seamless railway,the grooved rail plays a vital role in the railway switches,the bridges and the urban railway system in that the manner,quality and efficiency of the rail connection have become the important factors that will directly affect the train’s running safety,the passengers’ experience,the urban infrastructure construction and the enterprise’s benefits.In this sense,it is of great significance to the entire railway construction.Considering the connection quality of the rail joints will limit the application of grooved rails,in order to ensure the qualit y of such joints,reliable connection method and connecting equipment are the necessities.Regarding the technical requirements of a large-size domestic railway enterprise,for the connection of grooved rails of different materials and different sections,the existing methods of welding are trapped in such problems of high heat input,high metal filling in the groove and great influence on the rail material performance,this paper thus probed into the seamless welding technology and the automatic welding equipment by applying the ultra-narrow gap welding with constrained arc by flux strips to the seamless welding of grooved rails,in hope of achieving high quality welding of grooved rails with low linear energy.The main research contents are as follows:(1)In view of the “special-shaped” structure and the discontinuous characteristics of the cross section of grooved rails,in order to form a continuous groove,avoid relative displacement of butting during welding and guarantee the welding quality,a specialized fixture and the forced molding block suitable for welding grooved rails are then designed with the welding gun’s shape,insulation and conductivity improved at the meantime.Thus the welding gun featuring more compact structure,lighter weight,quicker installation,better insulation and conductivity can reduce the possibility of scratches during welding,enabling the welding gun to progress more smoothly in the groove and finally improving the welding efficiency.(2)As the ultra-narrow gap welding with constrained arc by flux strips demands automatic operation,an ultra-narrow gap automatic welding system with constrained arc by flux strips for grooved rails was then designed,including the wielding power,the welding carriage and the control system etc.Meanwhile,the digital control scheme covering the preset voltage,the preset current and the welding speed was designed to enable this automation system to control the system parameters and weld the grooved rails according to different groove widths and the process requirements at different welding stages.(3)The automatic platform for ultra-narrow gap welding with constrained arc by flux strips targeting groove rails firstly improved the preparation process of flux strips so as to increase the welding quality,making it more suitable for the welding of overload gap of grooved rails;then the signal acquisition and the analysis system were designed to record and analyze the real-time data during welding;afterwards,the waveform changes of welding speed,arc voltage and welding current that may affect the welding quality of groove rails were analyzed and summarized through experiments,thus establishing the process parameter models matching with different groove widths,which has laid down foundation for seeking the optimal welding parameters;finally,the welding process parameters suitable for different groove widths and the process requirements at different welding stages were set through analysis of the welding experimental data,thus realizing the single-pass continuous and multi-layer welding of the grooved rails characterized by discontinuous grooves.