Research On Ultrasonic Test Of Aluminum Heat Weiding Defect In Rail

Through rail welding,the seamless line replaces the common joint.This saves a lot of joint materials and provides a solid foundation for high-speed rail loading.Subsequently,the quality of welded rail is becoming more and more serious?Especially the thermite welding for casting properties of materials,and key parts for connecting the switch,it is the weak link of seamless line,once the quality problems without timely detection,traffic safety will be seriously endangered.Therefore,it is urgent to analyze the causes of the damage and the ultrasonic echo characteristics of the welding damage and establish a complete set of ultrasonic testing technology for the rail welded joints.In this paper,the construction process of two kinds of thermite welding and the common defects of aluminum welding in China are introduced in detail.Focus on the analysis of ultrasonic testing of Thermit aluminium heat welding,generally found suspected low magnification defects in rail head and a specific range,Railtech aluminium heat welding does not appear similar to the problem.By random sampling,metallographic analysis method,this paper determined the internal reasons for the coarse grain instead of sand defects,determine the existence of Thermit thermit welding ultrasonic non scrap welding head.The difference between the appearance of the rail thermit welding and the base metal is great.The ultrasonic examination has many reflecting surfaces and is prone to interference echo,so it is difficult to detect.The conventional rail weld detection technology can make the most of the regional thermit welding full section controlled,but the weld rail triangle area because of its special position,the detection process is influenced by the site conditions and other factors,can not effectively detect.Therefore,this paper focuses on how to solve the problem of effective detection of the bottom triangle area of aluminum welding seam.The arc K2.5 probe is designed and used to solve the problem of ultrasonic coupling in this part.Combined with ultrasonic detection theory,taking into account the rail base triangle damage position uncertainty,analyzes how to use the double arc K2.5 probe variable position K scan methods to find the damage,damage localization and quantification of the feasibility of the theory.In order to verify the effectiveness of the method,a comparative test block of artificial weld defects was designed and manufactured,and the validity of the flaw detection method was tested on the premise that the damage was known,and good results were obtained.In the actual operation,the natural damage of the triangle area of the bottom rail of the thermit welding is found,and the anatomical verification is carried out,thus solving the difficult problem of detecting the triangle area of the bottom of the welded seam.The main content of this thesis is focused on the thermit welding defects,analysis of its causes and how to use the ultrasonic flaw detector of thermite welding head for full face detection,timely detection of defects in service in the weld,major accidents to prevent unqualified thermit welds may lead,in order to achieve the safety of railway transportation objective.