Three Methods Of Welding Rails And Their Advantages And Disadvantages That Railway Maintenance Personnel Should Know
Nov 27, 2021| Three methods of welding rails and their advantages and disadvantages that railway maintenance personnel should know
In order to meet the needs of the new CWR, the rail welding problem arises for the rail. At present, the common methods of rail welding include flash contact welding, pneumatic welding and thermit welding. The following is a comparison of these three welding methods.
Flash contact welding
The first method is flash contact welding, which is mainly used in various rail welding plants, because in plant welding can ensure the welding quality of rail. When welding in the factory, the 100m long fixed gauge rail is usually placed in specific machines and tools (as shown in the figure below), and then heated according to the principle of thermal effect of current. When the rail is heated to plastic state, it is extruded at a very fast speed. The utility model has the advantages that the strength of the rail welded by this method is equivalent to that of the base metal, and the surface is smooth and easy to grind and form. The disadvantage is that this method has certain limitations and can only weld the rail in the factory.
Gas pressure welding
The second is pneumatic welding. This welding method mainly uses the heat generated by the reaction of acetylene gas and oxygen to weld the rail. Like flash welding, when the rail is heated to the plastic state, the two rails are squeezed together under the pre applied pressure to weld the rail. This method is generally applicable to outdoor construction sites. Due to the interference of the external environment, the welding quality is far inferior to flash contact welding. This welding method is usually not used when it is a last resort. The advantage is convenient and suitable for outdoor operation.
Thermit welding
The third welding method is thermit welding, which is the same as pneumatic welding. This welding method is also applicable to outdoor construction sites. Its welding principle is to use the redox reaction of iron and aluminum, which will release a lot of heat in the oxidation process, and the generated molten iron will weld the two rails together.
Method comparison
Flash contact welding has the advantages of fast welding speed and stable welding quality, but the investment of welding machine is large and the power required is also large.
Pneumatic welding has the advantages of small one-time investment, no high-power power supply, short welding time and good welding quality. The disadvantage is that the requirements for the treatment of joint section during welding are very strict, and the steel rail needs to move longitudinally during welding. Therefore, it is difficult to weld ultra long steel rail, especially the on-line welding of cross section CWR.
The welding method of thermit welding is relatively simple, the requirements for operators are relatively low, and the welding time is short. It can be welded when the rail is fixed, but the welding quality is not as good as contact welding and pneumatic welding.
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