What is Railroad Thermite Welding?

Dec 20, 2017

what is thermite welding?

This is an informational post, please check the rail thermite welding page if you are searching for the product.

Railroad thermite welding is a common method in railway construction. As we know, there is an interface at the rail joint between two steel rails. There is an issue in the railway industry. When the train passes away, the enormous pressure will cause shake even crack. These problems will threaten the service life of the steel rails and the safety of trains. So how to solve the interface is an important project for the rail technology.

With the development of the manufacturing industry, there are two main methods to weld the railroad tracks. The one is electric soldering, and another one way is thermite welding. What is thermite welding? The railroad thermite welding is regarded as the most high-efficiency method to weld railroad tracks. Because of the high efficiency, reliable quality and high adaptability, the railroad thermite welding becomes the most popular way in railroad construction. The application of thermite welding is widespread. In the railroad construction, it is used to weld railroad tracks. The seamless rail can be made by the thermite welding technology.

The working principle is easy to understand. After setting the thermite welding machine, we preheat the steel rails to 600 degrees. Then put the welding portion into the crucible and light the welding portion. The welding portion will produce molten steel and slag. The high-temperature molten steel will fuse the interface between two steel rails.

The thermite welding is easy to operate. AGICO Rail provides the thermite welding kits like welding portion, sand mould, ignitor and others separate parts of the railroad thermite welding. How to weld the railroad tracks? What is the thermite welding procedure? AGICO Rail lists a simple guide for you. 


Process of railroad thermite welding

The railroad thermite welding procedure has 13 steps. We can divide into three parts. The first part is the preparation, the second part is operation and the third part is the inspection. First, we will introduce the preparation work.

Preparation work

  • First, we should prepare the welding scene. We need to dig a hole which depth is 300mm, and put the crucible into the hole. Then unload the railway fasteners and measure the temperature of the railway tracks. Meanwhile, verify the railway track model and check the thermite is suited for this railroad tracks.
  • Secondly, we should check the railroad track. Checking the surface has the oxide or not and check the position of rail end is right or not. The distance of rail end and railway sleeper should more than 10cm, or else we need to adjust the rail position.  
  • Thirdly, this is an important step. We need to ensure the rail ends in alignment. The four main parameters to check that are distance, vertical alignment, horizontal alignment and torsion.

The distance between the rails ends should be 23mm~27mm. the horizontal alignment means to keep the center line of each railroad tracks in alignment. The vertical alignment means that the distance between the railway sleepers should be 1.5mm. (The wooden sleeper distance should be 3.2mm.) The torsion means that keep the railhead and rail end in alignment.

Working process

thermit ewelding process

After all the things have been prepared, we begin to weld the railroad track.

  • First, put the sand mould on the steel rails and paint the leak-proof material. What’s more, workers must keep the central line of the sand mould and the axes of the steel rail in alignment.
  • The next step is preheating. Preheating aims to eliminate dampness and increase the sand mould temperature so that avoiding disappearing bubble and slag. The fuel is oxygen and propane. During this procedure, you can prepare the thermite and crucible.
  • Then the workers pour the thermite into the sand mould. After 5 minutes later, workers take away the waste plate and crucible and dismantle the sand mould.


thermite welding inspection

  • Hot grinding and cold grinding are necessary steps before using. During the hot grinding process, there are some tips to be noticed. First, take away the wedge after 15 minutes. Secondly, the inside and outside of the welding head are flush with both sides of the rails.
  • The cold grinding aims to remove any geometric discontinuities due to welding. The cold grinding should operate after pouring 1 hour later.

After all, workers should clean the welding site and do a mark on the weld.
So far, we have introduced the railroad thermite welding method. If you are interested in this railroad technology, you can contact us to learn more details. AGICO Rail supplies the thermite welding kit for you. What’s more, as a railway components manufacturer, we supply various standard steel rails and railway fasteners like rail tie plate and rail joint. Besides, we provide the professional service if you have needs! 

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