Why is aluminum powder used for welding train tracks?

Edit:Zongxiang Heavy Industry--Lucas Date:2020-04-07 09:53:44

The thermite welding method is currently the main method for welding joint of jointless track at home and abroad. It has the advantages of simple equipment, convenient operation and suitability for welding on the track. railway track material

(1) development of thermit welding method

Since the 20th century, all countries in the world have been developing and promoting seamless lines, especially in recent years, in order to meet the needs of high-speed line development, seamless lines are generally adopted. After the railway line is paved with seamless lines, the train running speed can be improved, the train running conditions can be improved, the maintenance workload can be reduced, the service life of equipment can be prolonged, and the driving can be smooth and passengers can be comfortable. railway track material

The thermite welding method was applied to the long rail welding of railway lines and started in 1924 in Germany. The thermite welding method has been considered as a fast welding method with high efficiency and has been adopted in many countries. After 1960, our country began to produce rail thermite flux in batches for joint welding.

The thermite welding method is not only used in railway, but also has been more and more widely used in other departments, such as infrastructure departments using it to weld crown block tracks, etc.

(2) the basic principle of thermit welding rail railway track material

The chemical principle of thermit welding is the principle that metals with higher activity can reduce metals with lower activity from their oxides. Because aluminum has strong activity at high enough temperature, it can extract oxygen from many oxides of heavy metals and reduce them. For example, aluminum can reduce iron, titanium, vanadium, chromium, manganese, tungsten and the like from their oxides, and at the same time release a large amount of heat, the temperature can reach 2500-3500 deg c, thus making these metals liquid.

The main chemical equation of the basic principle of thermit welded rail is:

3FeO+2Al=3Fe+Al2O3+834.9kJ

Fe2O3+2Al=2Fe+Al2O3+829.9kJ

3Fe3O4+8Al=9Fe+4Al2O3+3236.3kJ

In order to obtain high quality thermite steel, graphite powder (adjusting carbon content) and some alloy elements such as manganese, silicon, titanium, molybdenum, etc. can be added to thermite flux according to different requirements. railway track material

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