Thermit welding is similar to casting. A mixture of powered aluminium and iron oxide is placed inside a vessel. The mixture is ignited by heating to about 1,550°C with the help of barium oxide powder. A chemical reaction takes place in a vessel as shown in Figure 20.50.
Figure 20.50 Thermit Welding
Due to the chemical action, a bright white heat is produced and reaction leads to molten iron. The molten iron is tapped from the vessel and made to run in the cavity of the joint. The temperature attained is about 3,000°C.
Advantages
- It produces high quality welds because the metal solidifies from the inside towards the outside, and all air is executed from around the moulds.
- There is no limit to the size of welds that can be made by thermit welding.
Disadvantages
- It is an extremely old process and has been replaced to a large degree by alternative method such as electroslag welding.
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