Metal work

Basics of Thermit welding and its Advantages

Thermit welding is a welding methods, that uses heat generated by exothermic chemical reaction between the components of the thermit which is a mixture of a metal oxide and aluminum powder. The molten metal is produced by the reaction. It acts as a filler material joining the work pieces after solidification.

At the end of this articles, you’re expected to have basic understanding on thermit welding and its advantages.

Thermit welding is mainly used for joining steel parts. Its common thermit is composed from iron oxide (78%) and aluminum powder (22%), with the proportion 78-22 is determined by the chemical reaction of combustion of aluminum, which is 8Al + Fe 3O 4 = 9Fe + 4Al 2O3
The combustion reaction products (iron and aluminum oxide) heat up to 4500°F (2500°C). Liquid iron fills the sand (or ceramic) mold built around the welded parts, the slag (aluminum oxide), floating up , is then removed from the weld surface.

Thermit welding is used for repairing steel casings and
forgings, for joining railroad rails, steel wires and steel pipes, for joining large cast and forged parts.

Advantages of Thermit Welding

The followings listed below are advantages of thermit welding;

  • No external power source is required (heat of chemical reaction is utilized);
  • It can be used at the place where power supply is not easily available.
  • It does not require any external power source.
  • Very large heavy section parts may be joined.
  • It is highly stable to repeated short circuit pulses and the electrical resistance remains unchanged over lifetime of the installation.
  • In thermit welding, the weld formed has high mechanical strength, and excellent corrosion resistance as compared with other forms of weld.


I hope you understand reading this article, we’ve enlighten on thermit welding and its advantages. you can ask question through the comment box if you really don’t understand and don’t forget to share this articles!


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