Thermit welding is often used

Explanation:

The thermit welding reaction takes place between the metal oxide and aluminum. In this process, fine aluminum particles and metal oxide are blended and ignited by an external heat source. The reaction will proceed according to the following equation:

Metal Oxide + Aluminum → Aluminum Oxide + Metal + Heat

Examples:

\(F{e_2}{O_3} + 2Al \to 2Fe + A{l_2}{O_3} + \left( {\Delta H = 838\;kJ} \right)\)

\(3CuO + 2Al \to 3Cu + A{l_2}{O_3} + \left( {\Delta H = 1210\;kJ} \right)\)

The ignition temperature of thermit granules used for welding is about 1200°C, therefore it is safe from fire hazards if stored away from open heat sources.

Due to the thermit chemical mixture reaction, 3 products are produced,

• Iron - Used as filler rod
• Al2O3 - Used as a slag
• Heat - Used for the melting of the parent material.

Uses:

• A thermit welding application includes the joining of railway rail ends so that the rail becomes continuous which makes s smoother roadbed.
• Repair of Broken Machine parts of large sections. Repair welds are normally nonrepetitive and therefore, pre-manufactured molds are not used.
• Used for welding copper conductors.
• The reinforcement bars in the concrete beam are joined using thermit welding.
• Thermit welding is often used in replacing broken gear teeth, repairing broken shears and joining rails, truck frames and locomotive frames etc.