Which of the following is used in welding broken pieces of iron rails and machine parts?

Q. Which of the following is used in welding broken pieces of iron rails and machine parts?

1. Aluminium sulphate
2. Sodium Sulphate
3. Aluminium powder
4. Solder

Answer: Aluminium powder

Exothermic welding, also known as exothermic bonding, thermite welding (TW), and thermite welding, is a welding process that employs molten metal to permanently join the conductors. The process employs an exothermic reaction of a thermite composition to heat the metal, and requires no external source of heat or current. The chemical reaction that produces the heat is an aluminothermic reaction between aluminum powder and a metal oxide.

In exothermic welding, aluminium dust reduces the oxide of another metal, most commonly iron oxide, because aluminium is highly reactive. Iron(III) oxide is commonly used:

The products are aluminium oxide, free elemental iron, and a large amount of heat. The reactants are commonly powdered and mixed with a binder to keep the material solid and prevent separation.