Welding is the process of joining of two or more similar or dissimilar materials with or without application of pressure and filler materials.

A type of welding known as forge welding uses hammer. Hammer is used to generate impact or pressure between two joining materials. Forge welding is also known as hammer welding.

In forge welding, the metals to be joined are heated to soften them. Once they become soft,they are placed over each other and a blow of hammer is provided. This blow of hammer generates a high amount of pressure on the joining plates, thus it results in the welding of the two pieces.

So, the type of welding in which hammer is used to join heated and softened metal is known as forge welding.

Conclusion:

The type of welding in which hammer is used to join heated and softened metal is forge welding.