What is welding defined as?

Welding is defined as the joining of materials, primarily metals, through the application of heat, pressure, or both. This process creates a strong bond between the pieces being joined, resulting in a permanent connection that is often as strong as or stronger than the base materials. Various welding techniques, such as arc welding, MIG (Metal Inert Gas) welding, and TIG (Tungsten Inert Gas) welding, all fundamentally aim to achieve this joining of materials by melting the edges of the components and allowing them to fuse as they cool.

The other options describe different processes that are not specifically welding. For instance, cooling of metals involves solidification but does not focus on the joining aspect. Melting metal for casting refers to shaping materials into molds, while rolling metal sheets pertains to forming and shaping rather than joining. Therefore, the correct definition of welding accurately captures its essence as a method of effectively joining materials.