What process involves joining two pieces of metal by heating?

The process of joining two pieces of metal by heating is known as welding. This technique involves melting the edges of the metals, which creates a strong bond when the molten material cools and solidifies. Welding is essential in many industries, including construction, manufacturing, and repair work, because it allows for the creation of permanent joints that are often as strong as or stronger than the base materials themselves.

In contrast, cutting refers to separating material into smaller pieces through various methods, such as sawing or shearing, and does not involve joining. Forging involves shaping metal through compressive forces, usually when it is heated, but it does not focus on joining two pieces together. Machining is a material removal process used to shape parts or create features, which does not involve melting or joining metals. Therefore, welding is distinctly characterized by its focus on joining metals through the application of heat.