What process is referred to when joining two pieces of metal using heat?

The process of joining two pieces of metal using heat is best described as welding. Welding involves melting the base materials and often a filler material to create a strong joint when cooled. This technique can generate very high temperatures, sufficient to cause the metals to fuse, resulting in a permanent connection that can withstand significant stress.

In contrast, the other options refer to different methods of joining or manipulating metals. Brazing and soldering, while both utilize heat to join two materials, do not melt the base metals being joined; instead, they rely on the application of a filler material that has a lower melting point. Cutting involves severing metal and does not create a connection; therefore, it is unrelated to the process of joining. Understanding these distinctions helps clarify why welding is the most appropriate choice for this question.