Which of the following processes primarily involves the joining of metals without melting the base metals?

The process that primarily involves the joining of metals without melting the base metals is commonly referred to as soldering or brazing. Both these techniques use a filler material that has a lower melting point than that of the base metals being joined, which means the base metals do not reach their melting point during the process.

In soldering, the filler metal typically melts at a relatively low temperature (below 450°C or 842°F) and is often used in electronics and plumbing applications. It provides a strong electrical connection and can bond dissimilar metals effectively.

Brazing, on the other hand, involves a filler metal that is melted above 450°C but still below the melting point of the base metals. This method is used for applications requiring stronger joints than what is typically achieved with soldering and can be utilized for joining various types of metals.

Welding, in contrast, involves melting the base metals to form a joint and typically does not fall under the category of processes that join without melting the base materials. Therefore, the correct justification for the answer includes the recognition that both soldering and brazing are processes that connect metals without melting the base metals themselves, making them suitable options for manufacturing and repair applications across various industries.