Final answer:
The correct answer is option 3) It must be heated.Brazing often requires that the ambient air be heated to ensure the brazing material doesn't cool too quickly, resulting in a strong bond.
Step-by-step explanation:
In the brazing process, the ambient air does not typically need to be removed entirely, filtered, or cooled. Instead, it may need to be heated to prevent the brazing material from cooling too quickly, which could lead to a weak joint. It's important to maintain an appropriate temperature in the working area to ensure proper bonding between materials. The presence of air can sometimes lead to the formation of oxides on the metal surfaces, which can be reduced by heating or using a flux that shields the material from oxygen. However, none of the operations involves a significant change to the ambient air itself as part of the brazing process.
In the brazing process, ambient air needs to be removed completely because air contains oxygen and other impurities that can react with the metals being brazed.
When ambient air is present during brazing, it can cause oxidation and contamination, leading to weaker joints and reduced quality of the brazed joint. Therefore, it is important to create a controlled atmosphere that is free from ambient air during the brazing process.