What is necessary to prevent oxidation during the brazing process?

Using proper flux is essential in the brazing process to prevent oxidation. Flux serves multiple functions, but its primary role is to protect the surfaces being joined from oxidizing at high temperatures. When metals are heated during brazing, they can react with oxygen in the air, leading to the formation of oxides on their surfaces. These oxides can create barriers that prevent the filler metal from flowing and bonding effectively with the base metals. Proper flux not only inhibits this oxidation but also helps in cleaning the surfaces by dissolving any existing oxides before the filler metal is introduced, ensuring a stronger, more reliable joint.

In contrast, excessive heat can lead to overheating of the materials and can actually increase the oxidation process rather than prevent it. Low-pressure gas is not directly related to oxidation prevention and more about controlling the environment in which the brazing occurs. Frequent cooling can also lead to rapid temperature changes, which are not conducive to the brazing process and can introduce thermal stresses. Thus, the use of proper flux is the most critical factor in preventing oxidation during brazing.