The process of atmosphere brazing, which may also be known as controlled atmosphere brazing or CAB is not a new technology, but it continues to evolve with new developments.
In with this process, the very high heats that are required for either annealing or brazing also expose the surface of the metals to high levels of oxygen in the air. By introducing a controlled atmosphere or another gas the exposure to the oxygen in eliminated during the process, preventing oxidation. Without oxidation, there is no damage to the surface appearance of the alloy, particularly stainless steel, and the actual bonds of the braze are free from weak areas, forming a stronger overall finished component.
The Basics
With atmosphere brazing and a continual feed furnace, the layers of the furnace where the parts are heated are blanketed or covered in the inert gas. In most cases this will be nitrogen and hydrogen as it offers a low-cost, highly effective atmosphere to prevent oxygen from contacting the surface of the metal during heating.
The gas is pumped into the brazing area of the furnace, and it naturally moves out of the furnace through the design of the chamber. This also helps to prevent oxygen from moving into the brazing section or chamber of the furnace.
It is critical during atmosphere brazing for the furnace atmosphere to be carefully controlled and maintained. Any sudden changes in the mixture in the atmosphere can result in the presence of oxygen and the risk of oxidation during the heating and actual brazing time.
Components and Benefits
In most situations, atmosphere brazing is complete on large runs of components or when large orders are being processed. It is a more costly option to run, but with the increased volume of production with continual flow furnaces and the decrease in loss due to oxidation the costs can be easily offset by a well-run brazing process.
The results of a well-managed atmosphere brazing process is a bright, shiny braze or join area that is strong and dependable. The braze will always be consistent which is perfect for OEM components for any type of application.
Of course, with atmosphere brazing, other factors will also come into play. This includes the time the components are exposed to heat, the actual consistency of the furnace temperatures and the choice of the correct braze material given the various alloys and components in use.