An inert atmosphere contains a very low percentage of oxygen, and thus will not readily react with materials contained in it. Since oxygen is the most chemically reactive constituent of air, the atmosphere in an industrial furnace or oven can be made non-reactive by removing the oxygen. Inert atmosphere processing is commonly used in tempering, annealing, and normalizing heat treat applications.
When heating materials such as steel, aluminum, and certain plastics, oxygen in the air can react with the material and cause unwanted oxidation on the surface. This is due to the fact that oxidation occurs more rapidly at elevated temperatures. Steel, for example, will oxidize very quickly at temperatures above 450°F (232°C), resulting in dark, rust-like discoloration and surface roughness. Aluminum is very reactive with oxygen and forms a thin film of surface oxidation at room temperature. This film will become thicker at elevated temperature and is undesirable for certain end uses of the aluminum. Similarly, PTFE (Teflon), UHMW plastic, copper, and certain other materials are negatively affected by oxygen when heated.
To mitigate this effect, ovens and furnaces specially designed for atmosphere heat treating, such as Wisconsin Oven’s inert Nitrogen Atmosphere furnaces, are used to process these materials. For inert atmosphere processing to occur, the heating chamber is flooded with nitrogen gas, which is non-reactive, to displace the oxygen and reduce oxidation on the surface of the material. The design of the inert atmosphere oven utilizes a continuously welded shell to minimize infiltration of oxygen, special seals where accessories penetrate the oven shell, a sealed door design, and airtight cooling system that uses water passing through a heat exchanger to cool the furnace after the heating cycle is complete.
