Vacaero

Manufacturers of heat treating and brazing vacuum furnaces and controls, complete hot zone and vacuum furnace retrofits, thermal spray coatings, plasma, HVOF and paint coating services.

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Archives for September 2013

Decarburization

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Decarburization occurs when carbon atoms at the steel surface interact with the furnace atmosphere and are removed from the steel as a gaseous phase (1-8). Carbon from the interior will then diffuse towards the surface, that is, carbon diffuses from a region of high concentration to a region of low concentration to continue the decarburization process and establish the maximum depth of decarburization (MAD).

Because the rate of carbon diffusion increases with temperature when the structure is fully austenitic, the MAD will increase as the temperature increases above the Ac3. For temperatures in the two phase region, between the Ac1 and Ac3, the process is more complex. The diffusion rates of carbon in ferrite and in austenite are different and are influenced by temperature and composition.

Gas Molecules and Gas Flow

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If you are a homeowner with a garden and a lawn, watering and mowing are regular tasks that need to be carried out. When you are watering your flower bed or vegetable patch at home you turn on the hose tap and see the water coming from the spray nozzle. You can then direct the water to the places where it is needed. Similarly, when mowing your lawn you can see what area you have already cut and can direct the mower to cut the next area of long grass. These tasks are made easier because you can see what you are doing. Trying to water or mow with your eyes covered would be much more difficult.

When you are evacuating a vacuum system, one of the biggest problems is that you can’t see what you are evacuating. Gas molecules are so small that you cannot see them. So how do you know when they have been moved out of the system and how do you know the best way to move enough of them to allow you to complete your particular process? In this article we will try to understand what gas molecules are and how they behave at different pressures in a vacuum system. If you have a mental picture of the molecules using your imagination, it can possibly help you to understand how your vacuum system works and solve problems with its operation if something goes wrong.