Question: One of our furnace operators accidentally put aluminum in our brazing furnace with a steel assembly and ran it through our low-temperature silver-brazing cycle. The braze cycle reached 840°C (1544°F). So, as you’d expect, the aluminum melted. The molten aluminum got on the heating elements and bottom shields.
Other than replacing all the contaminated components, do you know of a way to remove the aluminum? Are there “gettering” materials that could be used to “soak it up?” Can we burn it out?
Answer: Many years ago a similar thing happened in one of our brazing furnaces when I was running the brazing shop, and we had to completely scrap the hot-zone cage and get a new one. It could not be effectively cleaned chemically or via high-temperature burnout. Additionally, we had to completely clean (grind) the walls of the furnace, then run a couple of bake-out cycles. Very expensive!
Aluminum contamination can be very costly, and there is no easy way to clean up each of the hot-zone components and then reuse them once again. I have neither heard of nor believe that a “gettering” operation would remove aluminum from the furnace. Total replacement of contaminated parts seems to be the cost of such mistakes, along with thorough grinding of the furnace walls. Therefore, be very careful with incoming materials, and train your people how to identify different metals (so as to avoid putting the wrong metals in the furnace) in order to prevent a repeat of this error.
IMPORTANT: We all learn by our mistakes. So, from a management perspective, I trust that you have not been too harsh with the operator who made that error. Proper discussions about what went wrong, what might be done to prevent it in the future, etc. will probably be far more productive than firing the person in order to make an example of him/her to other coworkers. Such strong measures may actually backfire in that his coworkers, out of fear of being fired, will not admit any mistakes, may hide them, blame them on others, etc. By reviewing the mistake with the offender, helping him/her to learn from that mistake, you probably have an excellent emissary on the shop floor who has learned from his/her error and will help others not to make the same mistake.