I have an issue that I have not come across before.
A lot of 10B22 nuts were processed though a continous furnace at a rate of 3,000 pounds per hour at 1600 degree (33 minutes in the furnace) and one nut was dead soft and the microstructure shows that it saw heat. The part was discolored like it was against some type of heat sink.
We have had a couple of batches with one or two nuts exiting the furnace with the same microstructure. We have notices that some parts 'roll ahead' after loading but the parts still see enough heat for the microstructure to transform.
we have sped up the belt speed and reduced the temperatures in zone 1 and 2 to 1500 degrees and the parts are still good.
We put green parts in the quench tank and checked them after the tempering furnace and the parts did not look like the soft parts that were originally found.
It is my understanding that the parts would have to see only heat in the range of 1200 degrees for about 15 minutes to see the type of microsctructure we are seeing.
Any ideas would be welcome and I have pictures of the microstructures available if anyone would like to see them
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