....That's interesting, considering that it's usually pointed out that the parts need to be brought to above 1333F for annealing. The lower temp would "Draw the Temper", (semantics, I know, but is really a stress relief measure usually used after case hardening) but would not be true annealing. Annealing, as was mentioned by Doug, requires parts being packed in a crucible with charcoal, (I think wood charcoal only for this could be used, no need for an energizer like bone) the crucible then being brought to above 1333F and allowed to cool down inside the oven. If this is incorrect, someone please speak up....
I only throw this out for consideration.
What Sam mentioned, particularly around 900*, is actually not tempering, but a process that might be called spheroidizing annealing. There are various good reasons to consider it, but two that come to my mind, the part never needs to reach critical temperature, and the exact make up of the hardened steel, that someone elects to soften, is unknown.
Because the hardened steel case is unknown, it is possible to convert that steel to a less than ideal form, distribution of the carbon, just by cooling it too slowly during annealing.
Steve, as an aside, I'm not so sure annealing can prevent over carburizing. On it's own, annealing shouldn't remove or add carbon to the steel case. I suspect if the steel skin is heated, particularly above critical, in a wood charcoal pack, presumably(?) to eliminate oxygen, there is a pretty fair chance that available carbon is driven towards the part under those conditions.
This is only discussion, and no heartburn with anyone's preferred methods. I appreciate the small look in other shops.
