To answer some of the questions:
The muffle tubes are 4 inches ID and 10 ft long. They are made of RA330, an austenitic alloy.
Depending on the wall thickness of the 304SS tubing we're processing, speed through the annealing oven varies from 24 fpm to 55 fpm @ 2000F. If 2000F is too hot, then...
We are continuous annealing 304 SS tubing between drawing passes to thin the tubing wall. We get galling of the outer surface of the tubing as it moves through and contacts the muffle tube in the annealing furnace. The furnace is about 2000F. We use disassociated ammonia for the atmosphere...