In order to reduce production areas, the movement of tape in passage furnaces can be carried out in several threads in the height of the furnace.
The intermediate annealing of the transformer steel strip at the Elektrostal plant is carried out in lingering continuous furnaces among dry hydrogen.
When used as a dawning medium of hydrogen, special attention should be paid to security issues. It is necessary to exclude air seeping into the furnace, since when mixing with air, hydrogen is explosive.
At the Leningrad Steel Rapatary Plant, an intermediate annealing of the tape is carried out in lingering furnaces without a protective atmosphere. In this case, a thin film of oxides is formed on the surface of the metal, which, if necessary, is easily removed when rolling a strip on a stanch of cold rolling with a slight squeezing.
At the Zaporizhstal factory, intermediate annealing of transformer steel is carried out in capacious power prints at 850 ° C with an excerpt of a cage weighing 20 t 8 h. A protective gas of the following composition is supplied under the muffle: 10-11% C02, 11-12% CO, 5-6% H2, the rest of the nitrogen.
At the Novolipetsk plant, an intermediate anneal was carried out in OKB-4005 furnaces using a protective environment (5% H2 and 95% 1H2) at a temperature of 780-800 ° C. On the furnaces OKB -4005, the average mass of the cage when annealing of transformer steel rolls is 23 tons, hourly performance is about 1.4 tons. These furnaces are equipped with a recording automatic potentiometer and light alarm devices.
At the MMK, intermediate annealing is carried out in gas caps at a temperature of 775-825 ° C with a protective atmosphere of the following composition: 5-10% CO, 2-4% C02, 0.4% SN4, 0.5-2% H2, the rest of the nitrogen. The duration of annealing with a mass of a cage 40 g is 40 hours. Cooling after annealing up to 150 ° C is carried out under the muffle for 40-45 hours.