DETERMINATION OF THE TEMPERATURES FIELD IN WORKING ROLLERS OF COLD ROLLING WITH HIGH SPEED HEATING IN THE CHAMBER FURNACE

The present article demonstrates the results of experimental and  calculated researches of the rapid (gradient) heating of the working  layer of the cold working roll barrel in the unit, consisting of a chamber  furnace with special design and a spraying unit, located under the furnace in special pit and able to move up for rapid cooling of the working  roll layer. In the process of the roll heating its barrel and some parts of  the necks are located within the working chamber area while the other  (external) parts of the necks are situated outside the heating chamber  and rest upon the drive rollers, which are designed to ensure rotation  of the roll barrel in the course of its heating and subsequent cooling.  Therefore, it is necessary to ensure hardening only of the working roll  layer that is why the neck parts located inside the furnace are equipped  with special heat-insulated inserts to prevent their hardening. The  experimental rolls are equipped with the thermocouples to measure  temperature both in different points of their surface and in the depth  of their barrel and necks with the aim to develop the various roll heat  treatment conditions. A process of heat treatment included rigid requirements concerning smoothness of the roll barrel surface heating at  very close limits for under-heating zones in the extreme sections near  surface end faces. Besides, it was necessary to ensure low temperature  of the necks located within the working furnace area. The experimental  researches of the temperature fields under different conditions of the  rapid roll heating allowed us to reach a high speed of the roll heating  and cooling and, respectively, the required structure of the working  roll barrel layer. At the same time, in the process of the experimental  researches and calculations of the temperature fields according to the  specially developed program, the authors have revealed intensive heat  leak via external open neck parts under the existing conditions of heating gas input and output and roll location with the necks being, par tially, beyond the heating chamber. The above-mentioned researches  allowed revealing also a sufficient (as compared with the admissible  one) non-uniformity of the temperature field of the barrel surface in  the end zones of the roll being heated. It was also determined in the  course of the experimental researches that change of the external heat  exchange conditions between the working furnace area and roll surface does not eliminate non-uniformity of the temperature field in the  end surface sections. A method of sufficient non-uniformity decrease  of heating of the end roll barrel sections has been offered and executed  calculations and analysis of the temperature fields have confirmed the  reality of its application.

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