Roller temperature in metallurgical machines with scale formation

Resumo

When hard water is used to cool the rollers of metallurgical machines, scale forms on the inner surface of the cooling channel. Predictions of the roller temperature usually fail to take into account that, in the initial period of roller operation, the cooling channel is scale-free and operates in conditions very different from those in the final period. With continuing growth of the scale layer, which has good mechanical properties and poor heat conduction, the working surface is heated to the temperatures at which the rollers in the machine are tempered. In the present work, the working temperature of the rollers is investigated when scale forms on the surface of the cooling channel. A method is proposed for estimating the working temperature of the rollers in those conditions. For the example of rollers in a continuous-casting machine, it is shown that, for the selected operating conditions, the maximum temperature of the roller’s external surface reaches its critical value after operation for half a year. By the proposed method, different approaches may be taken in determining the mean and maximum surface temperature of the rollers for different thermal loads, different cooling conditions, and different quality of the cooling water. The method provides the basis for determining the roller life and setting standards for the content of reagents in the cooling water.