The daily working efficiency of the hot rolling mill

The daily working efficiency of the rolling mill is significantly influenced by environmental factors, primarily temperature and humidity. To improve the efficiency of the rolling mill, strict requirements are placed on humidity, especially at the narrow exit of the reheating furnace. In situations where steel is not being discharged, sealing the furnace door can reduce air consumption and heat transfer, consequently lowering coal and gas costs.

High humidity around the rolling mill can lead to an increase in water vapor pressure inside the reheating furnace, resulting in a decrease in the average propelling force inside the furnace. To maintain the same heating efficiency under these conditions, it might be necessary to increase the length and width of the reheating furnace, in turn increasing investment costs.

The impact of different reheating furnace types on the humidity varies. For a stepped heating furnace, which has short residence times for steel billets, a larger propelling force is required to enhance the heating rate. Typically, the water vapor pressure in the exiting gas needs to be lower than half of the vapor pressure on the surface of the material. In contrast, for a regenerative heating furnace, the water vapor pressure in the exiting gas is generally around 60% of the vapor pressure on the surface of the steel billet.

The relationship between airspeed and relative humidity must also be considered, particularly for mills requiring a specific airspeed. When constructing the reheating furnace, the correlation between air volume and relative humidity should be taken into account. To meet the requirement of higher airspeeds, more air can be used, reducing the relative humidity and enhancing the heating rate of steel billets, thereby decreasing high-temperature losses.

Controlling the inlet temperature of the rolling mill is crucial for enabling steel billets to rapidly undergo deformation rolling. The inlet temperature should generally be maintained within the suitable range allowed for the steel billet, with an optimal temperature of around 1100 degrees.

In practical rolling processes, adjustments may need to be made based on factors such as the type of reheating furnace, humidity, and other considerations to achieve the best working efficiency for the rolling mill.