The Relationship Between Rolling Mill Efficiency and Ambient Humidity and Temperature

　　Practice has shown that numerous factors influence the efficiency of a rolling mill in daily operations, including environmental conditions such as temperature and humidity—both primary and ambient.

　　Therefore, to improve the operational efficiency of the rolling mill, the narrow furnace tap hole is subject to stringent humidity requirements. When no steel is present and the door is closed, this can reduce air consumption and heat loss, thereby lowering fuel costs for coal and natural gas. If the ambient humidity in the rolling‑mill area is high, it increases the partial pressure of water vapor inside the furnace, reducing the effective driving force and making it difficult to maintain consistent heating. In such cases, it becomes necessary to extend both the length and width of the furnace, which in turn raises capital investment.

　　Regarding the selection of heating furnaces, appropriate relative temperature values vary. For instance, in a walking-beam furnace, where billets remain in the furnace for a relatively short time, a rolling‑type furnace requires greater driving force to achieve the desired heating rate. Typically, the partial pressure of water vapor at the gas outlet must be less than half the external water vapor pressure. In a regenerative furnace, the water vapor fraction in the exhaust gas is generally about 60% of the billet’s surface water vapor pressure. For certain types of reheating furnaces, it is essential to maintain the required air velocity; therefore, when designing the furnace structure, both relative humidity and contact conditions should be carefully considered. To meet high air‑velocity requirements, a larger air flow can be employed to reduce relative humidity, thereby increasing the billet’s heating rate and minimizing heat loss.

　　The underlying reason is that the inlet temperature of the rolling mill must be carefully controlled to ensure that the steel billet quickly reaches the deformation‑rolling stage. Typically, the inlet temperature of the rolling mill should be maintained within an appropriate range—around 1150°C—allowing for variations in billet quality. Even for billets of the same type, deviations in furnace conditions can lead to differences in the allowable inlet temperature. Moreover, variations in the quenching heating temperature and holding time among different billets further influence the process. Consequently, during actual rolling, the rolling temperature must be adjusted according to specific requirements.