What are the characteristics of a hot rolling mill?

Hot rolling mill It is primarily composed of rolls, a drive system, a linear pressure‑adjustment mechanism, a roll‑deformation compensation mechanism, a heating system, a hydraulic system, a cooling system, a lubrication system, a frame, and a control system.

Rolls are the primary components of a hot rolling mill. Each hot rolling mill should be equipped with at least one pair of rolls, including a patterned roll. (Abbreviated as the patterned roll) and a smooth roll. The rolls are made of heat-resistant alloy steel. For most two-roll hot rolling mills, the patterned roll is typically mounted on the wall plate above it, while the smooth roll is usually positioned below; the smooth roll is supported by two hydraulic cylinders. Under the control of these cylinders, the patterned roll can be raised to press against or disengage from the smooth roll.

Hot rolling mill The transmission system provides the power required for the roller’s rotation and comprises components such as the motor, gearbox, and universal drive shaft. In hot‑rolling mills, the motor and gearbox are typically mounted on the frame. Due to space constraints and the need for the lower roll to move vertically, a universal joint shaft—capable of compensating for misalignment of the shaft axes and variations in center distance—is used to transmit torque between the gearbox output shaft and the roll.

Hot rolling mill The manufacturer defines line pressure as the pressure per unit length within the effective working width of the roll, with the commonly used unit being N/mm. The line-pressure adjustment mechanism is employed to regulate line pressure according to process requirements, typically by adjusting the hydraulic oil pressure in the lower-roll support cylinders. The operating line pressure is primarily determined by the percentage of the engraving area; a higher percentage of the area necessitates greater line pressure.

Hot rolling mill Manufacturers regard the roll‑deflection compensation mechanism as essential for maintaining uniform line pressure across the entire width. Depending on the design, numerous approaches exist to compensate for roll deformation, and the specific implementations vary considerably. The effectiveness of a roll‑deflection compensation system is a key performance indicator for hot‑rolling mills, particularly when processing thin, lightweight products with low basis weights. A wide range of methods are employed to address roll deformation, each influenced by factors such as strip width, roll diameter, line pressure, and product thickness ratio. Regardless of the compensation strategy adopted, the overarching goal is to ensure consistent line pressure across the full width during production of a variety of products within the specified target weight range.

Hot‑rolling mill manufacturers consider the heating system’s function to be providing energy for heating the press rolls. There are two heating methods used in hot‑rolling mills: induction heating and thermal‑oil heating. Induction heating employs the electromagnetic induction principle of alternating current to generate eddy currents in the steel rolls, thereby raising their temperature. The system’s energy‑conversion process—transforming electrical energy into thermal energy—occurs directly within the rolls, eliminating the need for an intermediate heat transfer medium; moreover, the heating system can also compensate for roll deformation. Thermal oil is typically used in hot‑rolling mills on nonwoven‑fabric production lines. A thermal‑oil system generally comprises one to two electrically powered thermal‑oil heaters, a high‑temperature oil pump, an expansion tank, piping and rotary joints, as well as an automatic temperature‑control unit.