The roll pressure of a rolling mill refers to the force applied by the roller to the rolled piece to cause plastic deformation. But usually, we call the point that the rolling piece acts on the roll (action force and reaction force) and transmits to the frame by pressing down the screw as the rolling force.
Rolling pressure is one of the important technical parameters in the rolling process. It not only provides a reference for the design of the rolling mill and the formulation of the rolling process, but also its distribution will directly affect the thickness and shape of the strip. Correct measurement and calculation of rolling force are of great significance for the design and use of rolling mills.
The rolling pressure of a rolling mill is affected by several factors, including the mill design, the material properties, the reduction ratio, the roll gap, the friction, and the temperature of the material. We will introduce them to you in detail one by one.
The design of the rolling mill has a significant impact on the rolling pressure. The number and arrangement of rolls, roll diameter, and roll speed all affect the pressure. For example, a mill with more rolls will generally have a higher rolling pressure, as will a mill with smaller roll diameters. Additionally, faster roll speeds can lead to higher rolling pressures.
The properties of the material being rolled can significantly affect the rolling pressure. The strength, thickness, and hardness of the material all play a role. Materials with higher strengths and hardnesses generally require higher rolling pressures to deform, while thicker materials require more force to reduce their thickness.
The reduction ratio refers to the ratio of the initial thickness of the material to the final thickness after rolling. Higher reduction ratios generally result in higher rolling pressures, as more force is required to reduce the thickness of the material.
The distance between the rolls, known as the roll gap, is another factor that affects the rolling pressure. A smaller roll gap will generally result in higher rolling pressure, as the material is more tightly compressed between the rolls.
The friction between the rolls and the material being rolled can also impact the rolling pressure. Higher friction will generally result in higher rolling pressures because it needs more force to overcome the resistance.
The temperature of the material being rolled can also affect the rolling pressure. Higher temperatures can lead to lower rolling pressures due to reduced resistance to deformation. This is because, at higher temperatures, the material is more malleable and easier to deform.
In summary, the rolling pressure is influenced by a combination of these factors. Optimizing the rolling process involves adjusting these factors to achieve the desired outcome. For example, increasing the speed of the rolls while decreasing the roll gap and increasing the temperature of the material can help reduce the rolling pressure required to achieve a certain reduction ratio.
In hot rolling industrial production, rolling pressure calculation is the most basic and important part. It is the basis of hot rolling production equipment configuration, the production process optimization, the guiding parameters of product development, and the applicable hot rolling mechanics model that is needed to control tension in continuous rolling production. There are three methods to determine the rolling force: theoretical calculation, empirical formula calculation, and actual measurement.
Rolling pressure has crucial engineering significance to the research of rolling pressure in the asynchronous rolling process. Asynchronous rolling refers to a rolling method in which the upper and lower rolls have different line speeds. Thanks to its characteristics, it has the advantages of low rolling pressure, strong rolling capacity, and refined grains. It is especially suitable for rolling extremely thin strips. It has obtained widespread concern in recent years.
Some scholars have carried out in-depth research on the rolling pressure in the asynchronous rolling process and deduced some rolling pressure calculation formulas through analytical methods. But these formulas are relatively complicated. There are many assumptions in the derivation process, and there is a certain scope of application. The calculation accuracy also needs to be further improved. At the same time, most of the research is focused on the case where the speed ratio is less than 1.5, in which the rolling pressure will decrease with the increase of the speed ratio. However, for the conditions of high speed ratio, we still know little about how the rolling pressure changes.