Cold Rolling Force and Calculation
The calculation of the rolling force and torque of the cold rolling process mainly considers the frictional conditions and the deformation resistance at the roll gap. At the same time, it is necessary to take into account the elastic deformation of the roll and the elastic deformations of the rolled material and the roll gap, which are actually simplified as equivalent loads.
The total rolling force F is the sum of the friction force Ff and the deformation resistance force Fr generated at the roll gap:
F = Ff + Fr
The deformation resistance force Fr can be divided into three components, the resistance of the rolled material to the longitudinal deformation, the resistance to lateral deformation, and the resistance to the curvature deformation of the roll gap, as shown in Fig. 1.
F, = Fa + Fb + Fc
Where:
Fa: The resistance force of rolled metal to the longitudinal deformation;
Fb: The resistance force to lateral deformation;
Fc: The resistance force to the curvature deformation of the roll gap.
When there is a small relative movement of the two rolls at the roll gap, the friction force Ff begins to generate at the roll gap, which brings a certain amount of resistance to the rolling process. The simple calculation method is as follows:
Ff = μF,
Where:
μ: friction coefficient; F,: Deformation resistance force of the roll gap.
The new roll gap is opened continuous during the cold roll forming, the rolling stress produced by the material deformation is significantly greater than that of the rolling force, and the rolling force does not change significantly with the rolling force. So, the total rolling force slightly changes when the roll gap changes from zero to its final size.
When rolling thick plate, the cold axial rolling force is as small as 10Mpa, but in the case of thin plate, the rolling force can reach 700Mpa or more. This is due to the fact that for thin plate, the deformation resistance is large, the relative movement of the two rolls at the gap is large, and the friction factor is large.
The torque of the rolling process is mainly generated by the frictional resistance and has a linear relationship with the rolling force:
T = cF
Where:
C: Total moment of inertia
The total moment of inertia depends on the moment of inertia of the roll, the rolling gap, and the rolling force. When the rolling force is low and the relative movement of the two rolls is small, the torque generated is small, and the situation is reversed when the rolling force is high.
In conclusion, the force and torque of the cold rolling process are related to the frictional resistance, deformation resistance, and elastic deformation of the roll and the roll gap. Through the calculation of the force and torque, it is possible to obtain the actual rolling parameters and judge the working condition of the equipment to ensure the carrying capacity of the equipment.
