The working principle of the rolling mill is a plastic deformation process where metal billets are rolled into the desired shape and size through the rotation of the rolls and the application of pressure. This process can be divided into the following stages:
1. Billet Preparation
The metal billet needs to be heated to 1000-1200℃ (for carbon steel as an example) to reduce the resistance to deformation and enhance plasticity, making it easier for subsequent rolling deformation.
2. Rolling Process
Entry stage
During the rotation of the rolls, the billet is pulled into the gap by the friction force between the surface roughness and the billet. The entry angle is controlled within the range of 15°-30° to ensure smooth entry.
Deformation stage
After entering the gap, the billet is subjected to the pressure of the rolls, resulting in a reduction in thickness, an increase in width and length. The rolling force varies according to the material, temperature and roll diameter. For high-strength materials such as stainless steel, a rolling force of several hundred to several thousand tons is required.
Extraction stage
The deformed billet is extruded from the gap, and the exit speed and tension need to be controlled to ensure dimensional accuracy and surface quality.
3. Rolling Adjustment
Thickness control
This is achieved by adjusting the roll gap (manual/automatic lowering device), with an accuracy of ±0.1mm.
Plate shape control
Optimize parameters such as roll convexity and bending force to reduce wave-like and cupping defects.
Tension adjustment
Adjust the rolling machine speed or the tension of the coiler to reduce the rolling force and improve surface quality.
4. Auxiliary Systems
Cooling and lubrication system
Spray emulsified liquid or water-based lubricant to reduce temperature and reduce friction.
Transmission system
Composed of motors, reducers, etc., it provides power for the rolls and supports speed/torque adjustment.
5. Differences in Rolling Mill Types
Profile rolling mill: Named after the diameter of the gear seat and the pitch circle diameter of the herringbone gears, mostly uses semi-dry friction sliding bearings.
Strip rolling mill: Named according to the length of the working rolls, commonly uses rolling bearings or liquid friction bearings.
Steel tube rolling mill: Named after the maximum pipe diameter, and needs to adapt to high-precision rolling requirements. Different types of rolling mills have differences in bearing selection, structural design and rolling parameters, but their core working principles are all based on the plastic deformation of metals.
