The rolling process is a process that the rolled piece is pulled between the rolls in different rotation directions through the friction between the rolled piece and the rolls, resulting in plastic deformation. More than 90% of the plastic processing of metal materials, especially steel materials, is completed by rolling. It can be seen that rolling engineering technology plays a very important role in metallurgical industry and national economic production.

Rolling process can be divided into four basic types according to product types: strip rolling, pipe rolling, profile rolling and bar and wire rolling. According to the production process, it can be divided into hot rolling and cold rolling processes; According to the thickness can be divided into thin plate (thickness; 60 mm, 700 mm thick). In practical work, medium plate and thick plate are collectively called "medium plate".

Rolling process is a pressure processing method in which the metal blank passes through the gap (various shapes) between a pair of rotating rollers, and the cross section of the material is reduced and the length is increased due to the compression of the rollers. This is the most commonly used production method for producing steel, mainly used for producing profiles, plates and pipes.

2 rolling deformation theory

2. 1 rolling deformation zone

When rolling, the part where the rolled piece is deformed under the action of the roll is called the rolling deformation zone.

2.2 Simple Ideal Rolling and Geometric Deformation Zone

Simple and ideal rolling conditions: the rollers have the same diameter, the same rotational speed, the rollers are cylindrical rigid bodies, the rolled piece is uniform and continuous, the deformation is uniform during rolling, and the rolled piece is straight.

Geometric deformation area: the geometric area between the contact surface of the rolled piece and the roll, that is, the area ACBD surrounded by the vertical plane of the rolled piece entering the roll bar and the vertical plane of the rolled piece leaving the roll.

2.3 Relationship between parameters of deformation zone during simple rolling

1) The angle formed by the connecting line between the first contact point of the workpiece and the roller and the connecting line between the centers of the two rollers when the workpiece bites into the roller.

2) Length of deformation zone The horizontal projection length of contact arc between rolled piece and roll. When the diameters of two rollers are equal:

3) contact area The horizontal projection area of the contact surface. The analytical formula is as follows:

2.4 deformation theory

2.4. 1 The deformation distribution of the rolled piece along the height direction is uneven.

The formation of coarse grain zone on the surface of strip steel is related to rolling state;

When 1) is rolled, there is a difficult-to-deform zone at the contact part between the rolled piece and the roll due to friction. When the rolling lubrication condition is not good, it is easy to produce coarse grain area on the surface. Lubrication can be improved by turning on the cooling water between the racks.

2) The deformation distribution of the rolled piece along the height direction is uneven, and the surface deformation is small. When the reduction distribution is unreasonable, the surface deformation of the rolled piece is small, resulting in coarse grains.

2.4.2 uneven deformation theory:

1) The deformation, stress and metal flow distribution of the rolled piece along the section height direction are uneven.

2) In the geometric deformation zone, there is not only relative sliding but also adhesion on the contact surface between the rolled piece and the roll, and there is no relative sliding between the rolled piece and the roll in the adhesion zone.

3) Deformation occurs not only in the geometric deformation zone, but also outside the geometric deformation zone, and its deformation distribution is uneven. Rolling deformation can be divided into deformation transition zone, forward sliding zone, backward sliding zone and adhesion zone.

4) There is a critical interface in the adhesion zone, and the velocity of metal is evenly distributed on this critical interface, which is equal to the horizontal speed of the roller.

3 Introduction of several rolling processes

3. 1 asynchronous rolling

Asynchronous rolling is a kind of rolling with unequal speed, and the surface linear velocity of the upper and lower work rolls is not equal to reduce the rolling force. So it is also called differential pressure rolling, and it is also called rubbing rolling. Asynchronous rolling is used to roll bimetallic plate, which will cause bending change of rolled piece. Asynchronous rolling can adjust the bending curvature of bimetallic plate, and to a certain extent, under the condition of the same asynchronous ratio and the same thickness ratio of two metal components, a straight rolled piece can be obtained. Asynchronous rolling is a new rolling process with many advantages. Adopting asynchronous rolling can greatly reduce the rolling force, so the equipment is light in weight, low in energy consumption, small in rolling mill deformation and high in product precision; The abrasion of the roller and intermediate annealing are reduced, and the production cost is reduced; Less rolling passes and high productivity; The rolling mill is very thick. Asynchronous rolling is not only suitable for cold rolled strip steel, but also suitable for hot rolled strip steel. This is a promising production process. The disadvantage of asynchronous rolling is that it is easy to cause vibration of rolling mill.

3.2 Cumulative lap welding

Accumulative roll welding (ARB) is to automatically roll weld two thin plates with the same size at a certain temperature after degreasing, work hardening and other treatments, and then repeat the same process for lamination and roll welding, so that the microstructure of the material is refined, the inclusion distribution is uniform, and the mechanical properties of the material are greatly improved.

3.3 Double Drive Rolling

Double-drive rolling is often used in ring processing, and its basic working principle is basically similar to that of conventional ring rolling, but the difference is that a driving torque is loaded on the core roller during double-drive rolling, which changes the rotation mode of the core roller from follow-up rotation to autonomous driving control rotation. Double-drive ring rolling equipment is based on the conventional ring rolling equipment, which changes the core roller assembly into a hydraulic driven rotating core roller, and can realize the independent movement of the core roller. Unde that rotating action of the drive roller and the core roller, the ring piece continuously enter the rolling pass formed by the drive roller and the core roller. Because the core roller runs independently and does not run together with the ring, under the friction between the roller and the ring surface, the rotation speed of the inner and outer surface materials of the ring does not match, just like the friction between the inner and outer surface materials of the ring, which increases the plastic deformation of the ring structure and makes the ring produce continuous local plastic deformation. While reducing the wall thickness, expanding the diameter and forming the cross-sectional profile, the internal structure of the ring has undergone great deformation, improving the microstructure and properties of the parts. When the diameter of the ring reaches a predetermined value after repeated multi-turn rolling, the outer surface of the ring contacts with the signal roller, the driving roller stops feeding, and the double-drive rolling process of the ring ends. In the rolling process, the guiding movement of the guide roller ensures the smooth rotation of the ring.