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Introduction of Rolling Technology

 

Introduction of Rolling Technology

1>Asymmetrical rolling

Asynchronous rolling is a kind of unequal speed rolling, the linear speed of the upper and lower work roll surface is different to reduce the rolling force; therefore, it is also called differential rolling, also known as rolling. Asynchronous rolling is used to rolling bimetallic plate, which will cause bending change of rolling piece. Asynchronous rolling can adjust the bending curvature of bimetallic plate, and under the same asynchronous ratio, the thickness ratio of two metal components is in a certain degree of deformation. Flat rolled pieces can be obtained. Asynchronous rolling is a new rolling process with many advantages. Asynchronous rolling can greatly reduce the rolling force, so the equipment weight is light, the energy consumption is low, the rolling mill deformation is small, the product precision is high, the roll wear and intermediate annealing are reduced, the production cost is reduced, the rolling pass is less, the productivity is high; Rolling mill can be rolled thick. Asynchronous rolling is not only suitable for cold rolled strip, but also can be used in hot rolling, which is a promising production process. The main deficiency of asynchronous rolling is that it is easy to cause rolling mill tremor. -Rolling Technology

 

2>Accumulative roll bonding

After degreasing and hardening, two pieces of sheet materials of equal size are rolled and welded automatically at a certain temperature, and then the same process is repeated again and again for rolling and welding, so that the structure of the material can be refined. The uniform distribution of inclusions greatly improves the mechanical properties of the materials.-Rolling Technology

 

3>Double drive rolling

Double drive rolling is often used in the manufacturing of ring parts. Its basic working principle is similar to that of conventional ring rolling. The difference lies in the loading of a driving moment on the core roll in the process of double drive rolling. The rotation mode of core roll is changed from follow-up rotation to self-driving control rotation. Based on the conventional ring rolling equipment, the ring double drive rolling equipment changes the core roll component into the core roll with hydraulic driving rotation, which can realize the independent movement of the core roll. Under the action of driving roll and core roll rotation, the ring piece continuously enters the rolling pass which is composed of driving roll and core roll. Because the core roll does not run independently with the ring, under the action of the friction between the roller and the surface of the ring, the rotation speed of the inner and outer surface of the ring does not match, as if the outer surface material is rubbed in the ring. By increasing the plastic deformation of the ring structure, the continuous local plastic deformation of the ring is produced. While the wall thickness is reduced, the diameter is enlarged and the section profile is formed, the structure and properties of the parts are improved because of the large plastic deformation of the inner structure of the ring. When the diameter of the ring reaches a predetermined value after repeated multi-rotation rolling, the outer surface of the ring is in contact with the signalling roll, the driving roll stops the feed movement, and the rolling process of the double drive of the ring is completed. In the rolling process, the guide motion of the guide roll ensures the smooth rotation of the ring. -Rolling Technology

1.Process of rolling

The rolling process is a process in which the friction force between the workpiece and the roll pulls the piece into the roll with different rotation directions to produce plastic deformation. More than 90% of metal materials, especially steel materials, are processed by rolling. -Rolling Technology

Rolling Technology1 - Introduction of Rolling Technology

According to the product type, the rolling process can be divided into four basic types: strip rolling, tube rolling, profile rolling, bar and wire rolling, hot rolling and cold rolling. According to the thickness, it can be divided into thin plate (thickness < 4mm), medium plate (thickness 4~20mm), thick plate (thickness 20~60mm), thick plate (thickness > 60 mm, thickest 700mm). -Rolling Technology

 

2.Rolling deformation theory

2.1 Rolling deformation zone

The part in which the workpiece deforms under the action of roll is called the rolling deformation zone.

Rolling Technology2 - Introduction of Rolling Technology

2.2 Simple ideal rolling and geometric deformation zone

The simple ideal rolling conditions are as follows: the roll diameter is the same, the rotational speed is equal, the roll is cylindrical rigid body, the workpiece is uniform continuum, the deformation is uniform and the workpiece is flat plate. Geometric deformation zone: the geometric zone between the workpiece and the roll contact surface, that is, the area ACBD formed from the vertical plane of the piece into the bar to the vertical plane of the roll out of the workpiece.

Rolling Technology3 - Introduction of Rolling Technology

2.3 Relationship between parameters of deformation zone in simple rolling

1) the angle between the first contact point of the roll and the connection between the center of the roll and the center of the two rolls when the workpiece is bitten into the roll.
 2) the horizontal projection length of the contact arc between the workpiece and the roll. When the diameter of the two rollers is equal:

Rolling Technology4 - Introduction of Rolling Technology

2.4 deformation theory

2.4.1Formation of coarse grain area on the surface of the strip along the direction of the height of the section of the rolled piece:
  • due to the existence of friction force during rolling, There is a difficult deformation zone in the contact part between the workpiece and the roll. When the rolling lubrication condition is not good, the coarse grain area is easy to be produced in the surface layer. The lubrication can be improved by opening the cooling water between the stands.
2) the deformation distribution along the top of the workpiece is uneven and the deformation of the surface layer is small. When the distribution of reduction amount is unreasonable, the deformation of the surface layer of the rolling piece is small, resulting in coarse grain.

Rolling Technology5 - Introduction of Rolling Technology

2.4.2 inhomogeneous deformation theory:
1) the distribution of stress and metal flow along the height of the section of the workpiece is not uniform.
2) in the geometric deformation zone and on the contact surface between the workpiece and the roll, there is not only relative slippage, There is also adhesion. There is no relative slippage between the workpiece and the roll in the adhesive zone.
3) deformation occurs not only in the geometric deformation zone, but also outside the geometric deformation zone, and the deformation distribution is uneven. The rolling deformation can be divided into three parts: the deformation transition zone, the front slip zone, the back slip zone and the adhesion zone.
4) there is a critical interface in the adhesion zone, on which the metal flow velocity is uniformly distributed and is equal to the horizontal speed of the roller.

 

 

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