1 Types and characteristics of six-high rolling mills
At present, HC rolling mills are commonly referred to as HC rolling mills with moving intermediate rolls, also known as HCM six-high rolling mills. In actual industrial production, due to the need to adapt to the needs of different products, six-high rolling mills have developed a variety of models. Its basic form is used in hot rolling mills, cold rolling mills and leveling. For example, if an intermediate roll is added between the work roll and the backup roll of the original four-high mill (HC mill), the intermediate roll can move around the left and right axes, and the positive and negative hydraulic bending rolls of the work roll and the axial movement of the intermediate roll are used to control the belt. The flatness of steel. This is the HCM six-high mill, the structure of which is shown in Figure 1
HCM six-high rolling mill adds intermediate roll bending device to become UCM six-high rolling mill, as shown in Figure 2:
The flatness of the strip is controlled by the hydraulic bending rolls of the work rolls, the intermediate rolls, and the axial movement of the intermediate rolls for rolling wide and thin strips. This is also one of the most common forms of domestic cold rolling equipment applications.
The UCMW six-high rolling mill adopts both work rolls and intermediate rolls that can move, and adopts the form of work rolls and intermediate roll bending rolls, as shown in Figure 3. This model can carry out ultra-bo college rolling.
Compared with an ordinary four-high rolling mill, HC rolling mill has the following characteristics;
(1) Through the axial movement of the rolls, the harmful contact parts between the roll bodies by accident of the plate width are eliminated, and the stiffness of the roll gap is improved:
(2) Because one end of the work roll is cantilevered, under the action of the bending force, the deformation of the edge of the work roll increases significantly. If the requirements for bending control flatness ability remain unchanged, a smaller bending force can be selected on the HC mill, which increases the service life of the work roll bearings and reduces the rolling mill load:
(3) Since it can be adjusted by two means of bending force and roll axial movement, the rolling mill has good shape control ability;
(4) Since it can be adjusted by two means of bending force and roll axial movement, the rolling mill has good shape control ability;
(5) Cylindrical rollers can be used for both work rolls and backup rolls, which reduces the grinding process and saves energy consumption.
Therefore, the six-high rolling mill has improved in terms of shape control force, control of strip edge thinning ability, an increase of reduction, and reduction of rolling functions.
2 The working principle of a six-high rolling mill
The disadvantage of the four-high mill is that the contact area between the work roll and the backup roll is larger than the width of the rolling strip. No matter how large the diameter of the backup roll is, the rolling load will increase the radius of the work roll, as shown in Figure 4.
For flatness, this is a detrimental contact area, which can lead to disadvantages such as work rolls requiring an original crown, difficulty in reducing work roll diameters, ineffective roll bending, and increased inventory of spare work rolls.
At present, the hydraulic bending device has been widely used in strip cold rolling mills to improve the plate shape. Due to the high requirements on the thickness tolerance of cold-rolled strips, in order to increase the reaction speed of the rolling mill reduction device, a fully hydraulic reduction device and an automatic strip thickness control device are used on the cold rolling mill to ensure the thickness tolerance of the strip. For high-speed, high-quality strip cold rolling mills, computer control is implemented. As one of the main actuators of the modern AGC system, the use of hydraulic transmission instead of mechanical transmission greatly improves the response speed, which is the development direction of the transformation of the reduction device of the tandem cold rolling mill.
The six-high rolling mill is one of the ideal advanced equipment for producing high-quality sheet products. It can not only ensure high-quality strip rolling products but also improve productivity, success rate, and energy-saving effect, expand the scope of application and improve the operating performance of the rolling mill. has obvious advantages. The domestic large-scale six-high rolling mill has been successfully widely used in industrial production, and its technical level and function have reached the level of similar foreign equipment.