1 Roll bending technology and positive and negative bending
In strip production, the bending and channeling roll devices are an indispensable part. Bending roller can improve strip shape; Roll channeling is horizontal roll channeling, improve the efficiency of roll, and extend roll life. However, in actual use, bending and shifting roller devices often appear oil leakage, internal leakage, piston rod strain, dust ring out, shifting roller in the process of steel, oil block rotating joint pipeline pull, and other malignant phenomena, bringing adverse effects to equipment and production.
Roll bending technology A technique of bending the roll body by mechanical force to control strip crown (see plate crown) and flatness (see flatness control). Hydraulic roll bending has been developing rapidly since its appearance in the early 1960s. Hydraulic roll bending device has become essential equipment in various strip mills.
Bending roller cylinder, including cylinder block, cylinder head, piston rod, seal, and so on. Work roll bending system cylinder is also used for balancing and pressing the work roll. The fixed seat is fixed on the inside of the archway window, with a replaceable slide plate, fixed with screws and wedge keys, used to support the mobile seat. Each moving block is equipped with a vertical bending/balancing hydraulic cylinder, work roll rolling cylinder, and work roll locking cylinder. There are also replaceable slide plates between them and the fixed seat and work roll-bearing seat. The work roll locking system is hydraulic locking, which is horizontally arranged on the operating side. Clamp the upper and lower work roll bearing seat and transfer the axial channeling momentum to the work roll, which needs to be opened when changing the roll.
Bending roll can improve the strip shape. When bending roll control is needed, the hydraulic system is changed from the pressing position to the bending position, and the bending force is applied to the work roll to change the roll gap of the mill, so as to achieve the purpose of controlling the strip shape.
2 Bending and channeling roll often occur fault
(1) The bending roller cylinder often appears oil leakage, internal leakage, piston rod strain, and dust ring out.
(2) Roll channeling cylinder often appears end cover leakage, roll channeling locking mother, piston rod screw sliding wire pull bad, roll channeling in the process of steel running.
(3) The pipeline of the rotary joint of the oil roadblock of the lower moving seat on the transmission side is pulled off, resulting in failure time and a large number of oil leakage.
Hydraulic roll bending technology can be divided into:
- Work roll bending: the ratio of roll length L to diameter D L/D<3.5
- Support roll bending roll: L/D≥3.5
There are positive bending and negative bending in the two bending ways.
Positive bending: the bending direction of the roll produced by bending force is opposite to that caused by rolling force, that is, the crown of the work roll increases when bending. The hydraulic cylinder is usually installed on the bearing seat of the lower work roll, and the hydraulic roller bending force acts between the upper and lower bearing seats.
Negative bending: the bending direction caused by roll bending force is the same as that caused by rolling force, that is, the crown of the work roll decreases during roll bending. The hydraulic cylinder is installed on the bearing seat of the supporting roll, and the bending force acts between the bearing seat of the working roll and the bearing seat of the supporting roll.
3 advantages of negative bending of work roll:
(1) Roll bending force does not interfere with the automatic control system of plate thickness;
(2) When replacing the work roll, there is no need to remove the high-pressure oil supply loop joint of the hydraulic cylinder;
(3) Can avoid iron oxide, emulsion, and other intrusions into the hydraulic cylinder. The adjustment range of the hydraulic bending roll can be enlarged by adding a negative bending roll.