RU2064352C1 - Method for preventing skewness of rolls of rolling mill with hydraulic screwdown mechanisms - Google Patents

Abstract

FIELD: rolled stock production, namely, methods of controlling hydraulic screwdown mechanisms. SUBSTANCE: method involves closing the working cavity of damaged hydraulic cylinder 1 (2) by hydraulic lock 14 (15); cutting off servovalve 7 (8) from cylinder 1 (2) by distributor 12 (13) and connecting main line between hydraulic lock and distributor with draining system; providing cylinder operation in mode of positional adjustment with use of signals of system for measuring position of sealed cylinder 1 (2). EFFECT: elimination of strip jamming, breakage of roll upon damage occurring, lowered idletime periods of mill. 1 dwg

Description

 A method for preventing skewing of rolls of a rolling mill with hydraulic pressure devices relates to the field of rolling production, in particular, to methods for controlling hydraulic pressure devices.

There are various methods and techniques used in cases of malfunctions in the equipment of hydraulic pressure devices (GNU) of rolling mills in order to eliminate emergency situations or to minimize their possible consequences. The most severe consequences on a continuous rolling mill can be caused by spontaneous skewing of the roll as a result of the failure of any elements of the hydraulic actuator (primarily the servo valve) or one of the branches of the GNU electrical control system. In the event of a malfunction, IHI (Japan) applies a quick opening of the roll gap followed by an emergency stop of the mill (materials from the IHI symposium held at Mintyazhmash, 1986)
With this approach, the opening of the gap should occur simultaneously in the stand with a faulty GNU and all subsequent stands. In this case, the rolled strip is inevitably rejected, and in addition, there remains a high probability of the strip getting stuck and breaking the rolls.

 The closest technical solution, selected as a prototype, is the Schlomann-Siemag (Germany) method of preventing skewing of rolls, which includes locking the working cavities of the cylinders with hydraulic locks, assigning servo valves that supply fluid to the working cavities from the cylinders with distributors, connecting the mains between the hydraulic locks and dispensers with drain. In the event of a malfunction, the Schlomann-Siemag GNU of the German Federal Republic gives a command to cut off the cylinders from the servo valves and the power line using controlled check valves (hydraulic locks) in order to be able to complete the rolling of the strip in the stands. At the same time, a command is sent to all the hydraulic locks of a given stand, i.e. both GNU cylinders acting on the rolls are blocked. Technical description of the Schlomann-Siemag company according to the GNU of the 2000 NLMK mill 1988. Appendix 9-2, 5.2, section 4.6.1.

 A significant disadvantage of this method is the possibility of an uncontrolled skew of the roll due to uneven response times of the hydraulic locks or the presence of uneven leaks through the hydraulic locks and cylinder seals. Skew, in turn, can lead to the ejection of the strip and its jam, breakage of the rolls, etc.

 The inventive method provides automatic support of the axis of the roll parallel to its position that it occupied at the time of the malfunction, thereby eliminating spontaneous skewing of the roll of the stand, possible jamming and ejection of the strip, breakage of the roll, significantly reducing the time of mill downtime and the associated loss of finished products.

 This technical result is achieved by performing the following interrelated actions. Locking the working cavity with a hydraulic lock of a faulty hydraulic pressure device, shutting off the servo valve from the cylinder with a distributor and connecting the line between the hydraulic lock and the distributor with a drain, and continuing to work the second cylinder in position control mode using the signal from the locked cylinder piston position measuring system.

 The following is a specific example of the implementation of the proposed method. The drawing shows a block diagram of a device according to the invention.

 The device contains hydraulic cylinders 1, 2, mounted under the pressure screws 3, 4 on the pillows 5, 6 of the backup rolls of the rolling stand.

 Electro-hydraulic servo valves (CK) 7, 8, designed to control cylinders 1, 2, are connected to the outputs of the electronic control system 9. Servo clans 7, 8 are supplied with pressure from the power line P pit. and pressure from the control line P control. to the control stage of the servo valve 7, 8. The outputs of the servo valves 7, 8 are connected to the working cavities 10, 11 of the cylinders 1, 2 through the valves 12, 13 and the hydraulic locks 14, 15. To control the hydraulic locks 14, 15, pilots 16, 17 are provided. 1, 2 are connected to a constant pressure line P pit. creating the necessary return force when moving the rolls towards the opening of the gap (in the absence of metal in the stand).

 On the bodies of cylinders 1, 2, position sensors 18, 19 and 20, 21 are installed in pairs, connected via blocks 22, 23 of position measurement systems to the electronic control system 9 of the GNU.

 The claimed method is implemented as follows.

 When the GNU is operating in normal mode, the electromagnets of the pilots 16, 17 and the distributors 12, 13 are turned on. According to the instructions of the electronic control system 9, the servo valves 7, 8 can either supply fluid to the working cavities 10, 11 of the cylinders 1, 2, or communicate these cavities with a drain. The magnitude of the opening of the servo valves 7, 8 in one direction or another is set by the electronic system 9, taking into account the feedback signals received from the position measurement systems 22, 23 and representing a half-sum of the signals of the position sensors 18, 19, 20.21.

 Each task value at the input of the electronic system 9 corresponds to a certain position of the pistons of the hydraulic cylinders 1, 2 (position control mode). For simplicity, the scheme does not show duplicate servo valves, the equipment necessary for their connection, protective filters, etc. not relevant to the invention.

 In the event of malfunctions in the hydraulic elements of the hydraulic valve (for example, failure of the servo valves 7, 8, switching elements from the worker to the backup servo valve) or in the electronic control system 9, leading to a malfunction of the hydraulic valve on one side of the stand (for example, the left one) and with a working measurement system the position of the cylinder 1, the electromagnets of the pilot 16 and the distributor 12 are turned off. The hydraulic lock 14 locks the working cavity of the cylinder 1 of the GNU, the servo valve is cut off from the cylinder 1 by the distributor 12, and the line between the hydraulic lock 14 and the distributor Telem 12 is connected to the drain. This eliminates the recharge of the cavity of the cylinder 1 through a faulty servo valve 7 from the power line.

 The position measuring system, which is supposed to be operational, continues to provide feedback signal from the locking cylinder 1 of the GNU to the electronic system 9. Possible leaks through the hydraulic lock 14 or seals of the cylinder 1 will lead to a drift of the piston of the cylinder 1. A working positional regulation loop of the right side of the stand, the electronic control system 9 will automatically maintain the axis of the roll parallel to its position that it occupied at the time of the malfunction, thereby eliminating spontaneous misalignment of the shaft of this stand, possible jamming of the strip, breakage of the roll, etc. the strip in the cage group can be rolled.

 In the event of a malfunction of the GNU on the right side of the stand and a functioning system for measuring the position of the hydraulic cylinder, its locking and maintaining a given skew of the roll are carried out similarly to that described.

 The possibility of rolling the strip in a continuous group of stands by preventing roll skewing, eliminating strip ejection or jamming, and breakage of the roll in the event of malfunctions in the GNU, significantly reduces the time of mill downtime and the associated loss of finished products.

Claims (1)

 A method for preventing the skewing of rolls of a rolling mill with hydraulic pressing devices, including locking the hydraulic locks of the working cavities of the cylinders, cutting off the servo valves supplying liquid to the working cavities from the cylinders by the distributors, connecting the lines between the hydraulic locks and the distributors with the drain, characterized in that in the event of malfunctions leading to a violation the functioning of the hydraulic pressure device on one side of the stand and while maintaining the operability of the piston position measuring system of the device’s cylinders, they lock the working cavity of the faulty hydraulic pressure device with a hydraulic lock, cut off the servo valve from the cylinder with a distributor and create a line between the hydraulic lock and the distributor with a drain, continue the second cylinder in position control mode using the signal from the locked cylinder piston position measuring system.