JPH0459046B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a single-choke work roll bending method for a rolling mill.

<Conventional technology> Roll bending of rolling mills was introduced in September 1973.
20th, Steel Manufacturing Method (Second Volume) 205, published by Maruzen Co., Ltd.
There are back-up roll bending and work roll bending, and the latter is Increase bending, in which the work roll is bent into a convex crown by a hydraulic cylinder between the upper and lower work roll chock, as shown in Figure 3A, and the work roll chock and back-up roll, as shown in Figure 3B, There is day crease bending in which the work roll is bent into a concave crown by the force of the hydraulic cylinder between the chock.

For this work roll bending, special public
As described in FIGS. 1 to 5 and 6 to 10 of Japanese Patent No. 26142, there are a single chock type work roll bending method and a double chock type work roll bending method.

The present invention relates to an improvement of the single chock type work roll bending method.

<Problems to be Solved by the Invention> In recent years, the bending hydraulic pressures used in single-chock work roll bending methods are: Increase bending above the work roll balance hydraulic pressure Increase bending below the work roll balance hydraulic pressure Work roll There are three types of decrease bending that are performed using a hydraulic system separate from the balance hydraulic system.

The work roll balance hydraulic pressure related to ~ brings the work roll during non-rolling into contact with the back-up roll at a predetermined contact pressure. If the conditions are not correct, smooth and stable rolling cannot be maintained, so it is important to maintain the oil pressure and maintain normal operating conditions.

Under these circumstances, in the above case, the hydraulic pressure supplied to the increase bending cylinder is the work roll balance hydraulic pressure when not rolling, and during rolling,
The increase bending pressure is less than the work roll balance oil pressure, and is the soft touch pressure necessary for the cylinder to contact the chock, which will be described later.

Therefore, when the plate is engaged or pulled out, the work roll balance hydraulic pressure is switched to or hydraulic pressure.
Next, a switch is made to return to work roll balance hydraulic pressure.

The problem lies in the switching at the time of return, and in particular, a delay in control when the plate is pulled out makes it impossible to maintain roll balance, which is fatal, as will be described later. Therefore, it is common practice to predict blanking and to preventively complete the switching before the prediction occurs.

Because of this, there are parts of the board where bending is not applied at the top and bottom. This preventive switching part causes a large change in bending force, and the resulting change in the plate crown causes problems such as off-gauge, instability of the plate path, and end drawing, making it impossible to continue smooth and stable rolling. Become.

As described in Japanese Patent Publication No. 51-26142, the inability to maintain the roll balance due to the control delay during the above-mentioned sheet removal causes a collision between the upper and lower work rolls immediately after the sheet is removed, and this can be prevented. Therefore, as mentioned above, release the hydraulic pressure before the board comes out. As a result, there inevitably arises a portion of the rolled material that is not bent, so the proposal proposes a double chock method as a method to solve this problem. However, this method increases equipment costs and maintenance costs.

The present invention solves these problems, cancels the bending hydraulic pressure before the strip is removed from the rolling mill, and enables rolling to perform sufficient bending without changing to the work roll balance hydraulic pressure in advance. This provides a work roll bending method using a single check method that can be continued.

<Means for Solving the Problems> The present invention is a method for solving the above problems, in which the cylinder for roll balance and the cylinder for increase bending are used together, and increase bending is performed at a pressure lower than the roll balance hydraulic pressure. Or, when performing Decrease Bending by setting the cylinder pressure to a soft touch hydraulic pressure lower than the roll balance hydraulic pressure, the surge pressure generated in the Increase Bending cylinder when the rear end of the rolled material exits the rolling mill is reduced. This is a work roll bending method for a rolling mill, characterized in that the hydraulic pressure supplied to the cylinder is switched from the increase bending hydraulic pressure or the soft touch hydraulic pressure to the roll balance hydraulic pressure.

<Function> In solving the above-mentioned problems, the present inventors have realized that an increase in equipment costs and an increase in maintenance costs as seen in the proposal in the above-mentioned Japanese Patent Publication No. 51-26142 will inevitably occur. We considered a method that does not use the double chock method, focused on the change in the oil pressure inside the increase cylinder when the mill spring changes from elongation during rolling to contraction during sheet removal, and investigated the actual situation and found that it was 200Kg/cm. A surge oil pressure of about ² is generated, and it takes about 0.5 seconds to drop to the work roll bending oil pressure. If this surge oil pressure is used, the bending oil pressure can be released before the rolling mill rolls out. It has been found that it is possible to switch from increase bending hydraulic pressure or soft touch hydraulic pressure to work roll balance hydraulic pressure without any trouble.

Based on this knowledge, the present inventors investigated the relationship between rolling load, surge pressure, and its duration, and also conducted increase bending in the same system with a hydraulic pressure lower than the work roll balance hydraulic pressure, and in different systems. We investigated and examined the minimum surge pressure required to smoothly and stably switch from decrement bending to work roll balance hydraulic pressure and the minimum time required to maintain that hydraulic pressure.

According to these confirmation results by the inventors, the time required to maintain surge pressure is generally the minimum in rolling mills commonly used in the industry.
This is about 0.3 seconds, and it has been found that if the time is shorter than this, the valve operation necessary for switching will not be completed, so it must be avoided.

This maintenance time is controlled by the relationship between the magnitude of the surge pressure generated from the relationship between the mill spring constant and the rolling load, and the diffusion and extinction rate of the surge pressure, and this diffusion and extinction rate is controlled by the airtightness of the hydraulic system. Therefore, it differs depending on the equipment or line. In the normally used work roll bending hydraulic system or roll balance hydraulic system in a rolling line with a rolling load of about 1000 tons, the time for surge pressure to disappear is about 0.5 seconds.
In order to increase this surge pressure and extend its duration, it has been found that in addition to making each cylinder airtight, it is desirable to contain the surge pressure near the cylinder.

The present invention has been made based on the above knowledge.

<Example> The present invention will be described in detail below based on the drawings showing an example of the present invention.

In Fig. 1, S is the rolled material, 1 _WU is the upper work roll, 1 _WL is the lower work roll, 1 _BU is the upper back up roll, 1 _BL is the lower back up roll,
F _IW is the work side hydraulic cylinder for increase bending, F _ID is the drive side hydraulic cylinder for increase bending, F _DW is the work side hydraulic cylinder for decrease bending, F _DD is the drive side hydraulic cylinder for decrease bending. For both F _DW and F _DD , U is for the upper roll and L is for the lower roll.

Both of the increase bending hydraulic cylinders F _IW and F _ID mentioned above also function as work roll balance cylinders.

Hydraulic cylinder for increase bending
The hydraulic pressure of F _IW , F _ID and Decrease bending hydraulic cylinders F _DWU , F _DWL , F _DDU , F _DDL is controlled by INC circuit 2 and DEC circuit 3, and piping 2
2 and 23 to each cylinder.

The INC circuit 2 includes a roll balance circuit including a pressure reducing valve 4 and a relief valve 5 set to a required roll balance pressure, and an operation command device (not shown).
and an increase bender circuit equipped with a pressure control valve 6 for controlling the increase bending pressure or soft touch pressure commanded by the controller, and switching between the two circuits is performed by an electromagnetic switching valve 7. In the figure, when the electromagnetic switching valve 7 is excited a, it becomes a roll balance circuit, and when it is excited b, it becomes an increase bending circuit. The outlet pressure of the pressure control valve 6 is controlled to the pressure set by the pressure detector 8 from the above-mentioned operation command device.

In addition, the DEC circuit includes a soft touch circuit equipped with a pressure reducing valve 9 and a relief valve 10 that are set to the required soft touch pressure, and a pressure control valve that controls the decrement bending pressure to the decrement bending pressure commanded by the operation control device, similar to the INC circuit 2. It consists of a DEC circuit with 11 and a DEC circuit with
This is done by In the figure, when the electromagnetic switching valve 12 is excited a, it becomes a soft touch circuit, and when it is excited b, it becomes a decrease bending circuit. The outlet pressure of the pressure control valve 11 is controlled to a pressure set in the pressure detector 13 by the above-mentioned operation command device. The soft touch pressure and soft touch circuit referred to here refer to the increase bending cylinders F _ID , F _IW or the decrease bending cylinders F DWU , F _DWL , F _DDU when decrease bending or decrease bending is not _used . , F _DDL is kept in constant contact with each work roll chock to ensure a quick and accurate response when switching to increase bending or decrease bending, and the pressure is controlled by a circuit. be.

In the INC circuit configured in this way, when the work roll bending pressure is lower than the work roll balance pressure, the solenoid valve 7 is energized by a before the rolled material S is bitten by the work rolls 1 _WU and 1 _WL , and the roll balance circuit is The roll balance pressure is supplied to the increase bending cylinders F _ID and _FIW , which functionally also serve as roll balance cylinders. In this state, the pressure control valve 6 is controlled so that the required increase bending pressure set in the pressure detector 8 can be output from the operation command device. Next, the rolled material S is transferred to work rolls 1 _WU and 1 _WL.
At the same time, the solenoid valve 7 is switched to b excitation to supply increase bending pressure to the increase bending cylinders F _ID and _FIW . When the rolling is completed and the rolled material S is released from the work rolls 1 _WU and 1 _WL , the solenoid valve 7 is energized again to supply roll balancing pressure to the cylinder.

In the case of decrease bending, the pressure control valve 11 supplies hydraulic pressure controlled to, for example, 80 kg/cm ² to the decrease bending cylinders F _DW and F _DD .
Increase bending cylinder F _ID , F _IW
For soft touch, a hydraulic pressure of 30 kg/cm ² is supplied through the pressure control valve 6 for rolling, and at the same time as the rolled material S is released, the increase bending cylinders F _ID and F _IW are activated by the solenoid valve 7. By excitation a, the roll balance pressure is switched to hydraulic pressure of 80 kg/cm ² , and at the same time, the decrement bending cylinders F _DW and F _DD are set to a soft touch pressure of 30 by excitation a of the solenoid valve 12.
Switch to Kg/ ^cm2 . Figure 2 shows the hydraulic pressure switching situation during this time. In the figure, A shows an example of the present invention, and B shows a conventional example.

As is clear from FIG. 2A, in the example of the present invention, the increase bending cylinders F _ID ,
F _IW changes continuously from soft touch pressure to roll balance pressure through the surge pressure generated by the release of the rolled material S (generated by the compression of the increase bending cylinder due to recovery contraction of the extension by the mill spring). Since it is switched,
The bending control necessary for the rolled material S is sufficiently performed. In contrast, the conventional example is shown in Fig. 2B, and as mentioned above, the decrement bending pressure is already released before the rolled material S is released, and the pressure is changed to soft touch pressure, and the increase bending cylinder F _ID , Since the F _IW is supplied by switching from soft touch pressure to roll balance pressure, there are parts of the rolled material S where bending control is not performed, resulting in unavoidable shape defects and lower yields. . This also applies to increase bending, which is performed at a hydraulic pressure lower than the work roll balance pressure.

In carrying out the present invention, switching to roll balance pressure, bending pressure, and soft touch pressure is performed by switching the solenoid valves 7 and 12 as in this example.
The supply pressure may be continuously switched by controlling each electromagnetic valve with b excitation using the pressure control valves 6 and 11.

<Effects of the Invention> The present invention suppresses surge hydraulic pressure caused by the compression action generated in the bending cylinder installed in the rolling mill by the rolling load and the constant of the mill spring that is inevitably included in the rolling mill. Since the bending pressure or soft touch pressure is switched to the roll balance pressure through the press, the bending control of the rolled material can be carried out over the entire rolled material, which improves the accuracy and effectiveness of the shape control of the rolled material, and improves the yield. , rolling operability, and workability are significantly improved.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of the configuration of a device used in an embodiment of the present invention, Fig. 2 is a diagram showing changes over time in the bending oil pressure in an embodiment of the present invention and a conventional example, and Fig. 3 A and B. FIG. 2 is a diagram showing a work roll bending method and the positional relationship of bending cylinders. S...Rolled material, F _DD ...Drive side cylinder for decrease bending, F _DW ...Work side cylinder for decrease bending,
F _ID ...Drive side cylinder for increase bending, F _IW ...Low side cylinder for increase bending, I _W ...Work roll, I _B ...Backup roll, 2...INC circuit, 3... DEC circuit, 4, 9...Reducing valve, 5,
10... Relief valve, 6, 11... Pressure control valve,
7, 12... Solenoid valve, 8, 13... Pressure detector,
22, 23... Hydraulic piping.

Claims (1)

[Claims] 1. A cylinder for roll balance and a cylinder for increase bending are used together, and increase bending is performed at a pressure lower than the roll balance hydraulic pressure, or the cylinder pressure is decremented as a soft touch hydraulic pressure lower than the roll balance hydraulic pressure. When bending, when the rear end of the rolled material exits the rolling mill, the increase bending hydraulic pressure or soft touch hydraulic pressure is supplied to the increase bending cylinder via the surge hydraulic pressure generated in the increase bending cylinder. A work roll bending method for a rolling mill, characterized by switching from to roll balance hydraulic pressure. 2. A work roll bending method for a rolling mill according to claim 1, characterized in that the rolling load is maintained at 1000 tons or more.