JP2002178011A - Hot lubricating rolling method and apparatus for steel sheet - Google Patents

Abstract

(57) Abstract: The present invention relates to a hot rolling apparatus and a hot rolling method capable of performing stable rolling by preventing biting failure during hot lubricating rolling of a steel sheet. After the leading end of a rolled material (8) bites into a work roll (1), application of rolling lubricating oil to the work roll (1) is started, and lubricating rolling is performed until rolling of the rear end of the rolled material (8) is completed. After the rolling of the preceding rolled material is completed and before the succeeding rolled material bites into the work roll 1, the rolling lubricating oil adhered to the work roll 1 during the rolling of the preceding rolled material is removed. A characteristic hot rolling method. It is desirable that the rolling lubricating oil be removed by injecting hot water of 50 ° C. or higher onto the work roll 1 or the work roll 1 and the backup roll 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot rolling method and a hot rolling apparatus capable of preventing a biting defect in hot lubricating rolling of a steel sheet and enabling a stable rolling operation.

[0002]

2. Description of the Related Art Generally, a rolling load, a rolling torque, a motor power, and the like for determining a rolling reduction in hot rolling of a steel sheet are as follows.
It is limited by the equipment strength of the rolling mill, which depends on the strength of the rolling rolls. Normally, when a steel sheet is rolled by a hot-roll finishing tandem mill including 5 to 7 stands of rolling mills, the rolling temperature is the lowest in the rear end region of the rolled material. Therefore, a normal rolled material such as low carbon steel is rolled at a rolling reduction of about 40 to 50% even in a stand before the finishing mill in consideration of restrictions such as rolling load, rolling torque, and motor power.

In recent years, when hot-rolling a difficult-to-deform material having a high deformation resistance, which has been increasing in demand, it is necessary to reduce the rolling reduction at each stand as compared with a normal rolled material. Becomes difficult. On the other hand, in order to reduce the cost of production, the realization of a process for producing a hot-rolled product with a smaller number of stands is required, and even in a normal rolled material, it is possible to perform rolling at a higher pressure reduction rate. In addition, improvement in the rolling capacity of a hot rolling mill is expected.

[0004] As a method of increasing the rolling capacity of the hot rolling mill, a method of increasing the rolling load and rolling torque by reducing the diameter of the work roll, and a method of expanding the rolling torque by increasing the motor power. Etc. However, all of these methods require significant equipment modifications,
There is a problem that equipment costs increase.

The inventors of the present invention have proposed a method of solving the above-mentioned problem by using a lubricating oil to reduce the rolling load and rolling torque and improve the rolling capacity (Japanese Patent Laid-Open No. 63-63). -238904). Specifically, a hot rolling method using a lubricating oil having high lubricity such that the friction coefficient between the rolled material and the work roll is 0.2 or less (hereinafter, referred to as “hot lubricating rolling method”) As a measure for reducing the biting property of the rolled material during hot lubrication rolling, a method of applying a compressive force to the material to be rolled at the time of biting has been proposed. By adopting this method, the critical draft can be increased to about 70%. The hot lubricating rolling method is a technology that enables rolling at a high pressure reduction rate without requiring significant equipment remodeling because the rolling load and rolling torque can be significantly reduced.

[0006] However, if the coefficient of friction is too low, the ability of the leading end of the rolled material to bite into the work roll deteriorates.
In particular, when rolling a rolled material having a large thickness, the amount of reduction is limited, and there is a problem that rolling at a high reduction rate higher than conventionally performed cannot be performed. For example, when lubricating a rolled material having a thickness of 30 to 40 mm before finish rolling using a rolling mill having a work roll diameter of a finishing mill of about 800 mm, in a lubricating rolling having a friction coefficient of about 0.2, Considering the tip shape (vertical warpage called nose rising and nose falling) and mill rigidity, the tip biting angle is limited to about 12 °, and the rolling reduction that enables stable biting of the rolled material tip is Approximately 10mm (25% to 35% reduction).

[0007] Such a phenomenon is caused by difficult-to-work materials (rolled materials requiring high rolling load, rolling torque, high motor power, etc.).
Not only when lubricated rolling is performed, but also when lubricated rolling is performed and then rolling is performed without lubrication using the same rolling mill. This is because even if an attempt is made to lubricate the succeeding rolled material without lubrication, the lubricating oil applied when the preceding rolled material is lubricated and rolled remains on the work rolls and backup rolls. This is because the embedding property deteriorates.

Conventionally, in order to prevent the biting property of the succeeding rolled material from deteriorating, the application of lubricating oil is conventionally stopped during the rolling of the rear end region of the preceding rolled material, and the lubricating oil adhering to the roll is burned off by the heat of the rolled material. However, this method is not applicable to the rolling of difficult-to-machine materials in which the rolling load and the rolling torque need to be reduced even in the rear end region of the rolled material.

In the method disclosed in JP-A-63-88904, a compressive force is applied to the material to be rolled during biting to improve biting performance. There is a problem in that the compressive force becomes excessive, and ancillary facilities such as a compressive load device and guides for preventing buckling generated by the compressive load become large. In particular, since the compressive force is limited by the limit of the buckling prevention effect, the effect of improving the biting property is also limited.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide a lubricating roll using a lubricating oil having a friction coefficient of 0.2 or less, for example, in order to improve the biteability of the leading end of a rolled material into a work roll. It is an object of the present invention to provide a rolling method that enables stable rolling and a device that realizes the method.

[0011]

Means for Solving the Problems In order to solve the above problems, the present inventors have conducted various rolling tests and studies on improving the biting property of the rolled material tip and ensuring the stability of rolling during hot lubrication rolling. And obtained the following findings. (a) In order to stably reduce the rolling load and the rolling torque in all regions of the rolled material, it is necessary to continue to apply the lubricating oil to the work rolls from the start to the end of the rolling. However, in this case, the lubricating oil adheres and remains on the work roll and the backup roll, and deteriorates the biting property of the succeeding rolled material. If the lubricating oil adhering and remaining on the work roll is removed before the subsequent rolled material is bitten, the biting property of the subsequent rolled material can be improved. (b) In general, the finishing hot rolling mill for steel sheets is a multiplex rolling mill, and lubricating oil remains on the work roll and the backup roll. In the case where the succeeding rolled material bites immediately after the cleaning), even if only the work roll is cleaned, the biting property is greatly improved. (c) As a method of removing the lubricating oil, if the roll is washed by injecting hot water of 50 ° C. or more at a high pressure, the lubricating oil remaining on the roll can be removed, so that the biting property of the succeeding rolled material is reduced. It becomes equivalent to the rolling state in the case of non-lubricated rolling. (d) Roll cleaning with high-pressure hot water is more effective as the temperature is higher and the discharge pressure is higher. In particular, the effect of temperature is great. The present invention has been made based on the above findings,
The summary is as follows. (1) After the end of the rolled material bites into the work roll,
Start application of rolling lubricating oil to work rolls, perform lubricating rolling until rolling of the rear end of rolled material is completed, and after rolling of preceding rolled material is completed, succeeding rolled material bites into the work roll A hot rolling method comprising removing rolling lubricating oil adhered to a work roll during rolling of a preceding rolled material. (2) A hot rolling device having a work roll and a backup roll, wherein a rolling lubrication header for applying the rolling lubricant to the work roll, the work roll or the rolling lubricant adhering to the work roll and the backup roll is heated with high-pressure hot water. A hot-rolling apparatus comprising a roll cleaning header for cleaning, a detection device for detecting a state of the rolled material biting into a work roll, and a control device for controlling supply of high-pressure hot water to the roll cleaning header. .

In the hot rolling method (1), it is desirable to remove the rolling lubricating oil by injecting hot water of 50 ° C. or more onto the work roll or the work roll and the backup roll.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a hot rolling apparatus according to the present invention will be described.

FIG. 1 is a schematic side view showing an example of the hot rolling apparatus of the present invention. As shown in the figure, the apparatus of the present invention is a quadruple rolling mill composed of a work roll 1 and a backup roll 2, and includes a rolling lubrication header 3, a work roll water cooling header 4, and a roll cleaning header 5. Is its main component.

The rolling lubrication header 3 is a device for applying lubricating oil or an aqueous lubricating oil solution to the work roll 1, and is a pipe for supplying pressurized lubricating oil or an aqueous lubricating oil solution and a nozzle for injecting it into the roll. Consists of When the lubricating oil is mixed with water, the lubricating oil may be mixed using a normal water injection type mixing device and then sent to the header 3. The heat-insulating plate 6 installed under the rolling lubrication header 3 is necessary for mechanical and thermal protection of the lubrication header.
When lubrication is not used, the temperature of the header rises, and the lubricating oil has a role of preventing the nozzle from becoming clogged due to high viscosity. In addition, the draining plate 7 ensures that the lubricating oil adheres to the work roll,
This is for obtaining a stable lubrication effect.

The roll cleaning header 5 is an apparatus for cleaning the work roll 1 or the work roll 1 and the backup roll 2 from the mill exit side. The roll cleaning header 5 shown in FIG. 1 is for cleaning both the work roll 1 and the backup roll 2, but the work roll 1 and the backup roll 2 may be separately provided. In addition, even if only the work roll 1 is washed, the biting property can be improved. However, when the thickness of the rolled material is large, or when using a lubricating oil with high lubrication performance (a lubricating oil that greatly reduces the coefficient of friction and increases the load reduction effect), the biting performance is as stable as non-lubricated rolling. It is preferable to wash both the work roll 1 and the backup roll 2 in order to secure the condition.

The detecting device 9 is provided for detecting the work roll 1 of the rolled material 8.
This is a device for detecting the state of biting into the device. When a load equal to or more than a preset value is detected by a load cell for detecting a rolling load, it is determined that biting is being performed. The biting state detected in this way is transmitted to the control device 10.

The control device 10 controls the valve according to the biting condition.
Adjust the opening degree of 11, cleaning solution to the roll cleaning header 5,
For example, the supply of hot water is controlled. Specifically, the valve 11 is closed immediately after the rolled material 8 bites into the work roll 1, and the valve 11 is opened immediately after the rear end region of the rolled material 8 bites off. Control the supply. The control device 10 controls the supply of the cleaning liquid to the roll cleaning header 5 for each stand as shown in the figure, and also, for example, detects the biting condition detected by the detection device 9 on the upstream side of one stand. Accordingly, a device that controls the supply of the cleaning liquid to the roll cleaning header 5 may be used.

Next, an example of the hot rolling method of the present invention will be described with reference to FIG.

In the hot rolling method of the present invention, lubricating oil application to the work roll 1 starts immediately after the rolled material 8 bites into the work roll 1. This is because the temperature is high in the leading end region of the rolled material 8 and the rolling load is about 10 to 30% lower than that in the trailing end region, so that rolling can be performed without lubrication. This is because the biting performance of the workpiece 8 into the work roll 1 is better when the friction coefficient at the time of biting is high, that is, when lubrication is not performed before biting.

The lubricating oil is applied to the work roll 1 until the rear end region of the rolled material 8 comes out of the rolling device. this is,
As described above, since the temperature is lower and the rolling load is higher in the rear end region of the rolled material 8 than in the front end region, it is necessary to reduce the friction coefficient in the rear end region of the rolled material 8. As described above, in the hot rolling method of the present invention, a low rolling load can be secured from the front end to the rear end of the rolled material 8 while ensuring the biting property of the rolled material 8.

In the hot rolling method of the present invention, the work roll 1 or the work roll 1 and the backup roll 2 adhere to the work roll 1 from the end of the rolling of the preceding rolled material until the subsequent rolled material bites into the work roll 1. Wash rolling lubricant. This is because if the lubricating oil during the rolling of the preceding rolled material remains on the work roll 1 when the subsequent rolled material bites into the work roll 1, the friction coefficient in the leading end region of the subsequent rolled material is too low. This is because the biting property deteriorates.

The method of cleaning the roll is not particularly limited. Any material that can efficiently remove the lubricant remaining on the work roll may be used. For example, a method in which a cleaning liquid such as hot water is sprayed on the roll by an apparatus such as the roll cleaning header 5 shown in FIG. 1 described above, or a method in which a brush containing soapy water is pressed against a work roll may be used. A method of removing the lubricant remaining on the roll may be used. In particular, the former method is desirable in terms of cost and simple equipment.

When the rolls are washed by jetting hot water, the temperature of the hot water needs to be 50 ° C. or higher. These conditions were determined from the biting condition when hot lubricating rolling was performed under the following rolling conditions, lubricating conditions, and roll washing conditions. <Rolling conditions> Work roll (diameter: 200mm, barrel length: 4
0.05% carbon steel (thickness: 15mm, width: 300m) using a small quadruple rolling mill consisting of 50mm, rotation speed: 50mpm) and backup roll (diameter: 350mm, barrel length: 450mm)
m, temperature: 1000 ° C) with an opening of 8.2mm (bite angle: 15.0 °,
Hot rolling was performed at a rolling reduction of 45.3%). <Lubrication conditions> Lubricating oil of 0.2 l / min (viscosity of 10 ^{-4 at} 40 ° C mixed with synthetic ester oil, mineral oil and extreme pressure additive)
m ² / s of lubricating oil) was mixed with 6 l / min of water and sprayed from the water injection type rolling lubrication header 3 onto the upper and lower work rolls. <Cleaning conditions> A roll cleaning header having four nozzles was installed at a position 200 mm from the roll surface of the work roll and 250 mm from the roll surface of the backup roll on the exit side of the rolling mill. The work roll and the backup roll were sprayed with water for 7 seconds by the roll cleaning header.

Under the above conditions, the rolled material was continuously inserted into the rolling mill, and the result of examining the biting condition of the rolled material with respect to the temperature and pressure of the water sprayed from the roll washing header for the second rolled material was shown. It is shown in FIG.

[0026]

[Table 1] As shown in Table 1, the effect of improving the biting property increases as the washing water temperature increases and the water pressure increases. In particular, the effect of improving the biting property by the water temperature is remarkable, and a temperature of 50 ° C. or higher is required. The effect of the water temperature is large because the viscosity of ordinary lubricating oil is about 8 × 10 ^{-5 to} 1.5 × 10 ^-4 (m ² / s) at room temperature, but the viscosity sharply decreases due to the rise in lubricating oil temperature. Because you do. Specifically, if the temperature of the lubricating oil becomes 50 ° C., its viscosity becomes about half that at normal temperature, and 1/1 at 100 ° C.
It is about 0.

The roll cleaning header used in this test had no cleaning effect when the discharge pressure of the cleaning water was about 3 MPa or less. However, if the roll cleaning header is moved closer to the roll, the number of nozzles is increased, or the diameter or shape of the nozzle discharge port is changed, the impact force due to the ejection of the cleaning agent received by the roll (hereinafter simply referred to as “impact force”) "). That is, when using warm water as a cleaning agent, if the temperature is set to 50 ° C. or higher, the roll cleaning effect can be secured by adjusting the impact force applied to the roll by the above method, and the lubrication rolling time The biting property can be improved.

The required time of the washing water is determined by the relationship with the washing efficiency. When both the work roll and the backup roll are washed, it is sufficient to spray the work roll for about 5 rotations or more. The time is usually 5 seconds or more.

[0029]

EXAMPLE A test was conducted to confirm the effect of the present invention, taking washing as an example by hot water injection. The lubricating rolling was performed using a rolling mill similar to the rolling mill shown in FIG. 1 described above, and the result of evaluating the biting state is shown in Table 2. Note that the rolling was performed under substantially the same conditions as the above-described rolling conditions, lubricating conditions, and cleaning conditions, but with the roll opening, water pressure, and water temperature changed. Further, the next rolled material (following rolled material) was rolled within 5 seconds after the roll was washed.

[0030]

[Table 2] Test No. 1 is an example in which lubricating rolling was performed without washing, but even when the bite angle was 11.5 ° (reduction ratio: 26.7%), the succeeding rolled material did not bite. Test No. 2
As is clear from ~ 6, when the temperature of the washing water is 40 ° C., even if the water pressure is increased to 20 MPa, the removal of the lubricant adhered to the rolls is insufficient, so that the biting property of the subsequent rolled material is not improved. . On the other hand, in test No. 7, the rolling conditions were the same at the bite angle (13.5 °) as in tests Nos. 5 and 6, but since the temperature of the cleaning water was 50 ° C., the cleaning effect was low even when the water pressure was low. Yes, the biting property of the succeeding rolled material is improved.

Test Nos. 8 to 18 are examples in which the bite angle was further increased (14.1 to 15. °). As is clear from these examples, the temperature of the cleaning water sprayed on the roll is 50 ° C.
Even with the above, the biting performance may not be improved, but if the discharge pressure of the cleaning water is increased to increase the pressure of the cleaning water hitting the roll surface, the biting performance of the subsequent rolled material can be improved. .

From the above results, when washing is performed by jetting hot water, if the temperature is set to 50 ° C. or more, the impact force applied to the rolls is adjusted according to the washing conditions.
The biting property of the succeeding rolled material can be improved.

In this test, hot lubricated rolling was performed on a rolled material having a thickness of 15 mm before rolling using a work roll having a diameter of 200 mm. Under these conditions, in Test Nos. 12, 14, 16, and 18, rolling was possible at a rolling reduction of 46.7%. When this condition is converted into, for example, an actual rolling mill having a work roll diameter of 800 mm, the work roll diameter is four times, so a 60 mm rolled material with a sheet thickness of four times can be rolled with a rolling reduction of 28.0 mm (60 mm × 0.467). This corresponds to rolling. Therefore, when an actual rolling mill is used, a rolled material having a thickness of 40 mm before rolling is reduced to a rolling reduction of 7 mm.
It can be rolled at 0.1% ((28.0mm / 40mm) x 100%).

[0034]

According to the present invention, it is possible to perform high-load rolling even on difficult-to-process materials having a wide width and a thin thickness without major remodeling of equipment, so that high-load rolling can be performed. Range expands. Also, due to the rolling load reduction effect of the lubricating rolling, high-pressure rolling can be performed even with a compact hot-rolling finish rolling mill with a small number of mill stands.

[Brief description of the drawings]

FIG. 1 is a schematic side view showing an example of a hot rolling apparatus of the present invention.

[Explanation of symbols]

1. Work roll, 2. 2. backup roll; 3. Rolling lubrication header; 4. Work roll water cooling header; 5. Roll cleaning header, 6. heat shield Drainer, 8. 8. rolled material; Detection device, 10. Control device, 11. valve

Claims (3)

[Claims] After the leading end of a rolled material has been bitten by a work roll, application of rolling lubricating oil to the work roll is started,
Perform lubrication rolling until rolling of the rear end of the rolled material is completed,
Removing the lubricating oil adhering to the work roll during the rolling of the preceding rolled material between the end of the rolling of the preceding rolled material and the time the subsequent rolled material bites into the work roll; Rolling method. 2. The hot rolling method according to claim 1, wherein the removal of the rolling lubricating oil is performed by injecting hot water of 50 ° C. or more into the work roll or the work roll and the backup roll. 3. A hot-rolling apparatus having a work roll and a backup roll, comprising: a rolling lubrication header for applying a rolling lubricant to the work roll; a work roll or a rolling lubricant adhering to the work roll and the backup roll; Roll cleaning header for cleaning with hot water, detection device for detecting the state of biting of rolled material into work rolls,
And a control device for controlling the supply of high-pressure hot water to the roll cleaning header.