JPH02290605A - Water jacket type cooling method for rolling roll and control method thereof - Google Patents

Abstract

PURPOSE:To attain a high cooling power with the water jacket type cooling method for rolling rolls by specifying the relative speed of cooling water with the rolling rolls. CONSTITUTION:The target temp. or cooling power of the rolling rolls or the target relative speed according thereto varies with the rolling conditions and rolling schedules of a hot rolled steel strip and the positions of rolling stands or the like. Cooling water jackets W are, therefore,, provided to the rolling rolls WR and the relative speed of the cooling water flowing in the spacing thereof is controlled, by which the cooling of the rolling rolls WR is controlled. The relative speed of the cooling water is, thereupon, initially set at over 30m/sec in accordance with the rolling conditions and rolling equipment conditions relating to the rolled steel strip intended to be rolled and the outside circumferential speed of the rolling rolls WR is measured during the rolling. The flow rate of the cooling water is calculated in accordance with the measured outside circumferential speed and at least either of the spacing quantity or the flow rate of the cooling water to be supplied is regulated to meet the calculated flow rate of the cooling water.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a water jacket type cooling method for rolling rolls and a method for controlling the cooling.

[Conventional technology] In hot rolling, a large amount of heat flux is generated from the material to be rolled to the rolling rolls during rolling, resulting in rough skin due to thermal fatigue of the rolls and thermal expansion in the threaded portion of the rolls. Therefore, in order to prevent surface scratches and poor smoothness caused by these,
Cooling of the rolling rolls is required.

Conventionally, mill rolls have been cooled by spraying cooling water onto the surface of the mill roll during rolling, causing the sprayed cooling water to collide with the roll surface, where heat exchange occurs. This Soubrei cooling method is
Since high-pressure water of 0~30kg/c+r+2 is sprayed by a nozzle, the area in which the cooling water contacts the roll is limited, and the cooling area does not change even if the amount of cooling water increases, greatly increasing the cooling effect. The problem was that it could not be achieved.

In addition, the cooling water that is sprayed and collides with the rolling rolls scatters and falls onto the material to be rolled, which lowers the rolling temperature, which wastes a lot of energy and makes it difficult to control the material quality of the material to be rolled. There was also the problem of.

Furthermore, the cooling water after being sprayed onto the rolling rolls becomes hot water and falls into the sluice below the rolling mill, where it is collected together with descaling and other cooling water and oil after hydraulic rolling, and circulated through water treatment equipment. It is used.

Therefore, it is impossible to control the temperature or improve the water quality of the roll cooling water alone, and for this reason, there are limits to improving the quality of rolled materials in terms of temperature control and water quality of the roll cooling water. .

In contrast, as shown in Japanese Patent Publication No. 55-12322, for example, a cooling water jacket is installed along the surface of the rolling roll, and cooling water is supplied to the center of the cooling water jacket. A so-called cooling water jacket type roll cooling method has been proposed, which improves the cooling effect by simultaneously creating a current and a parallel flow.

Furthermore, as proposed in, for example, Japanese Utility Model Publication No. 58-52752, a closed cycle is formed in which the cooling water supplied to the cooling water jacket sealed around the outer peripheral surface of the rolling roll is directly collected and allowed to flow in the direction. This reduces the amount of cooling water used and prevents cooling water from leaking into the rolled material after cooling.

Furthermore, a usage method based on the above-mentioned closed-cycle cooling water jacket installed on a rolling roll has been proposed, for example, in Japanese Patent Application Laid-Open No. 62-68612, and this method is specifically The gap between the cooling water jacket and the outer peripheral surface of the roll is 2 to 5 +++ m, and the cooling water velocity within the cooling water jacket is 5 to 30 m.
/sec.

[Problems to be Solved by the Invention] When the invention disclosed in JP-A No. 62-68612, which is a prior example, is specifically examined from its detailed description and drawings, as clearly shown in FIG. Only the direction of water flow within the jacket is disclosed that coincides with the direction of the circumferential speed of the rolling rolls, and this is generally referred to as parallel flow. The present inventors had doubts about setting the cooling water velocity in the appropriate range of 5 to 30 m/sec in the invention disclosed in Japanese Patent Application Laid-Open No. 62-68612, which is a prior example. This is because hot strip hot finishing mills usually have 6 or 7 stands, and the circumferential speed of the last stand is about 10 times faster than the circumferential speed of the rolling roll of the first stand C. This is because it is highly unlikely that the two can be treated equally.

Therefore, Nagisa et al. conducted an experiment as detailed later, and found that, for example, when the cooling water speed was 30 m/sec and the roll peripheral speed was 20 m/sec, and the rolling roll was cooled under co-current conditions, the rolling The surface temperature of the roll is approximately 240°C, and in the case of conventional spray cooling, it is 180°C to 20°C.
It was found that the temperature was 60°C to 40°C higher than that of 0°C. In addition, the roll circumferential speed in the Moe experiment was reduced to half IO.
m/sec, and other conditions were the same, and it was confirmed that the temperature of the surface layer of the rolling roll was about 218°C. Therefore, it is necessary to find an appropriate range that takes into account the circumferential speed of the rolling mill, find a way to use a cooling water jacket that has a higher cooling capacity than the conventional Subray method, and establish a method for adjusting the cooling capacity using this. It is being

[A Thousand Steps to Solve the Problem] The present invention was made based on the knowledge obtained by organizing the results of various experiments in order to solve the above-mentioned problem, and describes how to use the rolling roll to achieve higher cooling than before. , it is an object of the present invention to provide a cooling adjustment method and a control method using the method. The first concrete method is to provide a cooling water jacket on a part of the outer periphery of the rolling roll.
A method for cooling a mill roll by flowing cooling water in one direction along the outer periphery of the mill roll in a gap on the outer periphery of the mill roll in the cooling water jacket, wherein the relative speed of the cooling water with respect to the mill roll is set to exceed 30 m/sec. A water jacket type cooling method for rolling rolls, which is characterized by the following:

Second, "In the first cooling method above, the outer peripheral speed of the rolling roll is measured, the cooling water flow speed is determined based on the measured value of the outer peripheral speed, and the amount of cooling water to be supplied or the rolling roll is adjusted according to the cooling water flow speed." ``A water jacket type cooling method for a roll roll characterized by adjusting at least one of the gap amounts on the outer periphery''; Find the outer peripheral speed,
A water jacket type cooling method for a rolling roll, characterized in that the cooling water flow velocity is determined based on the outer peripheral velocity, and at least one of the amount of supplied cooling water or the amount of gaps on the outer periphery of the rolling roll is adjusted in accordance with the cooling water flow velocity. "and,
An adjustment method using "a water jacket type cooling method for rolling rolls, characterized in that in any of the cooling methods described in the above, the cooling water is flowed in a direction opposite to the peripheral speed direction of the rolling rolls" It is.

Thirdly, a cooling water jacket is provided on the outer periphery of the rolling roll to cool the rolling roll by flowing cooling water along the outer periphery within the gap on the outer periphery, and cooling water flows through the gap. In a method of controlling cooling of a rolling roll by manipulating the relative speed of water to the rolling roll outer peripheral speed, a target value of the relative speed of the cooling water to the rolling roll is determined based on rolling conditions regarding a rolled steel strip to be rolled. , the target value is initially set for the rolling 17η, the outer circumferential speed of the rolling roll is measured during rolling, the cooling water flow rate is calculated based on the outer circumferential speed, and the gap amount or ``A method for controlling water jacket type cooling of a roll roll, characterized by controlling at least one of the amount of supplied cooling water,'' or ``a part of the outer circumference of the roll roll,
A cooling water jacket is provided to cool the rolling roll by flowing cooling water along the outer periphery in the gap on the outer periphery, and rolling is performed by manipulating the relative speed of the cooling water flowing in the gap with respect to the rolling roll outer circumferential speed. In a method of controlling roll cooling, a target value of the relative speed of cooling water to the rolling roll is determined based on rolling conditions for a rolled steel strip to be rolled, the target value is initialized before rolling, and the target value is initially set during rolling. To do this, the outer peripheral speed of the rolling roll is predicted from a predetermined speed pattern of the rolling mill, the cooling water flow speed is calculated based on the outer peripheral speed, and the gap amount or supply cooling water amount is adjusted according to the cooling water flow speed. This is a control method using a water jacket type cooling control method for a rolling roll, characterized in that at least one of the rolls is operated.

[Function] The present inventors provided the rolling roll with a cooling water jacket and a cooling water supply/discharge system as shown in FIGS.
In addition to changing the speed of the cooling water within the gap and the circumferential speed of the rolling rolls, we also conducted experiments in which the direction of the cooling water flow was changed between parallel flow and countercurrent (reverse direction). . The target steel strip at this time is 40mm thick x 900m
The same lot material is obtained by rolling m-wide rough bars to 2mm J5 x 900+nm width. The experimental results are organized and clarified as shown in Figure 1, where the vertical axis is the roll humidity at a point 1 mmF from the outside surface of the rolling roll, and the horizontal axis is the relative velocity between the cooling water flow velocity and the roll circumferential velocity. (=roll circumferential speed - cooling water speed). However, since the direction of the circumferential speed of the rolls is positive, in parallel flow there is a speed difference, and in countercurrent flow it is the sum of speeds. Note that the roll temperature indicated by diagonal lines in Figure 1 is 1.
The range from 80° C. to 200° C. represents the case of cooling by a conventional spray method at an injection pressure of about 30 kg/cm 2 .

This method of cooling rolling rolls using a cooling water jacket corresponds to turbulent heat transfer.
When the relative velocity is 30 m/sec in mm, the Reynolds number ne is approximately aoooo. Generally, the heat transfer coefficient in turbulent heat transfer is considered to be a function of the power of relative velocity, and is considered to have a very complicated relationship. However, as shown in Fig. 1, within the scope of the present experiment, the rolling roll temperature can be almost clearly expressed by the relative speed itself.

It was also found that when the relative speed was set to more than 30 m/sec, higher cooling than conventional spray cooling could be obtained. In the case of the above-mentioned JP-A No. 62-68fi12, the cooling water temperature is 5 to 30+n/sec and the circumferential speed of the rolling rolls is of course only parallel flow of zero or more, so the relative speed is a maximum of 30 l/sec, which is suitable for the present invention. It can be seen that IF does not overlap with range.

Now, the flow rate of cooling water is determined by dividing the amount of supplied cooling water by the cross-sectional area of the seven gaps on the outer surface of the rolling rolls, so in order to adjust the flow rate of cooling water, it is necessary to All that is required is to change at least one of the gaps. To adjust the amount of supplied cooling water, as shown in FIG. 3, it is preferable to provide a flow control valve FV in the middle of the cooling water supply pipe or a flow control valve FV in the middle of the cooling water discharge pipe. However, due to the characteristics of flow control valves, if the valve is turned down beyond a certain point, accurate adjustment becomes difficult. On the other hand, the gap can be adjusted by adjusting the position of the cooling water jacket.The rolling roll has some eccentricity, and the center point of the curvature of the cooling water jacket and the center point of the outer peripheral surface of the rolling roll are slightly different from each other. Therefore, if the gap is set to 1+nm or less, the rolling roll will come into contact with the cold water jacket, or even if it does not come into contact, the amount of the gap will vary greatly depending on the position, making it impossible to cool uniformly. . Furthermore, if the gap size is increased, the cooling water flow rate decreases when the amount of supplied cooling water is constant, so the heat transfer coefficient changes according to the relative speed, so if the flow is countercurrent, it decreases as the relative speed increases. Therefore, increasing the gap amount is useful for adjustment because the cooling capacity decreases as the thickness of the cooling water increases. An example of the characteristic of the cooling water flow velocity is shown in FIG.

In actual work, it is possible to maintain the cooling capacity of the rolling roll at a constant value by keeping the relative speed constant, or to adjust the relative speed according to the longitudinal position of the hot steel strip. required for rolling operations. Generally, rolling rolls are equipped with a speed meter called a generator (tachogenerator) or a pulse transmitter (pulse generator), and based on the measured value of the peripheral speed of the rolling roll, the target temperature or temperature of the rolling roll can be set. An appropriate method is to calculate the cooling water velocity from the target relative velocity according to the cooling capacity (or heat transfer coefficient) and adjust at least one of the supplied cooling water amount or the gap amount so as to achieve the calculated cooling water velocity. The present inventors determined that.

The target temperature or cooling capacity of the rolling rolls or the corresponding target relative speed are determined by the rolling conditions of the hot rolled steel strip, the rolling schedule (e.g. reduction amount distribution, steel strip temperature, speed distribution), and the location of the rolling stand. It changes depending on the situation.

Therefore, in a method of controlling the cooling of a rolling roll by providing a cooling water jacket on the rolling roll and manipulating the relative speed of the cooling water flowing in the gap between the cooling water jackets, it is necessary to The target value for the relative speed of the cooling water is determined based on the equipment conditions, and the target value is initially set. During rolling, the peripheral speed of the rolling roll is measured, and the cooling water flow speed is determined based on the peripheral speed. Calculate,
It has been found that a control method that adjusts at least one of the gap amount and the amount of supplied cooling water in accordance with the cooling water flow rate has been found to be desirable. Regarding the flow direction of cooling water, we came to the following opinion.

The flow direction of the cooling water includes parallel flow, which is made to coincide with the circumferential speed direction of the mill rolls, and countercurrent flow, which is made to flow in the opposite direction to the circumferential velocity direction of the mill rolls. When the relative speed is maintained at more than 30 m/sec, if the circumferential speed of the rolling roll is 30 m/sec or less, the direction of the cooling water only needs to flow counter-currently. In the case of hot strip hot finishing rolling mills, the circumferential speed of the rolling rolls generally does not reach 30 m/sec even at the final rolling stand, so usually countercurrent is sufficient. Therefore, the flow direction of the cooling water does not need to be changed at all in the control method.

Furthermore, the circumferential speed of the rolling rolls is calculated as a rolling schedule before rolling and determined as a rolling speed pattern, and during rolling, it is determined by actually measuring with a speed meter and determining from the rolling speed pattern. Therefore, the circumferential speed of the rolling roll can be determined using the rolling schedule for initial setting, and during rolling, it can be determined from the rolling speed pattern calculated in addition to the above-mentioned actual measurement, and can also be applied to cooling control. .

FIG. 4 shows a flowchart of the control method.

For the next steel material to be rolled, generally, the required cooling capacity (i.e. roll heat/heat removal calculation) is calculated based on the rolling schedule, e.g. reduction amount, steel strip temperature, etc., immediately after the previous rolling material is finished. Accordingly, the relative speed of the cooling water in the cooling water jacket with respect to the rolling roll is calculated and initialized to the target relative speed of the control system. When rolling starts,
The peripheral speed signal VR of the rolling roll is manually input, the deviation value between the target relative speed value and the rolling peripheral speed value is calculated as the cooling water speed, and the cooling water speed is multiplied by the cross-sectional area of the cooling water flow on the rolling roll. Then, the amount of cooling water is determined, and the flow rate of the cooling water is controlled to follow the amount of cooling water by adjusting the flow control valve or the gap amount. This control flow is repeated at regular intervals during the rolling of steel materials, or an analog circuit is used to operate constantly.

On the other hand, regarding a representative example of the operating end, referring to FIG. 3, the amount of cooling water is controlled by issuing a command to the flow control valve FV in the cooling water supply pipe using the flow rate controller FC.

The gap amount on the rolling rolls is controlled by operating the cylinder 10 connected to the bat body 2 in the cooling water jacket.

[Example] A typical example of the present invention is shown in FIG. Fig. 3 shows a cooling water jacket W provided on the outlet side of the upper and lower work rolls WH of a 4-high rolling mill, and cooling water is supplied from the supply pipe 6-A via the flow control valve FV.
Cooling water flows in the gap between R and bat body 2 in one direction in countercurrent to the circumferential direction of the work roll to cool the work roll, and after cooling, the cooling water is returned to the tank via the drain pipe 6-8. .

To adjust the flow rate of cooling water, use the flow control valve F.
This is done by manipulating the amount of cooling water supplied by V, and the gap amount is changed by manipulating the position of the butt body 2 by moving the cylinder IO backward. The cooling control method was as shown in FIG. 4, and the control was performed by operating the control valve FV in response to a command from the cooling water flow regulator FC.

The temperature of the roll was measured by embedding an embedded plug in the surface layer at the center point in the axial direction of the roll, and aligning the surface with the roll surface, as shown in FIG. 5({)(0). The embedded plug is a cylindrical bead made of the same material as the rolling roll, and thermocouples are attached from two directions from the surface as shown in the enlarged view of the same figure (opening).
0mm and 1.5mm, wire the thermocouple to the end of the roll through the cavity in the rolling roll, install an FM telemeter there, and transmit the emitted signal with a receiver. I received it and recorded it. Recording was done using a direct recording electromagnetic oscillograph due to roll rotation or high speed. FIG. 6 shows an example of a temperature measurement chart for one typical steel material. Here, one whisker-like signal represents one revolution of the rolling roll, and the highest point is the point where the temperature measurement point is in direct contact with the steel material and just before it leaves.

Table 1 summarizes examples of rolling roll cooling for steel strips of the same lot as in FIG. 1.

Here, the peripheral speed of the rolling roll changes greatly during rolling as shown in the speed patterns in FIGS. 4 and 6, so the value at the maximum speed is shown. Accordingly, both the required relative speed and the cooling water speed show values corresponding to the maximum speed of the rolling rolls. Number 1 from Table 1
〜4 The temperature of the mouth becomes lower than 195℃, and the first
It was confirmed that the cooling was similar to or better than the Soubray cooling shown in the figure. It was also confirmed that adjusting the amount of cooling water changes the speed of the cooling water, and it was also confirmed that adjusting the amount of gap (cap) also changes the speed of the cooling water.

FIG. 6 shows a fourth method for controlling cooling of rolling rolls.
Using the method shown in the figure, the cooling water flow rate was controlled using the FC-FV as shown in Figure 3, which shows the result of +1+{J control. Figure 6 shows the surface layer of the rolling roll for one steel material (IIIIII below the surface).
The temperature measurement chart (representatively indicated by the +) is shown on the upper side, and the rolling speed pattern corresponding to each time is shown on the lower side. As a result of h11, the rolling roll temperature was almost within 147±5℃,
It was confirmed that good control had been achieved.

Although the example shows the case of a four-high rolling mill, the present invention is not limited thereto, and it goes without saying that it can also be applied to multi-high rolling mills such as five-high or six-high rolling mills having intermediate rolls. . Although the example in which the rolling roll is applied to a work roll has been shown, the present invention is not limited to a work roll.

Since the work roll is the most severe in terms of heat load, the present invention is most often applied, and may also be applied to other auxiliary rolls (hack-up rolls) and intermediate rolls.

4 Explanation of Drawings Figure 1 shows the results of an experiment in which a rolling roll was cooled with a typical cooling water shack of the present invention shown in Figure 3. The temperature of the rolling roll and the relative speed of the cooling water to the rolling roll are shown in Figure 3. It is a relationship diagram.

FIG. 2 is a relationship diagram showing the cooling water flow velocity and pressure in the cooling water jacket of FIG. 3 using the gap amount as a parameter.

FIG. 3 is an overall view (partially sectional view) of a cooling device that is a typical embodiment of the present invention.

FIG. 4 is a flowchart of a method for controlling cooling of rolling rolls.

FIG. 5 is a layout diagram of the temperature measurement sensor of the rolling roll used in the example.

FIG. 6 is an example of an actual measurement chart showing the results of cooling control of the rolling roll.

FIG. 7 is an overall view of a cooling water jacket device in a prior example.

WJ...water jacket, Wto...work roll, FV...flow control valve, FC...
taffi 7A adjustment device, 2...bat body, 6-8.
...supply pipe, pipe, 10...cylinder

Claims (1)

[Claims] 1. By providing a cooling water jacket on a part of the outer periphery of the rolling roll, and allowing cooling water to flow in one direction along the outer periphery within the gap on the outer periphery of the rolling roll in the cooling water jacket. A water jacket type cooling method for a mill roll, characterized in that the relative speed of the cooling water to the mill roll is more than 30 m/sec. 2. Measure the outer peripheral speed of the roll, determine the cooling water flow velocity based on the measured value of the outer peripheral speed, and adjust at least one of the amount of supplied cooling water or the amount of gap on the outer periphery of the roll in accordance with the cooling water flow velocity. The water jacket type cooling method for rolling rolls according to claim 1, characterized in that: 3. Determine the peripheral speed of the rolling roll from a predetermined speed pattern of the rolling roll, determine the cooling water flow velocity based on the peripheral speed, and adjust the amount of cooling water to be supplied or the amount of gap on the outer periphery of the rolling roll according to the cooling water flow velocity. 2. The water jacket type cooling method for mill rolls according to claim 1, wherein at least one of the following is adjusted. 4. The water jacket type cooling method for a mill roll according to any one of claims 1 to 3, wherein the cooling water is flowed in a countercurrent direction with respect to an outer circumferential speed direction of the mill roll. 5. A cooling water jacket is provided on a part of the outer periphery of the rolling roll to cool the rolling roll by flowing cooling water along the outer periphery in a gap on the outer periphery, and the rolling roll has cooling water flowing through the gap. In a method of controlling the cooling of a rolling roll by manipulating the speed relative to the peripheral speed, a target value of the relative speed of the cooling water to the rolling roll is determined based on the rolling conditions for the rolled steel strip to be rolled, and the cooling water is controlled before rolling. During rolling, the peripheral speed of the rolling roll is measured, and the cooling water flow rate is calculated based on the peripheral speed. A method for controlling water jacket type cooling of a rolling roll, characterized in that one side is operated. 6. A cooling water jacket is provided on a part of the outer periphery of the rolling roll to cool the rolling roll by flowing cooling water along the outer periphery in a gap on the outer periphery, and the rolling roll has cooling water flowing through the gap. In a method of controlling the cooling of a rolling roll by manipulating the speed relative to the peripheral speed, a target value of the relative speed of the cooling water to the rolling roll is determined based on the rolling conditions for the rolled steel strip to be rolled, and the cooling water is controlled before rolling. During rolling, the peripheral speed of the rolling roll is predicted from a predetermined speed pattern of the rolling roll, the cooling water flow velocity is calculated based on the peripheral speed, and the cooling water flow velocity is A method for controlling water jacket type cooling of a rolling roll, the method comprising simultaneously controlling at least one of the gap amount and the amount of supplied cooling water.