JPH1157822A - Cooling method of rolling roll - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the quality of a rolled steel plate by falling a cooling water down to the circumference surface of total work roll length when a hot rolling work roll dismounted from the rolling mill is cooled in a way to form a water membrane of even thickness so as to prevent generation of uneven cooling around circumference of the roll and to improve circularity of a grinding roll. SOLUTION: A cooling header 3 is set along the rolling shaft directly above the roll fixed horizontally and falls the cooling water 9 over the total rolling length. At this time, the cooling water 9 is failed down evenly by a slit nozzle 8 in a straightened state from a portion equivalent to directly above the circumferential surface of the roll. A distance between the slit nozzle 8 and the work roll 1 surface is set at 200 mm or less, and a nozzle width, a nozzle length and a height of a water surface in the cooling water header 3 is kept within proper ranges. The cooling header 3 is a double tube type consisting of an inner tube 4, an outer tube 5, and the cooling water 9 from a cooling water supply tube 6 is stored below the outer tube 5. It is desirable to fall the water from the nozzle 8 set in a downward, longitudinal direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cooling method for cooling a rolling roll of a hot rolling mill off-line such as in a roll shop while preventing circumferential temperature unevenness with the rolling roll fixed. is there.

[0002]

2. Description of the Related Art Generally, rolling rolls (hereinafter referred to as "work rolls") in a hot rolling facility are designed to work after a certain rolling time or a certain rolling amount (production amount) because of the importance of surface quality of a rolled steel sheet. Re-grinding of the roll is performed. The processing accuracy required for this work roll is roundness, roll crown, and the like. Therefore, when performing re-grinding of the work roll after rolling, it is necessary to satisfy a predetermined surface accuracy and roundness, but the work roll immediately after rolling is heated to 500 to 600 ° C. by rolling, Since the rolling roll itself is also thermally expanded, it is disadvantageous to perform the grinding at the temperature as it is, and it is necessary to sufficiently cool the work roll and to perform the grinding when the temperature becomes close to room temperature.

In order to cool the work roll to room temperature, if the work roll is naturally cooled, it takes a long time of several days due to the large heat capacity of the work roll. As a result, hot rolling equipment, in other words, For example, when considering a work roll exchange cycle, it is necessary to have a large number of work rolls, which not only complicates the management of the rolls but also has the disadvantage of increasing the production cost. In view of such circumstances, in order to reduce the amount of work rolls held, the cooling of the work rolls used for rolling in hot rolling is accelerated,
It is necessary to shorten the preparation time until the next rolling chance. Therefore, for the purpose of reducing the thermal expansion of the work roll, water cooling is performed in an off-line roll shop before grinding.

FIG. 4 shows an example of such a cooling technique.
The work roll 1 having high heat is installed in the axle box 2 and the two cooling headers 3 having spray nozzles are disposed obliquely above the work roll surface. Then, there is a method of cooling the roll by spraying cooling water from the nozzle onto the roll surface. Alternatively, although not shown, a method of taking out the work roll 1 from the axle box 2 and immersing it in a separately provided roll cooling tank, or a method of cooling while rotating the work roll, or the like is adopted.

[0005]

However, in the system in which the cooling water is sprayed from obliquely above the surface of the work roll 1 in FIG. 5, only the collision portion of the cooling water on the work roll surface is locally cooled. In addition, uneven temperature occurs in the circumferential direction of the roll. Due to the uneven expansion caused by this temperature unevenness, the amount of grinding by the whetstone fluctuates during roll grinding,
At the time of the next rolling, there is a problem that a quality trouble such as a change in the thickness of the rolled sheet occurs due to the roll eccentricity.

In the method of separating the roll from the axle box and immersing the roll in a cooling bath, although the temperature unevenness in the circumferential direction of the roll is improved, the roll is separated from the axle box and cooled, and then cooled again. It must be incorporated in the axle box, which increases the work load and is not practical in a roll shop of a continuous hot rolling process aiming at high labor productivity. Furthermore, the method of cooling while rotating the rolling rolls off-line has a problem that the capital investment amount increases and the maintenance load increases.

The present invention has been made to solve the above problems, and has as its object to reduce the temperature unevenness in the circumferential direction of a work roll when cooling the work roll.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and the means are as follows. (1) When the rolls of the hot rolling mill are cooled off-line, the rolls are fixed horizontally and a cooling header is provided directly above the rolls along the roll axis, and cooling water from the cooling headers is distributed over the entire length of the rolls. A method for cooling a roll, wherein the roll is uniformly supplied in a rectified state to a portion directly above the roll surface in a circumferential direction. (2) In order to keep the cooling water from the cooling header in a rectified state, the slit nozzle width and slit nozzle length provided on the lower surface of the cooling header and the water surface height at the cooling header must be maintained within appropriate ranges. The method for cooling a rolling roll according to the above (1). (3) The distance between the tip of the slit nozzle provided on the lower surface of the cooling header and the roll surface is set to 200 mm or less when supplying the cooling water maintained in a rectified state onto the roll surface. ) Or (2).

(4) When the rolls of the hot rolling mill are cooled off-line, a cooling header provided immediately above the rolling rolls is composed of an inner tube and an outer tube, and both ends of the cooling header are closed, so that the inner tube is cooled. Cooling water is discharged from an opening provided in an upper longitudinal direction, and the discharged cooling water is stored in a lower portion of the outer tube and then discharged from a slit nozzle provided in a longitudinal direction on a lower surface of the outer tube ( The method for cooling a rolling roll according to any one of 1) to 3). (5) When the rolls of the hot rolling mill are cooled off-line, the cooling header provided immediately above the rolling rolls is configured in a gutter shape, and both ends of the cooling header are closed to cool the cooling water supplied to the cooling header. The method of cooling a rolling roll according to any one of (1) to (3), wherein the roll is stored in a lower portion of the header and is discharged from a slit nozzle provided in a longitudinal direction of a gutter-shaped lower surface portion.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present inventors have conducted various studies on a method of uniformly cooling a work roll fixed to an axle box without temperature unevenness. As a result, when cooling a work roll with water, a cooling water was used. Was supplied from above the roll, and it was found that it is best to supply the cooling water so that the supplied cooling water winds around the roll in the circumferential direction. In order to wind the cooling water around the work roll circumference in this way, it has been found that there are appropriate conditions for supplying the cooling water, and the conditions must be satisfied. In other words, the cooling water supplied directly above the roll immediately flows down from directly above the roll surface to directly below the roll surface while existing as a thin and uniform water film on the roll surface. Cool evenly. After cooling, the cooling water flows down from the lowermost part of the roll surface and plays a role.

In order to obtain a uniform water film on the roll surface as described above, the flow rate of water supplied on the roll surface,
Depending on the flow rate and the like, if these are too large, the cooling water supplied to the roll surface is disturbed, and a uniform water film may not be formed. As a result, a locally supercooled portion is generated on a part of the roll surface, which leads to uneven cooling of the entire roll.

Also, due to the turbulence of the water film of the cooling water, the cooling water does not flow down to just below the roll uniformly, and most of the cooling water flowing down the upper semicircular portion is directly transferred to the lower semicircular portion. , And falls from that part, and the roll lower surface becomes insufficiently cooled (conversely, the roll upper surface becomes overcooled). Therefore, the initially expected effect of uniform cooling in the circumferential direction of the roll cannot be obtained. Further, in some cases, the supplied cooling water has a strong momentum, so that the cooling water suddenly hits the roll surface, causing a state in which the cooling water scatters in all directions. In such a state, the same result as described above is produced, and the object of uniform cooling of the roll cannot be achieved.

Conversely, if the flow rate and flow rate of the cooling water are too small, a uniform water film is not formed on the roll surface, and the portion where the water film is not formed becomes a non-coolable portion on the roll surface, resulting in uneven cooling. Many non-uniform cooling parts occur frequently. Therefore, there are appropriate conditions for the supply of cooling water to the surface of the roll, and the cooling water must be discharged in a rectified state onto the surface directly above the roll. The length and water level at the cooling header are important factors.

In order to maintain the rectified state in the supply of cooling water, it can be obtained by calculation in terms of fluid dynamics. Therefore, if the specifications of the nozzle slits and the like are determined, the amount of water to be supplied into the cooling header per hour is naturally determined. You can keep that amount. According to the experience of the present invention, if such conditions are maintained, the flow rate of the cooling water becomes 2 m / sec or less, the Reynolds number becomes lower than 10 to the fifth power, and the fluid becomes laminar. It becomes possible to flow down while forming a water film wrapped around the roll surface in the circumferential direction.
At this time, it is also possible to provide a water level gauge on the cooling header and adjust the cooling water supply amount by a signal from the water level gauge.

Further, even if the cooling water flows out of the slit nozzle in a rectified state, it is difficult to maintain the rectified state if the distance from the cooling nozzle to the roll surface is long, so that an appropriate water film cannot be obtained. Occurs. Since the disturbance of the rectification state of the cooling water varies depending on the conditions such as the flow rate and flow rate of the cooling water from the slit nozzle, the distance cannot be uniformly defined, but the distance between the slit nozzle tip and the roll surface is not uniform. A shorter length is preferable because the influence of disturbance is small.

However, the distance cannot be extremely reduced due to the passive diameter of the work roll to be cooled or the restriction on equipment. From the experience of the present inventors, if the distance is 200 mm or less, the distance is within an allowable range as long as there is no large variation. It is necessary to adjust.

Next, the present invention will be described with reference to the drawings. FIG. 1 is a schematic side view of the entire cooling device used in the present invention. A work roll 1 is placed on a roll receiving base 15 in an axle box 2, and a cooling header 3 is attached to the work roll 1.
Directly above and over the entire length of the roll. In installation, details are omitted, but a turning device is attached to the base of a column 14 that supports the support 13, and by turning the turning device, the turning device is moved to a predetermined position above the axle box 2. A cooling header 3 can be brought. Further, since the cooling header 3 can be opened from the upper surface of the axle box 2 by turning the support 13, loading and unloading of the work roll can be facilitated.

FIG. 2 is an enlarged cross-sectional view of a part of the cooling device of the double tube type, in which (a) is a side view,
(B) is a plan view. The cooling header 3 is pivotally installed just above the work roll 1 set on the roll receiving table in the axle box 2 to prepare for roll cooling. The cooling header 3 comprises an inner tube 4 and an outer tube 5 and is closed at both ends.
A cooling water supply pipe 6 is connected to a substantially central portion in the longitudinal direction of the cooling header 3, and receives cooling water 9 from the supply pipe 6. Cooling water discharge ports 7 are provided on the upper surface of the inner pipe 4 at substantially equal intervals, and the cooling water is discharged from this discharge port and falls into the outer pipe 5 to be stored.

Although not shown, one end of the upper surface of the outer tube 5 is provided with a small hole, which communicates with the atmosphere.
The cooling water 9 is released from the supply water pressure and becomes equal to the atmospheric pressure. By storing the cooling water, a predetermined head pressure of the cooling water 9 is obtained, and uniform flowing water can be easily obtained. On the lower surface of the outer tube 5 of the cooling header, a slit nozzle 8 having a length corresponding to the work roll is provided in the longitudinal direction of the outer tube 5 so that the cooling water 9 can flow out evenly. The slit nozzle 8 needs to have an appropriate slit width and length so that the cooling water 9 maintains rectification, and it is necessary to prevent the cooling water 9 from becoming turbulent as much as possible.

As another example, FIG. 3 is an enlarged view of a part of a gutter-type cooling device and schematically shows a cross section thereof.
(A) is a side view, (b) is a front view. As in FIG. 2, the cooling header 3 has a large gutter 10, and a cooling water supply pipe 6 is connected to a middle part in the longitudinal center, and receives cooling water 9 supplied from the cooling water supply pipe 6 once. The small gutter 11 is mounted on the inner surface of the large gutter 10 and on the supply side of the cooling water 9 with an appropriate length in the longitudinal direction of the large gutter. Both ends of these gutters are closed.

On the inner surface side of the small gutter 11, cutouts 12 are provided on the upper side surface of the small gutter 11 at substantially equal intervals in order to allow the cooling water 9 to overflow evenly. Therefore, a predetermined head pressure of the cooling water 9 is maintained in the large gutter 10 by storing the cooling water 9 discharged from the notch 12. The installation of the slit nozzle 8 is exactly the same as in FIG.
There is no change in the subsequent use effects. Further, the cooling water supply pipe 6 may pass through the inside of the support 13 that supports the cooling header 3, or the support 13 itself may be used as the cooling water supply pipe.

[0022]

An embodiment of the present invention will be described in comparison with a conventional example. In a hot rolling mill, a work roll having a roll diameter of 800 mm and a roll length of 2400 mm after rolling 50 rolled materials was cooled. As the cooling device, the device shown in FIG. 2 was used. At this time, the outer diameter of the cooling header was 150 mm, and the inner diameter was 80 mm. The slit length in the cooling header longitudinal direction is 1600 mm,
The slit width was 10 mm and the slit length was 30 mm. The amount of supplied water was 3 m ³ / hr. The flow rate of the cooling water was maintained at about 2 m / sec under these conditions. Further, the distance between the lower end of the slit nozzle and the upper surface of the work roll to be ground was set to 100 mm.

As a result of continuing cooling for 40 minutes in this state,
A uniform roll surface cooling temperature as shown in FIG. 5 (a) was obtained. In contrast, cooling water from a cooling header having a conventional spray nozzle as shown in FIG.
Injection at an ejection pressure of kg / cm ² resulted in a roll surface cooling temperature as shown in FIG. In the conventional example, the work roll temperature at the time of roll cooling, the amount of cooling water, the cooling time, etc. were almost the same as those in the present embodiment, but as is clear from the figure, in the conventional example, the surface temperature was uneven in the roll circumferential direction. Had occurred. In the present invention, there was no temperature difference on the work roll surface between the present invention and the conventional example because uniform cooling was performed in the present invention.
° C, and the difference in effect on the roll surface temperature between the two is clearly proved to be better for the present invention.

[0024]

According to the present invention, the work roll can be cooled easily at low equipment cost, and the temperature unevenness in the circumferential direction of the roll can be reduced without increasing the work load as compared with the conventional cooling method. It has become possible to minimize it. As a result, it is possible to prevent the non-uniformity of the roundness of the grinding roll caused by the temperature difference in the conventional roll circumferential direction. Now you can do it.

[Brief description of the drawings]

FIG. 1 is a schematic side view showing an example of an entire roll cooling device used in the present invention.

FIG. 2 is a schematic side view showing an enlarged example of a cooling device used in the present invention.

FIG. 3 is an enlarged schematic side view showing another cooling device used in the present invention.

FIG. 4 is a schematic diagram showing a conventional cooling device.

FIG. 5 is a diagram showing a roll surface temperature distribution after cooling in an example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Work roll 2 Axle box 3 Cooling header 4 Inner pipe 5 Outer pipe 6 Cooling water supply pipe 7 Outlet 8 Slit nozzle 9 Cooling water 10 Large gutter 11 Small gutter 12 Notch 13 Support 14 Column 15 Roll holder

Claims (5)

[Claims] When a roll of a hot rolling mill is cooled off-line, a roll is fixed horizontally, a cooling header is provided directly above the roll along the roll axis, and cooling water from the cooling header is supplied to the entire length of the roll. A method for cooling a rolling roll, wherein the roll is uniformly supplied in a rectified state to a portion directly above the roll surface in a circumferential direction. 2. In order to keep cooling water from the cooling header in a rectified state, a slit nozzle width, a slit nozzle length and a water surface height at the cooling header provided on a lower surface portion of the cooling header are maintained within appropriate ranges. The method for cooling a rolling roll according to claim 1, wherein: 3. When supplying cooling water maintained in a rectified state onto the roll surface, the distance between the tip of the slit nozzle provided on the lower surface of the cooling header and the roll surface is set to 200 mm.
3. The method for cooling a rolling roll according to claim 1, wherein the cooling roll is set as follows. 4. When cooling a roll of a hot rolling mill offline, a cooling header provided immediately above the rolling roll is constituted by an inner tube and an outer tube, and both ends of the cooling header are closed, and The cooling water is discharged from the opening provided in the longitudinal direction of the part, and the discharged cooling water is stored in the lower portion of the outer tube.
The cooling method for a rolling roll according to any one of claims 1 to 3, wherein the water is discharged from a slit nozzle provided on a lower surface of the outer tube in a longitudinal direction. 5. When cooling a roll of a hot rolling mill offline, a cooling header provided immediately above the rolling roll is formed in a gutter shape, and cooling water supplied to the cooling header by closing both ends of the cooling header. 4. The method for cooling a rolling roll according to any one of claims 1 to 3, wherein the cooling roll is stored in a lower portion of the cooling header, and is discharged from a slit nozzle provided in a longitudinal direction of the gutter-shaped lower surface portion.