KR100973692B1 - Hot rolling facility of steel plate and hot rolling method - Google Patents

Abstract

Hot rolling facility of steel sheet and hot rolling of steel sheet which can manufacture steel sheet with excellent characteristics efficiently by controlling the temperature of the rolled material on the basis of excellent facility cost and facility integrity, and good cooling ability. Provide a method. Specifically, the cooling installation 20 which supplies cooling water to the upper and lower surfaces of the steel plate while passing through the steel plate 10 is arrange | positioned in the position near the entry side and the exit side of the rolling mill 12, The said cooling installation 20 is After supplying the upper header 21 with the upper nozzle 22 which sprays the rod-shaped cooling water 23 with dip θ _U = 30 degrees to 60 degrees with respect to the upper surface of the steel plate 10 to the upper surface of the steel plate 10. It is provided at the position where the retention cooling water 24 is blocked by the work roll 12a, and sprays the rod-shaped cooling water 33 at an elevation angle θ _L = 45 ° to 90 ° with respect to the lower surface of the steel plate 10. The lower header 31 having the nozzle 32 is provided between the work roll 12a and the table roller 13a adjacent thereto.

Hot Rolled, Cooling Equipment, Coolant

Description

Hot Rolling Equipment of Steel Sheet and Hot Rolling Method {HOT ROLLING FACILITY OF STEEL PLATE AND HOT ROLLING METHOD}

The present invention relates to a hot rolling facility and a hot rolling method of a steel sheet.

In recent years, in the process of manufacturing a steel plate by hot rolling, the temperature of a rolling material is controlled and the steel plate which has the outstanding characteristic is manufactured.

For example, by performing controlled rolling (CR) in which finish rolling is performed in a state where the temperature of the rolled material is in a non-recrystallization temperature range, a steel sheet having excellent performance is produced.

In addition, manufacturing a thin scale steel sheet by supplying cooling water to the steel sheet immediately after exiting the roll bite of a hot rolling mill, lowering the surface temperature of the steel sheet, and suppressing the amount of scale generation has been studied.

As a technique used when controlling the temperature of such a rolling material, there exist the following.

For example, there exists a technique of Unexamined-Japanese-Patent No. 2002-361315 as a technique of cooling a steel plate by supplying cooling water during the hot finishing rolling of a thin steel plate. This is said to be able to use for manufacture of a fine grained steel plate by spraying a film-shaped cooling water from the slit nozzle of a header provided between finishing stands, and obtaining a high cooling rate.

Moreover, there exists a technique of Unexamined-Japanese-Patent No. 62-260022 as a technique of cooling a hot steel plate by supplying cooling water. This raises and lowers the nozzle unit which sprays cooling water, and it is said that it can secure a wide range of cooling rates by using it together with the lamina nozzle and spray nozzle which were formed separately.

However, the techniques described in Japanese Patent Application Laid-Open No. 2002-361315 and Japanese Patent Laid-Open No. 62-260022 have the following problems in terms of equipment cost, equipment integrity, and cooling ability.

First, in the technique described in Japanese Laid-Open Patent Publication No. 2002-361315, the cooling water supplied to the upper surface of the steel sheet stays on the steel sheet for a while, but the cooling region of the steel sheet fluctuates due to the change of the retention state, so that high temperature control accuracy can be obtained. There is no problem. In addition, since the facility is large in that the header has a rectifier built in, the installation is limited in proximity to the rolling mill, which is not suitable for the production of thin scale steel sheets.

In addition, in the technique described in JP-A-62-260022, the slit nozzle unit must be brought close to the steel plate, and the steel sheet is slit when the tip or the uneven end is cooled. It collides with a nozzle unit, a slit nozzle unit may be damaged, a steel plate may not move, and a stop of a manufacturing line and a fall of a yield may be caused. Therefore, it is also possible to operate the lifting mechanism when the tip or tail end passes, and to retract the slit nozzle unit upward. However, in that case, cooling of the stern end is insufficient, so that the target material can be obtained. There will be no. Moreover, there also exists a problem that the installation cost for installing a lifting mechanism costs. Moreover, since there is a lifting mechanism and it is difficult to install a nozzle unit close to a rolling mill, it is not suitable for manufacture of a thin scale steel plate.

In addition, although the technique of Unexamined-Japanese-Patent No. 2002-361315 and Unexamined-Japanese-Patent No. 62-260022 presupposes using a slit-shaped nozzle, if the jet port is not always kept clean, the cooling water It does not become a film shape. For example, as shown in FIG. 6, when the foreign material 60 adheres to the jet port of the slit nozzle 52 and a blockage arises, the cooling water film 53 is ruptured. In addition, in order to prevent the cooling water in the spraying region (in the cooling region), it must be injected at a high pressure. However, when the film-like cooling water film 53 is sprayed at a high pressure, the balance of the injection pressure becomes worse and the cooling water film 53 bursts. There was a problem of being easy. If the cooling water film 53 is not well formed, the cooling water will leak out in the upstream or downstream direction of the injection zone, and it will stay on the steel plate 10 to partially cool the steel plate 10, resulting in a temperature nonuniformity. have. There is also a technique of excluding cooling water remaining on the upper surface of the steel sheet 10 by side spray or the like, but when the amount of cooling water is large, it cannot be completely eliminated, which causes a problem of temperature unevenness.

This invention is made | formed in view of the above circumstances, When performing hot rolling of a steel plate, it is excellent in equipment cost surface and equipment integrity, and has favorable cooling ability, and based on it, by controlling the temperature of a rolling material appropriately, It is an object of the present invention to provide a hot rolling facility of a steel sheet and a hot rolling method of the steel sheet capable of efficiently producing a steel sheet having excellent characteristics.

(Initiation of invention)

(Tasks to be solved by the invention)

In order to solve the said subject, this invention has the following characteristics.

[1] A cooling facility is provided to supply cooling water to the upper surface of the steel sheet while passing the steel sheet at a position close to the rolling mill on the inlet side and / or the exit side of the rolling mill for hot rolling the steel sheet, and the cooling facility is an upper surface of the steel sheet. And a header having a nozzle for injecting a rod-shaped cooling water toward the rolling mill at an angle of depression of 30 ° to 60 ° at a position such that the cooling water after being supplied to the steel sheet is blocked by the work roll of the rolling mill. Hot rolling equipment of steel sheet.

In addition, the rod-shaped cooling water (also called columnar cooling water) of this invention refers to the cooling water sprayed from the nozzle jet nozzle of circular shape (it also includes an ellipse or a polygonal shape). In addition, the rod-shaped cooling water of this invention is not a spray-shaped classification, but refers to the continuous and straight water flow cooling water in which the cross section of the water flow is kept almost circular until it hits a steel plate from a nozzle jet port.

[2] The cooling apparatus further includes a header having a nozzle for injecting a rod-shaped cooling water with respect to the lower surface of the steel sheet at an angle of elevation of 45 ° to 90 °, adjacent to the work roll of the rolling mill and adjacent thereto. Hot rolling equipment of the steel plate as described in said [1], provided with the table roller.

[3] Hot rolling of the steel sheet using the hot rolling facility of the steel sheet according to the above [1] or [2] while spraying the cooling water so that the cooling water after supplying the steel sheet reaches the work roll of the rolling mill. Rolling method.

[4] While the steel sheet is not being rolled using the hot rolling facility of the steel sheet according to the above [1] or [2], the cooling water is sprayed with a roll gap of the work roll within 2 mm. Hot rolling method of steel sheet.

In the present invention, when performing hot rolling of the steel sheet, the steel sheet having excellent characteristics can be efficiently produced by excellent control of the equipment cost and the integrity of the equipment, good cooling ability, and appropriately controlling the temperature of the rolled material based thereon. can do.

BRIEF DESCRIPTION OF THE DRAWINGS It is a layout view of the hot rolling facility of the steel plate in one Embodiment of this invention.

Fig. 2 is a layout view of another hot rolling facility of steel sheet in one embodiment of the present invention.

3 is a detailed view of a cooling installation in one embodiment of the present invention.

4 is a detailed view of a cooling installation in one embodiment of the present invention.

Fig. 5 is a diagram showing a nozzle arrangement column of the header in one embodiment of the present invention.

6 is an explanatory diagram of a prior art.

(Explanation of the sign)

10 steel sheet

11: heating furnace

12: rolling mill

12a: work roll

13: table roller

20: cooling equipment

21: upper header

22: upper nozzle

23: rod-shaped coolant

24: retention coolant

25: coolant

31: lower header

32: lower nozzle

33: rod-shaped coolant

34: cooling water after supply

Best Mode for Carrying Out the Invention [

Embodiment of this invention is described based on drawing.

1 and 2 are diagrams showing hot rolling equipment in an embodiment of the present invention. Fig. 1 shows a hot rolling facility of a thick steel sheet or a hot mill rolling facility of a thin steel sheet, and Fig. 2 shows a hot finish rolling facility of a thin steel sheet.

In Fig. 1, a heating furnace 11 for heating a slab at a predetermined temperature and a rolling mill for rolling the slab 10 extracted from the heating furnace 11 with a steel plate 10 having a predetermined plate thickness (here, a reversible rolling mill). (12) and the slab (steel plate) 10 while passing the slab (steel plate) 10 to positions close to the entrance side (upstream side) and the exit side (downstream side) of the rolling mill 12. Cooling facilities 20 for supplying cooling water are disposed on the upper and lower surfaces. In addition, the code | symbol 13 in FIG. Is a table roller.

In Fig. 2, a roughing mill 11 for roughly rolling the slab 10, which is heated at a predetermined temperature, and the slab 10 extracted from the heating furnace 11, with a steel plate 10 having a predetermined plate thickness (not shown). ), A finish rolling mill (here a tandem rolling mill) 12 for rolling the steel sheet 10 roughly rolled to a predetermined sheet thickness in a rough rolling mill to a predetermined finish sheet thickness, and the exit side of the rolling mill 12 (downstream). The cooling apparatus 20 which supplies cooling water to the upper and lower surfaces of the steel plate 10 is arrange | positioned at the position near the side). In addition, the code | symbol 13 in FIG. Is a table roller.

Then, the cooling equipment 20, as shown in Fig. 3, the plate 10 is a rod-shaped cooling water (23) with respect to the upper surface towards the work roll (12a) side of the rolling mill 12 of the dip angle θ _U = 30 The retention cooling water 24 after supplying the upper header 21 which has the upper nozzle (circular tube nozzle) 22 sprayed at degrees -60 degrees to the upper surface of the steel plate 10. It is provided at a position to be blocked by the work roll 12a of the rolling mill 12, and the rod-shaped cooling water 33 is attached to the work roll 12a side of the rolling mill 12 with respect to the lower surface of the steel plate 10. The lower header 31 having the lower nozzle (primary tube nozzle) 32 sprayed at an elevation angle θ _L = 45 ° to 90 ° toward the work roll 12a of the rolling mill 12 and adjacent thereto. It is provided between the table roller 13a.

5 shows a row of arrangements of the tube nozzles 22 attached to the upper header 21. In order to supply the cooling water to the full width of the steel plate 10 which passes through the cylindrical nozzle 22 in the conveyance direction of the steel plate 10 in multiple rows here (six rows here), and a plate width direction. It is arranged. In addition, the cylindrical pipe nozzle 32 attached to the lower header 31 is also arranged in the same manner as this.

The reason why the plurality of rows are arranged in the conveying direction is that the force for blocking the staying cooling water between the cooling water colliding with the steel sheet and the cooling water is weakened by the nozzles in one row. Therefore, it is preferable to arrange | position three or more rows in a conveyance direction. More preferably, 5 or more rows are arrange | positioned. Moreover, in the plate width direction, it is attached so that cooling water can be supplied to the full width of the steel plate 10 which passes. In addition, although one upper header was provided here, you may arrange | position the primary tube nozzle 22 in two or more headers.

Incidentally, in this embodiment, the cooling water injected from the upper nozzle 22 is a rod-shaped cooling water. The rod-shaped cooling water is stably formed in water flow as compared with lamina flow, and the force blocking the staying cooling water is increased. Because of the size.

Moreover, when spraying a film-shaped cooling water at an angle, when the distance from a steel plate to a nozzle becomes large, the water film of the steel plate vicinity will become thin and it will become easy to fall further.

The dip θ _U of the rod-shaped coolant 23 injected from the upper nozzle 22 is set to 30 ° to 60 °, so that the dip-shaped coolant 23 is smaller than the angle of the angle θ _U. This is because the vertical direction velocity component of N) becomes smaller and the collision to the steel sheet 10 becomes weaker, and the cooling capacity is lowered. When the dip θ _U is larger than 60 °, the conveyance direction velocity component of the rod-shaped cooling water 23 is This is because the force for blocking the retention cooling water 24 is not sufficient because the retention cooling water 24 leaks outward in the conveying direction, and the cooling region becomes unstable. More preferable dip (θ _U ) is 40 ° to 50 °.

Further, the angle of elevation θ _L of the rod-shaped cooling water 33 injected from the lower nozzle 32 is 45 ° to 90 °. When the elevation angle θ _L is smaller than 45 °, the vertical angle of the rod-shaped cooling water is decreased. This is because the directional velocity component becomes smaller, the collision to the steel sheet 10 is weakened, the cooling ability is lowered, and the distance between the work roll 12a and the table roller 13a must be increased. When θ _L ) is larger than 90 °, since the cooling water is scattered around the rolling mill 12, it is not preferable in terms of operability and equipment integrity.

And the cooling installation 20 supplies cooling water from the upper header 21 so that the water density of a steel plate surface may become 4 m <3> / m <2> min or more toward the upper surface of the steel plate 10, and Similarly, cooling water is supplied from the lower header 31 toward the lower surface so that the water density of the steel sheet surface is 4 m 3 / m 2 min or more.

Here, the reason why the water content density is 4 m <3> / m <2> min or more is demonstrated. The retention cooling water 24 shown in FIG. 3 is formed by being blocked by the rod-shaped cooling water 23 to be supplied. At this time, if the water density is small, the blocking itself cannot be prevented. If the water density becomes larger than any amount, the amount of the remaining cooling water 24 that can be blocked increases, and the amount of cooling water discharged from the plate width end and the amount of cooling water supplied are balanced. The retention cooling water 24 is kept constant.

In the case of thick steel sheets, when the general plate width is 2 to 5 m and cooled to a water density of 4 m 3 / m 2 min or more, the retention cooling water can be kept constant in these plate widths, and thus passes through the steel sheet 10 during rolling. The desired amount of temperature drop can be obtained.

The larger the water density is 4 m 3 / m 2 min or more, the more the control rolled material which eliminates the cooling atmosphere. For example, if the water density is small, the cooling atmosphere can be solved only in the rolled material having a thin plate thickness. However, if the water density is increased, the cooling atmosphere can be eliminated even in the rolled material with a certain thickness. However, since the effect of shortening the cooling wait time for increasing the quantity of water decreases gradually as the quantity of water is increased, the quantity of water is preferably determined in consideration of the shortening effect such as the cooling waiting time and equipment cost. . More preferable water density is 4-10 m <3> / m <2> min.

It is preferable that the injection speed of the rod-shaped cooling water 23 from the upper nozzle 22 shall be 8 m / s or more. What is necessary is just to determine an upper limit of a thermal number suitably according to the size of a steel plate to cool, a conveyance speed, a target temperature fall amount, etc. In addition, when the injection speed exceeds 30 m / s, the pressure loss increases, and the wear on the nozzle inner surface increases. In addition, the capacity of the pump and the outer diameter of the pipe also increase, resulting in excessive equipment cost. For this reason, 30 m / s or less of injection speed is preferable.

In addition, the nozzle is hard to be clogged, and the nozzle inner diameter may be in the range of 3 to 8 mm in order to secure the injection speed of the cooling water. In order to prevent the cooling water from flowing out between the gaps of the rod-shaped cooling water, the distance between the nozzles adjacent to each other on the imaginary line drawn in the plate width direction may be set within 10 times of the nozzle inner diameter.

In addition, when supplying the film-shaped cooling water which is not stable in water flow to the steel plate 10, when supplying the rod-shaped cooling water 23 to the steel plate, while it is necessary to bring the header close to the steel plate 10, The upper header 21 can be arrange | positioned in the position upwardly apart from a pass line. Therefore, in order to prevent the image nozzles 22a and 22b from being damaged by the bending of the steel plate 10, it is good to keep the position of the tip of the image nozzle 22 away from the pass line. However, if it is too far apart, the cooling water is dispersed and does not become a rod shape, so that the action of blocking the cooling water is lost. Therefore, the distance between the tip of the upper nozzle 22 and the pass line is preferably 500 mm to 1800 mm.

And when performing hot rolling of the steel plate using the hot rolling facility comprised as mentioned above, the retention cooling water 24 after supplying to the upper surface of the steel plate 10, and the cooling water 34 after supplying to the lower surface of the steel plate 10 are rolling mills. Rolling is performed while injecting rod-shaped cooling water 23 and 33 so as to reach the work roll 12a of (12).

Thus, in this embodiment, the rod-shaped cooling water 23 is sprayed toward the work roll 12a side with dip θ _u = 30 ° to 60 ° with respect to the upper surface of the steel plate 10, and the steel plate 10 Since the retention cooling water 24 after supplying to the upper surface of the is reached to the work roll 12a, the retention cooling water 24 is blocked between the work roll 12a and the rod-shaped cooling water 23, and stable cooling is performed. An area is formed. Thereby, the problem that the retention cooling water 24 moves on the steel plate 10 arbitrarily, unevenly cools the steel plate 10, and the temperature nonuniformity arises can be eliminated, and the steel plate 10 can be cooled uniformly.

Here, a cooling area | region means the area | region between the position where the rod-shaped cooling water from the raw-pipe nozzle of the row of the side (outermost row) of the side which is furthest from a rolling roll collides with the steel plate 10, and a rolling roll.

And by forming a cooling area | region in this way, the distance from the roll bite of the work roll 12a to a cooling start position (position where cooling by cooling water starts) becomes zero.

In addition, since the position of the front end of the upper nozzle 22 can be separated from the pass line to some extent, even when the front end or the end is cooled down, the steel sheet 10 collides with the upper header 21, The header 21 may not be damaged or the steel sheet 10 may not move, resulting in a stop of the production line or a decrease in yield. Therefore, in order to avoid the steel plate 10 colliding with the upper header 21, it is not necessary to provide a lifting device, and therefore, the installation cost can be reduced.

Moreover, since it does not have a lifting device etc., it becomes possible to form the upper header 21 close to the rolling mill 12. FIG. Thereby, by supplying cooling water to the steel plate 10 immediately after exiting the roll bite of the rolling mill 12, since the surface temperature of the steel plate 10 can be reduced and scale generation amount can be suppressed, it is suitable also for manufacture of a thin scale steel plate. .

In addition, since the cooling water 24, 34 after being supplied to the steel sheet 10 hits the surface of the work roll 12a, and also has an effect of cooling the work roll 12a, a cooling device for roll cooling may be provided separately. There is no need, and the cost of equipment can be held down.

Further, even when the work roll 12a does not bite the steel sheet 10, such as between the rolling passes or between the preceding rolled material and the subsequent rolled material, when the cooling water 23, 33 is sprayed, the cooling water 25 after the spraying ) Flows as shown in FIG. 4, a large amount of cooling water can be supplied to the upper and lower work rolls 12a. Thereby, growth of a thermal crown is suppressed and high precision dimensional control is attained. At that time, when there is a margin in setting the roll gap, for example, when the gap between the preceding rolled material and the subsequent rolled material is opened for 45 seconds or more, the roll gap of the work roll 12a is once narrowed to about 2 mm, and the cooling water ( 23, 33) may be injected. This is because the cooling water 25 can be prevented from escaping from the roll gap and scattered, and the cooling water 25 is supplied to the work roll 12a in a wider range in the circumferential direction. Of course, when the roll cooling between the rolling passes as described above is not required, the injection of the cooling water 23, 33 may be stopped.

Thus, in this embodiment, when carrying out the hot rolling of a steel plate, it is excellent in equipment cost surface and equipment integrity, and has a favorable cooling ability, and has the outstanding characteristic by controlling the temperature of a rolling material appropriately based on it. Steel sheet can be manufactured efficiently.

In addition, in this embodiment, in FIG. 1, the upper header 21 and the lower header 31 are provided in the entry side and exit side of the rolling mill 12, respectively, and the upper header 21 is shown in the exit side of the rolling mill 12 in FIG. Although 21 and the lower header 31 are provided, this invention is not limited to this. When there is a limitation in the installation space or when the effect obtained may be limited, for example, the lower header 31 may not be provided only on either the entry side or the exit side of the rolling mill 12. Instead, only the upper header 21 may be provided. However, in order to suppress the generation | occurrence | production of the curvature at the time of rolling material infiltrating into the rolling mill 12, it is preferable to provide both the upper header 21 and the lower header 31, and to make cooling ability the same level up and down.

(Example 1)

As Example 1 of this invention, control rolling was performed in the hot rolling line of a thick steel plate. Here, after rolling a sheet thickness to 28 mm, controlled rolling was performed at predetermined rolling temperature in the last 3 passes.

In that case, as Example 1 of this invention, the cooling installation provided in the entry side and exit side of the rolling mill 12 in 4 passes before performing control rolling using the hot rolling facility (FIG. 1) shown in embodiment mentioned above. The rod-shaped cooling water is sprayed from 20, and rolling is performed while cooling the steel plate 10 so that the temperature of the steel plate 10 becomes a predetermined temperature when the four passes are completed, and then controlled rolling in the final three passes. Was performed.

Further, the dip θ _U of the upper nozzle 22 was 45 °, and the elevation angle θ _L of the lower nozzle 32 was 60 °.

In addition, the inner diameter of the upper nozzle 22 and the lower nozzle 32 was 6 mm, and the injection speed of the rod-shaped cooling water was 8 m / s.

On the other hand, as a comparative example 1, controlled rolling was performed using the hot rolling facility which is not equipped with the cooling installation for cooling a steel plate during rolling. The steel sheet rolled to a plate thickness of 28 mm at a relatively high temperature was subjected to an air-cooling atmosphere of 30 s to a predetermined temperature before performing controlled rolling, and then controlled rolling was performed in the final three passes.

In addition, as Comparative Example 2, instead of the cooling installation 20 of the invention example 1, using the hot rolling equipment provided with the cooling installation described in Japanese Patent Laid-Open No. 62-260022, the invention example 1 and In the same manner, control rolling was performed. That is, in four passes before control rolling, a film-shaped cooling water is injected from the slit nozzle, and rolling is performed while cooling the steel sheet so that the temperature of the steel sheet becomes a predetermined temperature when the four passes are completed, and then the final Control rolling was performed in three passes. In addition, the header was installed at a place where the distance from the roll bite of the work roll to the cooling start position (the position at which cooling by the cooling water starts) became 4 m, and cooled while passing the steel sheet.

The results are shown in Table 1. In Table 1, the case where the fall of productivity and the quality appeared was x, and the case where it was not was set as (circle).

Cooling start
To location
Street(※)
cooling water
Supply way
equipment
cost
Of equipment
damage
role
Cooling
effect
Rolling
pitch

yield
Comparative Example 1

Cooling system
none

-
-
-
X none
210s
standard
Comparative Example 2


4m
Membrane shape
cooling water
X high price
X scatter
X none
186 s
10% drop
Inventive Example 1


0m
Rod shape
cooling water
○ cheap
○ none
○ Yes
180 s
Comparative Example 1
Same as

※ Distance from roll bite of work roll to cooling start position

As shown in Table 1, in the comparative example 1, since 30s of air cooling atmospheres are performed before control rolling, the rolling pitch is 210s and rolling efficiency is low.

Moreover, in the comparative example 2, since the elevating mechanism had to be provided, the installation cost was expensive. Then, the steel plate with the distal end collided with the nozzle unit, causing damage to the equipment. Since the steel plate which damaged facility was deformed and it does not become a product, the yield fell 10%. In addition, although controlled rolling could be performed without performing 30s of air cooling atmospheres, conveyance time increased by the extent to which the conveyance distance of the steel plate in 4 passes before performing controlled rolling increased, and the rolling pitch of the rolling pitch was compared with the comparative example 1 as a whole. It was 24s short 186s.

Moreover, both the comparative examples 1 and 2 needed the cooling apparatus which cools a rolling roll elsewhere, and the installation cost for it was expensive.

In contrast, in Example 1 of the present invention, the retention cooling water 24 is blocked between the work roll 12a and the rod-shaped cooling water 23 to form a stable cooling region, whereby the retention cooling water 24 is formed. The problem that the steel sheet 10 was unevenly cooled to unevenly cool the steel sheet 10 and the temperature irregularity occurred was solved, and the steel sheet 10 could be uniformly cooled.

In addition, even when the tip or the tail end is cooled, the steel sheet 10 collides with the upper header 21 to damage the upper header 21, or the steel sheet 10 cannot move, thus stopping the production line. There was no such thing as causing a decrease in yield. Therefore, it is not necessary to provide the elevating apparatus for avoiding the steel plate 10 colliding with the upper header 21, and the installation cost was restrained.

And since rolling could be carried out without performing 30s of air cooling atmospheres, while the conveyance distance of the steel plate in four passes before performing control rolling was about the same as that of the comparative example 1, the rolling pitch was more than the comparative example 2 It was a short 180s, an additional 6s.

In addition, since the cooling water 24, 34 after being supplied to the steel sheet 10 hits the surface of the work roll 12a, and also has an effect of cooling the work roll 12a, a cooling device for roll cooling may be provided separately. There was no need to reduce the equipment cost.

(Example 2)

As Example 2 of this invention, rough rolling in the hot rolling line of the thin steel plate was performed. Here, the slab was rolled to a plate thickness of 42 mm by a rough rolling mill.

At that time, as Example 2 of the present invention, in the three-pass in rough rolling using the hot rolling facility (Fig. 1) shown in the above-described embodiment, the cooling facility 20 provided on the entry and exit side of the rolling mill 12 is shown. ) Was rolled while cooling the steel plate 10 by spraying rod-shaped cooling water. Further, the dip θ _U of the upper nozzle 22 was 45 °, and the elevation angle θ _L of the lower nozzle 32 was 60 °. In addition, the inner diameter of the upper nozzle 22 and the lower nozzle 32 was 6 mm, and the injection speed of the rod-shaped cooling water was 8 m / s.

On the other hand, as a comparative example 3, rough rolling was performed using the hot rolling facility which does not have the cooling installation for cooling a steel plate during rolling. When the slab was heated at a relatively high temperature, since the end temperature of rough rolling was high, an air cooling atmosphere of 15 s was performed at the inlet side of the finish rolling mill in order to suppress occurrence of scale scratches.

In addition, as Comparative Example 4, instead of the cooling installation 20 of the invention example 2, using the hot rolling equipment provided with the cooling installation described in Japanese Patent Laid-Open No. 62-260022, the invention example 2 and In the same manner, rough rolling was performed. That is, in three passes in rough rolling, rolling was performed while spraying a film-like cooling water from the slit nozzle to cool the steel sheet. In addition, the header was installed at a place where the distance from the roll bite of the work roll to the cooling start position (the position at which cooling by the cooling water starts) became 4 m, and cooled while passing the steel sheet.

The results are shown in Table 2. In Table 2, the case where the fall of productivity and quality appeared was x, and the case where it was not was set as (circle).

Cooling start
To location
Street(※)
cooling water
Supply method
equipment
cost
Of equipment
damage
role
Cooling
effect
Rolling
pitch

yield
Comparative Example 3

Cooling system
none

-
-
-
X none
105s
standard
Comparative Example 4


4m
Membrane shape
cooling water
X high price
X scatter
X none
93s
10% drop
Inventive Example 2


0m
Rod shape
cooling water
○ cheap
○ none
○ Yes
90 s
Comparative Example 3
Same as

※ Distance from roll bite of work roll to cooling start position

As shown in Table 2, in the comparative example 3, when the slab is heated to comparatively high temperature, since 15s of air cooling atmospheres are performed at the inlet side of a finishing mill, a rolling pitch is 105s and rolling efficiency is low.

Moreover, in the comparative example 4, since the elevating mechanism had to be provided, the installation cost was expensive. Then, the steel plate with the distal end collided with the nozzle unit, resulting in damage to the equipment. Since the steel plate which damaged facility was deformed and it does not become a product, the yield fell 10%. In addition, although it was not necessary to perform the 15s air cooling atmosphere at the finish rolling mill entrance side, conveyance time increased by the extent to which the conveyance distance to a cooling installation became long, and the rolling pitch was 93 s 12s shorter than the comparative example 3 as a whole.

Moreover, all the comparative examples 3 and 4 needed the cooling apparatus which cools a rolling roll elsewhere, and the installation cost for it was expensive.

In contrast, in the present invention example 2, the retention cooling water 24 is blocked between the work roll 12a and the rod-shaped cooling water 23 to form a stable cooling region, whereby the retention cooling water 24 is formed. The problem that the steel sheet 10 was unevenly cooled to unevenly cool the steel sheet 10 and the temperature irregularity occurred was solved, and the steel sheet 10 could be uniformly cooled. Thereby, generation | occurrence | production of the scale flaw was able to be suppressed suitably, without causing a variation of a material.

In addition, even when the tip or the tail end is cooled, the steel sheet 10 collides with the upper header 21 to damage the upper header 21, or the steel sheet 10 cannot move, thus stopping the production line. There was no such thing as causing a decrease in yield. Therefore, in order to avoid the steel plate 10 colliding with the upper header 21, it is not necessary to provide a lifting device, and the installation cost can be suppressed.

And since the conveyance distance of the steel plate at the time of cooling in the cooling installation 20 was also about the same level as the comparative example 3, not having to carry out 15s of air cooling atmospheres at the finish rolling mill entrance side, the rolling pitch is a comparative example. It was a short 90s, 3s more than 4, more.

In addition, since the cooling water 24, 34 after being supplied to the steel sheet 10 hits the surface of the work roll 12a, and also has an effect of cooling the work roll 12a, a cooling device for roll cooling may be provided separately. There was no need to reduce the equipment cost.

(Example 3)

As Example 3 of this invention, finish rolling in the hot rolling line of the steel sheet was performed. Here, it rolled to the finish plate thickness of 3 mm with the 7-stage finish rolling mill of F1-F7.

In that case, as Example 3 of this invention, the cooling installation 20 provided in the exit side of the rolling mill 12 in four stands of F4-F7 using the hot finishing rolling installation shown in embodiment mentioned above (FIG. 2). The rod-shaped cooling water was sprayed from the steel sheet, and rolling was performed while cooling the steel sheet 10. Further, the dip θ _U of the upper nozzle 22 was 45 °, and the elevation angle θ _L of the lower nozzle 32 was 60 °. In addition, the inner diameter of the upper nozzle 22 and the lower nozzle 32 was 6 mm, and the injection speed of the rod-shaped cooling water was 8 m / s.

On the contrary, as Comparative Example 5, instead of the cooling equipment 20 of Inventive Example 3, using the hot rolling equipment provided with the cooling equipment described in Japanese Laid-Open Patent Publication No. 2002-361315, In the same manner, finish rolling was performed. In other words, in four stands of F4 to F7, film cooling water was sprayed from the slit nozzle to perform rolling while cooling the steel sheet. In addition, the header was installed in the place where the distance from the roll bite of a work roll to a cooling start position (position where cooling by cooling water starts) becomes 2 m.

In addition, as Comparative Example 6, instead of the cooling equipment 20 of the invention example 3, using the hot rolling equipment provided with the cooling equipment described in Japanese Patent Application Laid-open No. 62-260022, the invention example 3 and In the same manner, finish rolling was performed. In other words, in four stands of F4 to F7, film cooling water was sprayed from the slit nozzle to perform rolling while cooling the steel sheet. In addition, the header was installed in the place where the distance from the roll bite of a work roll to a cooling start position (position where cooling by cooling water starts) becomes 2 m.

The results are shown in Table 3. In Table 3, the case where the fall of productivity and quality appeared was x, and the case where it was not was set as (circle).

Cooling start
To location
Street
(※)
cooling water
supply
system
equipment
cost
To stay
By temperature
Heterogeneous
Occur

Of the product
material
Deviation
equipment
of
damage
foil
scale
Grater
Produce
role
Cooling
effect

yield
Comparative example
5

2 m

Membrane shape
cooling water
×
high price
×
has exist
×
has exist
○
none
×
Impossible
×
none
standard
Comparative example
6

2 m
Membrane shape
cooling water
×
high price
○
none
○
none
×
Sporadic
×
Impossible
×
none
10%
Lowering
example
Inventive Example
3

0m
Rod shape
cooling water
○
cheapness
○
none
○
none
○
none
○
possible
○
has exist
Comparative Example 5
same

※ Distance from roll bite of work roll to cooling start position

As shown in Table 3, in the comparative example 5, the retention state of the cooling water which stayed in the upper surface of the steel plate changed, the cooling area | region of the steel plate changed, and the temperature nonuniformity became large. As a result, the variation in the material (strength) of products such as tensile strength became large (difference between the maximum strength and the minimum strength: 3 kg / mm 2 or more), and a high quality steel sheet could not be produced.

Moreover, in the comparative example 6, since the elevating mechanism had to be provided, the installation cost was high. Then, the steel plate with the distal end collided with the nozzle unit, resulting in damage to the equipment. Since the steel plate which damaged facility was deformed and it does not become a product, the yield fell 10%.

In addition, in Comparative Examples 5 and 6, since the header was provided at a place 2 m away from the work roll, scale generation of the steel sheet immediately after exiting the roll bite could not be suppressed, and a thin scale steel sheet could not be produced.

Moreover, all the comparative examples 5 and 6 needed the cooling apparatus which cools a rolling roll elsewhere, and the installation cost for it was expensive.

In contrast, in Example 3 of the present invention, the retention cooling water 24 is blocked between the work roll 12a and the rod-shaped cooling water 23 to form a stable cooling region, whereby the retention cooling water 24 is formed. The problem that the steel sheet 10 was unevenly cooled to unevenly cool the steel sheet 10 and the temperature irregularity occurred was solved, and the steel sheet 10 could be uniformly cooled. Thereby, steel plate with high quality with small variation in material such as tensile strength (difference between maximum strength and minimum strength: 1 kg / mm 2 or less) and high quality could be produced.

In addition, even when the tip or the tail end is cooled, the steel sheet 10 collides with the upper header 21 to damage the upper header 21, or the steel sheet 10 cannot move, thus stopping the production line. There was no such thing as causing a decrease in yield. Therefore, in order to avoid the steel plate 10 colliding with the upper header 21, it is not necessary to provide a lifting device, and the installation cost can be suppressed.

Moreover, since the cooling water was supplied to the steel plate 10 immediately after exiting the roll bite of the rolling mill 12, and the surface temperature of the steel plate 10 was reduced, generation | occurrence | production of a scale can be suppressed and a thin scale steel plate can be manufactured. there was.

In addition, since the cooling water 24, 34 after being supplied to the steel sheet 10 hits the surface of the work roll 12a, and also has an effect of cooling the work roll 12a, a cooling device for roll cooling may be provided separately. There was no need to reduce the equipment cost.

Claims (4)

Cooling equipment for supplying cooling water to the upper surface of the steel sheet while passing the steel sheet to a position close to the entrance or exit of the rolling mill for hot rolling the steel sheet, or to the rolling mill at the entry and exit side The cooling apparatus is arranged so that the cooling water after supplying the header having a nozzle for injecting a rod-shaped cooling water to the rolling mill side at an angle of depression of 30 ° to 60 ° with respect to the upper surface of the steel sheet, Hot rolling facility of steel plate provided in the position to be blocked by work roll. The method of claim 1, The cooling apparatus further includes a header having a nozzle for injecting a rod-shaped cooling water with respect to the lower surface of the steel sheet at an angle of elevation of 45 ° to 90 ° to the work roll of the rolling mill and the work roll. Hot rolling facility of steel plate provided between adjacent table rollers. The hot rolling method of the steel plate which rolls, spraying cooling water so that the cooling water after supplying to a steel plate may reach the work roll of a rolling mill using the hot rolling facility of the steel plate of Claim 1 or 2. The hot rolling method of the steel plate which injects cooling water into the roll gap of a work roll within 2 mm, using the hot rolling facility of the steel plate of Claim 1 or 2, while not rolling.

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