JPH1058026A - Method and device for cooling high temperature steel plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To speedily and precisely cool a high temp. steel plate with simple structure suitable to the control-cooling of a thick steel plate or the like. SOLUTION: In this cooling method, cooling water is collided against the surface of the steel plate as plural parallel high-speed water screens which form a prescribed angle to the transporting direction and have a prescribed intervals to the width direction of the steel plate and the cooling water after colliding is equally separated right and left by taking a colliding region as a boundary, flowing water regions are formed along the surface of the steel plate and the end parts of the colliding regions are connected to each other without overlapping as seen from the transporting direction of the steel plate and cooling is executed. In such a case, plural slot nozzles 10 are arranged in parallel forming the prescribed angle θ to the transporting direction of the steel plate and spacing at prescribed intervals L2 to the width direction and adjacent nozzles are arranged so that their end parts 10a , 10b , are connected each other without overlapping in the transporting 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 and apparatus for cooling a high-temperature steel sheet at a high cooling rate and uniformly in the surface and the front and back surfaces of the steel sheet.

[0002]

2. Description of the Related Art In recent years, in a steel plate manufacturing process, a combination of controlled rolling, which is characterized by large rolling under a low temperature range, and controlled cooling, which is characterized by rapidly cooling to around 500 ° C. and then air cooling, is combined with high strength. The technology for obtaining high-toughness steel sheets is widely applied to actual production. By this method, a high-strength, high-toughness steel sheet having a low alloy and excellent weldability can be manufactured at low cost.

In order to perform controlled cooling effectively, a technique capable of rapidly cooling to a target temperature in order to obtain a fine-grained structure, and a technique for preventing the uniformity of the material and the shape of the steel sheet from being deteriorated even by performing the rapid cooling. A technique for uniformly cooling the inside of the steel sheet or the front and back surfaces is required. The demands on these technologies have become severe as the demands on the performance of steel sheets have increased, and various cooling methods have been devised in response to the demands.

[0004] In order to increase the cooling rate when cooling a high-temperature steel sheet, it is effective to increase the amount of cooling water or increase the speed of cooling water. Examples of the cooling method include an immersion method, a spray method, a laminar method, and a method of jetting high-pressure water from a slit nozzle. The spray method is a method in which water is pressurized and ejected from a nozzle to form a group of droplets and is cooled. The cooling water is ejected from the nozzle and spreads radially, so that a surface having a certain size can be cooled. However, since the supply water is dispersed, the impact force on the steel sheet surface is weak, and the cooling rate is generally slow. Laminar cooling is cooling using a laminar flow generated when the outflow speed from the nozzle is low, and is a cooling method using a water column or a water film. Since the injection distance is long, cooling can be performed with the nozzle retracted above the steel plate. For this reason, it is widely used for cooling hot rolled steel sheets and the like, but there is a limit in improving the cooling capacity.

FIG. 11 shows an apparatus disclosed in Japanese Patent Application Laid-Open No. Sho 62-161415 as an example of an apparatus for cooling using a slit nozzle suitable for high-speed cooling. This cooling method, a water jet was injected with a slope of injection angle α on the surface of the steel sheet from the slit nozzle 10 _J, a steel plate 2 _a shut off water flow to the downstream by installing a draining roll 3 _a downstream The cooling is performed (hereinafter, this method is referred to as an inclined slit jet method).

[0006] This inclined slit jet cooling method can use a large amount of high-speed cooling water, and therefore has a high cooling capacity and a large heat capacity compared with other cooling methods (for example, the above-mentioned laminar cooling method). It can be used for cooling steel plates. However, even in the cooling method using such a slit nozzle, an extremely high cooling capacity can be obtained in a portion where the high-speed cooling water collides with the steel sheet surface (hereinafter referred to as a collision area). The part flowing above (hereinafter,
In the water flow area, the cooling capacity decreases as the distance from the collision area increases due to the rise in the temperature of the flowing water, friction with the steel plate, and the decrease in the flow velocity due to the entrapped water, and overall efficiency still improves. Room is left.

In Japanese Patent Publication No. 63-8168, a cooling water jetted from a nozzle jets a steel sheet using a spray header provided with a plurality of flat spray nozzles for jetting a droplet flow forming a flat collision area on the steel sheet surface. A method of cooling (hereinafter, referred to as a flat spray method) is disclosed. In this method, by arranging the flat spray nozzles so that the directions of the flat spray nozzles are symmetrical between the adjacent spray headers, stagnation flow cooling water (hereinafter referred to as “stagnant water”) that hinders cooling is eliminated. Methods have been proposed to facilitate cooling.

However, the cooling ability of the flat spray method in the collision area of spray water is inferior to that of the slit jet method. In addition, in the case of the flat spray method, the flow of droplets ejected from the nozzle spreads. However, as the distance from the center to the end decreases, the impact pressure becomes weaker and the cooling capacity decreases. In addition, the decay rate of the cooling capacity in the flowing water area was larger than that of the inclined slit jet method, and both the uniformity and the cooling capacity were inferior to those of the inclined slit jet method.

Japanese Patent Publication No. 5-86298 discloses a method of enlarging the cooling area of the lower surface of the steel sheet in order to enhance the cooling of the lower surface. This uses a header provided with a plurality of rows of nozzles for jetting columnar cooling water between the rolls that transport the steel sheet, and cooling so that this cooling water is jetted in a fan shape in the longitudinal direction of the steel sheet. This is a method of expanding the cooling area on the lower surface by using a nozzle in which the direction of jetting water is changed. In this method as well, since the collision area is narrow due to the columnar cooling water, the cooling capacity is not sufficient as a means for cooling a high-temperature steel plate having a large heat capacity, and cooling unevenness is likely to occur. Furthermore, when this device is used on the upper surface of a steel plate, the accumulated water cannot be discharged quickly,
The cooling capacity is reduced, and the retention height of the retained water is different between the center and the end in the plate width direction, so that the cooling is not uniform in the plate width direction.

[0010]

An object of the present invention is to provide a method for cooling a high-temperature steel plate uniformly and accurately with a simple structure, a higher cooling rate than before, and no flat defects. And its equipment.

[0011]

Means for Solving the Problems The present inventors have studied the use of the high cooling ability of the slit nozzle and a method for achieving uniform cooling using the same, and completed the present invention. The gist of the present invention resides in the following method and apparatus for cooling a high-temperature steel sheet. (See FIGS. 1, 4, 6, and 7) (1) The cooling water is supplied at a predetermined angle θ with respect to the transport direction of the steel sheet.
Without a predetermined plurality parallel with a distance L ₂ of the high-speed water film (hereinafter, referred to as slit jet water) with respect to the width direction of the steel sheet as collide with the hot steel plate 2 surface, after the collision The cooling water of each slit jet forms a flowing water area 13 that flows along the surface of the steel sheet in a substantially equal amount on the boundary of the collision area 11 for each slit jet, and mainly forms the collision area 11 and the flowing water area 13. A method of cooling the steel plate 2 by using an end 11 _{a of the} collision area 11.
And to the end 11 _b of the impact zone of the adjacent, characterized in that when seen from the transporting direction of the steel plate cooling arranged so as to be continuous without overlapping each other, the cooling method of hot steel plate.

(2) In order to cool both the upper and lower surfaces of the hot steel plate 2 conveyed while being sandwiched between the transport rolls 4 and the draining rolls 3 installed on the upper side of the transport rolls 4, and between the transport rolls 4 and draining In the steel plate cooling device 5 having the nozzle header 8 provided between the rolls 3, the nozzle header 8 has a predetermined angle θ with respect to the conveying direction of the steel plate 2 and has a predetermined angle θ with respect to the width direction of the steel plate 2. a plurality of the slit nozzle 10 is provided for ejecting a slit jet water arranged in parallel with a gap L ₂ of, and the ends of the end portion 10 _a of the slit nozzle 10 adjacent next to the slit nozzle 10
_b . The cooling device 5 for the high-temperature steel sheet 2, which is arranged so as to be continuous with respect to _b without overlapping each other when viewed from the transport direction of the steel sheet 2.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The method and apparatus for cooling a high-temperature steel sheet according to the present invention will now be described in detail with reference to FIGS.

(1) Cooling Method FIG. 7 is a diagram conceptually showing the flow of cooling water when high-pressure slit jet water from the slit nozzle 10 collides with the surface of the steel plate 2 according to the present invention. The slit jet water jetted from the slit nozzle 10 at high pressure hardly spreads and collides with the surface of the steel plate 2 to form a collision area 11, and is further divided on both sides of the collision area 11 and along the surface of the steel sheet 2. The flowing water area 13 is formed. The flowing water area 13 is a one-dimensional flow formed as a layer having a thickness on the surface of the steel plate 2. Watershed 13
Collides with running water from the adjacent slit nozzle
A stagnant water area 14 is formed above the upper part 13. The direction of the water flow in the stagnant water area is irregular and fluctuates, the flow velocity is low, and the cooling capacity is weak. Further, as the thickness of the stagnant water area formed above the flowing water area increases, the cooling capacity of the flowing water area is hindered. For this reason, it is desirable that the retained water be quickly discharged out of the system.

FIG. 8 is a diagram showing the relationship between the distance from the collision point of the cooling water on the steel sheet surface and the cooling capacity. Although the cooling capacity in the flowing water area decreases as the distance from the collision area increases, it maintains a high cooling capacity close to the collision area from the collision area to 100 mm, and has good cooling capacity even at a distance of 150 mm .

In the spraying method and the cooling method using columnar cooling water, the cooling water colliding with the steel sheet surface spreads two-dimensionally on the steel sheet surface, so that the flow velocity is rapidly reduced and the cooling capacity is rapidly reduced. In the case of the slit jet water, unlike the above, especially in the flow area near the collision area, since the flow velocity is hardly reduced because of a one-dimensional flow, a high cooling capacity can be obtained. In the present invention, a region having a high cooling capacity of a flowing water area (for example,
The interval between the slit jet water and the angle θ with respect to the transport direction of the steel sheet is selected so that only the collision area (within 150 mm) is formed on the steel sheet surface.

Further, in the present invention, the time required for the steel sheet 2 to pass through the collision zone 11 and the flowing water area 13 while passing through the cooling device 5 is equalized at any position in the width direction, so that the width of the steel sheet 2 Achieve uniform cooling in the direction. For this,
Adjacent slit jet water collision areas are arranged so as to be continuous without overlapping in the transport direction of the steel plate 2 (see FIG. 6). For example, the collision area 11 shown in FIG.
And the length of the watershed 13 are equal.

When the slit jet water is injected obliquely to the steel plate surface, the lengths of the left and right water jets in the collision zone 11 are not equal, and the flow of the adjacent slit jet water is disturbed, thereby impairing the cooling ability. For this reason, it is preferable that the injection angle α of the slit jet water with respect to the steel plate surface (see FIG. 11) is in a range of 90 ± 15 °. As shown in FIG. 7, it is more preferable to inject the steel sheet 2 perpendicularly (injection angle 90 °) onto the surface of the steel sheet 2.

(2) Cooling Apparatus FIG. 1 is a diagram showing an example of an arrangement in a case where the cooling apparatus according to the present invention is applied to a thick steel plate cooling facility. The steel plate 2 which has been rolled to a predetermined thickness by the finish rolling mill 1 is provided with a plurality of cooling units according to the present invention provided on the upper and lower surfaces of the steel plate immediately after leaving the rolling mill or while being conveyed on a roller table. The device 5 cools down to a predetermined temperature.

A transport roll 4 and a draining roll 3 are arranged at vertically symmetric positions between the cooling devices 5 and at the front and rear ends of the cooling equipment. The draining roll 3 can be moved up and down, and its height can be changed according to the thickness of the steel plate 2. The drain roll 3 rotates while being in contact with the upper surface of the steel plate 2 during cooling, and serves to shut off cooling water accumulated on the upper surface of the steel plate 2 between adjacent cooling devices.

2 to 4 show one example of the cooling device of the present invention. FIG. 2 is a front view of the cooling device 5 according to the embodiment of the present invention, FIG. 3 is a side view thereof, and FIG. 4 is a diagram showing an arrangement of slit nozzles 10 in a nozzle plate 9 provided in the cooling device 5. As shown in FIG. 2, the cooling device 5 includes a water supply pipe 7,
It comprises a nozzle header 8 and a nozzle plate 9. The water supply pipe 7 is connected to the water supply pipe 6 via a control valve for controlling an inflow amount of the cooling water. The width of the nozzle plate 9 only needs to be large enough to cover the steel plate 2 to be cooled. It is preferable to use a material having both strength and corrosion resistance. The mounting method of the nozzle header and the nozzle plate withstands high pressure and high temperature,
When performing maintenance, any method may be used as long as it can be easily removed.

As shown in FIG. 4, the plurality of the slit nozzle 10 is provided in parallel to each other with a predetermined distance L ₂ in the width direction for ejecting slit jet water in the nozzle plate 9. These slit nozzle 10 has a certain angle θ with respect to the conveying direction and the end portion 10 _a and the end portion 10 _b of the slit nozzle adjacent do not overlap each other when viewed from the conveying direction of the steel sheet, and a continuous It is arranged to be.

FIG. 5 is a diagram showing the position of the collision area 11 on the surface of the steel plate 2 when the cooling device 5 of the present invention is used. FIG.
FIG. 5 shows an enlarged view of the flow of the cooling water in the part A shown in FIG.

The accumulated water flows through the upper part of the flowing water area 13 toward the front and rear draining rolls 3, and is quickly discharged along the draining rolls 3 toward the end of the steel plate.
As a result, there is no decrease in the cooling capacity of the jet due to the retained water,
Uniform cooling in the width direction of the steel sheet can be realized without causing cooling unevenness between the end and the center of the steel sheet.

The shape of the opening of the slit nozzle 10 may be any shape as long as the cooling ability in the longitudinal direction of the slit becomes uniform, and may be rectangular, and neither long side nor short side may be linear. . The dimensions (L ₁ , t), the interval L ₂ between the slit nozzles adjacent in the width direction, and the angle θ between the slit nozzle 10 and the conveying direction of the steel sheet uniquely determined from these.
May be determined in consideration of the interval between the rolls, the width of the nozzle plate, the number of nozzles, and the like. From the viewpoint of maintenance and stability, the dimension t of the opening of the nozzle is preferably 5 to 10
mm, the number of nozzles is 50 or less per nozzle header.

The angle θ formed by the slit nozzle 10 with respect to the transport direction of the steel plate 2 may be set to an angle at which the accumulated water is smoothly discharged, and is preferably in the range of 15 ° to 60 °. If θ is less than 15 °, the discharge power of the stagnant water from between the collision areas is not preferable. In addition, when it exceeds 60 °, the running water that collides with the draining roll and rebounds prevents the retained water from being discharged in the width direction of the plate, and the interval L ₂ between the nozzles increases, so that the flowing water area becomes longer, and the flowing water area becomes longer. It is not preferable because the cooling ability is reduced.

Even when the cooling device 5 of the present invention is used for cooling the lower surface of the steel plate 2, the collision zone 11 and the flowing water zone 13 are formed similarly to the cooling of the upper surface. Since the accumulated water falls downward, the accumulated water area 14 is not formed. Therefore, uniform cooling can be performed at high speed on the lower surface as well as on the upper surface. In addition, when the cooling method of the present invention is used for cooling both the upper and lower surfaces of the steel sheet 2, since the cooling capabilities of both are substantially equal, there is no temperature difference between the upper and lower surfaces, and no poor flatness occurs. A steel sheet can be stably manufactured.

If the nozzle plate 9 is made of a single plate having a large plate thickness, it is hardly damaged even if the steel plate collides during operation, and the durability is excellent.

[0029]

【Example】

[Embodiment 1] A preferred embodiment of the present invention will be described below with reference to the drawings. As shown in FIG. 1, twelve cooling devices 5 of the present invention were installed on the upper surface and the lower surface of a steel plate 2 conveyed on a roller table. The spacing between adjacent cooling devices 5 was 750 mm, and rolls 3 each having a diameter of 300 mm for draining were arranged in the middle of each cooling device and at the front and rear ends of the cooling equipment. The rolls 3 are located above transport rolls 4 which are also set at intervals of 750 mm.

The nozzle plate 9 fixed to the cooling device 5
Is made of a stainless steel plate having a width of 5000 mm, a length of 400 mm and a thickness of 20 mm, and is attached to the nozzle header 8 so as to be detachable by bolts.

Slit nozzle 10 provided on nozzle plate
Has an opening t of 5 mm and a length L ₁ of 350 in the transport direction.
mm, and the distance L ₂ between the adjacent slit nozzle is 200 mm
And In this case, the angle θ between the direction of the slit nozzle and the transport direction is 29.7 degrees. Each slit nozzle has the same size and shape, and was arranged parallel to each other in the width direction.

FIG. 11 is a view showing a cooling method by the inclined slit jet method disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 62-161415. As a comparative example, an experiment using this device was also performed. Here, the nozzle header 8 has one rectangular slit which is opened linearly in the plate width direction.
Was used, the width of the opening of the slit nozzle 10 _a 5 mm, the injection angle α of the cooling water to the steel sheet surface was 20 °. The number of nozzle headers, the distance between draining rolls, the diameter, and the number of nozzles were the same in both the method of the present invention and the comparative example, and the amount of water was 8 m ³ / min per nozzle header. The ejection pressure at the nozzle header was 15 kgf / cm ² .

After cooling steel plates of various thicknesses from 800 ° C. to 450 ° C. and assuming the average temperature in the thickness direction of the steel plates to be re-heated for 30 seconds, measure the temperature of the upper surface of the steel plate at the center of the width of the steel plate. did.
FIG. 9 shows the result. As can be seen, according to the method and apparatus of the present invention, the cooling rate is significantly improved even with the same amount of cooling water as compared with the comparative example, and a high cooling capacity is obtained.

FIG. 10 is a diagram showing the result of comparison of the temperature distribution in the sheet width direction after cooling is completed. Here, a thick plate having a thickness of 25 mm and a width of 4200 mm was water-cooled from 800 ° C. to 450 ° C., reheated in the same manner as described above, and the temperature of the steel sheet surface was measured. FIG.
As can be seen from the figure, in the inclined slit jet method, the cooling capacity at the center of the steel sheet is reduced, but according to the method and apparatus of the present invention, the cooling is uniform. In the comparative example, a large amount of accumulated water remained at the center of the plate width, and it is estimated that the cooling rate was reduced due to this effect.

[0035]

According to the method of the present invention, it is possible to obtain a higher cooling rate as compared with the conventional method, and it is also possible to accurately control the temperature distribution over the entire steel sheet, thereby resulting in poor flatness and fluctuations in mechanical properties. , And high-speed cooling can be accurately realized. For this reason, a high-performance and homogeneous steel plate can be stably manufactured.

The cooling device of the present invention has a simple structure, is economical, is easy to maintain, and is suitable for cooling a high-temperature steel plate at high speed and with high accuracy.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of use of a cooling device of the present invention.

FIG. 2 is a front view of the cooling device of the present invention.

FIG. 3 is a side view of the cooling device of the present invention.

FIG. 4 is a view showing an example of the arrangement of slit nozzles in the nozzle plate of the present invention.

FIG. 5 is a diagram conceptually showing a distribution of a collision area where jet water from a slit nozzle collides with a steel plate surface.

FIG. 6 is a diagram conceptually showing a way of flowing cooling water on the surface of the steel sheet by enlarging a portion A in FIG. 5; The direction of the flow of on-board water is indicated by a thick arrow, and the direction of the retained water is indicated by a thin arrow.

FIG. 7 is an elevational view conceptually showing how the cooling water flows on the surface of the steel sheet in the section BB in FIG. 5; The direction of the flow of on-board water is indicated by a thick arrow, and the direction of the retained water is indicated by a thin arrow.

FIG. 8 is a diagram showing the relationship between the distance from the collision area of the slit jet water and the cooling capacity of the water area.

FIG. 9 is a diagram showing a relationship between a plate thickness and a cooling rate. The solid line shows the case where the cooling method of the present invention was used, and the dotted line shows the case where the inclined slit jet method as a comparative example was used.

FIG. 10 is a diagram illustrating a temperature distribution in a plate width direction at the end of cooling. The solid line shows the case where the cooling method of the present invention was used, and the dotted line shows the case where the inclined slit jet method as a comparative example was used.

FIG. 11 is a conceptual diagram illustrating a cooling method using an inclined slit jet method as a comparative example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Finishing rolling mill 2 Steel plate 3 Drain roll 4 Conveyance roll 5 Cooling device 6 Water supply pipe 7 Water supply pipe 8 Nozzle header 9 Nozzle plate 10 Slit nozzle 11 Collision area 12 Flowing water area 13 Stagnant water area

Claims (2)

[Claims] 1. A plurality of parallel water film cooling waters having a predetermined angle with respect to a conveying direction of a steel sheet and having a predetermined interval with respect to a width direction of the steel sheet collide with a hot steel sheet surface. After the collision, the cooling water forms a flowing water area that flows along the surface of the steel sheet, splitting right and left in approximately equal amounts at the boundary of the collision area for each water film. Cooling the steel sheet by supplying cooling water so that the end of the collision area is continuous with the end of the adjacent collision area without overlapping each other when viewed from the conveyance direction of the steel sheet. Characteristic cooling method of high temperature steel sheet. 2. A cooling roll is provided between transport rolls and between drain rolls to cool both upper and lower surfaces of a high-temperature steel sheet transported while being sandwiched between the transport rolls and a drain roll installed above the transport rolls. In a steel plate cooling device having a nozzle header, the nozzle header has a plurality of slit nozzles arranged at a predetermined angle with respect to a conveying direction of the steel plate and arranged at predetermined intervals in a width direction of the steel plate. The cooling device for a high-temperature steel plate is provided, wherein the ends of the slit nozzles adjacent to each other are arranged so as to be continuous without overlapping each other when viewed from the conveying direction of the steel plate.