JP2010042445A - Cooling equipment and cooling method of hot steel sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide technology for uniformly cooling a hot steel sheet at high cooling speed when supplying cooling water onto the upper and lower surfaces thereof. <P>SOLUTION: An upper header 1, upper cooling water injection nozzles 3, and an upper partition wall 5a are provided at the upper surface side of the hot steel sheet. A plurality of upper water supply ports 6a inserting the lower ends of the upper cooling water injection nozzles 3 and a plurality of upper drainage ports 7a for discharging the cooling water supplied to the upper surface of the heat steel sheet onto the upper partition wall 5a are provided at the upper partition wall 5a. A lower header 2 and lower cooling water injection nozzles 4 are provided at the lower surface side of the hot steel sheet. The lower cooling water injection nozzles 4 are arranged to allow injection lines from the nozzles to pass through the upper drainage ports 7a disposed at the upper partition wall 5a. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a thermal steel sheet cooling facility and a cooling method.

  In the process of manufacturing steel plates such as thick plates and thin plates by hot rolling, water cooling or air cooling is performed on the steel plates (hot steel plates) after hot rough rolling and finish rolling in the equipment as shown in FIG. 13, for example. To go and control the organization. When cooling to a relatively low temperature, for example, about 450 to 650 ° C. by water cooling, fine ferrite and bainite structure can be obtained and the strength of the steel sheet can be secured. Therefore, there is a technology for cooling the steel sheet with spray cooling water, laminar cooling water, etc. It is common. In recent years, the development of techniques for increasing the strength of steel sheets by obtaining a high cooling rate and making the structure finer is increasing.

  For example, there are technologies of Patent Document 1 and Patent Document 2 as a technology for cooling a hot steel sheet by supplying a large amount of rod-shaped cooling water. This is one in which cooling water is jetted at high speed from nozzles installed on the upper and lower surfaces of a steel plate, and a very high cooling rate can be obtained and a product excellent in material characteristics can be manufactured.

  Moreover, there exists a technique of patent document 3 as another technique which cools a hot-steel plate by supplying cooling water. This is to form a pool by filling the area surrounded by the steel plate, roll and side wall with the cooling water sprayed from the nozzle, and it becomes a steady cooling state and reduces uneven cooling in the width direction. It is supposed to be possible.

JP 2002-239623 A JP 2004-66308 A JP 2006-35233 A

However, the conventional technique has a problem in securing the cooling capacity and the cooling uniformity.
In the techniques of Patent Documents 1 and 2, cooling water sprayed from a plurality of cooling nozzles passes through one hole or slit of a protective plate provided between the cooling water header and the hot-rolled steel strip, and The supplied cooling water is discharged from the same hole or slit. That is, since the functions of the injection port and the drainage port coexist, the flow of the cooling drainage flow is reverse to the rod-shaped cooling water sprayed from the nozzle tip as shown in FIG. Also, the discharged water after reaching the steel plate rises by colliding with each other, and the flow path is bent until it reaches the drain outlet that is also used as the nozzle port, so this part becomes a stagnation and the discharged water Smooth flow was hindered.

  Thus, it has been found that the techniques of Patent Documents 1 and 2 have some difficulty in smooth discharge of the cooling water supplied to the steel strip surface. Therefore, in order to ensure that the cooling water reaches the steel plate, a high injection pressure is applied to the header and the cooling water has to be injected at a high speed, resulting in an increase in equipment costs.

  Also, if a slit-shaped hole is made, the part between the slits of the protective plate becomes a thin plate, so the rigidity of this part decreases, and if the warped steel sheet enters the cooling equipment and collides, the equipment is damaged. There is also a risk of doing. Therefore, there is no problem if the thickness of the steel sheet to be cooled is 2 to 3 mm, but if the thickness is 15 mm or more, it is difficult to process the slit because a thick protective plate must be used to prevent equipment damage. There is also.

  Furthermore, when slit-like holes having different sizes are formed, the flow resistance varies depending on the position of the nozzle, and thus there is a problem that uneven cooling temperature occurs in the width direction of the steel sheet.

  The technique of Patent Document 3 has a structure in which the cooling water supplied to the upper surface of the steel plate forms a pool in a space surrounded by the steel plate, the roll, and the side wall, and flows upward. Therefore, there is a problem that the state of the cooling water becomes unsteady within the range of the number of tips of the steel sheet, and uneven cooling temperature and warpage in the longitudinal direction of the steel sheet are likely to occur.

  Moreover, in the technique of patent document 3, although the case where a side wall is not provided is also described, in this case, as shown by a dotted arrow in FIG. 17, the discharged water is directed on the guide plate toward the end in the width direction. Will flow. Here, in the technique of Patent Document 3, since the tip of the cooling nozzle is above the guide plate, the flow in the width direction of the discharged water interferes with the cooling water ejected from the cooling nozzle.

Since this width direction flow increases at the end in the width direction of the steel sheet, the interference becomes stronger toward the end in the width direction of the steel sheet, and a part or all of the cooling water sprayed from the cooling nozzle cannot reach the upper surface of the steel sheet. Therefore, uniform cooling cannot be performed in the width direction.
Furthermore, in any of the techniques of Patent Documents 1 to 3, cooling water is injected from above and below, but cooling is performed before the steel sheet enters the cooling device or in an area outside the width of the steel sheet to be cooled. When there is no power steel plate, the cooling water sprayed from above and below collides and scatters around. Since the scattered water breaks the water bundle of cooling water sprayed from the surrounding cooling nozzles, there is a problem that a stable cooling capacity cannot be secured at the forefront, the rearmost end and the widthwise ends of the steel plate.

  Moreover, before the steel plate tip reaches the zone for supplying cooling water, splashed water may get on the steel plate and cool the steel plate tip, or after the steel plate tail end passes through the zone for supplying cooling water. Spattered water rides on the steel plate and cools the tail end of the steel plate, and uniform cooling cannot be performed in the longitudinal direction. Furthermore, there is a concern that the measurement with various sensors cannot be performed due to the splashing of the cooling water to the surroundings, and the maintainability of the peripheral equipment is deteriorated.

  In view of the above, an object of the present invention is to provide a technique for uniformly cooling at a high cooling rate over the entire length of a steel plate when supplying cooling water to the upper and lower surfaces of the hot steel plate.

  In order to solve the above problems, the present invention has the following features.

  (1) 1st invention is the cooling equipment of the hot-steel plate installed in the hot rolling line of a steel plate, Comprising: On the upper surface side of the hot-steel plate, it suspended from the upper header which supplies cooling water, and an upper header An upper cooling water injection nozzle for injecting rod-shaped cooling water and an upper partition wall installed between the hot steel plate and the upper header are provided, and a lower end portion of the upper cooling water injection nozzle is inserted in the upper partition wall. A plurality of upper water supply ports, and a plurality of upper water discharge ports for draining the cooling water supplied to the upper surface of the hot steel plate onto the upper partition wall, and a lower header for supplying cooling water to the lower surface side of the hot steel plate, A lower cooling water injection nozzle that injects bar-shaped cooling water vertically upward from the lower header, and the lower cooling water injection nozzle is configured so that an injection line from the nozzle penetrates an upper drainage port provided in the upper partition wall It is characterized by being arranged in Steel plate which is the cooling equipment.

  (2) The second invention further includes a lower partition wall between the lower header and the thermal steel plate on the lower surface side of the thermal steel plate, and the lower partition wall is a lower portion in which the upper end portion of the lower cooling water injection nozzle is inserted. A plurality of lower water outlets for draining the cooling water supplied to the lower surface of the hot steel plate below the lower partition wall are provided, and the lower drain port provided in the lower partition wall is an injection line from the upper cooling water injection nozzle. Is a cooling facility for a hot-steel sheet according to the first aspect of the invention.

  (3) The third invention further includes a protective plate for protecting the lower cooling water injection nozzle on the lower surface side of the thermal steel plate, and the protective plate includes an injection line from the lower cooling water injection nozzle and an upper cooling water injection nozzle. The thermal steel sheet cooling facility according to the first aspect of the present invention is provided at a position avoiding the spray line from the upper end of the lower cooling water spray nozzle so as to be closer to the hot steel sheet than the upper end of the lower cooling water spray nozzle. It is.

(4) The fourth invention is such that the inner diameter of the upper and lower cooling water injection nozzles is 3 to 8 mm, the flow rate of cooling water injected from the cooling water injection nozzle is 6 m / s or more, and the amount of water on the upper surface side of the hot steel sheet density 1.5~4.0m ³ / ^m 2 · min, the water density of the lower surface side to the first or third invention, characterized in that the 2.0~6.0m ³ / ^m 2 · min This is a cooling facility for the hot steel sheet described.

(5) The fifth invention is such that the inner diameter of the upper and lower cooling water injection nozzles is 3 to 8 mm, the flow rate of the cooling water injected from the cooling water injection nozzle is 6 m / s or more, The water density on the side is set to 1.5 to 4.0 m ³ / m ² · min, respectively.
(6) In the sixth invention, when cooling the hot-rolled steel sheet after hot rolling, the steel sheet is cooled by the rod-shaped cooling water sprayed from the hot steel sheet cooling facility according to any one of the first to fifth inventions. Is a method for cooling a hot steel sheet.

  Since the high cooling rate is obtained by using the cooling equipment and the cooling method of the hot steel sheet of the present invention, the steel sheet can be quickly cooled to the target temperature. Moreover, cooling of the upper and lower surfaces of the steel sheet can be performed uniformly in both the longitudinal direction and the width direction of the steel sheet from the foremost end of the steel sheet to the rearmost end, and a technique for producing a high-quality steel sheet can be provided. Furthermore, since the cooling water is prevented from being scattered around, the maintainability of peripheral facilities is also improved.

It is a figure explaining arrangement of cooling equipment concerning a 1st embodiment of the present invention. It is a figure explaining upper surface side nozzle arrangement | positioning. It is a figure explaining lower surface side nozzle arrangement. It is a figure explaining arrangement | positioning of the cooling equipment which concerns on the 2nd Embodiment of this invention. It is a figure explaining upper surface side nozzle arrangement | positioning. It is a figure explaining lower surface side nozzle arrangement. It is a figure explaining arrangement | positioning of the cooling equipment which concerns on the 3rd Embodiment of this invention. It is a figure explaining upper surface side nozzle arrangement | positioning. It is a figure explaining lower surface side nozzle arrangement. It is a figure explaining the flow of the cooling waste water on a partition. It is a figure explaining the steel plate width direction temperature distribution by a prior art example. It is a figure explaining the steel plate width direction temperature distribution by this invention. It is a figure explaining the outline of a thick plate rolling line. It is a figure explaining the flow of the cooling water by a prior art example. It is a figure explaining the flow of the cooling water by the example of the present invention. It is a figure explaining non-interference with the cooling drainage on the partition of the example of the present invention. It is a figure explaining interference with the cooling drainage on a partition when a nozzle tip is above a partition.

  Hereinafter, an example of an embodiment of the present invention will be described with reference to the drawings. Here, the case where the present invention is used for cooling a steel plate in a thick plate rolling process will be described as an example.

FIG. 13 is a schematic view showing an example of a thick plate rolling line used for carrying out the present invention.
The slab extracted from the heating furnace is subjected to rough rolling and finish rolling by a rolling mill to a predetermined finishing temperature and finishing plate thickness, and then conveyed to an accelerated cooling facility online. It is suitable for the steel plate shape after cooling to perform accelerated cooling after adjusting the shape of the steel plate through a pre-leveler before cooling. In the accelerated cooling facility, the steel sheet is cooled to a predetermined temperature by the cooling water sprayed from the upper surface cooling facility and the lower surface cooling facility. Thereafter, the shape of the steel sheet is corrected with a hot leveler as necessary.

(First embodiment)
FIG. 1 is a side view showing the arrangement of the upper and lower surface cooling facilities according to the first embodiment of the present invention.

1.1 Upper surface cooling facility The upper surface cooling facility includes an upper header 1 for supplying cooling water to the upper surface of the hot steel plate 12, an upper cooling water injection nozzle 3 suspended from the upper header 1, an upper header 1, and a hot steel plate 12. And an upper partition wall 5a having a large number of through holes (water supply port 6a and drain port 7a) installed horizontally across the width direction of the steel plate. The upper cooling water injection nozzle 3 is composed of a circular tube nozzle 3 for injecting rod-shaped cooling water, and the tip thereof is inserted into a through hole (water supply port 6a) provided in the upper partition wall 5a, so that the upper partition wall 5a. It is installed so that it may become above the lower end part.

  The upper cooling water injection nozzle 3 is inserted into the upper header 1 so that the upper end of the upper cooling water injection nozzle 3 protrudes into the upper header 1 in order to prevent the bottom foreign material in the upper header 1 from being sucked and clogged. Is preferred.

  Here, the rod-shaped cooling water in the present invention is cooling water injected in a state of being pressurized to some extent from a circular (including elliptical or polygonal) nozzle outlet, and is cooled from the nozzle outlet. The water injection speed is 6 m / s or more, preferably 8 m / s or more, and the water flow jetted from the nozzle outlet has a substantially circular cross-section and is a continuous and straight water flow cooling water. Say. That is, it is different from a free fall flow from a circular tube laminar nozzle or a liquid ejected in a droplet state such as a spray.

  The reason why the tip of the circular tube nozzle 3 is inserted into the through hole and is located above the lower end of the upper partition wall 5a is that the upper partition wall 5a is provided even when a steel sheet whose tip is warped upward enters. This is to prevent the circular tube nozzle 3 from being damaged. Thereby, since the circular tube nozzle 3 can be cooled over a long period of time in a good state, it is possible to prevent the occurrence of temperature unevenness of the steel sheet without performing equipment repair or the like.

  Further, since the tip of the circular tube nozzle 3 is inserted into the through-hole, as shown in FIG. 16, it does not interfere with the flow in the width direction of the discharged water indicated by the dotted arrow flowing through the upper surface of the upper partition wall 5a. Therefore, the cooling water sprayed from the circular tube nozzle 3 can reach the upper surface of the steel plate equally regardless of the position in the width direction, and uniform cooling in the width direction can be performed.

  As shown in FIG. 2, a large number of through holes having a diameter of 10 mm are formed in the upper partition wall 5 a in a grid pattern at a pitch of 80 mm in the steel plate width direction and 80 mm in the transport direction. A circular tube nozzle 3 having an outer diameter of 8 mm and an inner diameter of 3 mm is inserted into the water supply port 6a. The circular tube nozzles 3 are arranged in a staggered pattern, and the through holes through which the circular tube nozzles 3 do not pass serve as cooling water drains 7a. As described above, the large number of through holes provided in the upper partition wall 5a of the cooling facility according to the present invention are composed of substantially the same number of water supply ports 6a and drain ports 7a, and share the role and function of each.

  At this time, the total cross-sectional area of the drain port 7a is sufficiently larger than the total cross-sectional area of the inner diameter of the circular tube nozzle 3, and about 11 times the total cross-sectional area of the inner diameter of the circular tube nozzle 3 is secured. As shown, the cooling water supplied to the upper surface of the steel plate is filled between the surface of the steel plate and the partition wall 5, led to the upper side of the upper partition wall 5 a through the drain port 7 a, and quickly discharged. Then, as shown in FIG. 10, the discharged water 9 that has flowed above the upper partition wall 5a flows through the drainage channel between the header 1 and the upper partition wall 5a to the outside in the steel plate width direction and is drained.

  As shown in FIG. 14, when the drainage port and the water supply port are installed in the same through hole, the cooling water hardly collides with the steel plate and then does not easily escape above the upper partition wall 5 a, so that the thermal steel plate 12 and the upper partition wall are provided. It flows between 5a toward the edge part in the steel plate width direction. Then, since the flow rate of the cooling drainage between the hot steel plate 12 and the upper partition wall 5a increases as it approaches the end in the plate width direction, the force that the injected cooling water reaches the steel plate through the staying water film is the plate width direction. The edge will be inhibited.

  In the case of a thin plate, since the plate width is about 2 m at most, the influence is limited. However, in the case of a thick plate having a plate width of 3 m or more, the influence cannot be ignored. Accordingly, the cooling at the end in the width direction of the steel sheet becomes weak, and the temperature distribution in the width direction of the steel sheet in this case becomes a non-uniform temperature distribution having a concave shape as shown in FIG.

  On the other hand, in the cooling facility of the present invention, as shown in FIG. 15, the water supply port and the water discharge port are separately provided and share the roles of water supply and water discharge, so that the cooling water is discharged from the upper partition wall 5a. It passes through the opening 7a and smoothly flows above the upper partition wall 5a. Thereby, since the drainage after cooling is quickly removed from the upper surface of the steel plate, the cooling water supplied thereafter can easily penetrate the staying water film, and a sufficient cooling capacity can be obtained. In this case, the temperature distribution in the width direction of the steel sheet can obtain a uniform temperature distribution in the width direction as shown in FIG.

  If the total cross-sectional area of the drain port 7a is 1.5 times or more the total cross-sectional area of the inner diameter of the circular tube nozzle 3, the cooling water is quickly discharged. This can be realized, for example, by making a hole larger than the outer diameter of the circular tube nozzle 3 in the upper partition wall 5a and making the number of drain ports equal to or more than the number of water supply ports.

  If the total cross-sectional area of the drain port 7a is smaller than 1.5 times the total cross-sectional area of the inner diameter of the circular tube nozzle 3, the flow resistance of the drain port increases and it becomes difficult for drained water to drain. Then, the amount of cooling water that can reach the surface of the steel sheet is greatly reduced, and the cooling ability is lowered. More preferably, it is 4 times or more.

  On the other hand, if there are too many outlets or the sectional diameter of the outlet becomes too large, the rigidity of the upper partition wall 5a will be reduced and it will be easily damaged when the steel plates collide. Therefore, the ratio of the total cross-sectional area of the drain outlet and the total cross-sectional area of the inner diameter of the circular tube nozzle 3 is preferably in the range of 1.5 to 20.

  The distance between the lower surface of the header 1 and the upper surface of the upper partition wall 5a is 1 in the total cross-sectional area of the inner diameter of the circular tube nozzle 3 in the cross-sectional area in the steel plate width direction in the space surrounded by the lower surface of the header 1 and the upper surface of the upper partition wall 5a. .5 times or more, for example, about 100 mm or more. If the cross-sectional area of the flow passage in the steel plate width direction is not 1.5 times or more than the total cross-sectional area of the inner diameter of the circular tube nozzle 3, the cooling drainage discharged from the drain port 7a provided in the upper partition wall 5a smoothly flows in the steel plate width direction. This is because it cannot be discharged.

1.2 Arrangement of Lower Surface Cooling Equipment and Upper and Lower Cooling Water Injection Nozzles The lower surface cooling equipment shown in FIG. 1 extends downward from the lower header 2 for supplying cooling water to the lower surface of the thermal steel plate 12 and vertically upward from the lower header 2. And a lower cooling water injection nozzle 4. And the lower cooling water injection nozzle 4 consists of the circular tube nozzle 4 which injects rod-shaped cooling water.

  The arrangement of the upper and lower cooling water injection nozzles 3 and 4 of the cooling facility of FIG. 1 having the upper partition wall 5a is shown in FIG. 2 with the arrangement of the upper cooling water injection nozzle 3 and the drain port 7a, and FIG. Indicates placement. Both are arranged in a staggered manner, and the cooling water sprayed from the upper cooling water spray nozzle 3 reaches the landing point 21 shown in FIG. The lower cooling water injection nozzle 4 does not cross the injection line.

  On the other hand, the cooling water jetted from the lower cooling water jet nozzle 4 is disposed so as to penetrate the drainage port 7a of FIG. 2, and does not intersect with the cooling water jetted from the upper cooling water jet nozzle 3, but the upper partition wall 5a. It passes through the drainage port 7a and enters the space between the upper header 1 and the upper partition wall 5a.

  Assuming that the injection lines of the upper and lower cooling water injection nozzles 3 and 4 coincide with each other, the rod-like cooling water injected at high speed collides and scatters to the surroundings when there is no hot steel plate 12 to be cooled. To do. For example, assuming that the tip of the hot steel plate 12 enters the cooling zone where the cooling water is injected from above and below, the rod-shaped cooling water injected toward the most advanced portion of the steel plate is injected from the top and bottom immediately downstream thereof. As the cooling water collides, the water bundle is broken and the cooling capacity changes. Therefore, it cannot cool uniformly from the most advanced part of the steel plate.

  Similarly, the rod-shaped cooling water sprayed toward the end in the width direction of the steel sheet also breaks the water bundle due to the scattering of the injected cooling water immediately outside. Furthermore, the cooling water sprayed toward the steel plate's rearmost end part breaks the water bundle due to the splashing of the cooling water immediately upstream.

  On the other hand, in the cooling facility of the present invention, since the injection lines of the cooling water injected from the upper and lower cooling water injection nozzles 3 and 4 do not intersect, for example, before the hot steel plate 12 enters the cooling zone, the cooling equipment is viewed from above and below at high speed. The injected cooling water does not collide and splash around.

  Further, since the cooling water jetted from the lower cooling water jet nozzle 4 enters the space between the upper header 1 and the upper partition wall 5a, when the hot steel plate 12 enters the cooling zone, the upper header is already present. The space between 1 and the upper partition wall 5a is filled with cooling water, and after the hot steel plate 12 enters the cooling zone, it can quickly shift to a steady state as shown in FIG.

Therefore, it can cool uniformly over the full length from the steel plate front end to the tail end.
Furthermore, even in the width direction end portion of the hot steel plate 12 to be cooled, it is possible to cool uniformly over the entire width without being affected by the scattering of the jet cooling water outside thereof.

1.3 Others In order to allow the upper surface cooling water to reach the hot steel plate 12 through the staying water film, it is necessary to optimize the inner diameter of the circular tube nozzle 3, the injection speed of the cooling water, and the nozzle distance. .

  That is, the inner diameter of the circular tube nozzle is preferably 3 to 8 mm. If it is smaller than 3 mm, the bundle of water sprayed from the nozzle becomes thin and the momentum becomes weak. On the other hand, if the nozzle diameter exceeds 8 mm, the flow rate becomes slow and the force penetrating the staying water film becomes weak. The jetting speed of the cooling water from the nozzle is required to be 6 m / s or more, preferably 8 m / s or more. If it is less than 6 m / s, the force through which the cooling water penetrates the staying water film becomes extremely weak. If it is 8 m / s or more, a larger cooling capacity can be secured, which is preferable.

  The distance from the lower end of the cooling water jet nozzle 3 for cooling the upper surface to the surface of the steel plate 12 is preferably 30 to 120 mm. If it is less than 30 mm, the frequency with which the hot steel plate 12 collides with the upper partition wall 5a becomes extremely high, and equipment maintenance becomes difficult. This is because if the thickness exceeds 120 mm, the force through which the cooling water penetrates the staying water film becomes extremely weak.

The range of the water density of the top surface cooling that is most effective in the present invention is 1.5 m ³ / m ² · min or more. When the water density is lower than this, the staying water film does not become so thick, and even if the known technology of cooling the steel plate by free-falling the rod-shaped cooling water is applied, the temperature unevenness in the width direction does not become so large There is also.

On the other hand, even when the water density is higher than 4.0 m ³ / m ² · min, it is effective to use the technique of the present invention, but there are problems in practical use such as an increase in equipment cost. The most practical water density is 1.5 to 4.0 m ³ / m ² · min.

  On the other hand, in order to allow the lower surface cooling water to reach the hot steel plate 12, it is necessary to optimize the inner diameter of the circular tube nozzle 4, the injection speed of the cooling water, and the nozzle distance. That is, the inner diameter of the circular tube nozzle 4 is preferably 3 to 8 mm as in the case of the top surface cooling. If the diameter is smaller than 3 mm, the water bundle sprayed from the nozzle becomes thin and easily broken. On the other hand, if the nozzle inner diameter exceeds 8 mm, the flow rate becomes slow and the cooling capacity decreases.

  The jetting speed of the cooling water from the nozzle is required to be 6 m / s or more, preferably 8 m / s or more. If the speed is less than 6 m / s, the momentum when the cooling water collides with the lower surface of the steel sheet is weak, the water hardly spreads along the lower surface of the steel sheet, and the cooling capacity decreases. If it is 8 m / s or more, a larger cooling capacity can be secured, which is preferable.

  Moreover, 30-180 mm is suitable for the distance from the upper end of the cooling water injection nozzle 4 of a lower surface cooling to the lower surface of the steel plate 12. FIG. If it is less than 30 mm, the frequency with which the hot steel plate 12 collides with the circular tube nozzle 4 becomes extremely high, and equipment maintenance becomes difficult. This is because if it exceeds 180 mm, there is a high probability that the cooling water falling after colliding with the hot steel plate 12 breaks the water bundle of the newly injected cooling water.

In this embodiment in which the lower surface cooling water colliding with the steel plate falls as it is, the water amount density of the lower surface cooling is desirably about 1.3 to 2.0 times the water amount density of the upper surface cooling, and the range is 2.0 to 6 0.0 m ³ / m ² · min. Although the water density is higher than that of the upper surface cooling, it can be realized by increasing the inner diameter of the nozzle, increasing the number of nozzles, or increasing the injection pressure.

When the water density is lower than 2.0 m ³ / m ² · min, the lower surface cooling becomes weaker than the upper surface cooling, and thus warpage occurs during the cooling. Even when the water density is higher than 6.0 m ³ / m ² · min, it is effective to use the technique of the present invention, but there are problems in practical use such as an increase in equipment cost. 0 to 6.0 m ³ / m ² · min is the most practical water density.

  In cooling the upper surface of the steel plate, it is preferable to install draining rolls 10 before and after the upper header 1 so that the cooling water does not spread in the longitudinal direction of the steel plate. Thereby, the cooling zone length becomes constant and the temperature control becomes easy.

  However, the cooling technique of the present invention can be applied even when the draining roll 10 is not provided. For example, the upper header 1 is relatively long in the longitudinal direction (when it is about 2 to 4 m), and a water spray for purging is sprayed before and after the upper header 1 to prevent the upper surface cooling water from leaking into the non-water cooling zone. It is also possible to apply to a cooling facility.

(Second Embodiment)
FIG. 4 is a side view showing the arrangement of the upper and lower surface cooling facilities according to the second embodiment of the present invention. Since the items other than the items relating to the lower partition described below are basically the same as those in the first embodiment, the same portions are denoted by the same reference numerals and the description thereof is omitted.

2.1 Lower surface cooling apparatus A partition may be provided also in lower surface side cooling of a hot-steel plate. The lower surface cooling facility shown in FIG. 4 includes a lower header 2 that supplies cooling water to the lower surface of the thermal steel plate 12, a lower cooling water injection nozzle 4 that extends vertically upward from the lower header 2, and the lower header 2 and heat. A lower partition wall 5b having a large number of through holes (water supply port 6b and drain port 7b) is provided between the steel plate 12 and the steel plate 12 in the horizontal direction in the width direction of the steel plate. The lower cooling water injection nozzle 4 is composed of a circular tube nozzle 4 for injecting rod-shaped cooling water, and the tip thereof is inserted into a through hole (water supply port 6b) provided in the lower partition wall 5b, so that the lower partition wall 5b It is installed so as to be lower than the upper end.

  The tip of the circular tube nozzle 4 is inserted into the through-hole and is set to be lower than the upper end of the lower partition wall 5b. Even if the hot steel plate 12 whose tip is warped downward enters, This is to prevent the circular tube nozzle 4 from being damaged by the lower partition wall 5b.

  As shown in an example in FIG. 6, the lower partition wall 5b has a large number of through-holes having a diameter of 10 mm, and the water supply port 6b is loaded with a circular tube nozzle 4 having an outer diameter of 8 mm and an inner diameter of 3 mm. The tube nozzles 4 are arranged in a staggered pattern. A through hole through which the circular tube nozzle 4 does not pass serves as a cooling water drain port 7b, and the cooling drainage that cools the lower surface of the steel plate naturally falls and is discharged from the drain port 7b. As described above, the large number of through holes provided in the lower partition wall 5b of the cooling facility of the present invention are composed of substantially the same number of water supply ports 6b and drainage ports 7b, and share the role and function of each.

  When the lower partition wall 5b is not installed, only the portion where the rod-shaped cooling water collides with the lower surface of the steel plate is cooled. However, when the lower partition wall is provided, the space between the upper surface of the lower partition wall and the lower surface of the steel plate is cooled. The water is filled and stirred and cooled, and water cooling is performed on the entire bottom surface of the steel plate. That is, from point cooling to surface cooling.

  And since the said space is very narrow, since the time until a cooling water is filled after the front-end | tip of a steel plate approachs is very short, the temperature nonuniformity of a steel plate longitudinal direction does not generate | occur | produce easily.

  The distance between the lower partition wall 5b and the hot steel plate 12 for obtaining the effect of stirring and cooling is preferably 30 to 120 mm. If it is less than 30 mm, the frequency with which the thermal steel plate 12 collides with the partition wall 5b becomes extremely high and equipment maintenance becomes difficult, and if it exceeds 120 mm, the force of the cooling water penetrating through the full water film and reaching the lower surface of the steel plate is extremely weak. In addition, it takes time for the cooling water to fill up, and temperature unevenness in the longitudinal direction of the steel sheet tends to occur.

2.2 Arrangement of upper and lower cooling water injection nozzles The arrangement of the upper and lower cooling water injection nozzles 3 and 4 of the cooling facility in FIG. 4 having the upper and lower partition walls 5a and 5b is shown in FIG. FIG. 6 shows the arrangement of the lower cooling water injection nozzle 4 and the drain port 7b. All are staggered, and the cooling water sprayed from the upper cooling water spray nozzle 3 in a state where there is no thermal steel plate 12 passes through the drain ports 7b disposed in the staggered portion of the lower partition wall 5b in FIG. Thus, it passes through the drainage port 7b of the lower partition wall 5b and enters the space between the lower header 2 and the lower partition wall 5b without intersecting with the cooling water sprayed from the lower cooling water spray nozzle 4. Yes.

  On the other hand, the cooling water jetted from the lower cooling water jet nozzle 4 is arranged so as to penetrate the drainage port 7a of FIG. 5, and the upper partition wall 5a does not intersect with the cooling water jetted from the upper cooling water jet nozzle 3. It passes through the drainage port 7a and enters the space between the upper header 1 and the upper partition wall 5a. Thereby, the injection lines of the upper and lower cooling water injection nozzles 3 and 4 are arranged so as not to cross each other.

  In this way, since the injection lines of the cooling water injected from the upper and lower headers do not intersect, the cooling water injected from above and below at high speed before the hot steel plate 12 enters the cooling zone, as in the first embodiment. The high cooling capacity can be ensured uniformly in the cooling zone over the entire length from the foremost end of the steel plate to the end of the steel plate.

2.3 Others In the present embodiment, the cooling equipment on the upper surface side may be the same as that in the first embodiment, such as the inner diameter of the circular tube nozzle 3, the injection speed of the cooling water, the nozzle distance, and the water amount density.

On the other hand, in the present embodiment including the lower partition wall, the cooling water is filled in the space between the upper surface of the lower partition wall and the lower surface of the steel plate, and cooling is almost similar to the cooling on the upper surface side. Is equivalent to the upper surface cooling, and is preferably 1.5 to 4.0 m ³ / m ² · min. Further, the cooling water injection speed from the lower cooling water injection nozzle needs to be 6 m / s or more, preferably 8 m / s or more in order to penetrate the filled water film. The inner diameter of the circular tube nozzle 4 may be 3 to 8 mm similarly to the upper surface cooling.

(Third embodiment)
FIG. 7 is a view showing an upper and lower surface cooling facility according to the third embodiment of the present invention, and is a side view showing an arrangement of the cooling facility. Since the items other than the items relating to the protective plate described below are basically the same as those in the first embodiment, the same portions are denoted by the same reference numerals and the description thereof is omitted.

  In the case where no partition wall is provided for cooling the lower surface of the steel plate, a protective plate 22 is preferably installed to protect the lower cooling water jet nozzle 4. As shown in FIGS. 7 and 9, the protective plate 22 avoids the lower cooling water injection nozzle 4 and the upper cooling water landing point 21 and surrounds the lower cooling water injection nozzles 4 at both ends in the longitudinal direction of the steel plate, and in the width direction of the steel plate. In consideration of the strength of the protective plate, it is preferable to install them at a constant pitch in the width direction of the steel plate.

  If the upper end of the protective plate 22 is at least 10 mm higher than the tip of the lower cooling water injection nozzle 4 and lower than the upper end of the table roll by 20 mm or more, the lower cooling water injection nozzle 4 or It becomes difficult to collide with the protection plate 22.

  Even if the warped hot steel sheet 12 enters, it only hits the protective plate 22 and can prevent the lower cooling water injection nozzle 4 from being damaged. If the protective plates are installed at a width direction pitch of 100 to 300 mm, the hot steel plate 12 does not hit the lower cooling water injection nozzle 4. Although FIG. 9 shows an example in which the protection plate 22 is assembled in a ladder shape and the region surrounding the nozzle is rectangular, the region surrounding the nozzle may be a parallelogram or the like.

  Also in this case, as in the case of the cooling facility of FIG. 1, the jet lines of the upper and lower cooling water jet nozzles 3 and 4 are arranged so as not to cross each other.

  In the present embodiment, the inner diameters of the circular tube nozzles 3 and 4 of the cooling device on the upper surface side and the lower surface side of the steel plate, the injection speed of the cooling water, the nozzle distance, the water density, and the like are the same as in the first embodiment. That's fine.

  Hereinafter, as an embodiment of the present invention, a case of cooling a steel plate having a tensile strength of 590 MPa class in a thick plate rolling process will be described with reference to the drawings.

  In the thick plate rolling facility shown schematically in FIG. 13, the slab extracted from the heating furnace is roughly rolled, then finish rolled to a steel plate having a plate thickness of 25 mm and a plate width of 4.5 m, and rolled at a steel plate surface temperature of 820 ° C. Ended. After rolling, accelerated cooling was performed through a hot leveler. The cooling conditions were a cooling start temperature of 780 ° C. and a cooling end temperature (a value obtained by measuring the temperature after recuperation at the exit side of the accelerated cooling facility) of 560 ° C.

  The cooling equipment used in the accelerated cooling test is the case where the upper and lower surfaces shown in FIG. 4 have partition walls (Example 1 of the present invention) and the case where the upper partition wall and lower protection plate shown in FIG. 7 are provided (Example 2 of the invention). there were.

The nozzle dimensions were 5 mm inside diameter, 9 mm outside diameter, and the nozzle pitch in the steel plate width direction was 50 mm, and 10 rows of nozzles were arranged in the longitudinal direction in a zone with a distance between table rolls of 1 m. The upper surface cooling water injection speed is 8.9 m / s, the water density is 2.1 m ³ / m ² · min, and the lower surface cooling water injection speed is 8.9 m / s in the case of the present invention example 1. In the case of Example 2, it was 12.7 m / s. The water volume density of the lower surface cooling water was 2.1 m ³ / m ² · min in Invention Example 1 and 3.0 m ³ / m ² · min in Invention Example 2.

  The lower end of the nozzle for cooling the upper surface was installed so as to be in the middle position between the upper and lower ends of the partition wall having a thickness of 25 mm, and the distance to the upper surface of the steel plate was 80 mm. In Example 1 of the present invention, the upper end of the nozzle for cooling the lower surface was set to be an intermediate position between the upper and lower ends of the partition wall having a thickness of 25 mm, and the distance to the lower surface of the steel plate was 80 mm. In Example 2 of the present invention, the distance from the upper end of the lower surface cooling nozzle to the lower surface of the steel sheet was 120 mm.

  The upper and lower parts of Example 1 of the present invention and the upper partition wall of Example 2 of the present invention are formed with holes having a diameter of 12 mm like a grid and arranged in a staggered pattern as shown in FIGS. A circular pipe nozzle was inserted into the water supply port, and the remaining holes were used as drainage ports.

  In the present invention examples 1 and 2, as shown in FIG. 15, the water after the top surface cooling is quickly removed from the top surface of the steel sheet, so that the cooling water supplied subsequently can easily penetrate the staying water film. did it. Since the water after the bottom surface cooling falls between the nozzles as it is in the present invention example 2, it does not hinder the injection of the cooling water supplied subsequently. In Example 1 of the present invention, water was filled between the lower surface of the steel plate and the partition walls, but since the spray distance was as short as 80 mm, the film of the filled water was broken to reach the lower surface of the hot steel plate.

  As a result, a high cooling capacity was ensured uniformly on the upper and lower surfaces. In this case, the temperature distribution in the width direction of the steel sheet was 550 to 560 ° C., and a uniform temperature distribution in the width direction as shown in FIG. 12 could be obtained.

  Even if the steel plate was injected before it entered, the cooling water injected from the upper and lower headers did not collide or scatter, so the temperature unevenness at the most advanced 2m and 2m ends of the steel plate was within 10 ° C. It was. Since the temperature unevenness was small, the pass rate of the material test was as high as 99.5%, and the yield was also sufficiently high.

  The cooling time for setting the cooling stop temperature at the center of the plate width to 560 ° C. was 2.5 seconds. Since the cooling rate became high, it became possible to reduce the steel alloy components (for example, Mn) necessary for obtaining high strength, and to reduce the manufacturing cost.

  Since the injection lines of the cooling water injected from the upper and lower headers do not intersect, the cooling water injected at a high speed does not scatter before the hot steel plate 12 enters the cooling zone, and the equipment maintainability is good.

  Since the lower end of the upper surface cooling nozzle is the middle position of the upper and lower ends of the upper partition wall, in the present invention example 1, the upper end of the lower surface cooling nozzle is the middle position of the upper and lower ends of the lower partition wall, and the lower protection plate is provided in the present invention example 2. The nozzle did not break even when a steel plate with a bent tip entered.

  On the other hand, as a comparative example, a conventional cooling facility provided with slit-like holes in the partition walls described in Patent Document 2 was used. The conditions other than the arrangement in which the hole shape provided in the partition wall and the injection lines of the upper and lower cooling water injection nozzles intersect with each other are the same as those in Example 1 of the present invention described above. In the cooling equipment of this comparative example, as shown in FIG. 14, the cooling water after colliding with the steel plate is difficult to escape upward, so that the cooling stop temperature at the center of the plate width is 560 ° C. I needed time.

  The distribution of the cooling stop temperature in the plate width direction has a concave shape as shown in FIG. The highest temperature near the edge of the plate was 600 ° C., and the temperature unevenness in the width direction (maximum temperature−minimum temperature) was 40 ° C.

  When jetting was performed before the steel sheet entered, the cooling water sprayed from the upper and lower headers collided, and the scattering of the cooling water was intense. The scattered cooling water destroys the surrounding cooling water bundle, and as a result, a stable cooling capacity cannot be obtained, and the temperature unevenness at the most advanced 2m and 2m ends of the steel sheet is 40 ° C. It was.

  As a result of taking out a part of the product and conducting a material test, the acceptance rate was as low as 70% and the yield was also poor.

  As Example 2 (Invention Example 3) of the present invention, a case where a cooling facility having partition walls (upper partition walls) only on the upper surface shown in FIG. 1 is used in the thick plate rolling process similar to Example 1 will be described. .

The nozzle dimensions were 8 mm inside diameter, 11 mm outside diameter, 50 mm nozzle pitch in the steel plate width direction, and 10 rows of nozzles were arranged in the longitudinal direction in a zone with a distance between table rolls of 1 m. The upper surface cooling water injection speed is 6.3 m / s, the water density is 3.8 m ³ / m ² · min, the lower surface cooling water injection speed is 9.5 m / s, and the water density is 5.7 m ³ / m ^2. -It was min.

  The lower end of the nozzle for cooling the upper surface was installed so as to be in the middle position between the upper and lower ends of the partition wall having a thickness of 30 mm, and the distance to the upper surface of the steel plate was 50 mm. The distance from the upper end of the lower surface cooling nozzle to the lower surface of the steel sheet was 80 mm.

  In the upper partition wall, holes of 11 mm in diameter and holes of 14 mm in diameter are alternately formed like a grid, and as shown in FIG. 5, circular nozzles with holes of 14 mm in diameter arranged in a staggered pattern as water supply ports Was inserted and the remaining hole with a diameter of 11 mm was used as a drain outlet.

  In Example 3 of the present invention, as shown in FIG. 15, the water after the top surface cooling was quickly removed from the top surface of the steel sheet, so that the cooling water supplied subsequently could easily penetrate the staying water film. . Since the water after cooling the bottom surface falls between the nozzles as it is, it does not hinder the injection of the cooling water supplied subsequently.

  The cooling time for setting the cooling stop temperature at the center of the plate width to 560 ° C. is 2.1 seconds, and the temperature distribution in the width direction of the steel plate is 550 to 560 ° C., which is a substantially uniform distribution as shown in FIG. Similar to Examples 1 and 2, uniform cooling could be performed at a high cooling rate.

  In addition, even when spraying before the steel sheet enters, the cooling water sprayed from the upper and lower headers did not collide or scatter, so the temperature unevenness at the most advanced 2m and 2m end of the steel sheet is within 10 ° C. The same effects as those of Examples 1 and 2 of the present invention were confirmed, including equipment maintainability.

1 Upper header 2 Lower header 3 Upper cooling water injection nozzle (circular tube nozzle)
4 Lower cooling water injection nozzle (circular tube nozzle)
5a Upper partition wall 5b Lower partition wall 6a Upper water supply port 6b Lower water supply port 7a Upper drainage port 7b Lower drainage port 8 Injection cooling water 9 Drained water 10 Draining roll 11 Table roll 12 Hot steel plate 21 Landing point 22 Protection plate

Claims (6)

  An apparatus for cooling a hot steel plate installed in a hot rolling line for a steel plate, and an upper header for supplying cooling water to the upper surface side of the hot steel plate, and an upper cooling water for injecting rod-like cooling water suspended from the upper header An injection nozzle, and an upper partition wall disposed between the hot steel plate and the upper header, the upper partition wall having an upper water supply port for inserting a lower end portion of the upper cooling water spray nozzle, and the hot steel plate A large number of upper drain outlets for draining cooling water supplied to the upper surface of the upper partition wall are provided, and on the lower surface side of the thermal steel plate, a lower header for supplying cooling water, and a bar shape vertically upward from the lower header A lower cooling water injection nozzle for injecting cooling water, wherein the lower cooling water injection nozzle is arranged so that an injection line from the nozzle passes through an upper drainage port provided in the upper partition wall. Heating steel sheet cooling equipment.   Furthermore, a lower partition is provided between the lower header and the hot steel plate on the lower surface side of the hot steel plate, and the lower partition wall has a lower water supply port for inserting an upper end portion of the lower cooling water injection nozzle and a lower surface of the hot steel plate. There are a large number of lower drainage outlets for draining the supplied cooling water below the lower partition, and the lower drainage openings provided in the lower partition are arranged so that the injection lines from the upper cooling water injection nozzles pass therethrough. The thermal steel sheet cooling facility according to claim 1.   A protective plate for protecting the lower cooling water spray nozzle is further provided on the lower surface side of the thermal steel plate, and the protective plate avoids the spray line from the lower cooling water spray nozzle and the spray line from the upper cooling water spray nozzle. The apparatus for cooling a hot steel sheet according to claim 1, wherein the upper end thereof is provided closer to the hot steel sheet than the upper end of the lower cooling water spray nozzle. The inner diameter of the upper and lower cooling water injection nozzles is 3 to 8 mm, the flow rate of cooling water injected from the cooling water injection nozzle is 6 m / s or more, and the water density on the upper surface side of the hot steel sheet is 1.5 to 4.0 m. The cooling facility for hot-steel sheets according to claim 1 or 3, wherein the water density on the lower surface side is ^{3 to} m ² · min, and the water density on the lower surface side is 2.0 to 6.0 m ³ / m ² · min. The inner diameter of the upper and lower cooling water spray nozzles is 3 to 8 mm, the flow rate of cooling water sprayed from the cooling water spray nozzle is 6 m / s or more, and the water density on the upper surface side and lower surface side of the hot steel sheet is 1.5 respectively. It is set to -4.0m < ³ > / m < ² > * min, The cooling equipment of the hot-steel plate of Claim 2 characterized by the above-mentioned.   A method for cooling a hot steel sheet, comprising: cooling the hot steel sheet after hot rolling with rod-shaped cooling water sprayed from the hot steel sheet cooling facility according to any one of claims 1 to 5. .

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