JP5347781B2 - Thermal steel sheet cooling equipment and cooling method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide technology for uniformly cooling a hot steel sheet at a high cooling speed when supplying cooling water on the upper surface thereof. <P>SOLUTION: Cooling equipment of the hot steel sheet installed at a hot-rolling line of the steel sheet includes: a header for supplying the cooling water onto the upper surface of the hot steel sheet; a cooling water injection nozzle for injecting bar-like cooling water suspended from the header; and a partition wall installed between the hot steel sheet and the header. The partition wall is provided with a plurality of water supply ports inserting the lower end of the cooling water injection nozzle and a plurality of drainage ports for discharging the cooling water supplied to the upper surface of the hot steel sheet onto the partition wall. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

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

  In the process of manufacturing a steel plate such as a thick plate or a thin plate by hot rolling, water cooling or air cooling is performed on the steel plate (hot steel plate) after hot rough rolling and finish rolling in the equipment as shown in FIG. 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 in Patent Document 1 and Patent Document 2 as a technology for cooling a hot steel sheet by supplying a large amount of rod-shaped laminar 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 drain port coexist, the flow of the cooling waste water is a reverse flow with respect 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 it describes also about the case where a side wall is not provided, in this case, as shown by the dotted line arrow in FIG. 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.

  In view of the above, an object of the present invention is to provide a technique for uniformly cooling at a high cooling rate when supplying cooling water to the upper surface of a hot steel sheet.

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

  (1) The first invention is a hot steel sheet cooling facility installed in a hot rolling line for steel sheets, and includes a header for supplying cooling water to the upper surface of the hot steel sheet, and rod-shaped cooling water suspended from the header. A cooling water spray nozzle for spraying, a partition wall installed between the hot steel plate and the header, and a water supply port for interpolating a lower end portion of the cooling water spray nozzle in the partition wall, and the heat A hot steel sheet cooling facility characterized in that a large number of drain outlets for draining cooling water supplied to the upper surface of the steel sheet onto the partition walls are provided.

  (2) In the second invention, the total cross-sectional area of the drain outlet provided in the partition wall and the cross-sectional area in the width direction of the steel plate in the space surrounded by the header lower surface and the partition upper surface are both cooling water injection nozzles. The hot steel sheet cooling facility according to the first aspect of the invention, characterized in that the total cross-sectional area of the inner diameter is 1.5 times or more.

  (3) A third invention is the thermal steel sheet cooling facility according to the first invention or the second invention, wherein a draining roll is arranged before and after the header.

(4) In the fourth invention, the cooling water injection nozzle has an inner diameter of 3 to 8 mm, a length of 120 to 240 mm, a distance from the lower end of the cooling water injection nozzle to the surface of the hot steel plate of 30 to 120 mm, and is injected from the cooling water injection nozzle. The flow rate of the cooling water is 6 m / s or more, and the water density is 1.5 to 4.0 m ³ / m ² · min. It is a cooling facility for hot steel sheets.

  (5) A fifth invention is characterized in that a clearance between an outer peripheral surface of a cooling water injection nozzle inserted in a water supply port provided in a partition wall and an inner surface of the water supply port is 3 mm or less. To a cooling facility for a hot steel sheet according to any one of the fourth to fourth aspects of the invention.

  (6) In the sixth invention, among the cooling water injection nozzles arranged in the steel plate width direction, the cooling water injection nozzle in the uppermost stream side row in the steel plate conveyance direction is inclined 15 to 60 degrees upstream in the steel plate conveyance direction. The cooling water jet nozzles in the most downstream row in the steel plate transport direction are inclined 15 to 60 degrees in the downstream direction in the steel plate transport direction, according to any one of the first to fifth inventions. This is a thermal steel sheet cooling facility.

  (7) In the seventh invention, when cooling the hot-rolled steel sheet after hot rolling, the steel sheet is cooled by the rod-like cooling water sprayed from the hot-steel sheet cooling equipment according to any one of the first to sixth inventions. A method for cooling a hot steel sheet, wherein the upper surface side is cooled.

  By using the thermal steel sheet cooling equipment and cooling method of the present invention, a high cooling rate can be obtained, and the steel sheet can be quickly cooled to the target temperature, which can contribute to productivity improvement. In addition, since the upper surface of the steel plate can be cooled uniformly in the width direction of the steel plate and can be uniformly performed, a high quality steel plate can be manufactured.

It is a side view of the cooling equipment concerning one embodiment of the present invention. It is a side view of other cooling equipment concerning one embodiment of the present invention. It is a figure explaining the example of nozzle arrangement of the partition concerning one embodiment of the present invention. It is a figure explaining the flow of the cooling waste water on a partition. It is a figure explaining other flows of cooling drainage 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. 8 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.

  FIG. 1 is a side view showing an arrangement of cooling nozzles, showing an upper and lower surface cooling facility according to an embodiment of the present invention.

  The top surface cooling facility is horizontally disposed across the steel plate width direction between the header 1 for supplying cooling water to the top surface of the hot steel plate 12, the cooling water injection nozzle 3 suspended from the header 1, and the header 1 and the hot steel plate 12. A partition wall 5 having a large number of through holes (water supply port 6 and drain port 7) is provided. The cooling water injection nozzle 3 is composed of a circular pipe nozzle 3 for injecting rod-shaped cooling water, and the tip thereof is inserted into a through hole (water supply port 6) provided in the partition wall 5 so that the lower end portion of the partition wall 5 It is installed to be on the top. The cooling water injection nozzle 3 is preferably inserted into the header 1 so that the upper end of the cooling water injection nozzle 3 protrudes into the header 1 in order to prevent the foreign matter at the bottom in the header 1 from being sucked and clogged.

  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 circular tube nozzle 3 is installed so that the tip of the circular tube nozzle 3 is inserted into the through-hole and above the lower end of the partition wall 5 even if a steel plate whose tip is warped upward enters. This is to prevent the 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 in 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. 11, it does not interfere with the flow in the width direction of the drained water indicated by the dotted arrow flowing through the upper surface of the partition wall 5. 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 an example, as shown in FIG. 3, a large number of through-holes having a diameter of 10 mm are formed in the partition wall 5 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, an inner diameter of 3 mm, and a length of 140 mm is inserted into the water supply port 6. 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 7. As described above, the large number of through holes provided in the partition wall 5 of the cooling facility of the present invention are composed of substantially the same number of water supply ports 6 and drain ports 7, and share their roles and functions.

  At this time, the total cross-sectional area of the drain port 7 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 steel plate surface and the partition wall 5, led to the upper side of the partition wall 5 through the drain port 7, and quickly discharged. FIG. 4 is a front view for explaining the flow of cooling drainage in the vicinity of the end in the width direction of the steel plate on the partition wall. The drainage direction of the drainage port 7 is upward opposite to the cooling water injection direction, and The cooling drainage that has passed through is turned to the outside in the width direction of the steel sheet and flows through the drainage flow path between the header 1 and the partition wall 5 and is drained.

  On the other hand, in the example shown in FIG. 5, the drain port 7 is inclined in the steel plate width direction so as to be inclined in the width direction outward so that the drain direction is directed outward in the steel plate width direction. By doing in this way, the flow of the discharged water on the partition wall 5 in the width direction of the steel plate becomes smooth and drainage is promoted, which is preferable.

  Here, as shown in FIG. 9, when the drainage port and the water supply port are installed in the same through hole, the cooling water does not easily escape above the partition wall 5 after colliding with the steel plate, and the steel plate 12 and the partition wall. 5 flows toward the end in the steel sheet width direction. Then, since the flow rate of the cooling drainage between the steel plate 12 and the partition wall 5 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 end in the plate width direction. It will be hindered.

  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 plate is weakened, and the temperature distribution in the width direction of the steel plate 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. 10, the water supply port 6 and the drainage port 7 are provided separately and share the roles of water supply and drainage. The water flows smoothly through the drain port 7 and above the partition wall 5. Accordingly, since the drainage after cooling is quickly removed from the upper surface of the steel sheet, the cooling water supplied subsequently 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.

  Incidentally, if the total cross-sectional area of the drain port 7 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 partition wall 5 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 7 is less 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 the accumulated water becomes difficult to be drained. 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 drain ports or the cross-sectional diameter of the drain ports becomes too large, the rigidity of the partition walls 5 will be small, and 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 gap between the outer peripheral surface of the circular tube nozzle 3 inserted into the water supply port 6 of the partition wall 5 and the inner surface of the water supply port 6 is preferably 3 mm or less. If this gap is large, the cooling drainage discharged to the upper surface of the partition wall 5 is drawn into the gap between the outer peripheral surface of the circular pipe nozzle of the water supply port 6 due to the influence of the accompanying flow of the cooling water jetted from the circular pipe nozzle 3. Since it is supplied again onto the steel plate, the cooling efficiency is deteriorated. In order to prevent this, it is more preferable that the outer diameter of the circular tube nozzle 3 is substantially the same as the size of the water supply port 6, but in consideration of work accuracy and mounting error, a gap of up to 3 mm that is substantially less affected. Is acceptable. More preferably, it is 2 mm or less.

  Furthermore, in order to allow the cooling water to penetrate the staying water film and reach the steel plate, it is necessary to optimize the inner diameter and length of the circular tube nozzle 3, the cooling water injection speed and the nozzle distance.

  That is, the nozzle inner diameter 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 length of the circular tube nozzle is preferably 120 to 240 mm. The length of the circular tube nozzle here means the length from the inlet at the upper end of the nozzle that penetrates into the header to some extent to the lower end of the nozzle inserted into the water supply port of the partition wall. If the circular tube nozzle is shorter than 120 mm, the distance between the lower surface of the header and the upper surface of the partition wall becomes too short (for example, if the header thickness is 20 mm, the protrusion amount of the nozzle upper end into the header is 20 mm, and the insertion amount of the nozzle lower end into the partition wall is 10 mm). Therefore, the drainage space above the partition wall becomes small, and the cooling drainage cannot be discharged smoothly. On the other hand, if the length is longer than 240 mm, the pressure loss of the circular tube nozzle increases, and the force penetrating the staying water film becomes weak.

  The jetting speed of the cooling water from the nozzle needs to be 6 m / s or more, preferably 8 m / s or more. This is because if it is less than 6 m / s, the force of the cooling water penetrating through 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 steel plate 12 collides with the partition wall 5 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.

  In cooling the upper surface of the steel plate, it is preferable to install draining rolls 10 before and after the 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. Here, since the flow of the cooling water in the steel plate conveyance direction is blocked by the draining roll 10, the cooling drainage flows to the outside in the width direction of the steel plate, but the cooling water tends to stay in the vicinity of the draining roll 10.

  Therefore, as shown in FIG. 2, among the rows of circular tube nozzles 3 aligned in the steel plate width direction, the cooling water jet nozzle in the uppermost stream side row in the steel plate conveyance direction is inclined 15 to 60 degrees upstream in the steel plate conveyance direction. The cooling water injection nozzles in the most downstream row in the steel plate conveyance direction are preferably inclined 15 to 60 degrees in the downstream direction in the steel plate conveyance direction. By carrying out like this, a cooling water can be supplied also to the position near the draining roll 10, and since a cooling water does not stay in the draining roll 10 vicinity, a cooling efficiency improves, and is suitable.

  The distance between the lower surface of the header 1 and the upper surface of the partition wall 5 is such that the cross-sectional area in the width direction of the steel plate in the space surrounded by the lower surface of the header and the upper surface of the partition wall is 1.5 times or more of the total cross-sectional area of the cooling water jet nozzle inner diameter. For example, about 100 mm or more. If the cross-sectional area of the flow path in the steel plate width direction is not 1.5 times or more than the total cross-sectional area of the cooling water jet nozzle inner diameter, the cooling drainage discharged from the drain port 7 provided on the partition wall to the top surface of the partition wall 5 is smooth. It is because it cannot discharge in the direction.

The range of the water density 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.

  The cooling technique of the present invention is particularly effective when draining rolls are arranged before and after the cooling header, but can also be applied when there is no draining roll. For example, the header is relatively long in the longitudinal direction (when it is about 2 to 4 m), and is applied to a cooling facility that sprays a water spray for purging before and after the header to prevent water leakage to the non-water cooling zone. Is also possible.

  In the present invention, the cooling device on the lower surface side of the steel plate is not particularly limited. In the embodiment shown in FIGS. 1 and 2, an example of the cooling header 2 including the circular tube nozzle 4 similar to the cooling device on the upper surface side is shown, but in cooling on the lower surface side of the steel plate, the injected cooling water is applied to the steel plate. Since it falls spontaneously after the collision, there is no need for the partition wall 5 for discharging cooling drainage such as cooling on the upper surface side in the steel plate width direction. Moreover, you may use the well-known technique which supplies film-like cooling water, spray-like spray cooling water, etc.

  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 equipment schematically shown in FIG. 8, the slab extracted from the heating furnace is formed by a rolling mill, subjected to tenter rolling, then rough rolled, and further subjected to finish rolling to obtain a plate thickness of 25 mm, The plate width was 4.5 m. The steel sheet surface temperature measured immediately after finish rolling, that is, the finish temperature was 820 ° C. Thereafter, accelerated cooling was performed in an accelerated cooling facility through a hot leveler. Cooling was performed from a cooling start temperature of 780 ° C. to a cooling end temperature of 560 ° C. (a value obtained by measuring the temperature after reheating on the accelerated cooling equipment exit side).

  As Example 1 of the present invention, the top surface cooling facility shown in the above embodiment was used. This cooling facility is a facility provided with a flow path for allowing cooling water supplied to the upper surface of the steel plate to flow above the partition as shown in FIG. 1 and draining from the side in the width direction of the steel plate as shown in FIG. is there.

  In the partition wall, holes with a diameter of 12 mm were formed like a grid, and as shown in FIG. 3, circular pipe nozzles were inserted into water supply ports arranged in a staggered pattern, and the remaining holes were used as drainage ports. . Further, as shown in FIG. 2, the cooling water injection nozzle in the uppermost stream side row in the steel plate conveyance direction is inclined 30 degrees in the upstream direction in the steel plate conveyance direction, and the cooling water injection nozzle in the lowermost row in the steel plate conveyance direction is The cooling water was also supplied to a position close to the draining roll by being inclined 30 degrees in the downstream direction of the steel plate conveyance direction. The distance between the header lower surface and the partition upper surface was 100 mm.

The nozzle had an inner diameter of 5 mm, an outer diameter of 9 mm, and a length of 170 mm, and its upper end protruded into the header. Moreover, the injection speed of the rod-shaped cooling water was 8.9 m / s. 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 rollers of 1 m. The water density on the upper surface was 2.1 m ³ / m ² · min. The lower end of the nozzle for cooling the upper surface was installed so as to be at an intermediate position between the upper and lower surfaces of the partition wall having a thickness of 25 mm, and the distance to the steel plate surface was 80 mm.

  As for the bottom surface cooling equipment, the cooling equipment similar to the top surface cooling equipment is used except that no partition wall is provided as shown in FIG. did.

  In the top surface cooling facility of Example 1 of the present invention, the total cross-sectional area of the drain outlet is sufficiently wide, about 6 times the total cross-sectional area of the nozzle inner diameter, so that the injected cooling water hitting the steel plate flows upward and is quickly discharged. . Furthermore, since the cross-sectional area of the flow path to the outer sides in the steel plate width direction in the space between the header lower surface and the partition upper surface was sufficiently wide, about 5 times the total cross-sectional area of the nozzle inner diameter, drainage from the plate edge is also possible It was very good. Since the cooling drainage after cooling is quickly eliminated, the cooling water supplied subsequently can easily penetrate the staying water film, and a higher cooling capacity than before can be obtained.

  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 is increased, it is possible to reduce the steel alloy components (for example, Mn) necessary for obtaining high strength, and to reduce the manufacturing cost.

  The temperature distribution in the width direction of the steel sheet was 550 to 560 ° C., which was a substantially uniform distribution as shown in FIG. 7, and the temperature unevenness in the width direction of the steel sheet was small and became 10 ° C. For this reason, the pass rate of the material test was as high as 99.5%, and the yield was also sufficiently high.

Since the lower end of the nozzle is in the middle position between the upper and lower ends of the partition wall, even if the steel plate that could not correct the upper warp generated by the pre-leveler or the steel plate that has warped during cooling hits the partition wall, the partition wall is a protective plate 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. In addition, conditions other than the hole shape provided in a partition were aligned with the above-mentioned Example 1 of this invention. In the cooling equipment of this comparative example, as shown in FIG. 9, 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. 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.

  Moreover, although the hole was vacant in the slit shape in the partition, the rigidity of this part was weak, and when the warped steel plate collided, the partition and the nozzle were deformed and damaged.

  As Example 2 of the present invention, a case where the following cooling conditions are changed in the same plate rolling process as Example 1 will be described.

  The cooling facility used in Invention Example 2 is the same top surface cooling facility as that of Invention Example 1 shown in FIG. 1, in which holes with a diameter of 11 mm and holes with a diameter of 14 mm are alternately formed like a grid on the partition wall. As shown in FIG. 3, circular nozzles were inserted using holes with a diameter of 14 mm arranged in a staggered pattern as a water supply port, and the remaining holes with a diameter of 11 mm were used as a drain port. The distance between the header lower surface and the partition upper surface was 100 mm.

The nozzle had an inner diameter of 8 mm, an outer diameter of 11 mm, and a length of 170 mm, and its upper end protruded into the header. Moreover, the jet speed of the rod-shaped cooling water was set to 6.3 m / s. The water density on the upper surface was 3.8 m ³ / m ² · min. The lower end of the nozzle for cooling the upper surface was installed so as to be at an intermediate position between the upper and lower surfaces of the partition wall having a thickness of 30 mm, and the distance to the steel plate surface was set to 50 mm. The conditions other than the above were the same as Example 1 of the present invention.

  In addition, about the lower surface cooling equipment, the cooling equipment similar to an upper surface cooling equipment except having no partition as shown in FIG. 1 was used, and the distance from the nozzle tip to the steel plate surface was 80 mm. Further, the jet speed and the water density of the rod-shaped cooling water were set to 1.5 times the upper surface.

  In the upper surface cooling facility of Example 2 of the present invention, the total cross-sectional area of the drain outlet is sufficiently wide, about twice the total cross-sectional area of the nozzle inner diameter, so that the jet cooling water hitting the steel plate flows upward and is quickly discharged. . In addition, the cross-sectional area of the flow path to the outside in the width direction of the steel plate in the space between the header lower surface and the partition upper surface was sufficiently wide, approximately twice the total cross-sectional area of the nozzle inner diameter, so that the drainage from the plate edge is also possible It was very good.

  The cooling time for setting the cooling stop temperature at the center of the plate width to 560 ° C. is 2.0 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. As in Example 1, uniform cooling could be performed at a high cooling rate.

1 Upper header 2 Lower header 3 Upper cooling water injection nozzle (circular tube nozzle)
4 Lower cooling water injection nozzle (circular tube nozzle)
5 Bulkhead 6 Water supply port 7 Drainage port 8 Injection cooling water 9 Drained water 10 Draining roll 11 Table roller 12 Steel plate

Claims (6)

A cooling facility for a hot steel plate installed in a hot rolling line for a steel plate, a header for supplying cooling water to the upper surface of the hot steel plate, a cooling water injection nozzle for injecting rod-like cooling water suspended from the header, A partition wall provided between the hot steel plate and the header, and a water supply port for inserting a lower end portion of the cooling water injection nozzle in the partition wall, and cooling water supplied to the upper surface of the hot steel plate A plurality of drain outlets for draining the partition wall onto the partition wall, and the total cross-sectional area of the drain ports provided in the partition wall and the cross-sectional area in the width direction of the steel sheet in the space surrounded by the header lower surface and the partition upper surface , Both of which are at least 1.5 times the total cross-sectional area of the cooling water jet nozzle inner diameter, and a cooling facility for hot steel sheets. The cooling equipment for hot steel sheets according to claim 1, wherein a draining roll is arranged before and after the header. The inner diameter of the cooling water injection nozzle is 3 to 8 mm, the length is 120 to 240 mm, the distance from the lower end of the cooling water injection nozzle to the surface of the hot steel sheet is 30 to 120 mm, and the flow rate of the cooling water injected from the cooling water injection nozzle is 6 m / The cooling facility for hot-steel sheets according to claim 1 or 2 , wherein the water density is 1.5 to 4.0 m ³ / m ² · min. Heat steel sheet according to any one of claims 1 to 3, characterized in that the gap between the outer peripheral surface and the inner surface of the water inlet of the cooling water jetting nozzles interpolated to the water supply port provided in the partition wall and 3mm or less Cooling equipment. Among the cooling water injection nozzles arranged in the steel plate width direction, the cooling water injection nozzle in the uppermost stream side row in the steel plate conveyance direction is inclined 15 to 60 degrees in the upstream direction in the steel plate conveyance direction, and the most downstream row in the steel plate conveyance direction. The cooling water jet nozzle according to any one of claims 1 to 4 , wherein the cooling water spray nozzle is inclined 15 to 60 degrees in a downstream direction of the steel plate conveyance direction. When cooling a hot steel sheet after hot rolling, the upper surface side of the steel sheet is cooled by rod-shaped cooling water sprayed from the hot steel sheet cooling facility according to any one of claims 1 to 5 . Cooling method.

Images