CN106794500B

CN106794500B - Manufacturing equipment and manufacturing method of thick steel plate

Info

Publication number: CN106794500B
Application number: CN201580045928.4A
Authority: CN
Inventors: 田村雄太; 福田启之; 安达健二
Original assignee: Jeffrey Steel Co Ltd
Current assignee: Jeffrey Steel Co Ltd
Priority date: 2014-08-26
Filing date: 2015-08-14
Publication date: 2020-01-31
Anticipated expiration: 2035-08-14
Also published as: CN106794500A; EP3195946A1; EP3195946B1; KR101940428B1; JP6264464B2; KR20170036003A; BR112017003566B1; JPWO2016031168A1; EP3195946A4; WO2016031168A1; BR112017003566A2

Abstract

The present invention aims to provide a thick steel plate manufacturing facility and a thick steel plate manufacturing method which perform uniform cooling in a cooling step by making scale generated on the surface of the thick steel plate uniform in a descaling step and are excellent in the shape and mechanical properties of the thick steel plate. A thick steel plate manufacturing facility, characterized in that a hot rolling mill, a shape straightening device, a descaling device and an accelerated cooling device are arranged in order from the upstream side in the conveying direction, the spray nozzles of the descaling device are arranged in 2 rows relative to the longitudinal direction of the thick steel plate, and the energy density E carried by the descaling water sprayed from the spray nozzles in the 2 rows to the surface of the thick steel plate is set to be 0.08J/mm in total²The above.

Description

Manufacturing equipment and manufacturing method of thick steel plate

Technical Field

The present invention relates to a thick steel plate manufacturing facility and a thick steel plate manufacturing method for hot rolling, shape straightening and accelerated cooling of a thick steel plate.

Background

In recent years, the application of controlled cooling has been expanding as a process for manufacturing a thick steel sheet, however, in general, the shape and surface properties of a hot-rolled thick steel sheet are not uniform , and therefore, temperature unevenness is likely to occur in the thick steel sheet during cooling, and deformation, residual stress, material unevenness, and the like are generated in the thick steel sheet after cooling, resulting in poor quality and handling problems.

Accordingly, patent document 1 discloses a method of performing descaling (scaling) at least of the finish rolling immediately before and after the final pass, followed by hot straightening, then performing descaling, and performing forced cooling, and patent document 2 discloses a method of performing controlled cooling after performing descaling after the finish rolling and hot straightening, and patent document 3 discloses a method of performing descaling while controlling the impact pressure of cooling water immediately before the controlled cooling.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 9-57327

Patent document 2: japanese patent No. 3796133

Patent document 3: japanese patent laid-open publication No. 2010-247228

Disclosure of Invention

Problems to be solved by the invention

However, when a thick steel plate is actually manufactured by the methods of patent documents 1 and 2, there are the following problems: in the descaling process, scale (scale) is not completely peeled off, but the scale is partially peeled off by the descaling, that is, uneven scale occurs, and uniform cooling cannot be performed during controlled cooling. In addition, in order to prevent scale unevenness from occurring in the method of patent document 3, a high impact pressure is required. Therefore, there are the following problems: the uneven scale of the oxide film occurs at a low impact pressure, and as a result, uniform cooling cannot be performed at the time of controlled cooling.

In particular, in recent years, the level of material uniformity required for thick steel plates has become more stringent, and the above-described unevenness in scale causes the cooling rate to be controlled during cooling, and particularly the adverse effect on the material uniformity in the width direction of the thick steel plate cannot be ignored.

Accordingly, the present invention has been made keeping in mind the above problems unsolved by the prior art examples, and an object of the present invention is to provide a thick steel plate manufacturing apparatus and a thick steel plate manufacturing method, which include: by making the scale generated on the surface of the thick steel plate uniform in the descaling step, uniform cooling is performed in the cooling step, and the thick steel plate is excellent in shape and mechanical properties.

Means for solving the problems

The inventors of the present application conducted an intensive study on the force by which scale is peeled off by descaling water, and as a result, found that when descaling is performed after hot shape straightening, 2 or more rows of spray nozzles of a descaling device are arranged in the longitudinal direction of a thick steel plate, and the energy density of the descaling water sprayed from the 2 or more rows of spray nozzles to the thick steel plate is 0.08J/mm in total²As described above, the thickness of the scale formed on the surface of the product after the production is uniform. As a result, when passing through the accelerated cooling equipment, uniform cooling can be performed with almost no deviation in the surface temperature at the position in the width direction of the steel plate, and a steel plate having an excellent steel plate shape can be obtained.

The gist of the present invention is as follows.

[1] Thick steel plate manufacturing facility, characterized in that the hot rolling mill, the shape straightening device, the descaling device and the accelerated cooling device are arranged in order from the upstream side in the conveying direction, the spray nozzles of the descaling device are arranged in 2 rows relative to the length direction of the thick steel plate, and the energy density E carried by the descaling water sprayed from the spray nozzles of the 2 rows to the surface of the thick steel plate is set to be 0.08J/mm in total²The above.

[2] Thick steel plate manufacturing facility, characterized in that the hot rolling mill, the shape straightening device, the descaling device and the accelerated cooling device are arranged in order from the upstream side in the conveying direction, the spray nozzles of the descaling device are arranged in 2 or more rows relative to the longitudinal direction of the thick steel plate, and the energy density E carried by the descaling water sprayed from the spray nozzles in 2 or more rows to the surface of the thick steel plate is set to be 0.08J/mm in total²The above.

[3]Such as [1]]Or [ 2]]The thick steel plate manufacturing facility is characterized in that the conveying speed from the descaling device to the accelerated cooling device is set to V [ m/s ]]The temperature of the thick steel plate before cooling is T [ K ]]From the descaling device to the accelerated coolingDistance L [ m ] of the device]L is less than or equal to V multiplied by 5 multiplied by 10^-9Xexp (25000/T).

[4] The thick steel plate manufacturing facility according to [3], wherein a distance L from the descaling device to the accelerated cooling device is 12m or less.

[5] The apparatus for manufacturing a thick steel plate as recited in any one of items in [1] to [4], wherein a distance H from a spray nozzle of the descaling device to a surface of the thick steel plate is set to 40mm or more and 200mm or less.

[6] The apparatus for manufacturing a thick steel plate as claimed in any of [1] to [5], wherein the accelerated cooling equipment includes a header (header) for supplying cooling water to an upper surface of the thick steel plate, a cooling water spray nozzle for spraying rod-shaped cooling water suspended from the header, and a partition plate provided between the thick steel plate and the header, wherein the partition plate is provided with a plurality of water feed ports and drain ports, the water feed ports are water feed ports into which lower end portions of the cooling water spray nozzles are inserted, and the drain ports are drain ports for draining the cooling water supplied to the upper surface of the thick steel plate onto the partition plate.

[7]A method for manufacturing kinds of thick steel plates, characterized in that, in the method for manufacturing thick steel plates by sequentially carrying out a hot rolling process, a hot straightening process and an accelerated cooling process, a descaling process is provided between the hot straightening process and the accelerated cooling process, and the descaling process is 0.08J/mm in total energy density E²The surface of the thick steel plate was subjected to the descaling process of 2 times in the above manner.

[8]A method for manufacturing kinds of thick steel plates, characterized in that, in the method for manufacturing thick steel plates by sequentially carrying out a hot rolling process, a hot straightening process and an accelerated cooling process, a descaling process is provided between the hot straightening process and the accelerated cooling process, and the descaling process is 0.08J/mm in total energy density E²The surface of the thick steel plate was subjected to the descaling process of descaling 2 or more times in the above manner.

[9]According to [7]Or [ 8]]The method of manufacturing a thick steel plate is characterized in that the descaling step is completed and the accelerated cooling step is startedTime t [ s ] of start]T is less than or equal to 5 multiplied by 10^-9X exp (25000/T), wherein T: temperature (K) of the steel plate before cooling.

Effects of the invention

According to the present invention, by making the scale generated on the surface of the thick steel plate uniform in the descaling step, uniform cooling can be performed in the cooling step, and a thick steel plate excellent in the shape and mechanical properties of the thick steel plate can be manufactured.

Drawings

Fig. 1 is a schematic view showing equipment for manufacturing thick steel plates according to embodiments of the present invention.

FIG. 2 is a diagram illustrating a temperature distribution in the width direction of a steel plate according to a conventional example.

FIG. 3 is a graph showing a relationship between an energy density of the sprayed descaling water and a thickness of an oxide scale generated on a product surface of a thick steel plate in the descaling apparatus.

FIG. 4 is a graph showing a relationship between a jet distance of a jet nozzle and a fluid velocity in the descaling device.

FIG. 5 is a view showing a surface temperature distribution at a position in the width direction of a thick steel plate according to the present invention.

Fig. 6 is a schematic view showing the arrangement relationship of the spray nozzles of the descaling device, (a) is a schematic view showing the positional relationship of the spray nozzles, and (b) is a schematic view showing the spray pattern.

Fig. 7 is a side view of an accelerated cooling device according to embodiments of the present invention.

Fig. 8 is a side view of another accelerated cooling apparatus according to embodiments of the present invention.

Fig. 9 is a diagram illustrating an example of nozzle arrangement of the partition plates according to the embodiments of the present invention.

Fig. 10 is a view illustrating the flow of cooling drain water on the separator.

Fig. 11 is a view for explaining another flow of cooling drain water on the separator.

Fig. 12 is a view for explaining the acceleration of the flow of cooling water in the cooling device.

Fig. 13 is a view for explaining the acceleration of the flow of cooling water in the cooling device.

FIG. 14 is a view for explaining non-interference with cooling water drainage on a partition plate in an accelerated cooling equipment.

Detailed Description

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

Fig. 1 is a schematic diagram showing manufacturing facilities of slabs according to an embodiment of the present invention, in fig. 1, arrows indicate a conveying direction of a slab, and a heating furnace 1, a descaling device 2, a rolling mill 3, a shape straightening device 4, a descaling device 6, a descaling device 7, and an accelerated cooling device 5 are arranged in this order from an upstream side in the conveying direction of the slab, in fig. 1, a slab (not shown) as a rolling material is reheated by the heating furnace 1, and thereafter is removed times by the descaling device 2, so the slab is descaled, and then the slab is subjected to rough rolling and finish rolling by the rolling mill 3, thereby being rolled into a slab (not shown) having a predetermined thickness, and the illustrated rolling mill 3 is constituted by only 1 machine, it should be noted that the rolling mill 3 may be constituted by a rough rolling mill and a finish rolling mill 3, after being straightened by the shape straightening device 4, the descaling device 6 and the finish rolling mill 7 may be subjected to scale removal, and the straightening device may be configured by a surface-rolling mill 6 and a straightening device for straightening of a hot-rolled steel plate having a shape, and a shape of which is preferably, a hot-rolled, and a straightening device is configured by a straightening device for straightening by a straightening method of a straightening device for straightening method of a straightening mill, a straightening device of a straightening device for straightening, a straightening device for straightening method of a straightening, a straightening device for straightening, a straightening device for.

In the accelerated cooling apparatus 5, the steel plate is cooled to a predetermined temperature by cooling water sprayed from the upper surface cooling facility and the lower surface cooling facility, and then, the shape of the steel plate is straightened by a shape straightening apparatus (not shown) provided on the line (online) or under the line (offline) downstream in a step as necessary.

In the present embodiment, 2 descaling devices, that is, a descaling device 6 and a descaling device 7 are disposed between the shape leveler 4 and the accelerated cooling device 5. The total of spray nozzles having an energy density E of 2 rows of the descaling water sprayed from the descaling devices 6 and 7 onto the surface of the thick steel plate was 0.08J/mm²The above. The scale produced on the surface of the thick steel plate is removed by the descaling device 6 and the descaling device 7, and then the thick steel plate is cooled by the accelerated cooling device 5, whereby the steel plate shape and mechanical properties of the thick steel plate can be improved. The descaling device shown in fig. 1 has only 2 rows. The descaling device may be configured by 3 or more rows. When the descaling device is more than 3 rows, the energy density E of the descaling water sprayed to the surface of the thick steel plate is 0.08J/mm in total of the spray nozzles of the formed rows²The above.

The reason for this is as follows. In a conventional rolling facility, when scale is removed by a descaling device after shape straightening, scale may be partially peeled off. In this case, since the scale is not uniformly peeled off, a variation in the thickness of the scale of about 10 to 50 μm occurs. In this case, it is difficult to uniformly cool the thick steel plate in the subsequent accelerated cooling device. That is, in the conventional rolling mill, when the thick steel plate in which the variation in the scale thickness distribution is generated is subjected to accelerated cooling, as shown in fig. 2, the variation in the surface temperature at the position in the width direction becomes large, and uniform cooling cannot be performed. As a result, the shape of the thick steel plate is affected.

This applicationThe inventors of the present invention have found that scale peeling is not sufficiently performed depending on the descaling conditions, but rather, the scale is not uniform. Further, the conditions under which scale peeling can be sufficiently performed have been studied with great care. As a result, it was found that: in the case of performing descaling after the straightening of the shape, 2 or more rows of descaling devices are arranged in the longitudinal direction of the steel plate between the shape straightening device and the accelerated cooling device, and the energy density E of the descaling water sprayed from 2 or more rows of spray nozzles of the descaling devices onto the surface of the steel plate is set to 0.08J/mm in total of the 2 or more rows of spray nozzles²In the above case, the thickness of the scale to be regenerated thereafter becomes 5 μm or less uniformly.

In descaling, the surface of the scale is cooled by the descaling water, so that thermal stress is generated in the scale and an impact force by the descaling water acts. As a result, the scale is removed by peeling or breaking. The inventors of the present application have conducted extensive studies and found that the effect of thermal stress generated when descaling is performed 2 or more times can be obtained by descaling 2 or more times after hot shape straightening. As shown in fig. 3, it is found that the oxide scale can be more efficiently removed by performing the treatment 2 times than by performing the treatment 1 time only. Further, the energy density E of the descaling water sprayed from the 2 rows of spray nozzles of the descaling device to the thick steel plate was 0.08J/mm in total²In the above case, the product scale is reduced in thickness and can be made uniform. The number of injections shown in fig. 3 is 2. The inventors of the present application confirmed that the same effect can be obtained even when the number of injections is 3 or more. This is because the scale is once uniformly and completely peeled off by the descaling, and thereafter, the scale is thinly and uniformly regenerated. Therefore, according to the present invention, since the scale thickness of the thick steel plate before passing through the accelerated cooling equipment is uniformly reduced, the thick steel plate can be uniformly cooled with almost no variation in surface temperature at the position in the width direction of the thick steel plate when passing through the accelerated cooling equipment, and the thick steel plate having excellent shape and mechanical properties of the thick steel plate can be obtained.

Energy density E (J/mm) of descaling water sprayed onto a thick steel plate²) By removingAn index of the ability of scale to remove scale is defined by the following formula (1).

E＝Qρv²t÷(2dW)…(1)

Wherein, Q: spray flow of descaling Water [ m ]³/s]D: spray thickness of flat nozzle [ mm ]]W: spray width of flat nozzle [ mm ]]Fluid density rho [ kg/m ]³]And the fluid velocity v [ m/s ] at the time of impact on the thick steel plate]Time of impact t [ s ]](t is d/1000V, and the transport speed V [ m/s ]])。

Since the fluid velocity v is not always easily measured when a thick steel plate is impacted, a large amount of labor is required to strictly determine the energy density E defined by the formula (1).

The inventors of the present application conducted further and found that the energy density E (J/mm) of the descaling water sprayed to the thick steel plate²) The simple definition of (2) is defined as water density x injection pressure x impact time. Here, the water volume density (m)³/(mm²Min)) is a value calculated from "spray flow rate of descaling water ÷ descaling water impact area". Injection pressure (N/m)²(Pa)) is defined by the discharge pressure of the descaling water. The impact time(s) is a value calculated from "impact thickness of descaling water ÷ conveyance speed of the steel plate". In the present invention, there is no upper limit to the energy density E as the descaling capability. In addition, when the total of the 2 or more rows of the spray nozzles is 0.80J/mm²In the above case, the discharge pressure of the pump is undesirably increased.

The inventors of the present application studied the fluid velocity v of the descaling water sprayed from the spray nozzles of the descaling devices 6 and 7. As a result, it was found that the relationship between the fluid velocity v and the ejection distance is as shown in fig. 4. The longitudinal axis, i.e., the fluid velocity, is obtained by solving equations of motion that take into account buoyancy and air resistance. The fluid velocity v of the descaling water is decelerated compared to that at the time of spraying until the descaling water reaches the thick steel plate. Therefore, the smaller the throw distance, the larger the fluid velocity v at the time of the thick steel plate impact, and the larger the energy density can be obtained. As is clear from fig. 4, the ejection distance H is preferably 200mm or less because the attenuation is large particularly when the ejection distance H is larger than 200 mm.

In the embodiments of the present invention shown in fig. 1, since the thick steel plate that has been shape-straightened by the shape straightening device 4 moves within the descaling device 6 and the descaling device 7, there is a possibility that the spray nozzles of the descaling device 6 and the descaling device 7 approach the surface of the thick steel plate, but the spray distance is preferably 40mm or more in consideration of the contact between the spray nozzles and the thick steel plate, and from the above, it is understood that the spray distance H is preferably 40mm or more and 200mm or less in the present invention.

Since the discharge capacity of the pump used in the usual descaling device 6 and descaling device 7 is 14.7MPa or more, the spray pressure of the descaling water is preferably 14.7MPa or more. The upper limit of the injection pressure is not particularly determined. However, since the energy consumed by the pump for supplying the descaling water increases when the injection pressure is increased, the injection pressure is preferably 50MPa or less.

As described above, according to the present embodiment, the energy density E of the descaling water discharged from 2 or more spray nozzles is set to 0.08J/mm²The descaling devices 6 and 7 described above remove scale formed on the surface of the thick steel plate. As a result, since the variation in the scale thickness distribution disappears, when the steel plate is cooled by the accelerated cooling equipment 5, as shown in fig. 5, the steel plate can be uniformly cooled so that there is almost no variation in the surface temperature at the position in the width direction, and a steel plate having an excellent steel plate shape and excellent mechanical properties can be manufactured.

In the descaling device 6 and the descaling device 7 according to the present invention, for example, as shown in fig. 6(a), the descaling header 6-1 of the descaling device 6 and the descaling header 7-1 of the descaling device 7 are arranged in 2 rows with respect to the longitudinal direction of the thick steel plate. The scale removal header shown in fig. 6(a) has 2 rows. The descaling header may be configured to have 3 or more rows. Here, the upper limit is preferably 3 columns because the above effect is saturated when the number is more than 3 columns. The scale removing water is sprayed from a plurality of spray nozzles 6-2 and 7-2 provided in the scale removing header toward the thick steel plate, and the spray pattern 22 as shown in fig. 6(b) is formed.

The arrangement relationship of the spray nozzles 6-2 and 7-2 of the descaling device 6 and the descaling device 7 is preferably set to be apart from each other by 500mm or more in the longitudinal direction in order to prevent the splashed water of the descaling water in the row 2 from interfering with the descaling water in the row 1. Further, the ejection patterns in the width direction are preferably arranged so that the 1 st row and the 2 nd row are staggered as shown in fig. 6 (b). Further, the energy density of the descaling water sprayed from the 2 spray nozzles 6-2 and 7-2 can be more efficiently removed when the scale is removed at a high energy density by the descaling in the 2 nd row after the cracking is generated in the scale by the thermal stress effect of the descaling in the 1 st row. Therefore, in order to cause cracks in the oxide scale by the thermal stress effect of the descaling in the 1 st row, the energy density of the descaling water in the 1 st row is preferably 0.01J/mm²As described above, the energy density of the descaling water in column 2 is preferably 0.04J/mm higher than that in column 1²The above. Similarly, the descaling device is provided in 3 rows or more, and the nozzle rows are preferably arranged alternately at intervals of 500mm or more in the longitudinal direction. In addition, when the number of the descaling devices is 3 or more, the energy density of the descaling water sprayed from the spray nozzles of the descaling devices in the row immediately before the final row is preferably 0.01J/mm for the same reason as that in the case of the number of the descaling devices in 2²As described above, the energy density of the descaling water sprayed from the spray nozzles of the descaling device of the final row is preferably 0.04J/mm greater than that of the row immediately before the final row²The above.

Further, since the shape of the steel plate is straightened by the shape straightening device 4, the spray nozzles of the descaling devices 6 and 7 may come close to the surface of the steel plate having been straightened. As a result, the descaling performance is improved.

The stability of the thick steel plate during cooling by the accelerated cooling equipment 5 is affected. Regarding the scale on the surface of the thick steel plate, the growth of the scale on the thick steel plate can be generally determined by diffusion control (diffusion control), and is known to be represented by the following formula (2).

ξ²＝a×exp(-Q/RT)×t…(2)

Wherein ξ is the thickness of the scale, a is a constant, Q is activation energy, R is a constant, T is the temperature [ K ] of the thick steel plate before cooling, and T is time.

Therefore, the constant of the above equation (2) is derived experimentally by considering the growth of the scale after the scale removal by the descaling devices 6 and 7 and performing a simulation experiment of the growth of the scale at various temperatures and times, and the thickness of the scale and the cooling stability are further investigated .

When the thickness of the scale is 15 μm or less, the following formula (3) can be derived based on the above formula (2). That is, when the following expression (3) is satisfied by the time t [ s ] from the end of scale removal of the thick steel plate by the downstream-side descaling device 7 of the descaling devices 6 and 7 to the start of cooling of the thick steel plate by the accelerated cooling device 5, the cooling by the accelerated cooling device 5 is stabilized.

t≤5×10^-9×exp(25000/T)…(3)

Wherein, T: the temperature of the thick steel plate before cooling [ K ].

When the thickness of the scale is 10 μm or less, the following formula (4) can be derived based on the above formula (2). That is, when the following expression (4) is satisfied by the time t [ s ] from the end of the removal of scale from the thick steel plate by the descaling device 7 to the start of the cooling of the thick steel plate by the accelerated cooling device 5, the cooling by the accelerated cooling device 5 is more stable.

t≤2.2×10^-9×exp(25000/T)…(4)

When the thickness of the scale is 5 μm or less, the following formula (5) can be derived based on the above formula (2). That is, when the time t [ s ] from the end of scale removal of the thick steel plate by the descaling device 7 to the start of cooling of the thick steel plate by the accelerated cooling device 5 satisfies the following expression (5), cooling by the accelerated cooling device 5 is very stable.

t≤5.6×10^-10×exp(25000/T)…(5)

Further , the distance L from the outlet side of the descaling device 7 to the inlet side of the accelerated cooling device 5 is set so as to satisfy the following expression (6) with respect to the transport speed V of the steel plate and the time t (time from the end of the descaling process by the descaling device 7 to the start of the process by the accelerated cooling device 5).

L≤V×t…(6)

Wherein, L: distance (m) from the descaling device 7 to the accelerated cooling device 5, V: conveying speed (m/s) of thick steel plate, t: time(s).

From the above expressions (6) and (3), the following expression (7) can be introduced. In the present invention, the formula (7) is more preferably satisfied.

L≤V×5×10^-9×exp(25000/T)…(7)

Further, from the above-mentioned expressions (6) and (4), the following expression (8) can be derived, and in the present invention, it is preferable that step satisfies expression (8).

L≤V×2.2×10^-9×exp(25000/T)…(8)

Further, from the above-mentioned expressions (6) and (5), the following expression (9) can be derived. In the present invention, the formula (9) is preferably satisfied.

L≤V×5.6×10^-10×exp(25000/T)…(9)

From the above expressions (7) to (9), when the temperature of the thick steel sheet before cooling by the accelerated cooling equipment 5 is set to 820 ℃ and the conveyance speed of the thick steel sheet is set to 0.28 to 2.50m/s, for example, the cooling is stabilized under the condition that the distance L from the descaling device 7 to the accelerated cooling equipment 5 is 12m to 107m, the cooling is more stabilized at 5m to 47m, and the cooling at 1.3m to 12m is very stabilized.

Accordingly, when the distance L from the descaling device 7 to the accelerated cooling device 5 is set to 12m or less, cooling is stable even when the transport speed V of the thick steel plate is low (for example, V is 0.28m/s), and on the contrary, cooling is very stable when the transport speed V of the thick steel plate is high (for example, V is 2.50m/s), which is preferable. More preferably, the distance L from the descaling device 7 to the accelerated cooling device 5 is 5m or less.

In addition, in general, in most of the thick steel plates that require controlled cooling, the distance L further , which is a condition where cooling is very stable under the condition of the transport speed V, is preferably 2.5m or less, considering that the transport speed V is 0.5m/s or more.

In addition, in the case where the temperature of the thick steel plate before cooling by the accelerated cooling equipment 5 is 820 ℃.

Next, the accelerated cooling device 5 of the present invention will be described. As shown in fig. 7, the upper surface cooling apparatus of the accelerated cooling device 5 of the present invention includes: an upper water collecting base 11 for supplying cooling water to the upper surface of the thick steel plate 10, a cooling water spray nozzle 13 for spraying rod-like cooling water suspended from the upper water collecting base 11, and a partition plate 15 provided between the thick steel plate 10 and the upper water collecting base 11. Preferably, the partition plate 15 is provided with a plurality of water supply ports 16 and drain ports 17, the water supply ports 16 being water supply ports into which the lower end portions of the cooling water injection nozzles are inserted, and the drain ports 17 being drain ports for draining the cooling water supplied to the upper surface of the thick steel plate 10 onto the partition plate 15.

Specifically, the upper surface cooling apparatus includes: an upper water collecting base 11 for supplying cooling water to the upper surface of the thick steel plate 10, a cooling water spray nozzle 13 suspended from the upper water collecting base 11, and a partition plate 15 having a plurality of through holes (a water supply port 16 and a water discharge port 17) horizontally provided between the upper water collecting base 11 and the thick steel plate 10 in the width direction of the thick steel plate. The cooling water spray nozzle 13 is formed of a circular tube nozzle that sprays rod-like cooling water, and the tip thereof is inserted into a through hole (water feed port 16) provided in the partition plate 15 and is provided above the lower end of the partition plate 15. In order to prevent the clogging of the bottom portion of the upper header 11 by sucking foreign matter, it is preferable that the cooling water spray nozzle 13 is inserted into the upper header 11 so that the upper end thereof protrudes into the upper header 11.

Here, the rod-like cooling water in the present invention is cooling water that is sprayed from a circular (including elliptical and polygonal) nozzle outlet in a state where is pressurized to a certain extent, and is cooling water that has a continuous and straight-ahead water flow in which the spraying speed of the cooling water from the nozzle outlet is 6m/s or more, preferably 8m/s or more, and the cross section of the water flow sprayed from the nozzle outlet is kept substantially circular, that is, is different from a free-fall flow from a circular tube laminar nozzle or a flow sprayed in a droplet state such as a shower.

The reason why the cooling water jet nozzle 13 is provided so that the tip end thereof is inserted into the through hole and is positioned above the lower end portion of the partition plate 15 is because damage to the cooling water jet nozzle 13 by the partition plate 15 can be prevented even if a thick steel plate whose tip end is raised upward enters. Thus, the cooling water spray nozzles 13 can be cooled in a good state over a long period of time, and therefore, the occurrence of temperature unevenness in the thick steel plate can be prevented without performing maintenance of the equipment.

Further, since the tip of the circular tube nozzle 13 is inserted into the through hole, as shown in fig. 14, it does not interfere with the flow of the discharged water flowing in the width direction of the broken-line arrow on the upper surface of the partition plate 15. Therefore, the cooling water sprayed from the cooling water spray nozzles 13 can uniformly reach the upper surface of the thick steel plate regardless of the position in the width direction, and uniform cooling can be performed in the width direction.

As shown in FIG. 9, in the case of examples of the partition plate 15, a large number of through holes having a diameter of 10mm are formed in a grid pattern at a pitch of 80mm in the width direction of the steel plate and at a pitch of 80mm in the transport direction of the steel plate, and cooling water spray nozzles 13 having an outer diameter of 8mm, an inner diameter of 3mm and a length of 140mm are inserted into the water feed ports 16, the cooling water spray nozzles 13 are arranged in a staggered grid pattern, and the through holes which do not pass through the cooling water spray nozzles 13 serve as the water discharge ports 17 for cooling water, and as described above, the large number of through holes provided in the partition plate 15 of the accelerated cooling device of the present invention are constituted by the water feed ports 16 and the water discharge ports 17 having substantially the same number, and they share functions.

At this time, the total cross-sectional area of the drain port 17 is sufficiently larger than the total cross-sectional area of the interior of the circular tube nozzle 13 of the cooling water injection nozzle 13, and is secured to be about 11 times the total cross-sectional area of the interior of the circular tube nozzle 13, and as shown in fig. 7, the cooling water supplied to the top surface of the thick steel plate fills the space between the surface of the thick steel plate and the partition plate 15, is introduced into the upper side of the partition plate 15 through the drain port 17, and is quickly discharged. Fig. 10 is a front view illustrating the flow of cooling drainage water in the vicinity of the end portions of the thick steel plate in the width direction on the separator. The drainage direction of the drainage port 17 is opposite to the cooling water spraying direction and is upward, and the cooling drainage water passing through the upper side of the partition plate 15 changes its direction to the outer side in the width direction of the thick steel plate, flows through the drainage flow path between the upper water collecting base 11 and the partition plate 15, and is drained.

In reference to , the example shown in FIG. 11 is preferable because the drain port 17 is inclined in the steel plate width direction and the drain direction is inclined outward in the width direction so as to be directed outward in the steel plate width direction, whereby the flow of the drain water 19 on the separator 15 in the steel plate width direction becomes smooth and the drain is promoted.

Here, as shown in fig. 12, if the drain port and the water feed port are provided in the same through hole, the cooling water passes above the separator 15 after striking the thick steel plate, and flows toward the end in the thick steel plate width direction between the thick steel plate 10 and the separator 15, and thus the flow rate of the cooling drain water between the thick steel plate 10 and the separator 15 increases closer to the end in the plate width direction, and the force of the jetted cooling water 18 penetrating the stagnant water film and reaching the thick steel plate is more obstructed closer to the end in the plate width direction.

In the case of a thin steel sheet, since the sheet width is at most about 2m, the influence thereof is limited. However, particularly in the case of a thick steel plate having a plate width of 3m or more, the influence thereof cannot be ignored any more. Therefore, the cooling of the end portions in the width direction of the thick steel plate becomes weak, and the temperature distribution in the width direction of the thick steel plate at this time becomes uneven.

In contrast, as shown in fig. 13, in the accelerated cooling device of the present invention, since the water supply port 16 and the water discharge port 17 are provided separately and distribute the functions of water supply and water discharge, the cooling water discharge flows smoothly above the partition plate 15 through the water discharge port 17 of the partition plate 15. Therefore, since the drain water after cooling is quickly removed from the upper surface of the thick steel plate, the cooling water supplied subsequently can easily penetrate the stagnant water film, and a sufficient cooling capacity can be obtained. The temperature distribution in the width direction of the thick steel plate at this time becomes uniform, and a uniform temperature distribution in the width direction can be obtained.

Incidentally, when the total sectional area of the drain port 17 is 1.5 times or more the total sectional area of the inside of the circular tube nozzle 13, the discharge of the cooling water can be performed quickly. This can be achieved by, for example, forming holes larger than the outer diameter of the circular tube nozzle 13 in the partition plate 15 so that the number of the water discharge ports is equal to or greater than the number of the water feed ports.

When the total cross-sectional area of the drain port 17 is less than 1.5 times the total cross-sectional area of the interior of the circular tube nozzle 13, the flow resistance of the drain port increases, and the retained water becomes difficult to be drained, and as a result, the amount of cooling water that can pass through the retained water film and reach the surface of the steel plate decreases greatly, and the cooling capacity decreases, which is not preferable, the total cross-sectional area of the drain port 17 is more preferably 4 times or more the total cross-sectional area of the interior of the circular tube nozzle 13, and further , when the drain port is too large, the cross-sectional diameter of the drain port becomes too large, the rigidity of the partition plate 15 decreases, and damage is likely to occur after impact with the steel plate, and therefore, the ratio of the total cross-sectional area of the drain port to the total cross-sectional.

The gap between the outer peripheral surface of the circular pipe nozzle 13 inserted into the water supply opening 16 of the partition 15 and the inner surface of the water supply opening 16 is preferably 3mm or less. When the gap is large, the cooling water discharged to the upper surface of the partition 15 is drawn into the gap between the water feed port 16 and the outer peripheral surface of the circular tube nozzle 13 by the effect of the wake of the cooling water sprayed from the circular tube nozzle 13, and is supplied again to the thick steel plate, so that the cooling efficiency is deteriorated. To prevent this, it is more preferable that the outer diameter of the circular tube nozzle 13 is almost the same as the size of the water feed opening 16. However, in consideration of working accuracy and mounting error, a small clearance up to 3mm is allowed to be substantially affected. More preferably 2mm or less.

In order to allow the cooling water to penetrate the stagnant water film and reach the thick steel plate, the inner diameter and length of the circular tube nozzle 13, the injection speed of the cooling water, and the nozzle distance need to be optimized.

That is, the nozzle inner diameter is preferably 3 to 8mm, and when the nozzle diameter is less than 3mm, the water jet jetted from the nozzle becomes thin and the force becomes weak, and when the nozzle diameter is more than 8mm, the flow velocity becomes weak and the force penetrating the water retention film becomes weak .

The length of the circular tube nozzle 13 is preferably 120 to 240mm, and here, the length of the circular tube nozzle 13 is a length from an inlet at the upper end of the nozzle penetrating into the interior of the water collection base to the lower end of the nozzle inserted into the water supply port of the partition plate, and when the circular tube nozzle 13 is shorter than 120mm, the distance between the lower surface of the water collection base and the upper surface of the partition plate becomes too short (for example, when the thickness of the water collection base is 20mm, the amount of projection of the upper end of the nozzle into the water collection base is 20mm, and the amount of insertion of the lower end of the nozzle into the partition plate is 10mm, the distance is less than 70 mm.), the drainage space above the partition plate becomes small, and cooling drainage cannot be smoothly discharged, and in , when the length is longer than 240mm, the pressure loss of the circular tube nozzle 13 becomes large, and the force penetrating the.

The spray velocity of the cooling water from the nozzle needs to be 6m/s or more, preferably 8m/s or more. When the flow rate is less than 6m/s, the force of the cooling water penetrating the stagnant water film becomes extremely weak. When the ratio is 8m/s or more, a larger cooling capacity can be secured, and therefore, it is preferable. The distance from the lower end of the cooling water spray nozzle 13 for cooling the upper surface to the surface of the thick steel plate 10 may be 30 to 120 mm. When the thickness is less than 30mm, the frequency of the thick steel plate 10 striking the diaphragm 15 becomes extremely high, and maintenance of the apparatus becomes difficult. When the thickness is larger than 120mm, the force of the cooling water penetrating the stagnant water film becomes extremely weak.

For cooling the upper surface of the thick steel plate, water stop rollers (draft rollers)20 may be provided in front and rear of the upper water collecting base 11 so that cooling water does not diffuse in the longitudinal direction of the thick steel plate. This makes the length of the cooling zone constant, and facilitates temperature control. Here, since the flow of the cooling water in the steel plate conveying direction is stopped by the water stop rollers 20, the cooling drain flows outward in the steel plate width direction. However, in the vicinity of the water-stop roller 20, the cooling water is liable to stagnate.

Therefore, as shown in fig. 8, it is preferable that, among the rows of the circular tube nozzles 13 arranged in the width direction of the thick steel plate, the cooling water jet nozzles in the most upstream row in the thick steel plate conveying direction are inclined by 15 to 60 degrees in the upstream direction of the thick steel plate conveying direction, and the cooling water jet nozzles in the most downstream row in the thick steel plate conveying direction are inclined by 15 to 60 degrees in the downstream direction of the thick steel plate conveying direction. This is preferable because cooling water can be supplied to a position close to the water-stop roll 20, and the cooling water does not remain near the water-stop roll 20, thereby improving cooling efficiency.

The distance between the lower surface of the upper header 11 and the upper surface of the spacer 15 is set so that the flow path cross-sectional area in the width direction of the thick steel plate in the space surrounded by the lower surface of the header and the upper surface of the spacer is 1.5 times or more the total cross-sectional area of the inside of the cooling water spray nozzle, and is, for example, about 100mm or more. When the flow path cross-sectional area in the width direction of the thick steel plate is not 1.5 times or more the total cross-sectional area inside the cooling water injection nozzle, the cooling drain water discharged from the drain port 17 provided in the partition plate to the upper surface of the partition plate 15 cannot be smoothly discharged in the width direction of the thick steel plate.

For the accelerated cooling device of the present inventionThe range of the water density which can exert the most effect is 1.5m³/(m²Min) or more, when the water density is less than this, the stagnant water film does not become so thick, and even when a known technique of cooling a thick steel plate by freely dropping rod-like cooling water is applied, the temperature unevenness in the width direction may not become so large, and further, , the water density is higher than 4.0m³/(m²Min), the use of the technique of the present invention is also effective. However, since practical use has a problem such as increase in equipment cost, 1.5 to 4.0m is required³/(m²Min) is the most practical water density.

The cooling technique according to the present invention is particularly effective when the water stop rollers are disposed in front of and behind the cooling water collection base. However, it can be applied even when the water-stopping roller is not provided. For example, the present invention is also applicable to a cooling device in which a water collection base is long in the longitudinal direction (about 2 to 4 m), and water for purging is sprayed from the front and rear of the water collection base, thereby preventing water leakage to a non-water-cooled area.

In the present invention, the cooling device on the lower surface side of the thick steel plate is not particularly limited. In the embodiment shown in fig. 7 and 8, an example of the lower cooling header 12 having the circular tube nozzle 14 similar to the cooling device on the upper surface side is shown. Since the sprayed cooling water naturally drops after impinging on the steel plate, the cooling of the lower surface side of the steel plate may be performed without the partition plate 15 for discharging the cooling water in the width direction of the steel plate, as in the case of the upper surface side cooling. In addition, known techniques such as supplying film-like cooling water, spraying cooling water in a spray form, and the like may be used.

As described above, in the apparatus for manufacturing a thick steel plate according to the present invention, as the descaling device 6 and the descaling device 7, the spray nozzles for descaling water are arranged in 2 rows or more, and the energy density E sprayed from the spray nozzles in 2 rows or more onto the surface of the thick steel plate 10 is set to 0.08J/mm in total²As described above, the oxide scale generated in the thick steel plate 10 can be made uniform, and the accelerated cooling device 5 can realize thisAnd (4) uniformly cooling. As a result, the thick steel plate 10 having an excellent thick steel plate shape can be manufactured.

Further, the shape of the thick steel plate 10 is straightened by the shape straightening device 4, and thereby the spray nozzles of the descaling devices 6 and 7 can be brought close to the surface of the thick steel plate 10.

Further, when the throw-distance H (the distance between the spray nozzles of the descaling devices 6 and 7 and the surface of the thick steel plate 10) is 40mm or more and 200mm or less, the descaling performance is improved. Further, since the injection pressure, the injection flow rate, and the like for obtaining the predetermined energy density E may be small, the pumping capacity of the descaling device 6 and the descaling device 7 can be reduced.

Further, the distance L from the downstream side descaling device 7 to the accelerated cooling device 5 among the descaling device 6 and the descaling device 7 satisfies L.ltoreq.Vx5 x 10^-9Xexp (25000/T), the cooling of the thick steel plate 10 by the accelerated cooling equipment 5 can be stabilized.

As shown in fig. 7, in the accelerated cooling device 5 of the present invention, the cooling water supplied from the upper cooling water spray nozzle 13 through the water feed port 16 cools the upper surface of the thick steel plate 10 to be high-temperature drain water, and the drain port 17 not penetrating the upper cooling water spray nozzle 13 is used as a drain flow path to flow from above the partition plate 15 to the width direction of the thick steel plate 10. Since the cooled drain water is quickly removed from the thick steel plate 10, the cooling water flowing from the upper cooling water injection nozzle 13 through the water feed port 16 sequentially comes into contact with the thick steel plate 10, and thereby, a sufficient and uniform cooling capacity in the width direction can be obtained.

It is noted that, according to the results of the studies by the inventors of the present invention, it is found that the widthwise temperature unevenness of the steel plate subjected to the accelerated cooling without performing the descaling as described in the present invention is about 40 ℃, and that shows that the widthwise temperature unevenness of the steel plate subjected to the cooling by the accelerated cooling device 5 is reduced to about 10 ℃ after the descaling by the descaling device 6 and the descaling device 7 of the present invention, and that the widthwise temperature unevenness of the steel plate subjected to the accelerated cooling using the accelerated cooling device 5 shown in fig. 7 is reduced to about 4 ℃ after the descaling by the descaling device 6 and the descaling device 7.

Further, according to the present invention, since the strain generated during rolling is straightened by the shape straightening device 4, and the scale of the thick steel plate 10 is removed by the scale removing device 6 and the scale removing device 7, and the controllability of cooling is stabilized, the flat property of the thick steel plate 10 itself straightened by the shape straightening device provided on the line or under the line downstream of the thick steel plate manufacturing facility is high, and the temperature of the thick steel plate 10 is also uniform. Thus, the straightening force of the shape straightening device disposed downstream does not need to be substantially increased. Further, the distance between the accelerated cooling equipment 5 and the shape straightening equipment provided downstream may be set longer than the maximum length of the thick steel plate 10 produced in the pass line. Accordingly, since reverse straightening is often performed by the shape straightening device provided downstream, the effect of preventing the reversed thick steel plate 10 from jumping up on the conveying rolls and striking problems such as the accelerated cooling device 5, and the effect of making minute temperature deviations generated in cooling by the accelerated cooling device 5 uniform and avoiding the occurrence of warping due to the temperature deviations after straightening can be expected.

Example 1

Here, the conditions for stabilizing the cooling are calculated from the above expressions (3), (4) and (5), and the time t from the end of removing the scale from the thick steel plate by the descaling device 7 to the start of cooling the thick steel plate by the accelerated cooling device 5 is preferably 42s or less, more preferably 19s or less, and further preferably 5s or less in the steps, as calculated from the above expressions (3), (4) and (5).

The descaling device 6 and the descaling device 7 are provided as follows: the injection pressure of the nozzle was 17.7MPa, and the injection pressure was 1 nozzle per nozzleThe flow rate was 45L/min (═ 7.5X 10)^-4m³(s), a spray distance (distance between the spray nozzles of the descaling devices 6 and 7 and the surface of the steel plate) of 130mm, a nozzle spray angle of 66 ° and an attack angle of 15 °, and nozzles arranged in the width direction such that spray areas of adjacent nozzles overlap to a certain extent of were arranged in 2 rows in the longitudinal direction, a shower spray thickness of 3mm, and a shower spray width of 175 mm.

The accelerated cooling equipment 5 was a device provided with a flow path through which cooling water supplied to the upper surface of the thick steel plate can flow upward of the separator as shown in FIG. 7, and through which water can be drained from the lateral side of the thick steel plate in the width direction as shown in FIG. 10, steps were performed.A hole having a diameter of 12mm was formed in the separator in a grid-like manner, an upper cooling water jet nozzle was inserted into a water supply port arranged in a staggered grid pattern as shown in FIG. 9, and the remaining hole was used as a water drain port.A distance between the lower surface of the upper water collecting base and the upper surface of the separator was 100 mm.

The upper cooling water spray nozzle of the accelerated cooling device 5 was set to have an inner diameter of 5mm, an outer diameter of 9mm, and a length of 170mm, and its upper end was protruded into the water collection base. The jet speed of the rod-like cooling water was set to 8.9 m/s. The nozzle pitch in the width direction of the thick steel plate was set to 50mm, and 10 rows of nozzles were arranged in the longitudinal direction in a region of a distance of 1m between the roller tables. The water density of the upper surface is 2.1m³/(m²Min). The lower end of the nozzle for cooling the upper surface was disposed at the middle position between the upper and lower surfaces of the partition plate having a thickness of 25mm, and the distance to the surface of the thick steel plate was set to 80 mm.

As shown in fig. 7, the lower surface cooling device was the same as the upper surface cooling device except that the partition plate was not provided, and the spray velocity and water density of the rod-like cooling water were 1.5 times as high as the upper surface.

Then, as shown in table 1, the distance L from the descaling device 7 to the accelerated cooling device 5, the conveying speed V of the thick steel plate, and the time t from the descaling device 7 to the accelerated cooling device 5 were varied in various ways. In table 1, T is a thick steel plate temperature (K) before cooling.

The shape of the steel plate was evaluated by the re-straightening ratio (%). Specifically, if the warp of the entire length of the thick steel plate and/or the warp of the entire width of the thick steel plate is within a reference value determined by a product standard corresponding to the thick steel plate, it is determined as pass, and if the warp is greater than the reference value, it is determined as a re-straightening implement, and the re-straightening rate is calculated as (number of re-straightening implements)/(total number of target articles) × 100.

[ Table 1]

In the invention examples 1 to 5 shown in Table 1, the energy densities were all 0.08J/mm²As described above, the re-straightening rate due to the shape defect was low, and good results were obtained. This is presumably because, when cooling is performed by the accelerated cooling equipment 5, the steel sheet is uniformly cooled with almost no variation in surface temperature at the widthwise position, and as a result, the steel sheet has excellent mechanical properties and flatness (presumably due to the temperature distribution of the thick steel sheet) as compared with the conventional art, and as a result, the re-straightening rate due to the shape defect is lowered. In addition, in all of inventive examples 1 to 5, the scale was removed, and the surface properties were also good. In the evaluation of the surface properties, the presence or absence of scale was judged by image processing (using the difference in color tone between the scale remaining portion and the peeled portion) using an image of the surface of the thick steel plate cooled to room temperature, and the evaluation was performed.

In particular, in the present invention examples 1 to 4 in which the distance from the descaling device 7 in the most downstream row to the accelerated cooling device 5 in the conveyance direction was 5m, the time t from the end of scale removal of the thick steel plate by the descaling device 7 to the start of cooling of the thick steel plate by the accelerated cooling device 5 was a condition under which cooling by the accelerated cooling device 5 was more stable, that is, 19s or less, regardless of the conveyance speed V of the thick steel plate. Therefore, the re-straightening ratio is good and is 5% or less. Further, in the case of invention example 5, the yield of the re-straightening was 12%, but it was inferior to those of invention examples 1 to 4. This is because the time from the end of scale removal to the start of cooling by the accelerated cooling equipment 5 is long, 46 seconds, and therefore the scale becomes thick and cooling becomes unstable.

On the other hand, , in comparative example 1 (in which the scale removal by the descaling devices 6 and 7 was not performed and the cooling by the accelerated cooling device 5 was performed), the scale formed on the surface of the thick steel plate was not made uniform, but the cooling by the accelerated cooling device 5 was performed, and therefore, the re-straightening ratio became 40% due to the deterioration of flatness (presumably due to the temperature distribution of the thick steel plate), and the mechanical properties also varied.

In comparative example 2 (the conditions of the descaling devices 6 and 7 were set to 10MPa water pressure and the jet flow rate per 1 nozzle was 39L/min (6.5 × 10)^-4m³(s), the spray distance is 130mm, the spray angle of the nozzle is 66 degrees, the attack angle of the nozzle is 15 degrees, and the energy density is 0.06J/mm²) Since the energy density of the descaling water is not sufficiently increased, the scale is partially peeled off, and the temperature distribution in the width direction of the thick steel sheet is deteriorated. Therefore, the re-straightening ratio becomes 70%, and the mechanical properties also vary.

Comparative example 3 (number of descaling passes was 1, injection pressure of the nozzle was 17.7MPa, and injection flow rate per 1 nozzle was 45L/min (═ 7.5 × 10)^-4m³(s), the jet distance is 130mm, the jet angle of the nozzle is 66 degrees, the attack angle is 15 degrees, and the energy density is 0.09J/mm²) Since the number of descaling was 1 and the effect of thermal stress generated during descaling was only 1, the scale was partially peeled off, and the temperature distribution in the width direction of the steel plate was deteriorated. Therefore, the re-straightening ratio becomes 72%, and the mechanical properties are also biasedAnd (4) poor.

Comparative example 4 (the number of descaling was 3, the injection pressure of the nozzle was 10MPa, and the injection flow rate per 1 nozzle was 34L/min (═ 5.6 × 10)^-4m³(s), the spray distance is 130mm, the spray angle of the nozzle is 66 degrees, the attack angle is 15 degrees, and the energy density is 0.06J/mm in the total of 3 descaling times²) Since the energy density carried by the descaling water is not sufficiently increased, the scale is partially peeled off, and the temperature distribution in the width direction of the thick steel sheet is deteriorated. Therefore, the realignment ratio becomes 69%, and the mechanical properties are also varied.

Description of the reference numerals

1 heating furnace

2 descaling device

3 rolling mill

4 shape straightening device

5 accelerated cooling device

6 descaling device

6-1 descaling water collecting head

6-2 spray nozzle

7 descaling device

7-1 descaling water collecting head

7-2 spray nozzle

10-thick steel plate

11 upper water collecting seat

12 lower water collecting seat

13 Upper cooling water spray nozzle (circular tube nozzle)

14 lower cooling water spray nozzle (circular tube nozzle)

15 partition board

16 water supply mouth

17 drainage outlet

18 jet cooling water

19 discharging water

20 water stop roller

21 water stop roller

22 spray pattern

Claims

1, kinds of thick steel plate manufacturing facilities, characterized in that the hot rolling mill and the shape straightening are arranged in order from the upstream side in the conveying directionThe spray nozzles of the descaling device are arranged in 2 rows relative to the length direction of the thick steel plate, and the energy density E of the descaling water sprayed from the 2 rows of spray nozzles to the surface of the thick steel plate is set to be 0.08J/mm in total²As described above, the energy density of the descaling water sprayed from the spray nozzles in the row immediately before the final row was set to 0.01J/mm²As described above, the energy density of the descaling water sprayed from the spray nozzles of the final row is made 0.04J/mm higher than that of the row immediately before the final row²The above.

2, Thick steel plate manufacturing facility, characterized in that the hot rolling mill, the shape straightening device, the descaling device and the accelerated cooling device are arranged in this order from the upstream side in the conveying direction, the spray nozzles of the descaling device are arranged in more than 2 rows with respect to the longitudinal direction of the thick steel plate, and the energy density E of the descaling water sprayed from the spray nozzles in more than 2 rows onto the surface of the thick steel plate is set to be 0.08J/mm in total²As described above, the energy density of the descaling water sprayed from the spray nozzles in the row immediately before the final row was set to 0.01J/mm²As described above, the energy density of the descaling water sprayed from the spray nozzles of the final row is made 0.04J/mm higher than that of the row immediately before the final row²The above.

3. The thick steel plate manufacturing facility according to claim 1 or 2, wherein a transport speed from the descaling device to the accelerated cooling device is set to V [ m/s ]]The temperature of the thick steel plate before cooling is T [ K ]]A distance L [ m ] from the descaling device to the accelerated cooling device]Satisfies the following formula: l is less than or equal to V multiplied by 5 multiplied by 10^-9×exp(25000/T)。

4. The apparatus for manufacturing a thick steel plate according to claim 3, wherein a distance L from the descaling device to the accelerated cooling device is 12m or less.

5. The thick steel plate manufacturing apparatus according to claim 1 or 2, wherein a distance H from the spray nozzles of the descaling device to the surface of the thick steel plate is set to 40mm or more and 200mm or less.

6. The thick steel plate manufacturing apparatus according to claim 3, wherein a distance H from the spray nozzles of the descaling device to the surface of the thick steel plate is set to 40mm or more and 200mm or less.

7. The thick steel plate manufacturing apparatus according to claim 4, wherein a distance H from the spray nozzles of the descaling device to the surface of the thick steel plate is set to 40mm or more and 200mm or less.

8. The thick steel plate manufacturing apparatus as claimed in claim 1 or 2, wherein the accelerated cooling device has: the cooling water supply device comprises a water collecting seat for supplying cooling water to the upper surface of the thick steel plate, a cooling water spray nozzle hanging from the water collecting seat and spraying rod-shaped cooling water, and a partition plate arranged between the thick steel plate and the water collecting seat, wherein the partition plate is provided with a plurality of water supply ports and a plurality of water discharge ports, the water supply ports are inserted into the lower end parts of the cooling water spray nozzles, and the water discharge ports discharge the cooling water supplied to the upper surface of the thick steel plate onto the partition plate.

9. The thick steel plate manufacturing apparatus as claimed in claim 3, wherein the accelerated cooling device has: the cooling water supply device comprises a water collecting seat for supplying cooling water to the upper surface of the thick steel plate, a cooling water spray nozzle hanging from the water collecting seat and spraying rod-shaped cooling water, and a partition plate arranged between the thick steel plate and the water collecting seat, wherein the partition plate is provided with a plurality of water supply ports and a plurality of water discharge ports, the water supply ports are inserted into the lower end parts of the cooling water spray nozzles, and the water discharge ports discharge the cooling water supplied to the upper surface of the thick steel plate onto the partition plate.

10. The thick steel plate manufacturing apparatus of claim 4, wherein the accelerated cooling device comprises: the cooling water supply device comprises a water collecting seat for supplying cooling water to the upper surface of the thick steel plate, a cooling water spray nozzle hanging from the water collecting seat and spraying rod-shaped cooling water, and a partition plate arranged between the thick steel plate and the water collecting seat, wherein the partition plate is provided with a plurality of water supply ports and a plurality of water discharge ports, the water supply ports are inserted into the lower end parts of the cooling water spray nozzles, and the water discharge ports discharge the cooling water supplied to the upper surface of the thick steel plate onto the partition plate.

11. The thick steel plate manufacturing apparatus of claim 5, wherein the accelerated cooling device comprises: the cooling water supply device comprises a water collecting seat for supplying cooling water to the upper surface of the thick steel plate, a cooling water spray nozzle hanging from the water collecting seat and spraying rod-shaped cooling water, and a partition plate arranged between the thick steel plate and the water collecting seat, wherein the partition plate is provided with a plurality of water supply ports and a plurality of water discharge ports, the water supply ports are inserted into the lower end parts of the cooling water spray nozzles, and the water discharge ports discharge the cooling water supplied to the upper surface of the thick steel plate onto the partition plate.

12. The thick steel plate manufacturing apparatus of claim 6, wherein the accelerated cooling device comprises: the cooling water supply device comprises a water collecting seat for supplying cooling water to the upper surface of the thick steel plate, a cooling water spray nozzle hanging from the water collecting seat and spraying rod-shaped cooling water, and a partition plate arranged between the thick steel plate and the water collecting seat, wherein the partition plate is provided with a plurality of water supply ports and a plurality of water discharge ports, the water supply ports are inserted into the lower end parts of the cooling water spray nozzles, and the water discharge ports discharge the cooling water supplied to the upper surface of the thick steel plate onto the partition plate.

13. The thick steel plate manufacturing apparatus of claim 7, wherein the accelerated cooling device comprises: the cooling water supply device comprises a water collecting seat for supplying cooling water to the upper surface of the thick steel plate, a cooling water spray nozzle hanging from the water collecting seat and spraying rod-shaped cooling water, and a partition plate arranged between the thick steel plate and the water collecting seat, wherein the partition plate is provided with a plurality of water supply ports and a plurality of water discharge ports, the water supply ports are inserted into the lower end parts of the cooling water spray nozzles, and the water discharge ports discharge the cooling water supplied to the upper surface of the thick steel plate onto the partition plate.

14, A method for manufacturing a thick steel plate, characterized in that, in a method for manufacturing a thick steel plate by sequentially performing a hot rolling process, a hot straightening process and an accelerated cooling process, a descaling process is provided between the hot straightening process and the accelerated cooling process, and the total energy density E of the descaling water in the descaling process is 0.08J/mm²The energy density of the above descaling water sprayed from the spray nozzles of the row immediately before the final row was 0.01J/mm²The energy density of the descaling water sprayed from the spray nozzles of the final row is 0.04J/mm greater than that of the row immediately before the final row²The surface of the thick steel plate was descaled 2 times in the above manner.

15, A method for manufacturing a thick steel plate, characterized in that, in a method for manufacturing a thick steel plate by sequentially performing a hot rolling process, a hot straightening process and an accelerated cooling process, a descaling process is provided between the hot straightening process and the accelerated cooling process, and the total energy density E of descaling water in the descaling process is 0.08J/mm²The energy density of the above descaling water sprayed from the spray nozzles of the row immediately before the final row was 0.01J/mm²The energy density of the descaling water sprayed from the spray nozzles of the final row is 0.04J/mm greater than that of the row immediately before the final row²The surface of the thick steel plate was descaled more than 2 times in the above manner.

16. The method of manufacturing a thick steel plate according to claim 14 or 15, wherein a time t [ s ] from completion of the descaling process to start of the accelerated cooling process]Satisfies the following formula: t is less than or equal to 5 multiplied by 10^-9X exp (25000/T), wherein T: temperature (K) of the steel plate before cooling.