TW201501829A - Thick steel plate manufacturing device and manufacturing method - Google Patents

Abstract

The purpose of the present invention is to provide a thick steel plate manufacturing device and manufacturing method in which, by leveling, in a descaling step, scale occurring on the surface of the thick steel plate, cooling is evenly performed in a cooling step, achieving excellent steel plate shape. In this thick steel plate manufacturing device, a hot-rolling device, a shape correction device, a descaling device and an accelerated cooling device are arranged in that order from the upstream side of the conveyance direction, wherein the energy density E of the cooling water sprayed at the surface of the thick steel plate by the descaling device is 0.10J/mm2 or greater.

Description

Thick steel plate manufacturing equipment and manufacturing method

The present invention relates to a manufacturing apparatus and a manufacturing method for a thick steel plate for hot rolling, shape correction and controlled cooling of a thick steel plate.

In recent years, as a manufacturing process for thick steel plates, the application of controlled cooling has been expanded. However, in general, the shape, surface properties, and the like of the hot-thick steel plate are not necessarily uniform. Therefore, temperature unevenness is likely to occur in the thick steel sheet during the cooling process, and the thick steel sheet after cooling is deformed, residual stress, material unevenness, etc., thereby causing poor quality or operational trouble.

Therefore, Patent Document 1 discloses a method of performing rust removal, followed by thermal correction, at least one of the final pass of the finish rolling and the final pass of the finish rolling. Then, the rust is removed and forced cooling is performed. Further, Patent Document 2 discloses a method of performing rust removal after finish rolling and heat correction, followed by controlled cooling. Further, Patent Document 3 discloses a method of controlling rust removal on the one hand of controlling the impact pressure of the cooling water on the one hand immediately before the controlled cooling.

[Previous Technical Literature] [Patent Literature]

Patent Document 1: Japanese Patent Laid-Open No. Hei 9-57327

Patent Document 2: Japanese Patent No. 3796133

Patent Document 3: Japanese Patent Laid-Open Publication No. 2010-247228

However, when the thick steel plate is actually produced by the methods of Patent Documents 1 and 2, there is a problem in that the scale is not completely peeled off during the rust removal, but the scale is uneven due to the rust removal, and cannot be performed when the cooling is controlled. Uniform cooling. Further, in the method of Patent Document 3, in order to prevent unevenness of the scale, a high impact pressure is required. Therefore, if the impact pressure is low, unevenness of the scale occurs, and as a result, there is a problem that uniform cooling cannot be performed when the cooling is controlled.

In particular, in recent years, the level of material uniformity required for thick steel plates has become severe, and the unevenness of the cooling rate at the time of controlled cooling due to the unevenness of the scale as described above cannot be ignored, especially for the width direction of the thick steel plate. Adverse effects due to material uniformity.

Accordingly, the present invention has been made in view of the unsolved problems of the above-described conventional examples, and an object thereof is to provide a manufacturing apparatus and a manufacturing method for a thick steel plate which are realized by a thickening step in a rust removing step. The scale produced on the surface of the steel sheet is uniformized, and uniform cooling is performed in the cooling step, so that it is excellent in the shape of the thick steel sheet.

The inventors of the present invention conducted intensive studies on the force of peeling off the scale by the cooling water, and found that the energy density of the cooling water sprayed from the descaling device to the thick steel plate when the rust is removed after the hot shape correction is performed. When it is 0.10 J/mm ² or more, the thickness of the scale produced on the surface after the product is uniform. As a result, it has been found that when the cooling device is accelerated, the surface temperature of the position of the thick steel plate in the width direction is almost non-existent and can be uniformly cooled, thereby forming a thick steel plate excellent in the shape of a thick steel plate.

The gist of the present invention is as follows.

[1] A manufacturing apparatus for a thick steel plate, characterized in that a hot rolling mill, a shape correcting device, a rust removing device, and an accelerated cooling device are disposed on the upstream side in the self-transporting direction, and the rust removing device is oriented toward the thick steel plate The energy density E of the cooling water sprayed on the surface is set to 0.10 J/mm ² or more.

[2] The apparatus for manufacturing a thick steel plate according to [1], wherein the conveying speed from the descaling device to the accelerated cooling device is V [m/s], and the temperature of the thick steel plate before cooling is set to In T[K], the distance L[m] from the above-described descaling device to the above-described accelerated cooling device satisfies the formula of L≦V×5×10 ^-9 ×exp(25000/T).

[3] The apparatus for manufacturing a thick steel plate according to [2], wherein each of the devices is disposed such that a distance L from the descaling device to the accelerated cooling device is 12 m or less.

[4] The apparatus for manufacturing a thick steel plate according to any one of [1] to [3] wherein the injection distance H from the injection nozzle of the descaling device to the surface of the thick steel plate is set to 40 mm or more and 200 mm or less. .

[5] The apparatus for manufacturing a thick steel plate according to any one of [1] to [4] wherein the accelerating cooling device is provided with a header for supplying cooling water to an upper surface of the thick steel plate, and is performed from the header a cooling water spray nozzle that sprays a rod-shaped cooling water that is suspended, and a partition wall that is disposed between the thick steel plate and the header, and a plurality of water supply ports and water discharge ports are provided in the partition wall, and the water supply ports The lower end portion of the cooling water spray nozzle is inserted into the mouthpiece, and the drain holes discharge the cooling water supplied to the upper surface of the thick steel plate toward the partition wall.

[6] A method for producing a thick steel plate, which is a method for manufacturing a thick steel plate in accordance with a sequence of a hot rolling step, a heat correcting step, and an accelerated cooling step, characterized in that: between the heat correcting step and the cooling step, having a thickness The surface of the steel sheet is subjected to a rust removing step of cooling water having an ejection energy density E of 0.10 J/mm ² or more.

[7] The method for producing a thick steel plate according to [6], wherein the time t[s] from the end of the descaling step to the start of the accelerated cooling step satisfies t≦5×10 ^-9 ×exp(25000/T Where T is the thick steel plate temperature (K) before cooling.

According to the present invention, by uniformizing the scale generated on the surface of the thick steel sheet in the rust removing step, uniform cooling can be performed in the accelerated cooling step, whereby a thick steel sheet excellent in the shape of the thick steel sheet can be produced.

1‧‧‧thick steel plate

2‧‧‧heating furnace

3‧‧‧ rolling press

4‧‧‧Descaling device

5‧‧‧1st shape correcting device

6‧‧‧Accelerated cooling device

7‧‧‧2nd shape correcting device

11‧‧‧Upper tube

12‧‧‧ Lower header

13‧‧‧Upper cooling water jet nozzle (round nozzle)

14‧‧‧Under cooling water jet nozzle (round nozzle)

15‧‧‧ partition wall

16‧‧‧Water supply

17‧‧‧Drainage

18‧‧‧Spray cooling water

19‧‧‧ discharged water

20‧‧‧Dewatering roller

21‧‧‧Dewatering roller

Fig. 1 is a schematic view showing an example of a thick plate rolling line.

Fig. 2 is a graph showing the relationship between the energy density of the sprayed cooling water in the descaling apparatus and the thickness of the scale produced on the surface of the product of the thick steel plate.

Fig. 3 is a view showing the relationship between the injection distance of the injection nozzle and the fluid velocity in the rust removing apparatus.

Fig. 4 is a side view of a cooling device according to an embodiment of the present invention.

Figure 5 is a side elevational view of another cooling device in accordance with an embodiment of the present invention.

Fig. 6 is a view for explaining an arrangement example of a nozzle of a partition wall according to an embodiment of the present invention.

Fig. 7 is a view for explaining the flow of the cooling water on the partition wall.

Fig. 8 is a view for explaining another flow of the cooling drain on the partition wall.

Fig. 9 is a view for explaining the temperature distribution in the width direction of a thick steel plate according to a conventional example.

Fig. 10 is a view for explaining the flow of cooling water in the accelerated cooling device.

Figure 11 is a non-interference between the cooling cooling device and the cooling water on the partition wall. Description of the map.

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

Fig. 1 is a schematic view showing an example of a thick plate rolling line for carrying out the present invention. The slab extracted from the heating furnace 2 is subjected to rough rolling and finish rolling by the rolling mill 3, and is rolled into a thick steel plate 1 having a predetermined thickness. Then, the scale generated on the surface of the thick steel plate 1 is removed by the rust removing device 4, and then the thick steel plate 1 is conveyed to the accelerated cooling device 6 on the line. Here, the case where the shape of the thick steel plate is adjusted by the first shape correcting device 5 and the accelerated cooling is performed is preferable for the shape of the thick steel plate after cooling. In the accelerated cooling device 6, the thick steel plate is cooled to a predetermined temperature by the cooling water sprayed from the upper surface cooling device and the lower surface cooling device. Thereafter, the shape of the thick steel plate is corrected by the second shape correcting device 7 as needed.

The rust removing device 4 is a device for removing the scale generated on the surface of the thick steel plate 1. In the rust removing device 4, the surface of the thick steel plate 1 after the shape of the strain generated on the thick steel plate 1 is corrected by the first shape correcting device 5 after the plurality of spray nozzles are rolled, and is sprayed and cooled from the nozzles. water.

The present inventors have found that the peeling of the scale is not sufficiently performed due to the rust removing condition, and conversely contributes to the unevenness of the scale. Further, the conditions for sufficiently performing the peeling of the scale were intensively studied. As a result, it was found that when the rust removal was performed after the shape correction, as shown in FIG. 2, the spray nozzle of the self-derusting device 4 was used. The energy density E of the cooling water sprayed on the surface of the thick steel plate 1 is set to 0.10 J/mm ² or more, and the thickness of the scale formed thereafter becomes uniform and 5 μm or less. The reason for this is considered to be that the scale is temporarily and completely peeled off by the rust removal, and thereafter, the scale is thin and uniformly regenerated.

In the present invention, the rust is generated by removing the rust from the surface of the thick steel plate 1 by setting the energy density E of the cooling water to 0.10 J/mm ² or more. Thereafter, accelerated cooling of the thick steel plate 1 is performed by the accelerated cooling device 6. In the present invention, since the thickness of the scale of the thick steel plate is thin and uniform by rust removal, when the cooling device is accelerated, the surface temperature deviation of the position of the thick steel plate in the width direction is almost non-existent and can be uniformly performed. It is cooled to become a thick steel plate excellent in the shape of a thick steel plate.

The reason is as follows. In the conventional rolling equipment, if the scale is removed in the rust removing apparatus after the shape correction, the scale is partially peeled off. As a result, the scale is not uniformly peeled off, and thus a variation in the thickness distribution 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. In other words, when the thick steel sheet having the variation in the thickness distribution of the scale generated in the conventional rolling equipment is accelerated and cooled, the variation in the surface temperature in the width direction position is large, and the cooling cannot be performed uniformly. As a result, it affects the shape of the thick steel plate.

Therefore, the rust removal device 4 performs derusting by setting the energy density E of the cooling water to 0.10 J/mm ² or more, and the deviation of the thickness distribution of the scale disappears. Therefore, the thick steel plate 1 is made by the accelerated cooling device 6. At the time of cooling, the deviation of the surface temperature in the position in the width direction hardly exists and can be uniformly cooled. As a result, the thick steel plate 1 excellent in the shape of a thick steel plate can be manufactured. Further, in the case of the present invention, even when the impact pressure is low, the same rust removal as in the case of using a high impact pressure can be achieved by adjusting the transport speed.

Here, the energy density E (J/mm ² ) of the cooling water sprayed to the thick steel plate refers to an index of the ability to remove the scale by rust removal, and is defined as in the following formula (1).

E=Q/(d×W)×ρv ² /2×t...(1)

Where Q: jet flow rate of rust-removing water [m ³ /s], d: spray spray thickness [mm] of flat nozzle, W: spray jet width [mm] of flat nozzle, fluid density ρ [kg/m ³ ] The fluid velocity v [m / s], impact time t [s] (t = d / 1000 / V, transport speed V [m / s]) when the thick steel plate is impacted.

However, since the measurement of the fluid velocity v at the time of impact of the thick steel plate is not necessarily easy, if the energy density E defined by the formula (1) is to be strictly obtained, great labor is required.

Therefore, the inventors of the present invention have further studied and found that the water density x the injection pressure x the impact time can be used as a simple definition of the energy density E (J/mm ² ) of the cooling water sprayed onto the thick steel plate. Here, the water amount density (m ³ /mm ² .min) is a value calculated from "injection flow rate of cooling water / impact area of cooling water". The injection pressure (N/m ² (=MPa)) is defined by the discharge pressure of the cooling water. The impact time (s) is a value calculated from "the impact thickness of the cooling water and the conveying speed of the thick steel plate". The relationship between the energy density of the cooling water calculated from the simple definition and the thickness of the scale generated on the surface of the product is also the same as that of Fig. 2, and the larger the energy density of the cooling water, the smaller the thickness of the scale. In other words, when the energy density E is less than 0.10 J/mm ² , there is a case where the variation in the thickness of the scale of the thick steel plate is large, and the cooling cannot be performed uniformly, and the thick steel plate excellent in the shape of the thick steel plate cannot be produced. On the other hand, if the energy density E is 0.10 J/mm ² or more, such an obstacle can be avoided. Therefore, in the present invention, the energy density E of the cooling water is preferably set to 0.10 J/mm ² or more, more preferably 0.15 J/mm ² or more.

Then, the inventors of the present invention investigated the fluid velocity v of the cooling water sprayed from the injection nozzle of the descaling device 4. As a result, the relationship between the fluid velocity v and the ejection distance was found as shown in FIG. The fluid velocity as the vertical axis is obtained by solving the equation of motion considering buoyancy and air resistance. Cooling before the cooling water reaches the thick steel plate The fluid velocity v of water is slower than when it is injected. Therefore, the smaller the ejection distance, the larger the fluid velocity v when the thick steel plate is impacted, and the larger the energy density can be obtained. According to Fig. 3, in particular, if the ejection distance H exceeds 200 mm, the attenuation becomes large, and therefore, the ejection distance H is preferably set to 200 mm or less.

Further, the shorter the injection distance, the smaller the injection pressure, the injection flow rate, and the like for obtaining a predetermined energy density, so that the pumping capacity of the descaling device 4 can be reduced. In the embodiment of the present invention as shown in Fig. 1, the thick steel plate 1 whose shape has been corrected by the first shape correcting device 5 is moved into the rust removing device 4, so that the spray nozzle of the rust removing device 4 can be made thicker. The surface of the steel plate 1. However, in consideration of the contact of the spray nozzle with the thick steel plate 1, the lower limit of the spray distance is preferably 40 mm or more. According to the above description, in the present invention, the ejection distance H is preferably 40 mm or more and 200 mm or less.

Moreover, in the rust removing apparatus 4, the injection pressure of the cooling water is preferably 10 MPa or more, and more preferably 15 MPa or more. Thereby, the energy density of the cooling water can be set to 0.10 J/mm ² or more without setting the conveying speed too small, which is effective. The upper limit of the injection pressure is not particularly limited. However, if the injection pressure is increased, the energy consumed by the pump for supplying high-pressure water is large, and therefore, the injection pressure is preferably 50 MPa or less.

Further, regarding the scale of the surface of the thick steel plate 1 which affects the stability of the thick steel plate 1 by the accelerated cooling device 6, the growth of the scale of the thick steel plate 1 is usually known by diffusion. The control is sorted and expressed by the following formula (2).

ξ ² = a × exp(-Q/RT) × t... (2)

Among them, ξ: thickness of scale, a: constant, Q: activation energy, R: constant, T: temperature of thick steel plate [K] before cooling, t: time.

Therefore, considering the growth of the scale after removing the scale by the rust removing device 4, A simulation experiment of scale growth at various temperatures and times was carried out, and the constant of the above formula (2) was experimentally derived, and further, the thickness of the scale and the cooling stability were studied intensively. As a result, the following findings were obtained: when the thickness of the scale was 15 μm or less, the cooling was stable, and when the thickness of the scale was 10 μm or less, it was more stable, and when the thickness of the scale was 5 μm or less, it was very stable.

When the thickness of the scale is 15 μm or less, the following formula (3) can be derived based on the above formula (2). In other words, when the time t[s] from the completion of the removal of the scale of the thick steel plate 1 by the descaling device 4 to the start of the cooling of the thick steel plate 1 by the accelerated cooling device 6 satisfies the following formula (3), The cooling by the accelerated cooling device 6 is stabilized.

T≦5×10 ^-9 ×exp(25000/T)...(3)

Where T: the thickness of the thick steel plate [K] before cooling.

Moreover, when the thickness of the scale is 10 μm or less, the following formula (4) can be derived based on the above formula (2). In other words, when the time t[s] from the completion of the removal of the scale of the thick steel plate 1 by the descaling device 4 to the start of the cooling of the thick steel plate 1 by the accelerated cooling device 6 satisfies the following formula (4) The cooling by the accelerated cooling device 6 is more stable.

T≦2.2×10 ^-9 ×exp(25000/T)...(4)

Further, when the thickness of the scale is 5 μm or less, the following formula (5) can be derived based on the above formula (2). In other words, when the time t[s] from the completion of the removal of the scale of the thick steel plate 1 by the descaling device 4 to the start of the cooling of the thick steel plate 1 by the accelerated cooling device 6 satisfies the following formula (5), The cooling by the accelerated cooling device 6 is very stable.

T≦5.6×10 ^-10 ×exp(25000/T)...(5)

On the other hand, the distance L from the exit side of the descaling device 4 to the entry side of the accelerating cooling device 6 is the conveying speed V with respect to the thick steel plate 1, and the time t (from the end of the step of the descaling device 4 to the accelerated cooling) The time until the start of the step of the device 6 is set to satisfy the following formula (6).

L≦V×t...(6)

Wherein: L: distance from the descaling device 4 to the accelerated cooling device 6 (m), V: conveying speed (m/s) of the thick steel plate 1, t: time (s)

Further, the following formula (7) can be derived from the above formula (6) and the above formula (3). In the present invention, it is more preferable to satisfy the formula (7).

L≦V×5×10 ^-9 ×exp(25000/T)...(7)

Further, the following formula (8) can be derived from the above formula (6) and the above formula (4). In the present invention, it is further preferred to satisfy the formula (8).

L≦V×2.2×10 ^-9 ×exp(25000/T)...(8)

Further, the following formula (9) can be derived from the above formula (6) and the above formula (5). In the present invention, it is preferred to satisfy the formula (9).

L≦V×5.6×10 ^-10 ×exp(25000/T)...(9)

According to the above formulas (7) to (9), for example, the temperature of the thick steel plate 1 before cooling by the accelerated cooling device 6 is 820 ° C, and the conveying speed of the thick steel plate 1 is set to 0.28 to 2.50 m/ s, the cooling is stabilized when the distance L from the descaling device 4 to the accelerated cooling device 6 is 12 m or more and 107 m or less, and the cooling is more stable when the distance L is 5 m or more and 47 m or less, and the cooling is very stable when the distance L is 1.3 m or more and 12 m or less.

Therefore, when the distance L from the descaling device 4 to the accelerated cooling device 6 is 12 m or less, the cooling is stabilized even when the conveying speed V of the thick steel plate 1 is slow (for example, V = 0.28 m/s). On the other hand, in the case where the conveying speed V of the thick steel plate 1 is fast (for example, V = 2.50 m/s), the cooling is very stable, which is preferable. Further, it is more preferable that the distance L from the descaling device 4 to the accelerated cooling device 6 is 5 m or less.

Further, in general, when the transport speed V of most of the thick steel sheets 1 that must be controlled to be cooled is 0.5 m/s or more, it is more preferable to carry the transport speed V. The condition that the cooling is very stable is that the distance L is 2.5 m or less.

Here, the case where the temperature of the thick steel plate 1 before cooling by the accelerated cooling device 6 is 820 ° C is described. In the same manner as the temperature of the thick steel plate 1 before cooling by the accelerated cooling device 6 is 820 ° C, the distance L from the descaling device 4 to the accelerated cooling device 6 is preferably 12 m or less. It is preferably 5 m or less, more preferably 2.5 m or less, and the cooling can be stabilized. The reason is that when the temperature of the thick steel plate 1 before cooling by the accelerated cooling device 6 is lower than 820 ° C, the values of the right side of the above formula (7), the above formula (8), and the above (9) are respectively When it is larger than T=820°C, the distance (L) from the descaling device 4 to the accelerated cooling device 6 which is appropriately set for the case of T=820°C is inevitably satisfied, and the above (7) and (8) are inevitably satisfied. Formula, the above formula (9). On the other hand, when the temperature of the thick steel plate 1 before cooling by the accelerated cooling device 6 is higher than 820 ° C, the above-mentioned (7) can still be satisfied by appropriately adjusting the conveying speed V of the thick steel plate 1 to be slightly lower. Formula, the above formula (8), and the above formula (9).

Then, as shown in FIG. 4, the accelerated cooling device 6 of the present invention preferably includes a header 11 for supplying cooling water to the upper surface of the thick steel plate 1, and a spray rod-shaped cooling water suspended from the upper header 11. a cooling water spray nozzle 13 and a partition wall 15 disposed between the thick steel plate 1 and the upper header 11, and a partition wall 15 provided with a plurality of water supply ports 16 for interposing the lower end portions of the cooling water spray nozzles 13, and The cooling water supplied to the upper surface of the thick steel plate 1 faces the drain port 17 discharged from the partition wall 15.

Specifically, the upper surface cooling device includes: an upper header 11 that supplies cooling water to the upper surface of the thick steel plate 1; a cooling water injection nozzle 13 that hangs from the upper header 11; and a partition wall 15 that is thick The width direction of the steel sheet is horizontally disposed between the upper header 11 and the thick steel plate 1, and has a plurality of through holes (a water supply port 16 and a water discharge port 17). Further, the cooling water spray nozzle 13 includes a round pipe nozzle 13 that sprays a rod-shaped cooling water, and is inserted at the front end thereof. The through hole (water supply port 16) provided in the partition wall 15 is provided above the lower end portion of the partition wall 15. Further, the cooling water spray nozzle 13 preferably penetrates into the upper header 11 so that the upper end thereof protrudes into the inside of the upper header 11 to prevent the foreign matter at the bottom of the upper header 11 from being sucked.

Here, the rod-shaped cooling water in the present invention refers to cooling water sprayed from a nozzle discharge port having a circular shape (including an elliptical or polygonal shape) in a state of being pressurized to some extent, and is sprayed from a nozzle. The jetting speed of the outlet cooling water is 6 m/s or more, preferably 8 m/s or more, and the cross section of the water jet jetted from the nozzle discharge port is maintained as a substantially circular cooling water having a continuous and straight flow of water. That is, it is different from the free fall flow from the laminar flow nozzle of the circular tube or the spray in the state of the droplet as in the case of a spray.

The reason why the front end of the cooling water spray nozzle 13 is inserted into the through hole and is located above the lower end portion of the partition wall 15 is that even when the thick steel plate which is warped upward at the front end enters the case, The partition wall 15 prevents the cooling water spray nozzle 13 from being damaged. Thereby, the cooling water spray nozzle 13 can be cooled for a long period of time in a good state. Therefore, it is not necessary to perform equipment maintenance or the like, and it is possible to prevent temperature unevenness of the thick steel plate.

Further, since the front end of the round nozzle 13 is inserted into the through hole, as shown in FIG. 11, interference does not occur in the width direction of the discharge water 19 which is a broken line arrow flowing along the upper surface of the partition wall 15. Therefore, the cooling water sprayed from the cooling water spray nozzle 13 can reach the upper surface of the thick steel plate uniformly regardless of the position in the width direction, so that uniform cooling can be performed in the width direction.

As an example of the partition wall 15, as shown in Fig. 6, a plurality of through holes having a diameter of 10 mm are formed in the partition wall 15 in a grid shape of 80 mm in the width direction of the thick steel plate and 80 mm in the transport direction. Further, a cooling water spray nozzle 13 having an outer diameter of 8 mm, an inner diameter of 3 mm, and a length of 140 mm was inserted into the water supply port 16. Cooling water spray nozzle 13 The through holes which are not arranged in the cooling water spray nozzle 13 are arranged in a staggered lattice shape to serve as the drain port 17 for the cooling water. As described above, the plurality of through holes provided in the partition wall 15 of the accelerated cooling device of the present invention include the water supply port 16 and the water discharge port 17 having substantially the same number, and share functions and functions, respectively.

At this time, the total cross-sectional area of the drain port 17 is sufficiently larger than the total cross-sectional area of the inner diameter of the round pipe nozzle 13 of the cooling water spray nozzle 13, and is ensured to be 11 times the total cross-sectional area of the inner diameter of the round pipe nozzle 13. Left and right, as shown in FIG. 4, the cooling water supplied to the upper surface of the thick steel plate is filled between the surface of the thick steel plate and the partition wall 15, and is guided to the upper side of the partition wall 15 through the drain port 17, and is quickly discharged. Fig. 7 is a front view for explaining the flow of the cooling water discharge in the vicinity of the end portion in the width direction of the thick steel plate on the partition wall. The drainage direction of the drain port 17 is an upward direction opposite to the direction in which the cooling water is sprayed, and the cooling water flowing through the partition wall 15 changes toward the outer side in the width direction of the thick steel plate, along the upper header 11 and the partition wall 15. The drainage flow path flows and is discharged.

On the other hand, in the example shown in FIG. 8, the drain port 17 is inclined in the width direction of the thick steel plate, and the drain direction is inclined toward the outer side in the width direction so as to face the outer side in the width direction of the thick steel plate. Thereby, it is preferable that the discharge water 19 on the partition wall 15 flows smoothly in the width direction of the steel sheet to promote drainage.

Here, if the drain port and the water supply port are provided in the same through hole as shown in FIG. 9, the cooling water impinges on the thick steel plate, and it is difficult to flow over the partition wall 15, and the thick steel plate 1 and the partition wall 15 are formed. The flow flows toward the end in the width direction of the thick steel plate. As a result, the flow rate of the cooling water discharge between the thick steel plate 1 and the partition wall 15 is closer to the end portion in the plate width direction. Therefore, the force of the jet cooling water 18 passing through the retained water film to reach the thick steel plate is more It is more obstructed near the end in the width direction of the board.

In the case of a thin plate, since the plate width is at most about 2 m, the above image The ringing is limited. However, especially in the case of a thick plate having a plate width of 3 m or more, the above effects cannot be ignored. Therefore, the cooling of the end portion in the width direction of the thick steel plate becomes weak, and in this case, the temperature distribution in the width direction of the thick steel plate becomes a non-uniform temperature distribution.

On the other hand, the accelerating cooling device of the present invention is provided with the water supply port 16 and the water discharge port 17 separately as shown in Fig. 10, and shares the effect of the water supply and the drainage. Therefore, the cooling water discharge smoothly flows through the water discharge port 17 of the partition wall 15 to Above the partition wall 15. Therefore, the cooled drain is quickly removed from the upper surface of the thick steel plate, so that the subsequently supplied cooling water can easily pass through the retained water film, and sufficient cooling capacity can be obtained. In this case, the temperature distribution in the width direction of the thick steel plate becomes a uniform temperature distribution, so that a uniform temperature distribution can be obtained in the width direction.

Further, as long as the total cross-sectional area of the drain port 17 is 1.5 times or more of the total cross-sectional area of the inner diameter of the round pipe nozzle 13, the discharge of the cooling water can be quickly performed. In this case, for example, it is sufficient that the partition wall 15 has a hole larger than the outer diameter of the nozzle 13 and the number of the drain ports is equal to or exceeds the number of the water supply ports.

If the total cross-sectional area of the drain port 17 is less than 1.5 times the total cross-sectional area of the inner diameter of the round pipe nozzle 13, the flow resistance of the drain port becomes large, and the retained water is difficult to be discharged. As a result, the water film can be retained to reach the thickness. The amount of cooling water on the surface of the steel sheet is greatly reduced, so that the cooling capacity is lowered, which is not preferable. More preferably 4 times or more. On the other hand, if the number of the drain ports is too large or the cross-sectional diameter of the drain port becomes too large, the rigidity of the partition wall 15 becomes small, and it is likely to be damaged when the steel plate is impacted. Therefore, the comparison of the total cross-sectional area of the drain port with the total cross-sectional area of the inner diameter of the round pipe nozzle 13 is preferably in the range of 1.5 to 20.

Further, the gap between the outer circumferential surface of the circular tube nozzle 13 and the inner surface of the water supply port 16 which is inserted into the water supply port 16 of the partition wall 15 is desirably set to 3 mm or less. If the gap is large, it is discharged to the room due to the accompanying flow of the cooling water sprayed from the circular nozzle 13 The cooling water discharge on the upper surface of the partition wall 15 is introduced into the gap between the water supply port 16 and the outer peripheral surface of the round pipe nozzle 13, and is again supplied to the thick steel plate, so that the cooling efficiency is deteriorated. In order to prevent this, it is more preferable to set the outer diameter of the circular nozzle 13 to be substantially the same as the size of the water supply port 16. However, in consideration of work accuracy or installation error, a gap of up to 3 mm is allowed to be substantially affected. More preferably, it is set to 2 mm or less.

Further, in order to allow the cooling water to pass through the retained water film and reach the thick steel plate, it is necessary to optimize the inner diameter and length of the round nozzle 13 and the injection speed of the cooling water or the nozzle distance.

That is, the inner diameter of the nozzle is preferably 3 to 8 mm. If it is less than 3 mm, the water jet that is ejected from the nozzle becomes thinner and the strength becomes weak. On the other hand, if the nozzle diameter exceeds 8 mm, the flow velocity becomes slow, and the force for penetrating the water film is weakened.

The length of the round nozzle 13 is preferably 120 to 240 mm. The length of the round pipe nozzle 13 as used herein means the length from the flow inlet of the upper end of the nozzle inside the header to some extent until the lower end of the nozzle of the water supply port of the partition wall. If the round nozzle 13 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 thickness of the header is set to 20 mm, the amount of protrusion of the upper end of the nozzle toward the header is set to 20 mm. When the insertion amount of the lower end of the nozzle toward the partition wall is 10 mm and less than 70 mm, the drainage space above the partition wall becomes small, and the cooling water discharge cannot be smoothly discharged. On the other hand, when it is longer than 240 mm, the pressure loss of the round pipe nozzle 13 becomes large, and the force which penetrates the water film is weakened.

The jetting speed of the cooling water from the nozzle must be 6 m/s or more, preferably 8 m/s or more. The reason for this is that if it is less than 6 m/s, the force of the cooling water flowing through the water film is extremely weak. If it is 8 m/s or more, it is preferable to ensure a larger cooling capacity. Further, the distance from the lower end of the cooling water spray nozzle 13 cooled from the upper surface to the surface of the thick steel plate 1 The distance is preferably set to 30 to 120 mm. If it is less than 30 mm, the frequency at which the thick steel plate 1 collides with the partition wall 15 is extremely high, and it is difficult to secure the equipment. When it exceeds 120 mm, the force of the cooling water flowing through the water film is extremely weak.

It is preferable to provide the dewatering roll 20 before and after the upper header 11 so that the cooling water does not diffuse in the longitudinal direction of the thick steel plate when the upper surface of the thick steel plate is cooled. Thereby, the length of the cooling zone becomes fixed, and temperature control becomes easy. Here, since the flow of the cooling water in the direction in which the thick steel plate is conveyed is blocked by the dewatering roller 20, the cooling water discharge flows outward in the width direction of the thick steel plate. However, it is easy to retain cooling water in the vicinity of the dewatering roller 20.

Therefore, as shown in FIG. 5, in the row of the circular tube nozzles 13 arranged in the width direction of the thick steel plate, the cooling water spray nozzles on the most upstream side in the direction in which the thick steel sheets are conveyed are inclined in the upstream direction of the thick steel sheet conveying direction. 15 to 60 degrees, the cooling water spray nozzle on the most downstream side of the thick steel plate conveying direction is inclined by 15 to 60 degrees in the downstream direction of the thick steel plate conveying direction. Thereby, the cooling water can be supplied to the position close to the dewatering roller 20, and the cooling water does not stay in the vicinity of the dewatering roller 20, and the cooling efficiency is improved, which is preferable.

The distance between the lower surface of the upper header 11 and the upper surface of the partition wall 15 is such that the cross-sectional area of the flow path 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 partition wall becomes the total cross-sectional area of the inner diameter of the cooling water spray nozzle. It is set to be 1.5 times or more, for example, about 100 mm or more. When the cross-sectional area of the flow path in the width direction of the thick steel plate is not more than 1.5 times the total cross-sectional area of the inner diameter of the cooling water spray nozzle, the cooling water discharged from the drain port 17 provided in the partition wall to the upper surface of the partition wall 15 cannot be smoothly performed. The ground is discharged along the width of the thick steel plate.

In the accelerated cooling device of the present invention, the most effective water density range is 1.5 m ³ /m ² . Min or above. When the water density is lower than this, the retained water film is not so thick, and there are cases where the temperature in the width direction is not uniform even if a known technique of cooling the thick steel plate by freely dropping the rod-shaped cooling water is applied. So big. On the other hand, it is convenient for the water density to be higher than 4.0 m ³ /m ² . The use of the techniques of the present invention is also effective in the case of min. However, there are problems in practical use such as high equipment cost, and therefore, 1.5 to 4.0 m ³ /m ² . Min is the most practical water density.

The use of the cooling technique of the present invention is particularly effective in the case where the dewatering roll is disposed after cooling the header. However, it can also be applied to the case without a dewatering roll. For example, it can also be applied to a cooling device which is relatively long in the longitudinal direction (about 2 to 4 m), and sprays a water spray for flushing before the header to prevent orientation. Water leakage in the water-cooled area.

Further, 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 Figs. 4 and 5, an example of cooling the lower header 12 having the same circular nozzle 14 as the cooling device on the upper surface side is shown. When the cooling water on the lower surface side of the thick steel plate is cooled, the sprayed cooling water is naturally dropped after hitting the thick steel plate. Therefore, the partition wall 15 that discharges the cooling water in the width direction of the thick steel plate as in the case of cooling on the surface side may not be provided. Further, a known technique of supplying film-like cooling water or spray-like spray cooling water can be used.

As described above, the apparatus for manufacturing a thick steel plate according to the present invention can realize the thick steel plate 1 by setting the energy density E of the spray nozzle from the descaling device 4 to the surface of the thick steel plate 1 to be 0.10 J/mm ² or more. The resulting scale is homogenized so that uniform cooling can be achieved by the accelerated cooling device 6. As a result, a thick steel plate 1 having a thick steel plate shape can be produced.

Further, by correcting the shape of the thick steel plate 1 by the first shape correcting device 5, the spray nozzle of the rust removing device 4 can be brought closer to the surface of the thick steel plate 1.

In addition, when the injection distance H (the surface distance between the injection nozzle of the rust removing device 4 and the thick steel plate 1) is 40 mm or more and 200 mm or less, the rust removing ability is improved. Moreover, since the injection pressure, the injection flow rate, etc., which are used to obtain a predetermined energy density E, can be set Small, therefore, the pumping capacity of the descaling device 4 can be reduced.

Further, by making the distance L from the descaling device 4 to the accelerating cooling device 6 satisfy L ≦ V × 5 × 10 ^-9 × exp (25000 / T), the cooling of the thick steel plate 1 by the accelerated cooling device 6 can be performed. stable.

Further, as shown in FIG. 4, the accelerated cooling device 6 of the present invention cools the upper surface of the thick steel plate 1 from the upper cooling water spray nozzle 13 through the cooling water supplied from the water supply port 16 to become a high-temperature drain, and is not cooled by the upper portion. The drain port 17 through which the water jet nozzle 13 is inserted is a drain flow path and flows in the width direction of the thick steel plate 1 from above the partition wall 15, so that the drained water is quickly removed from the thick steel plate 1, and therefore, the cooling water from the upper portion is removed. The cooling water flowing through the water supply port 16 of the injection nozzle 13 sequentially contacts the thick steel plate 1, whereby a sufficient cooling capacity in the width direction can be obtained.

In addition, the inventors of the present invention have found that the temperature unevenness in the width direction of the thick steel sheet obtained by the accelerated cooling after the rust removal as in the present invention is about 40 ° C. On the other hand, in the rust removing device 4 of the present invention, the energy density of the cooling water is set to 0.10 J/mm ² or more, and the temperature unevenness in the width direction of the thick steel plate obtained after the accelerated cooling is performed after the rust removal is performed. Reduce to about 10 °C. Further, it is understood that the temperature unevenness in the width direction of the thick steel sheet obtained by performing the accelerated cooling using the accelerated cooling device 6 shown in FIG. 4 after the rust removal by the rust removing device 4 is reduced to about 4 ° C. In addition, the temperature unevenness of the thick steel plate is measured by the scanning thermometer to measure the surface temperature distribution of the steel sheet after the accelerated cooling, and the temperature unevenness in the width direction is calculated based on the measurement result.

Further, in the present invention, the strain generated during the rolling process is corrected by the first shape correcting device 5, and the rust removing device 4 performs the rust removal of the thick steel plate 1 to stabilize the controllability of the cooling. The flatness of the thick steel plate 1 corrected by the second shape correcting device 7 is originally high, and the temperature of the thick steel plate 1 is also uniform. So about the second shape The corrective reaction force of the shape correcting device 7 does not need to be set higher. Further, it is preferable that the distance between the accelerated cooling device 6 and the second shape correcting device 7 is longer than the maximum length of the thick steel plate 1 produced on the rolling line. In this case, the second shape correcting device 7 is often subjected to reverse correction or the like. Therefore, it is expected that the thick steel plate 1 that has been reversed can be prevented from jumping on the transport roller and colliding with the failure of the accelerated cooling device 6 or the like. Or, a slight temperature deviation generated during the cooling process in the accelerated cooling device 6 is uniformized to avoid the effect of warpage due to temperature deviation after the correction.

[Example 1]

The thick steel plate 1 having a thickness of 30 mm and a width of 3,500 mm which was rolled by the rolling press 3 was passed through the first shape correcting device 5 and the rust removing device 4, and then controlled cooling from 820 ° C to 420 ° C was performed. Here, the conditions for the cooling stability are calculated based on the above equations (3), (4), and (5), and after the removal of the scale of the thick steel plate 1 by the descaling device 4 is completed, the accelerated cooling device 6 is used. The time t until the cooling of the thick steel plate 1 is started is preferably 42 s or less, more preferably 19 s or less, and still more preferably 5 s or less.

The injection pressure of the nozzle of the descaling device 4 is set to 17.7 MPa, and the injection flow rate per nozzle is set to 50 L/min (= 8.3 × 10 ^-4 m ³ /s), and the injection distance (the spray nozzle of the descaling device 4 and The surface distance of the thick steel plate 1 is set to 130 mm, the nozzle spray angle is set to 32°, the nozzle angle of attack is set to 15°, and one row is arranged in the width direction so that the spray areas of the adjacent nozzles overlap to some extent. The nozzle, the spray spray thickness was 3 mm, and the spray spray width was 77 mm. Here, the energy density of the cooling water is defined by the above-described water amount density × injection pressure × impact time. The impact time (s) is obtained by ejecting the rust-removing water to the surface of the thick steel plate by dividing the spray-spray thickness by the transport speed.

The accelerating cooling device 6 is provided as a device provided with a flow path which allows the cooling water supplied to the upper surface of the thick steel plate to flow above the partition wall as shown in FIG. As shown in Fig. 7, the water is drained from the width direction side of the thick steel plate. A hole having a diameter of 12 mm is formed in the partition wall as a grid. As shown in Fig. 6, the upper cooling water spray nozzle is inserted into the water supply port arranged in a staggered lattice shape, and the remaining hole is used as a drain port. The distance between the lower surface of the upper header and the upper surface of the partition wall was set to 100 mm.

The upper portion of the accelerating cooling device 6 has a cooling water jet nozzle having an inner diameter of 5 mm, an outer diameter of 9 mm, and a length of 170 mm, and has its upper end projecting into the header. Further, the jet velocity of the rod-shaped cooling water was set to 8.9 m/s. The nozzle pitch in the width direction of the thick steel plate was set to 50 mm, and 10 rows of nozzles were arranged in the longitudinal direction in a region where the distance between the conveying rollers was 1 m. The water density on the upper surface is 2.1 m ³ /m ² . Min. The lower end of the nozzle for cooling the upper surface was provided at a position intermediate to the upper surface of the partition wall having a thickness of 25 mm, and the distance from the surface of the thick steel plate was set to 80 mm.

Further, regarding the lower surface cooling device, the same cooling device as the upper surface cooling device except that the partition wall is not provided as shown in FIG. 4 is used, and the ejection speed and the water amount density of the rod-shaped cooling water are set to 1.5 on the upper surface. Times.

Further, as shown in Table 1, the distance L from the descaling device 4 to the accelerated cooling device 6, the conveying speed V of the thick steel plate, and the time t from the descaling device 4 to the accelerated cooling device 6 are variously changed.

The shape of the thick steel plate was evaluated by the additional correction rate (%). Specifically, if the warpage of the entire length of the steel sheet and/or the warpage of the full width of the steel sheet is within the standard value specified by the product specification corresponding to the steel sheet, it is judged to be acceptable, and if it exceeds the standard value, it is determined that the correction is additional. The amount of the additional correction rate is calculated by (the number of additional correction implements) / (the total number of target materials) × 100.

In the inventive examples 1 to 5 of Table 1, since the energy density was 0.10 J/mm ² or more, the additional correction ratio due to the shape defect was low, and good results were obtained. It is considered that the mechanism is such that when the cooling is performed by the accelerated cooling device 6, the deviation of the surface temperature in the width direction position is almost non-existent and can be uniformly cooled, and it is considered that the flatness of the temperature distribution due to the thick steel plate is excellent, and as a result, The additional correction rate due to poor shape is low. Further, in all of Examples 1 to 5 of the present invention, the scale was removed, and the surface properties were also good. Further, the evaluation of the surface properties was carried out by using an image of the surface of a thick steel plate cooled to room temperature, and using the image processing using the difference in the color difference between the remaining portion of the scale and the peeling portion to determine the presence or absence of scale.

In particular, in the first to third embodiments of the present invention in which the distance from the descaling device 4 to the accelerated cooling device 6 is 5 m, the removal of the scale from the thick steel plate 1 by the descaling device 4 is completed to the use of the accelerated cooling device 6 The time t until the cooling of the thick steel plate 1 is started is independent of the conveying speed V of the thick steel plate, and is a condition that the cooling by the accelerated cooling device 6 is more stable, that is, 19 sec or less. Therefore, the additional correction rate is preferably 5% or less.

Further, in the fifth example of the present invention, even if the impact pressure (1.0 MPa) is high as in Patent Document 1 or Patent Document 2, it is a good result that the energy density is within the range of the present invention.

On the other hand, in Comparative Example 1 in which the cooling by the accelerated cooling device 6 is not performed by the removal of the scale by the descaling device 4, it is considered that the flatness of the temperature distribution of the thick steel plate is deteriorated, and the additional correction ratio is 40. %.

Further, in Comparative Example 2, the temperature distribution in the width direction of the thick steel sheet was deteriorated due to partial peeling of the scale, and the flatness of the thick steel plate was also deteriorated. Therefore, the additional correction ratio was 70%. In Comparative Example 2, the rust removing apparatus was used. The setting conditions of 4 are set to a water pressure of 9 MPa, and an injection flow rate per one nozzle is 25 L/min (= 4.2 × 10 ^-4 m ³ /s). Other conditions are the same as in the second embodiment of the present invention, and the energy density is set to 0.08J/mm ² .

Further, Comparative Example 3 is as compared with Patent Document 1 or Patent Document 2 In the range of high impact pressure, but the energy density is outside the range of the present invention, the temperature distribution in the width direction of the thick steel plate is deteriorated due to partial peeling of the scale, and the flatness of the thick steel plate is also deteriorated. Therefore, additional correction is performed. The rate is 65%.

1‧‧‧thick steel plate

2‧‧‧heating furnace

3‧‧‧ rolling press

4‧‧‧Descaling device

5‧‧‧1st shape correcting device

6‧‧‧Accelerated cooling device

7‧‧‧2nd shape correcting device

Claims (7)

A manufacturing apparatus for a thick steel plate, characterized in that a hot rolling mill, a shape correcting device, a rust removing device, and an accelerated cooling device are disposed on the upstream side in the self-transporting direction, and the rust removing device is oriented toward the surface of the thick steel plate The energy density E of the jetted cooling water is set to 0.10 J/mm ² or more. The manufacturing apparatus of the thick steel plate according to the first aspect of the patent application, wherein the conveying speed from the descaling device to the accelerated cooling device is V [m/s], and the temperature of the thick steel plate before cooling is set to In T[K], the distance L[m] from the above-described descaling device to the above-described accelerated cooling device satisfies the formula of L≦V×5×10 ^-9 ×exp(25000/T). In the manufacturing apparatus of the thick steel plate of the second aspect of the invention, the apparatus is disposed such that the distance L from the descaling device to the accelerated cooling device is 12 m or less. The apparatus for manufacturing a thick steel plate according to any one of the first to third aspects of the invention, wherein the injection distance H from the injection nozzle of the descaling device to the surface of the thick steel plate is 40 mm or more and 200 mm or less. The apparatus for manufacturing a thick steel plate according to any one of claims 1 to 4, wherein the accelerated cooling device is provided with a header for supplying cooling water to an upper surface of the thick steel plate, and is sprayed from the header. a cooling water spray nozzle for hanging the rod-shaped cooling water, and a partition wall provided between the thick steel plate and the header, and a plurality of water supply ports and a water discharge port are provided in the partition wall, and the water supply ports are The lower end portions of the cooling water spray nozzles are interposed, and the drain ports discharge the cooling water supplied to the upper surface of the thick steel plate toward the partition walls. A method for manufacturing a thick steel plate, which is a method for manufacturing a thick steel plate in accordance with a sequence of a hot rolling step, a heat correcting step, and an accelerated cooling step, characterized in that: between the heat correcting step and the cooling step, having a surface of a thick steel plate A rust removal step of cooling water having a jet energy density E of 0.10 J/mm ² or more is applied. The method for manufacturing a thick steel plate according to claim 6, wherein the time t[s] from the end of the descaling step to the start of the accelerated cooling step satisfies t≦5×10 ^-9 ×exp(25000/T) Where T is the temperature of the thick steel plate (K) before cooling.