TWI413556B - Cooling apparatus and cooling method for hot rolling - Google Patents

Abstract

A cooling apparatus for hot rolling is installed on a downstream side of a finishing mill of a continuous hot rolling mill, and cools a steel sheet rolled by the finishing mill while being transportconveyed. The cooling apparatus includes first pinch rolls which, during an interval when the steel sheet fed out from a final stand of the finishing mill moves from a position of the final stand to a position where a surface temperature of the steel sheet reaches 850 DEG C or less, sandwichpinch the steel sheet while applying tension a tensile force of 3.9 MPa or greater.

Description

Hot rolling cooling device and cooling method Field of invention

The present invention relates to a cooling device and a cooling method for hot rolling of the steel sheet on a conveying table after finish rolling in continuous hot rolling of a steel sheet.

Background of the invention

The steel discharged from the furnace is sent to the finishing mill through the roughing mill. Fig. 6 is a perspective view showing an arrangement example of a hot rolling apparatus which performs a hot rolling step after the finish rolling mill 102. As shown in Fig. 6, the finishing mill 102 composed of the plurality of rolling stands F1a to F7a continuously rolls the steel material. Next, the steel sheet 103 which is hot-rolled through the final rolling table F7a to a desired thickness is conveyed by the conveying table 104 constituted by the plurality of conveying rollers 104a.

The conveying table 104 is disposed in the cooling device 105 disposed on the downstream side of the finishing mill 102. Further, cooling water is distributed on the upper surface of the steel sheet 103 from a plurality of cooling units 106 provided above the conveying table 104, whereby the steel sheet 103 can be cooled. The cooled steel sheet 103 is passed through the pre-winding press roll 107 and wound around the reel 108. The pre-roller pressing roller 107 has a function of inducing the steel sheet 103 to the coiler 108, and a function of maintaining the tension of the end portion of the steel sheet 103 after passing through the final rolling table F7a of the finishing mill 102. Further, the finishing mill 102 in Fig. 6 is configured by seven rolling stands, but it may be configured to have six rolling stands.

In the conventional hot rolling apparatus as described above, the front end portion of the high temperature steel sheet 103 after passing through the final rolling table F7a of the finishing mill 102, between the pressing rolls 107 before reaching the coiler, is in an unpressed state. Send it out. When the front end portion of the steel plate 103 is not given tension, wavy warping may occur, and then the cooling device 105 is passed in a warped shape. Even if the tension of the steel sheet 103 is imparted, the steel sheet 103 may vibrate when the steel sheet passes. When the cooling water is dispersed in a state in which the steel plate 103 is not flat, or when the steel plate 103 is vibrated, depending on the position of the steel plate 103, the cooling water to be sprayed may be uneven, and thus a temperature difference may occur. For example, when the plate shape of the steel plate 103 is wavy, a surface such as a mountain-like bulge is generated on the steel plate 103, and in the ridge surface, the cooling water is scattered on the upstream side of the steel plate 103 in the conveying direction. It is more intense, but the distribution of the cooling water with respect to the downstream portion in the conveying direction is weaker than the portion on the upstream side in the conveying direction. This is because the steel plate 103 continues to move in one direction.

Heretofore, for the reason described above, even if uniform cooling is required along the surface of the steel sheet 103, a temperature difference occurs, so that it is difficult to manufacture the steel sheet 103 having a stable quality.

As described above, in a state where no tension is applied to the steel sheet 103, the plate shape of the steel sheet 103 after passing through the final rolling table F7a of the finishing mill 102 may be warped. When the trailing end portions of the steel sheet 103 pass through the respective rolling stands F1a to F7a of the finishing mill 102, the rolling tables F2a to F7a after passing through the unpressed and unstressed state are passed. At this time, the steel sheet 103 may also be in a flat state and cause a large warpage. Further, even if tension is applied to the steel sheet 103, the steel sheet 103 may vibrate when the steel sheet passes. As a result, when the steel sheet 103 is cooled in a state of being warped or in a state of being vibrated, the cooling state is uneven depending on the respective positions of the steel sheets 103, so that the quality of the steel sheet 103 is more uneven.

The relationship between the surface temperature of the steel and the cooling capacity (thermal conductivity) indicates the boiling heat transfer characteristics of the water cooling, as shown in Fig. 7. That is, as shown in Fig. 7, the surface temperature of the steel material is an abnormal boiling region between T _CH and T _M , and a film boiling region is exceeded when T _M is exceeded. Further, the T _CH indicating the boundary between the nucleate boiling region and the metamorphic boiling region is about 400 to 450 ° C, and the T _M is about 550 to 600 ° C.

In the metamorphic boiling region, when the surface temperature of the steel material is slightly lowered, the cooling ability of water cooling is rapidly increased. Therefore, as shown in Fig. 7, for example, when the B point of a steel material is slightly higher than the surface temperature of the other point A in the film boiling region, if the two points are simultaneously water-cooled, the surface temperature of the steel material will be the same. 8 changes as shown. That is, since the surface temperature of the steel at point A is closer to T _M than point B, the metamorphic boiling region can be immediately reached and the temperature is rapidly lowered. On the other hand, the surface temperature temporarily at point B is still in the film boiling region (because the time to reach T _M is greater than point A), so the temperature drop is slower and reaches the metamorphic boiling region later than point A, and will not begin until after arrival. Rapid cooling. Therefore, there is a large temperature difference between point A and point B.

That is, the warpage caused by the steel sheet 103 or the like causes variations in the manner in which the cooling water is dispersed at each position on the surface of the steel sheet 103, so that a slight temperature difference is generated between the respective positions of the surface of the steel sheet 103. As a result, there is a slight deviation in the timing at which the metamorphic boiling regions are entered between the respective positions, and since the slight difference in the time points, the temperature difference between the respective positions is rapidly increased, and thus the steel sheet 103 of a uniform material cannot be obtained. Therefore, in order to stabilize the quality of the steel sheet 103, it is extremely important that the steel sheet 103 is in a uniform state without warpage or a state in which the steel sheet is less vibrated until it reaches the abnormal boiling region.

In the following Patent Document 1, the applicant proposes a rolling apparatus in which one or more sets of press rolls are provided on a conveyance table.

Prior technical literature Patent literature

Patent Document 1: JP-A-2001-321816

The invention described in the above-mentioned Patent Document 1 discloses that at least one set of press rolls are provided in order to reduce the necking of the steel sheet in the direction of the sheet, and the press rolls are placed at a position where the steel sheet temperature is 650 ° C or lower.

Usually, the surface temperature of the steel sheet after passing through the finishing mill is about 840 ° C or more and 1000 ° C or less, and the 650 ° C disclosed in Patent Document 1 above is required, and a long distance necessary for performing the cooling step after passing through the finishing mill. Therefore, the front end portion of the steel sheet is reached between the pressing rolls located far from the final rolling stand position of the finishing mill, and the front end portion of the steel sheet cannot be sandwiched. Further, the above Patent Document 1 does not specifically describe the case where tension is applied to the steel sheet. Therefore, the technique disclosed in Patent Document 1 does not mention a technique for sufficiently improving the warpage shape or the vibration of the steel sheet at the front end portion and the tail end portion of the steel sheet which causes the temperature deviation as described above.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a cooling device and a cooling method for hot rolling, which can make a front end portion and a rear end portion of a steel sheet in a cooling step after finish rolling in a continuous hot rolled steel sheet. The shape is stable and can suppress the vibration of the steel plate.

In order to solve the above problems, the present invention adopts the following aspects.

(1) The cooling device for hot rolling of the present invention is disposed on the downstream side of the finishing mill for continuous hot rolling, and can be cooled while carrying the steel sheet rolled by the finishing mill, and is provided with a first pressing roll. The steel sheet is sandwiched between the position of the final rolling table of the steel sheet and the surface temperature of the steel sheet which is sent from the final rolling stand of the finishing mill to a position where the surface temperature of the steel sheet is 850 ° C or less.

According to the cooling device for hot rolling described in the above (1), a tension of 3.9 MPa or more is applied to a range from a position of the final rolling table of the steel sheet to a position at which the surface temperature of the steel sheet is 850 ° C or lower, and the rolling can be reduced. The steel plate is warped in shape. In particular, when tension is applied to the front end portion or the end portion of the steel sheet which is likely to cause unevenness in cooling due to warpage, uniform cooling along the entire length of the steel sheet can be effectively obtained.

(2) The cooling device for hot rolling according to (1) above, wherein the first pressing roll may be disposed at a position immediately after the surface temperature of the steel sheet is cooled to 850 °C.

(3) The cooling device for hot rolling according to (1), wherein a lower limit of the surface temperature of the steel sheet to which the tension position is applied may be greater than 650 °C.

(4) The cooling device for hot rolling according to any one of the above (1) to (3), wherein a second pressing roll that is disposed at a position where the surface temperature of the steel sheet is 650 ° C to 550 ° C is further used. And a third pressing roll disposed at a position where the surface temperature of the steel sheet is 450° C. to 350° C., and a position at which the second pressing roll and the third pressing roll are disposed on the second pressing roll of the steel sheet and the third portion A structure in which a tension of 3.9 MPa or more is applied between the positions where the pressing rolls are disposed.

(5) The method for cooling hot rolling according to the present invention is a method of cooling the steel sheet rolled by the finishing mill while cooling the steel sheet which is rolled by the finishing mill on the downstream side of the continuous hot rolling mill, and has the following steps: The surface temperature of the steel sheet fed from the final rolling mill of the finishing mill is controlled to be 850 ° C or lower; and the second step is a position from the position of the final rolling mill to a position where the surface temperature of the steel sheet is 850 ° C or lower. In the case where a tension of 3.9 MPa or more is applied while the steel plate is sandwiched.

(6) The method of cooling hot rolling according to (5) above, wherein in the second step, the tension may be applied to a position immediately after the surface temperature of the steel sheet is cooled to 850 °C.

(7) The method of cooling hot rolling according to the above (5), wherein in the first step, the lower surface temperature of the position at which the tension is applied to the second step is set to a temperature higher than 650 °C.

(8) The method of cooling the hot rolling according to any one of the above (5) to (7), further comprising the third step of the step of the surface temperature of the steel sheet being 650 ° C to 550 ° C A tension of 3.9 MPa or more is applied between the position where the surface temperature is 450 ° C to 350 ° C.

According to the present invention, the shape of the front end portion and the end portion of the steel sheet can be improved, and the vibration at the time of passage of the steel sheet can be suppressed, and the surface of the steel sheet can be uniformly cooled by this, so that a steel sheet of stable quality can be produced.

Simple illustration

Fig. 1 is a perspective view showing an outline of a hot rolling facility including a cooling device for hot rolling according to a first embodiment of the present invention.

Fig. 2 is a graph showing a change in warpage ratio when tension is applied to a steel sheet.

Fig. 3 is a view schematically showing the effect of the calender shape correcting press roll provided in the cooling device, and Fig. 3(a) shows a conventional case in which the same calender shape correcting press roll is not provided, and Fig. 3(b) The figure shows the case of the present embodiment in which the same calendering shape correcting press roll is provided.

Fig. 4 is a graph showing the relationship between the size of warpage and the unevenness of the surface temperature of the steel sheet.

Fig. 5 is a perspective view showing an outline of a hot rolling facility including a cooling device for hot rolling according to a second embodiment of the present invention.

Fig. 6 is a perspective view showing an outline of a hot rolling facility having a conventional hot rolling cooling device.

Fig. 7 is a graph showing the cooling characteristics when the steel material is water-cooled, wherein the horizontal axis represents the surface temperature of the steel material, and the vertical axis represents the cooling capacity (in detail, the thermal conductivity).

Fig. 8 is a view showing changes in surface temperature of two types of steel sheets, such as the case of cooling from point A of Fig. 7 and the case of cooling from point B.

Form for implementing the invention

In the following, the present invention relates to a cooling device and a cooling method which are disposed on the downstream side of a finishing mill for continuous hot rolling and which can transport the steel sheet which is rolled by the finishing mill and perform cooling, and the cooling method is described below. Type. In the description of the embodiments, the same reference numerals will be given to the structures having substantially the same functions, and the overlapping description will be omitted.

[First embodiment]

The steel material discharged from the heating furnace is rolled by a roughing mill to a thickness of about 40 mm (not shown), and is continuously rolled to a thickness of about 1 mm to 4 mm by a finishing mill 2 to be described later.

Fig. 1 is a perspective view showing an outline of the structure of the apparatus after the finish rolling mill 2 in the hot rolling facility of the hot rolling apparatus 5 (hereinafter simply referred to as the cooling apparatus 5) of the present embodiment. The finishing mill 2 is provided with a plurality of rolling tables F1 to F7 (for example, seven in the illustrated example), and hot rolling is performed to obtain a steel sheet 3 having a desired thickness and a sheet width when passing through the final rolling table F7. The surface temperature of the steel sheet 3 after passing through the final rolling stand F7 of the finishing mill 2 is 840 ° C or more and 1000 ° C or less.

The steel sheet 3 after passing through the final rolling table F7 is conveyed by the transport table 4 composed of a plurality of transport rollers 4a. A plurality of coolers 6 are disposed directly above the transport table 4. The steel sheet 3 is cooled by water or the like sprayed by the cooler 6 between the conveyance table 4, and as a result, the steel sheet 3 is formed into a metal structure of a desired material. Each of the coolers 6 has an inherent cooling performance depending on the installation position, and is controlled by a control device (not shown).

Then, in the cooling device 5, the range between the final rolling table F7 and the calender shape correcting pressing roll 10 (first pressing roll) to be described later is an immediate quenching belt 5a which passes through the final rolling table F7 at 840 ° C. The steel sheet 3 having the above surface temperature of 1000 ° C or lower is rapidly cooled to a temperature of 850 ° C or lower by the quench cooler 6 . Further, the quenching cooler 6a located directly above the immediate quenching zone 5a is a part of the cooler 6, and the number of the quenching coolers 6a may be one or plural.

The steel sheet 3 cooled to a predetermined surface temperature (for example, 430 ° C) by the cooling device 5 is wound around the coiler 8. On the upstream side of the coiler 8 and on the downstream side of the cooling device 5, a pre-roller press roll 7 composed of a pair of upper and lower rolls is provided. The steel sheet 3 is induced by the pre-roller pressing roller 7, and the winding shape is adjusted and the reel is applied in a state where an appropriate tension is applied to the portion between the pressing roller 7 and the reel 8 before the reel. 8 Winding is performed.

Immediately after passing through the immediately-cooling belt 5a located on the downstream side of the final rolling mill F7 of the finishing mill 2, and the surface temperature of the steel sheet 3 is cooled to 850 ° C or lower, the upper and lower rolls are arranged, and the steel plate 3 can be corrected. The calender shape correcting press roll 10 which is warped in the direction.

The calendering shape correcting pressing roller 10 can apply 3.9 MPa to a portion of the steel sheet 3 fed from the final rolling table F7 of the finishing mill 2 from the final rolling table F7 to a position where the surface temperature of the steel sheet 3 is 850 ° C or lower. The above tension is rotated by sandwiching the steel sheet 3, and the steel sheet 3 is conveyed downstream. Further, the lower limit of the surface temperature of the steel sheet 3 to which the tension is applied is preferably more than 650 °C.

The setting position of the calendering shape correcting pressing roller 10 is preferably as close as possible to the final rolling table F7, but since the steel sheet 3 is sandwiched by the calendering shape correcting pressing roller 10 at a position where the temperature of the steel sheet 3 exceeds 850 ° C, the thickness of the steel sheet 3 may vary. Not very suitable. Therefore, the calendering shape correcting press roll 10 is preferably disposed at a position immediately after the surface of the steel sheet becomes 850 ° C or lower, or at a position at least 650 ° C or more before entering the metamorphic boiling region.

Further, the pressing roll diameter or the pressing force of the calendering shape correcting pressing roll 10 should be set so as not to change the thickness of the steel sheet 3. In the case of the present embodiment, in the case where the immediately-cooling belt 5a is provided adjacent to the downstream side of the finishing mill 2, it is preferable to provide the calender-shaped correction pressing roller 10 immediately after the quenching belt 5a. Since the position of the surface temperature of the steel sheet 3 at 850 ° C or lower is brought close to the finish rolling mill 2 by providing the immediately quenching belt 5a, the distance in the conveying direction between the press roll 10 for rolling shape correction and the finishing mill 2 can be shortened.

On the other hand, when the finish rolling temperature of most of the produced steel sheets is close to 840 ° C, the immediate quenching belt 5a or the quenching cooler 6a may be omitted.

When the front end portion of the steel sheet 3 passes through the final rolling table F7 of the finishing mill 2 and reaches the position of the calendering shape correcting pressing roll 10, the steel sheet 3 is sandwiched by the calendering shape correcting pressing roll 10. Since the portion on the tail end side of the steel sheet 3 is sandwiched by the respective rolling stands F1 to F7 of the finishing mill 2, the front end portion can be sandwiched by the calendering shape correcting pressing roller 10 for the front end portion and the final rolling table F7. A tension of 3.9 MPa or more is imparted between them. As a result, the steel sheet 3 can be prevented from being warped and maintained in a flat plate shape and conveyed.

When the installation position of the calendering shape correcting press roll 10 is not appropriate, the position at which the tension is applied to the steel sheet 3 is also inappropriate. In the present embodiment, the installation position of the calendering shape correcting press roll 10 is set as described above. Since the shape of the front end portion and the end portion of the steel sheet 3 is stabilized at an appropriate position, the vibration of the steel sheet can be reliably suppressed.

In addition, the upper limit of the tension applied to the steel sheet 3 by the calendering shape correcting press roll 10 is preferably 19.6 MPa.

Fig. 2 is a view showing a change in warpage ratio when tension is applied to the steel sheet 3. In other words, Fig. 2 is a view showing the warpage ratio of the steel sheet 3 when tension is applied with respect to the case where the warpage of the steel sheet 3 is 1 when there is no tension.

In addition, FIG. 3 is a view schematically showing an effect of the tension applied by the calendering-correcting pressing roller 10, and (a) shows a conventional situation in which the same calendering-correcting pressing roller 10 is not provided, and (b) shows that The present embodiment of the same calendering shape correcting press roll 10 is the same. That is, Fig. 3 shows the difference in the sinusoidal warp pattern by the presence or absence of the tension of the steel sheet 3 after passing through the final rolling table F7 of the finishing mill 2.

The thickness of the steel sheet 3 before rolling through the final rolling stage F7 was set to 3.3 mm, and the thickness after rolling was set to 3 mm, and the simulation calculation was performed. As a result, when the warpage height after rolling is 30 mm, if the rolling shape correction pressing roll 10 is provided with a tension of 3.9 MPa with respect to the portion 3a between the final rolling table F7, the warpage height after rolling is as shown in FIG. It can be reduced to about 1/3 as shown.

Further, as shown in the third figure (b), when the tension is released, that is, after the calendering shape correction pressing roll 10 is removed, the degree of warpage of the steel sheet 3 does not increase. Therefore, it is understood that when the above-described tension is applied, the press roll 10 for rolling shape correction can be transported without causing warpage. Further, as shown in Fig. 2, the amount of warpage reduction when the tension is 14.7 MPa is about 1/8 of the original. In the region where the tension is 3.9 MPa or more, as shown in Fig. 2, the ratio of warpage reduction is smaller than the region of 3.9 MPa or less.

As described above, by applying the tension to the portion 3a in the appropriate range of the steel sheet 3 by using the calendering shape correcting pressing roller 10, even if warpage occurs on the steel sheet 3 after passing through the finishing mill 2, the sheet can be deformed. flat.

Further, by allowing the steel sheets 3 to pass through the cooling device 5 in a flat manner, the cooling water sprayed from the respective coolers 6 can be uniformly sprayed on the surface of the steel sheet 3. As a result, since the respective positions on the surface of the steel sheet 3 can be cooled under uniform cooling conditions, various metal structures at respective positions can be stably formed (that is, metal structures between the respective positions do not cause a large difference).

Further, the warpage size of the steel sheet 3 and the temperature unevenness have a proportional relationship as shown in Fig. 4, and the warpage size is 1/3 or less, and the material uniformity can be made within the reference. That is, the aforementioned tension is 3.9 MPa, which is quite sufficient. Further, if the tension is increased by 4.9 MPa or more or 5.9 MPa or more, the warpage is further reduced, and the material uniformity can be further improved.

On the other hand, after the end portion of the steel sheet 3 passes through the first rolling table F1 of the finishing mill 2, the tension of the steel sheet 3 is gradually reduced by the coiler 8, when passing through the rolling table in the drawing, for example, the rolling table F3 or the rolling table F4 ( In the case of OFF), the rotational speed of the press roller 7 before the reel is lowered. As a result, when the end portion of the steel sheet 3 passes through the final rolling table F7, the end portion is not caught, so the tension applied to the front end side of the steel sheet 3 is slowed down, and as a result, the steel sheet 3 is lowered. Warp will occur. On the other hand, in the present embodiment, the end portion of the steel sheet 3 is sandwiched by the calendering shape correcting press roll 10, and the portion of the steel sheet 3 which is located on the downstream side of the calendered shape correcting press roll 10 is passed through the sheet. Appropriate tension is applied to the upstream side of the direction. Therefore, the warpage of the steel sheet 3 can be effectively suppressed from the front end portion to the rear end portion.

Further, as described above, since the present embodiment has the above-described immediate quenching belt 5a, the surface temperature of the steel sheet 3 after passing through the final rolling table F7 of the finishing mill 2 can be rapidly lowered to a desired temperature. As a result, since the distance between the final rolling table F7 and the calendering shape correcting pressing roller 10 can be shortened, when the trailing end portion of the steel sheet 3 leaves the final rolling table F7, the final rolling table F7 and the calendering shape correcting pressing roller 10 can be used. The accumulated elastic energy between the two is small. Therefore, since the defect which may occur in the aforementioned end portion can be made small by liberating the elastic energy, the plate-shaped warpage of the steel sheet 3 can be further reduced.

Next, a cooling method of hot rolling by the cooling device 5 of the present embodiment having the structure described above will be described. In the cooling method of the hot rolling, the steel sheet 3 rolled by the finishing mill 2 is conveyed while being cooled on the downstream side of the finish rolling mill 2 for continuous hot rolling.

The cooling method of the hot rolling includes the first step of controlling the surface temperature of the steel sheet 3 sent from the final rolling table F7 of the finishing mill 2 to 850 ° C or lower by cooling with the immediate cooling zone 5 a; In the second step, the portion 3a between the position of the final rolling table F7 and the surface temperature of the steel sheet 3 of 850 ° C or lower is applied with a tension of 3.9 MPa or more by the calendering shape correcting pressing roller 10 Those who live in steel plate 3.

Further, in the second step, tension was applied at a position immediately after the surface temperature of the steel sheet 3 was cooled to 850 °C.

Further, in the first step, it is preferable to set the lower limit of the surface temperature at the position where the tension is applied in the second step to be higher than 650 °C.

As described above, in the present embodiment, by providing the press roll 10 for calendering shape correction, the shape of the front end portion and the end portion of the steel sheet 3 passing through the cooling device 5 can be improved. In particular, between the cooling state of the steel sheet 3 and the abnormal boiling region, the plate shape of the steel sheet 3 is flat and uniformly cooled, and the temperature difference between the respective positions on the surface can be reduced. Thereby, the defective portion of the rolled shape and the cooled state of the steel sheet 3 can be reduced, and the quality of both the front end portion and the rear end portion of the steel sheet 3 can be improved.

The steel sheet 3 cooled to a desired temperature by the cooling device 5 is wound around the coiler 8. The hot-rolled steel plate thus obtained can be widely used as various structural parts such as automobiles, or can be sent to the subsequent cold rolling and surface treatment steps.

[Second embodiment]

Fig. 5 shows a second embodiment of the present invention. In the following description, only differences from the above-described first embodiment will be described, and overlapping description will be omitted.

In the present embodiment, the first intermediate press roll 11 (second press roll) and the second intermediate press roll 12 (third press roll) are provided in the cooling device 5. Further, the first intermediate pressing roller 11 is disposed at a position where the surface temperature of the steel sheet 3 is 650 ° C to 550 ° C, and the second intermediate pressing roller 12 is disposed at a position where the surface temperature of the steel sheet 3 is 450 ° C to 550 ° C. Each of the first intermediate press roll 11 and the second intermediate press roll 12 is composed of a pair of upper and lower rolls, and is disposed at a position where the first intermediate press roll 11 of the steel sheet 3 is disposed and the second intermediate press roll 12 is disposed. The portion 3b between the positions is applied with a tension of 3.9 MPa or more, and the steel plate 3 is sandwiched at the respective positions.

According to the above configuration, the third step can be performed by applying 3.9 MPa or more to the portion 3b between the position where the surface temperature of the steel sheet 3 is 650 ° C to 550 ° C and the position at which the surface temperature is 450 ° C to 550 ° C. Tension.

The first intermediate press roll 11 is disposed at a position where the surface temperature of the steel sheet 3 is the upper limit temperature T _M of the metamorphic boiling region shown in Fig. 7, and the second intermediate press roll 12 is placed at the metamorphic boiling shown in Fig. 7. The position of the lower limit temperature T _CH of the zone. By providing the first intermediate pressing roller 11 and the second intermediate pressing roller 12, it is possible to sandwich the portion 3b while applying appropriate tension to the portion 3b located in the range of the metamorphic boiling region, thereby maintaining the flat shape of the steel sheet 3 and suppressing it. The plate vibrates when the steel sheet passes. Therefore, in addition to the calendering shape correcting pressing roller 10, the first intermediate pressing roller 11 and the second intermediate pressing roller 12 are further provided, and the cooling can be performed in a more uniform cooling condition in the abnormal boiling region, so that no cause is caused. A higher quality steel sheet 3 can be obtained by a difference in temperature at a position on the surface of the steel sheet 3.

The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above examples. In the context of the technical idea described in the scope of the patent application, it is to be understood that various changes and modifications may be made without departing from the scope of the invention. For example, the calendering shape correcting press roll 10 may be provided at a position where the surface temperature of the steel sheet 3 is 650 ° C, and it also serves as the first intermediate press roll 11 . However, in this case, since the tension on both the upstream side and the downstream side of the calendering shape correcting roll 10 disposed at the new position is controlled, the control is complicated, and therefore the second embodiment is used. The structure is good.

Industry availability

The present invention is applicable to a cooling device and a cooling method for performing a cooling step after finish rolling of steel sheet continuous hot rolling.

2. . . Finishing mill

3. . . Steel plate

3a, 3b. . . section

4. . . Conveyor

4a. . . Transport roller

5. . . Cooling device

5a. . . Immediately cold belt

6. . . Cooler

6a. . . Quench cooler

7. . . Pre-roller press roll

8. . . Coiler

10. . . Press roll for calendering shape correction (first press roll)

11. . . First intermediate pressing roll (second pressing roll)

12. . . Second intermediate pressing roll (third pressing roll)

F1~F7. . . Rolling table

102. . . Finishing mill

103. . . Steel plate

104. . . Conveyor

104a. . . Conveyor roller

105. . . Cooling device

106. . . Cooler

107. . . Pre-roller press roll

108. . . Coiler

F1a~F7a. . . Rolling table

Fig. 1 is a perspective view showing an outline of a hot rolling facility including a cooling device for hot rolling according to a first embodiment of the present invention.

Fig. 2 is a graph showing a change in warpage ratio when tension is applied to a steel sheet.

Fig. 3 is a view schematically showing the effect of the calender shape correcting press roll provided in the cooling device, and Fig. 3(a) shows a conventional case in which the same calender shape correcting press roll is not provided, and Fig. 3(b) The figure shows the case of the present embodiment in which the same calendering shape correcting press roll is provided.

Fig. 4 is a graph showing the relationship between the size of warpage and the unevenness of the surface temperature of the steel sheet.

Fig. 5 is a perspective view showing an outline of a hot rolling facility including a cooling device for hot rolling according to a second embodiment of the present invention.

Fig. 6 is a perspective view showing an outline of a hot rolling facility having a conventional hot rolling cooling device.

Fig. 7 is a graph showing the cooling characteristics when the steel material is water-cooled, wherein the horizontal axis represents the surface temperature of the steel material, and the vertical axis represents the cooling capacity (in detail, the thermal conductivity).

Fig. 8 is a view showing changes in surface temperature of two types of steel sheets, such as the case of cooling from point A of Fig. 7 and the case of cooling from point B.

2. . . Finishing mill

3. . . Steel plate

3a. . . section

4. . . Conveyor

4a. . . Transport roller

5. . . Cooling device

5a. . . Immediately cold belt

6. . . Cooler

6a. . . Quench cooler

7. . . Pre-roller press roll

8. . . Coiler

10. . . Press roll for calendering shape correction (first press roll)

F1~F7. . . Rolling table

Claims (12)

A hot-rolling cooling device is disposed on the downstream side of a continuous hot rolling mill, and is capable of being cooled while transporting the steel sheet rolled by the finishing mill, and has a first pressing roll, The steel sheet fed from the final rolling stand of the finishing mill is sandwiched between the position of the final rolling table and the surface temperature of the steel sheet of more than 650 ° C and 850 ° C or less, while applying a tension of 3.9 MPa or more. Further, the cooling device for hot rolling further includes a second pressing roll disposed at a position where the surface temperature of the steel sheet is 650 ° C to 550 ° C, and a third pressing roller disposed at a position where the surface temperature of the steel sheet is 450 ° C to 350 ° C The roller and the second pressing roller and the third pressing roller apply a tension of 3.9 MPa or more between the position where the second pressing roller of the steel sheet is disposed and the position where the third pressing roller is disposed. A cooling device for hot rolling according to the first aspect of the invention, wherein the first pressing roll is disposed at a position immediately after the surface temperature of the steel sheet is cooled to 850 °C. A cooling device for hot rolling according to claim 1 or 2, wherein an immediate quenching zone is provided between the final rolling stand and the first pressing roll at a temperature at which the surface temperature of the steel sheet is rapidly cooled to 850 ° C or lower. A method of cooling by hot rolling is carried out by cooling a steel sheet which is rolled by the finishing mill while cooling on a downstream side of a continuous hot rolling mill, and has the following steps: the first step is from the foregoing The final rolling mill of the finishing mill The surface temperature of the steel sheet is controlled to be greater than 650 ° C and not higher than 850 ° C; and the second step is between the position from the final rolling station to the surface temperature of the steel sheet being greater than 650 ° C and below 850 ° C. And applying a tension of 3.9 MPa or more to sandwich the steel sheet; and the third step is a position where the surface temperature of the steel sheet is 650 ° C to 550 ° C and the surface temperature is 450 ° C to 350 ° C Between 3.9 MPa or more is applied between the tensions. In the cooling method of hot rolling according to the fourth aspect of the invention, in the second step, the tension is applied immediately after the surface temperature of the steel sheet is cooled to 850 °C. A method of cooling hot rolling according to the fourth or fifth aspect of the invention, wherein the quenching step of quenching is performed between the final rolling table and the surface of the steel sheet having a surface temperature of 850 ° C or lower. A hot-rolling cooling device is disposed on the downstream side of a continuous hot rolling mill, and is capable of being cooled while transporting the steel sheet rolled by the finishing mill, and has a first pressing roll, The steel sheet fed from the final rolling stand of the finishing mill is sandwiched between the position of the final rolling table and the surface temperature of the steel sheet of more than 650 ° C and 850 ° C or less, while applying a tension of 3.9 MPa or more. Between the final rolling table and the first pressing roll, there is an immediate urgency to rapidly cool the surface temperature of the steel sheet to 850 ° C or lower. Cold belt. A cooling device for hot rolling according to the seventh aspect of the invention, wherein the first pressing roll is disposed at a position immediately after the surface temperature of the steel sheet is cooled to 850 °C. A cooling device for hot rolling according to the seventh or eighth aspect of the invention, further comprising a second pressing roll disposed at a position where the surface temperature of the steel sheet is 650 ° C to 550 ° C, and a surface temperature of the steel sheet disposed at 450 ° C. The third pressing roll at a position of 350 ° C, and the position where the second pressing roll and the third pressing roll are disposed with respect to the position where the second pressing roll of the steel sheet is disposed and the position where the third pressing roll is disposed is applied 3.9. Tension above MPa. A method of cooling by hot rolling is carried out by cooling a steel sheet which is rolled by the finishing mill while cooling on a downstream side of a continuous hot rolling mill, and has the following steps: the first step is from the foregoing The surface temperature of the steel sheet fed by the final rolling mill of the finishing mill is controlled to be greater than 650 ° C and below 850 ° C; the second step is for the surface temperature from the position of the final rolling mill to the surface of the steel sheet being greater than 650 ° C and Between 850 ° C and below, a tension of 3.9 MPa or more is applied while sandwiching the steel sheet; and a quenching step is performed between the final rolling table and the first pressing roll to cool the surface temperature of the steel sheet To temperatures below 850 ° C. The method for cooling hot rolling according to claim 10, wherein in the second step, the surface temperature of the steel sheet is cooled to 850 immediately after the surface temperature The aforementioned tension is applied at a position after °C. The method for cooling hot rolling according to claim 10 or 11, wherein the third step is that the surface temperature of the steel sheet is 650 ° C to 550 ° C, and the surface temperature is 450 ° C to 350 ° C. A tension of 3.9 MPa or more is applied between the positions.