JP2012115895A - Method for cooling checkered steel plate after rolling - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for cooling a checkered steel plate after rolling, in which scale is hard to exfoliate, and in which cooling water does not remain in the upper surface of the steel plate by the time of rolling up of a coil, when cooling the checkered steel plate after rolling transferred with its protruding surface being an upper surface, in a cooling equipment of a hot rolling line.SOLUTION: A checkered steel plate 1 is cooled to a predetermined temperature by spraying cooling water to the upper and lower surfaces of the checkered steel plate 1 by a rapid cooling device 5 provided in the direct down-stream of the output side of a finishing rolling mill 2, the cooling water of the upper surface of the checkered steel plate 1 is drained by a draining roll 9 which is right downstream of a rapid cooling process in the rapid cooling device 5, a predetermined amount of the cooling water is sprayed to only the lower surface of the checkered steel plate 1 by a cooling line 7 of a predetermined length provided downstream thereof, and at the same time, the cooling water is blown away by spraying air on the upper surface of the checkered steel plate 1 from a purge device 6 according to need, thereby, while the checkered steel plate 1 is cooled rapidly, the cooling water of the upper surface of the checkered steel plate 1 is rapidly removed.

Description

  The present invention relates to a cooling method after rolling striped steel sheets having protrusions formed on one surface and conveyed with the protruding surface as an upper surface, and in particular, cooling the striped steel plates after rolling in a run-out after finish rolling having a quenching device. It is suitable for.

Since the striped steel plate has protrusions on the surface, the adhesion of the scale made of Fe ₃ O ₄ for rust prevention is low, and for example, peeling of the scale after coil winding often becomes a problem. Therefore, for example, as described in the following Patent Document 1, runout after finish rolling, that is, steep water cooling of the striped steel plate at the front stage of the cooling line after finish rolling, and slow water cooling at the rear stage, thereby suppressing the generation of scale, In addition, a method has been proposed in which the scale composition is changed mainly to Fe ₃ O ₄ having a high breaking strength.

  However, the striped steel plate has a special surface shape with a large number of protrusions on the surface, and the water drainage on the surface is poor, so the surface water ride cannot be sufficiently eliminated with the run-out draining device alone, that is, until coil winding. There is a problem that cooling water remains on the surface. Water riding not only causes measurement abnormality by a measuring instrument such as a temperature sensor, but also causes a non-uniform temperature distribution in the width direction, which causes hardness unevenness and shape defects. In order to solve this problem, for example, as described in Patent Document 2 below, there is a method in which the striped steel plate is transported with the surface on which the protrusion is formed as the lower surface, and both surfaces of the striped steel plate being transported are water-cooled. . Incidentally, striped steel plates are often rolled, cooled and wound on the same line as other types of steel plates as a type of steel plate.

Japanese Patent Laid-Open No. 10-235424 JP-A-4-41002

However, since the run-out after finish rolling conveys the steel sheet with a roller, the surface on which the protrusion is formed is used as the lower surface as in Patent Document 2, that is, the protrusion surface is placed on the roller for transportation. This is unrealistic because it causes deformation and wear of the protrusions and scale peeling.
The present invention has been made paying attention to the above problems, and provides a post-rolling cooling method for a striped steel sheet in which the scale is difficult to peel off and no cooling liquid remains on the upper surface of the steel sheet until coil winding. It is intended.

  In order to solve the above problems, the present inventor has obtained the following knowledge as a result of intensive studies. That is, in order to suppress the generation of scale on the protruding surface of the striped steel sheet after rolling and to make the scale difficult to peel off, it is necessary to cool the striped steel sheet as quickly as possible. It needs to be cooled by spraying water. However, when transporting with the projection surface of the striped steel plate after rolling as the upper surface, the cooling water tends to remain in the plane portion between the projections of the projection surface, but in order to avoid uneven hardness and shape defects of the striped steel plate In this case, it is necessary to remove the water on the protruding surface as soon as possible.

  Therefore, the cooling method after rolling of the striped steel sheet according to the present invention provides a finish rolling mill for cooling the rolled striped steel sheet, which has projections formed on one side and is transported with the projection surface as an upper surface, on the runout. Cooling water is sprayed onto the upper and lower surfaces of the striped steel plate by a quenching device provided immediately downstream of the side to rapidly cool to a predetermined temperature, and the cooling water on the upper surface of the striped steel plate is drained by a draining means provided immediately downstream of the quenching step. And it cools by spraying a cooling water only on the lower surface of a striped steel plate with the cooling line provided downstream of the draining means.

In the cooling line, air is blown to the upper surface of the striped steel plate to blow off the cooling water on the upper surface.
Further, the draining means is a hard draining roll that is not in contact with the upper surface of the striped steel plate.

  Thus, according to the post-rolling cooling method of the striped steel sheet of the present invention, when cooling the striped steel sheet after rolling with the projections formed on one surface and transported with the projection surface as an upper surface on the runout, the finish is finished. Cooling water is blown to the upper and lower surfaces of the steel sheet by a quenching device provided immediately downstream of the exit side of the rolling mill to cool to a predetermined temperature, and cooling water on the upper surface of the striped steel sheet is drained by a draining means provided immediately downstream of the rapid cooling process. Since the water is drained and cooled by spraying the cooling liquid only on the lower surface of the steel sheet in the cooling line provided downstream of the water draining means, the striped steel sheet after rolling can be quickly and quickly cooled, and the upper surface of the striped steel sheet This makes it possible to efficiently remove the cooling water, which makes it difficult for the scale to peel off, and it is difficult for the cooling liquid to remain on the upper surface of the striped steel plate before coil winding.

In addition, since air is blown onto the upper surface of the striped steel plate by the cooling line purge device to blow off the cooling water on the upper surface, the cooling water on the upper surface of the striped steel plate can be further reliably removed.
Moreover, since the draining means is a hard draining roll that is not in contact with the upper surface of the striped steel plate, the cooling water on the upper surface of the striped steel plate can be drained efficiently.

It is a schematic block diagram which shows one Embodiment of the steel plate cooling equipment with which the cooling method after rolling of the striped steel plate of this invention is applied. It is explanatory drawing of the cooling water spraying performed with the steel plate cooling equipment of FIG. It is explanatory drawing of the striped steel plate cooling method by the steel plate cooling equipment of FIG.1 and FIG.2. It is explanatory drawing of the draining of the striped steel plate upper surface by a draining roll. It is explanatory drawing of the cooling water spraying of the conventional striped steel plate cooling method performed with the steel plate cooling equipment of FIG. It is explanatory drawing of the temperature change of the steel plate by the steel plate cooling of FIG. 2, and the steel plate cooling of FIG.

Next, an embodiment of the post-rolling cooling method for striped steel sheets according to the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram showing a steel plate cooling apparatus to which the striped steel plate cooling method of the present embodiment is applied, and also cools steel plates other than the striped steel plates. Reference numeral 2 in the drawing denotes a steel plate finish rolling mill, and the rolled steel plate is conveyed from the left to the right in the drawing and wound by a coiler 3. The payout section from the finishing mill 2 to the coiler 3 is a so-called run-out. In the case of the striped steel plate 1, the striped steel plate 1 having a high temperature of about 850 ° C. on the exit side of the finishing mill 2 is run up to about 500 ° C. Must be cooled. In addition, the code | symbol 4 in a figure is the temperature sensor provided on the steel plate conveyance line of a runout. As the temperature sensor 4, for example, an infrared temperature sensor that can detect the temperature of the steel sheet in a non-contact manner is applied.

  In this runout, a quenching device 5 is provided immediately downstream of the exit side of the finish rolling mill 2. The quenching device 5 is for quenching by spraying a large amount of cooling water on the upper and lower surfaces of the steel sheet. Essentially, the quenching device 5 is adjusted to a desired metal structure such as refinement of crystal grain size and appropriate phase fraction. Therefore, the amount of cooling water to the steel plate, the cooling rate, and the distance between the steel plate and the cooling water nozzle can be adjusted, and such a striped steel plate that does not require the metal structure adjustment is not conventionally used. In the present embodiment, as will be described later, since it is necessary to cool the striped steel plate 1 as quickly as possible in order to suppress the generation of scale and to make the scale difficult to peel off, this quenching device 5 is used for the striped steel plate 1 and finish rolling. Cooling water is blown from the upper and lower surfaces of the striped steel plate 1 from the upper and lower sides of the steel plate conveying line of the rapid cooling device 6 from directly downstream, and the striped steel plate 1 is rapidly cooled to a predetermined temperature up to the exit side of the cooling device 6. In addition, the draining roll mentioned later is provided in the exit side vicinity of the rapid cooling apparatus 6, ie, immediately downstream of the rapid cooling process, and this draining roll is arrange | positioned close to the upper surface of the striped steel plate 1, ie, a projection surface (it does not contact). Thus, most of the cooling water on the upper surface of the striped steel plate 1 is removed (this is defined as draining). Further, a large number of purge devices 6 are provided above the conveying line of the striped steel plate 1, and for example, high-pressure air is obliquely inclined from the purge device 6 with respect to the conveying direction of the striped steel plate 1 as shown in the figure. The cooling water on the upper surface of the striped steel plate 1 can be blown off.

  A cooling line 7 having a length of, for example, about 120 m is provided between the exit side of the quenching device 5 and the coiler 3. The cooling line 7 of the present embodiment has a cooling area from the first station 1ST to the (n) station (n) ST from the quenching device 5 to the coiler 3, and the steel sheet conveyed at all stations. Cooling water can be discharged from above and below. However, in the cooling method after rolling striped steel sheets of this embodiment, cooling water is sprayed only on the lower surface of the striped steel sheets 1 and cooled without discharging cooling water from above the striped steel sheets 1 at all stations. The purge device 6 is also provided above the conveying line of the cooling line 7, and high-pressure air is blown from each purge device 6 to blow off the cooling water on the upper surface of the striped steel plate 1.

  FIG. 2 is an explanatory diagram of the cooling water discharge amount at each station of the cooling line 7. Black squares at each station conceptually indicate the flow rate of the coolant (cooling water). However, the cooling water discharge amount of the (n-3) station (n-3) ST to the (n) station (n) ST is, for example, on the entry side of the (n-3) station (n-3) ST. This is based on feedback control based on the measured plate temperature of the temperature sensor 4 provided, and is variable.

FIG. 3 conceptually illustrates a method of cooling the striped steel plate 1 from the quenching device 5 by the cooling line 7. Inside the quenching device 5, cooling water heads 8 are provided above and below the steel plate conveying line, and cooling water can be sprayed from the cooling water head 8 onto the upper and lower surfaces of the steel plate being conveyed. As described above, the cooling water head 8 can be moved in the vertical direction, whereby the distance between the cooling water nozzle and the steel plate can be adjusted. Further, the cooling water head 8 can discharge a large amount of cooling water, for example, 2000 m ³ or more per minute, and this cooling water discharge amount can also be adjusted as described above. The cooling method after rolling requires less cooling water than usual.

  Further, a draining roll 9 for draining the cooling water on the upper surface of the striped steel plate 1 is disposed in the vicinity of the exit side of the quenching device 5, that is, immediately downstream of the quenching process by the cooling water head 8. Since the draining roll 9 is made of a hard metal, it cannot be brought into contact with the upper surface of the striped steel plate 1 that is a protruding surface. Therefore, as shown in FIG. 4, the draining roll 9 is disposed in a non-contact state with a slight separation from the upper surface of the striped steel plate 1. However, in the cooling process, a large amount of cooling water is sprayed on the upper and lower surfaces of the striped steel plate 1 and a large amount of cooling water is also on the upper surface of the striped steel plate 1, so even in a non-contact state, The cooling water on the upper surface of the steel plate 1 can be drained efficiently.

  The cooling water remaining mainly on the upper surface of the striped steel plate 1, that is, the plane between the protrusions, is efficiently blown off with high-pressure air from the purge device 6 until reaching the coiler 3. In addition, the cooling water on the upper surface of the striped steel plate 1 can be removed. If there is no cooling water on the upper surface of the striped steel plate 1, the plate temperature measurement by the temperature sensor 4 becomes accurate, and hardness unevenness and shape defects due to temperature unevenness due to remaining cooling water can be avoided.

  FIG. 5 is an explanatory diagram of a conventional cooling water discharge amount at each station of the cooling line 7. Since the cooling line 7 is the same as that in FIG. 1, the same reference numerals are given to the same components. The black squares in each station conceptually indicate the flow rate of the cooling water, as in FIG. In addition, the cooling water discharge amount of the (n-3) th station (n-3) ST to the (n) th station (n) ST is, for example, on the entry side of the (n-3) th station (n-3) ST. This is based on feedback control based on the measured plate temperature of the temperature sensor 4 provided, and is variable. As is apparent from the figure, in the conventional cooling method of the striped steel plate 1, the cooling water is applied not only to the bottom surface of the striped steel plate 1 but also to the top surface at the first station 1 ST to the fourth station 4 ST that are the previous stage of the cooling line 7. In the subsequent stations, cooling water is discharged only to the lower surface of the striped steel plate 1. In addition, as described above, in the conventional post-rolling cooling method for striped steel sheets, the striped steel sheet 1 is not rapidly cooled by the quenching device 5, and naturally the top surface of the striped steel sheet 1 is not drained by the draining roll 9. .

  6, the distance from the inlet side of the quenching device 5 showing the embodiment of the cooling method after rolling the striped steel plate 1 by the quenching device 5 and the cooling line 7 of FIG. 2 and the temperature change of the striped steel plate, and the FIG. The distance at the entrance side of the quenching device 5 showing the conventional example of the cooling method after rolling the striped steel sheet 1 by the cooling line 7 and the temperature change of the striped steel sheet 1 are shown. In both cases, the cooling line 7 starts at a distance of about 15 m from the entry side of the quenching device 5, and the area around the distance of 40 m from the entry side of the quenching device 5 corresponds to the fifth station 5ST of the cooling line 7. In the conventional example of FIG. 5, there is no initial quenching by the quenching device 5, whereas in the embodiment of FIG. 2, there is an initial quenching by the quenching device 5, so the temperature of the striped steel plate 1 rapidly decreases at that stage. is doing. On the other hand, both the conventional example of FIG. 5 and the embodiment of FIG. 2 have substantially the same temperature change after the fifth station 5ST of the cooling line 7.

  Therefore, in the conventional example of FIG. 5, a large amount of cooling water is discharged onto the upper and lower surfaces of the striped steel plate 1 at the first station 1ST to the fourth station 4ST of the cooling line 7 to rapidly cool the temperature. On the other hand, in the embodiment of FIG. 2, the cooling water is discharged only to the lower surface of the striped steel plate 1 at the first station 1ST to the fifth station 5ST of the cooling line 7, so that it is compared with the conventional example of FIG. The cooling is slow.

  Both the above example and the conventional example are run-outs of the same steel sheet rolling line, and the rapid cooling device 5 is already installed. However, conventionally, the quenching device 5 is not used for cooling the striped steel plate 5 because it is for adjusting the metal structure. In the present embodiment, the quenching device 5 conventionally used only for adjusting the metal structure is used for the initial quenching of the striped steel plate 1. As a result, the striped steel sheet 1 after rolling can be quickly and quickly cooled. The rapid and quick cooling of the striped steel plate 1 can suppress the generation of the scale and make the scale difficult to peel off. In addition, the cooling water on the upper surface of the striped steel plate 1 is efficiently drained by the draining roll 9 at the initial stage of the runout, and then the upper surface of the striped steel plate 1 is blown by the purge device 6 to cool the upper surface of the striped steel plate 1. Since the water is blown away, the cooling water on the upper surface of the striped steel plate 1 can be removed up to the coiler 3. On the other hand, in the conventional post-rolling cooling method for striped steel plates in which cooling water is discharged to the upper surface of the striped steel plate 1 on the downstream side of the quenching device 5 without draining, the upper surface of the striped steel plate 1 before the coiler 3. It was difficult to completely remove the cooling water.

  As described above, in the cooling method after rolling striped steel sheet according to the present embodiment, rapid cooling provided immediately downstream on the exit side of the finish rolling mill 2 is performed for cooling the striped steel sheet 1 after rolling with the protruding surface as the upper surface. The apparatus 5 sprays cooling water onto the upper and lower surfaces of the striped steel plate 1 to cool to a predetermined temperature, drains the cooling water on the upper surface of the striped steel plate 1 with a draining roll 9 provided immediately downstream of the rapid cooling step, and drains the roll 9 By spraying cooling water only on the lower surface of the striped steel plate 1 with a cooling line 7 of a predetermined length provided downstream of the striped steel plate 1 after rolling, the striped steel plate 1 after rolling can be cooled quickly and quickly, and the generation of scale is suppressed. The scale can be made difficult to peel off.

Further, since the cooling liquid on the upper surface of the striped steel plate 1 is blown off by blowing air onto the upper surface of the striped steel plate 1 from the purge device 6 provided above the steel plate conveyance line of the cooling line 7, the striped steel plate is taken up before coil winding. The cooling water on the upper surface of 1 can be removed.
In the above embodiment, a draining roll is used as the draining means immediately downstream of the rapid cooling step. However, for example, a flexible scraper can be used instead of the draining roll.

  Further, in the case where the cooling water on the upper surface of the striped steel plate 1 is dried before winding the striped steel plate 1, for example, a purge device at the latter stage of the runout is not necessarily required, but the cooling sprayed on the lower surface of the steel plate It is better to be there considering that the water wraps around the top surface.

  1 is a striped steel plate, 2 is a finish rolling mill, 3 is a coiler, 4 is a temperature sensor, 5 is a quenching device, 6 is a purge device, 7 is a cooling line, 8 is a cooling water head, and 9 is a draining roll.

Claims (3)

  When cooling the striped steel plate after rolling with the projection formed on one surface and transported with the projection surface as the upper surface on the runout, the upper and lower surfaces of the striped steel plate are cooled by a quenching device provided immediately downstream of the exit side of the finish rolling mill. The cooling water is sprayed onto the steel plate to rapidly cool to a predetermined temperature, and the cooling water on the upper surface of the striped steel plate is drained with a draining means provided immediately downstream of the rapid cooling step, and the striped steel plate is cooled with a cooling line provided downstream of the draining means. A cooling method after rolling a striped steel sheet, wherein cooling is performed by spraying cooling water only on the lower surface of the steel sheet.   2. The post-rolling cooling method for a striped steel sheet according to claim 1, wherein air is blown onto the top surface of the striped steel plate in the cooling line to blow off the cooling water on the top surface.   The post-rolling cooling method for a striped steel sheet according to claim 1 or 2, wherein the draining means is a hard draining roll that is not in contact with the upper surface of the striped steel sheet.

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