JP5015034B2 - Cooling device and method for hot-rolled steel strip excellent in uniform cooling and plate feed stability - Google Patents

Description

  The present invention relates to an apparatus and a method for cooling a hot-rolled steel strip conveyed on a run-out table from the lower surface, and more particularly to a cooling device and a cooling method for a hot-rolled steel strip excellent in uniform cooling performance and sheet feeding stability. Here, the run-out table is a hot-rolled steel strip conveying device arranged on the exit side of the hot finishing rolling mill, and is composed of a plurality of table rolls.

In a continuous hot rolling line, a slab is heated to a predetermined temperature in a heating furnace, the heated slab is rolled to a predetermined thickness with a roughing mill to form a rough bar, and the rough bar is composed of a plurality of stands. Finishing and rolling with a hot finish rolling mill to obtain a steel strip with a predetermined thickness, but in order to secure the sheet temperature on the exit side of the hot finishing mill, the heat removal from the roll at the hot finishing mill is reduced. Therefore, it is necessary to increase the finishing rolling speed. In particular, in recent years, there is an increasing demand for thinning of the hot-rolled steel strip. However, since the thin steel sheet has a large surface area and is liable to cause a temperature drop, the finish rolling speed must be increased.
Accordingly, there is an increasing need for high-speed conveyance of a hot-rolled steel strip (hereinafter referred to as a steel strip) on a run-out table disposed on the exit side of the hot finish rolling mill.

  However, when the steel strip is transported at high speed, a phenomenon called flying in which the tip of the steel strip rises due to the air reaction force from the front that occurs during high-speed transport, or the steel strip that falls between the table rollers is generated by high-speed transport. Phenomenon called waving which is greatly bent due to force and rises greatly when it gets over the table roll is likely to occur. These phenomena are caused by the stable conveyance of the steel strip and the winding machine arranged on the exit side of the run-out table. Since this hinders the winding operation, there is a problem that the conveyance speed is restricted.

  As a countermeasure for this, in continuous hot rolling lines after the above-mentioned phenomenon became clear, disk-like table rolls were arranged in a staggered manner to reduce the roll pitch, but the roll pitch was reduced. The improvement measures involve large-scale remodeling and require a large number of remodeling costs to be applied to the conventional continuous hot rolling line. As an alternative, steel can be installed by installing an apron to prevent the steel strip from dropping between the table rolls. We have secured stable running of the belt.

  On the other hand, in a continuous hot rolling line, for example, a cooling strip is sprayed from a plurality of cooling nozzles arranged in the plate width direction between table rolls, and a steel strip conveyed on the run-out table is set at a predetermined temperature. However, when the uneven cooling occurs, the characteristics deteriorate, so the steel strip needs to be cooled uniformly.

However, when an apron is installed between the table rolls in order to avoid the above-described flying and waving phenomenon, a new problem has arisen in which a cooling deviation occurs in the plate width direction.
In order to cope with this problem, Patent Document 1 proposes that the apron end be accommodated in a table roll having grooves in the circumferential direction. However, since the apron width becomes narrower than the pitch of the cooling nozzle, the surface pressure when the steel strip comes into contact with the apron becomes excessive, which causes the steel strip to become crushed and the apron to break.

Moreover, in patent document 2, in order to improve a plate | board property, the upper surface height of an apron shall be 10-30 mm from a table pass line, and the diameter of the guide hole of an apron guide is set to 3-10 times the injection hole of a nozzle. Therefore, a technology for smooth discharge of the cooling water ejected from the cooling nozzle is proposed. However, if there is a space of 10 to 30 mm, there is almost no effect of suppressing flying or waving. Also, even if the hole of the jet nozzle is expanded, the bounced cooling water after the collision does not reflect so as to change the direction by 180 degrees, but flows through the plate surface by changing the direction by 90 degrees. The cooling water stays in the space surrounded by the nozzles, and this reduces the momentum of the cooling water ejected from the nozzle, so that the cooling capacity is lowered. Therefore, when the apron is installed at the full width, the accumulated cooling water can only be discharged from the end of the plate, so that a secondary flow having a flow velocity in the plate width direction is generated, resulting in a cooling deviation in the plate width direction. .
JP 2000-5807 A JP 2002-239623 A

  The problem to be solved by the present invention is to provide a cooling apparatus and a cooling method for a hot-rolled steel strip that can simultaneously achieve both stable running of the steel strip conveyed on the run-out table and uniform cooling in the plate width direction. is there. That is, it is to provide a steel strip cooling device and a cooling method that are excellent in uniform cooling and plate passing stability.

  As a result of repeated various experimental studies and theoretical studies to solve the above-mentioned problems, the inventor forms a drain hole in an intermediate portion between the nozzle hole of the apron disposed between the table rolls and the nozzle hole, By discharging cooling water that collides with the lower surface of the steel strip and descends toward the apron from the drain hole, it is possible to cool uniformly in the plate width direction while ensuring stable running of the steel strip. Obtained knowledge.

  Based on the above findings, the present inventor has conceived a cooling apparatus and a cooling method for a hot-rolled steel strip that can simultaneously achieve both stable running of the steel strip transported on the run-out table and uniform cooling in the plate width direction. . The gist is as follows.

(1) A device for cooling a hot-rolled steel strip conveyed on a run-out table from the lower surface, a plurality of cooling nozzles arranged in the plate width direction between the table rolls, and a nozzle arranged between the table rolls An apron with a straight drainage hole in the plate direction is formed in the middle of the hole and the nozzle hole, and the apron is arranged so that the distance from the upper surface of the apron to the lower surface of the hot-rolled steel strip is less than 10 mm A hot-rolled steel strip cooling device excellent in uniform cooling and plate feed stability.

(2) The cooling device for a hot-rolled steel strip excellent in uniform cooling and plate feeding stability according to (1) , wherein a surface layer portion of the apron on the hot-rolled steel strip side is formed of a carbon-based material.

(3) The cooling apparatus for a hot-rolled steel strip having excellent uniform cooling and plate feeding stability according to (1) or (2) , wherein the apron has a width of 150 to 550 mm.
(4) Uniform cooling and passing plate according to any one of (1) to (3) , wherein the plurality of cooling nozzles arranged in the plate width direction have the same inner diameter and water head pressure. Cooling device for hot-rolled steel strip with excellent stability.

(5) A method of cooling the hot-rolled steel strip conveyed on the run-out table from the lower surface,
The apron is arranged so that the distance from the upper surface of the apron to the lower surface of the hot-rolled steel strip is less than 10 mm, and the cooling water is sprayed from a plurality of cooling nozzles arranged in the plate width direction between the table rolls. Uniform cooling and passing plate characterized in that cooling water that collides with the lower surface of the belt and descends toward the apron is discharged from a linear drainage hole formed in the intermediate portion between the nozzle hole and the nozzle hole. Cooling method for hot-rolled steel strip with excellent stability.

(6) The method for cooling a hot-rolled steel strip excellent in uniform cooling and plate feeding stability according to (5) , wherein a surface layer portion of the apron on the hot-rolled steel strip side is formed of a carbon-based material.

(7) The method for cooling a hot-rolled steel strip excellent in uniform cooling and plate feeding stability according to (5) or (6) , wherein the apron has a width of 150 to 550 mm.
(8) The above-described (5) to (7), wherein the apron has a narrower width than the hot-rolled steel strip, and the plurality of cooling nozzles arranged in the plate width direction have the same inner diameter and water head pressure. The method for cooling a hot-rolled steel strip according to any one of the above, which is excellent in uniform cooling and plate feeding stability.

(A) The apron included in the cooling device according to the present invention is formed with a plurality of nozzle holes in the plate width direction, and water drain holes are formed at intermediate positions between the nozzle holes and the nozzle holes. The intermediate portion between the nozzle hole and the nozzle hole is a portion where the cooling water ejected from the adjacent cooling nozzles collides with each other by radially expanding the lower surface of the steel strip and descends toward the apron. Therefore, in the cooling device according to the present invention, the cooling water that collides with the lower surface of the steel strip and descends toward the apron is quickly discharged from the drain hole. Thus, even when the apron is not installed at the full width, the apron is not overcooled at the plate center portion, and no cooling deviation occurs in the plate width direction. In addition, since the cooling water descending toward the apron is quickly discharged from the apron, the cooling water does not stay in the space surrounded by the apron and the steel strip, and the problem of supercooling cannot occur. . That is, according to the cooling device of the present invention, it is possible to uniformly cool the steel strip in the plate width direction while ensuring stable running of the steel strip.
Similarly, in the cooling method according to the present invention, the cooling water that collides with the lower surface of the steel strip and descends toward the apron is discharged from the drain hole formed at the intermediate portion between the nozzle hole and the nozzle hole. Even if the full width is not installed, there is no overcooling at the plate center where the apron is present, and no cooling deviation occurs in the plate width direction. Further, since the cooling water descending to the apron is quickly discharged from the apron, the cooling water does not stay in the space surrounded by the apron and the steel strip, and the problem of supercooling cannot occur. That is, according to the cooling method of the present invention, it is possible to uniformly cool in the plate width direction while ensuring stable running of the steel strip.

(B) According to the cooling device and the cooling method according to the present invention in which the apron is arranged so that the distance from the upper surface of the apron to the lower surface of the steel strip is 10 mm or less, it is possible to ensure further stable traveling of the steel strip. it can.
(C) According to the cooling device and the cooling method according to the present invention in which the surface layer portion of the apron on the steel strip side is formed of a carbon-based material, even if the steel strip comes into contact with the apron, the steel strip will not be crushed. .

(D) According to the cooling device and the cooling method according to the present invention in which the apron width is 150 to 550 mm, further uniform cooling of the steel strip can be ensured.
(E) According to the cooling device and the cooling method according to the present invention in which the inner diameters and the water head pressures of the plurality of cooling nozzles arranged in the plate width direction are the same, a more reliable uniform cooling property can be ensured. . Further, it is not necessary to adjust each of the inner diameter and the water head pressure of the cooling nozzles arranged in the plate width direction according to the plate width of the steel strip being conveyed, and uniform cooling can be ensured very easily.

Hereinafter, the best mode for carrying out the present invention will be described with reference to FIGS.
FIG. 1 is a plan view of an apparatus for cooling a hot-rolled steel strip 1 (hereinafter referred to as a steel strip) conveyed on a run-out table 7 according to the prior art from the lower surface. That is, it is the figure seen from the upper surface side of the steel strip.
An apron 2 having a plurality of nozzle holes 3 formed between the table rolls 6 and having the same width as the roll body length is disposed. Similarly, a plurality of cooling nozzles 5 are disposed between the table rolls in the plate width direction. The steel strip is cooled by injecting cooling water from the cooling nozzle 5 toward the lower surface of the steel strip 1. Needless to say, the pitch of the nozzle holes 3 and the pitch of the cooling nozzles 5 are the same.

  FIG. 2 is a cross-sectional view showing the behavior of the cooling water ejected from the cooling nozzle 5 and is a view seen from the sheet passing direction of the steel strip 1. And when (a) does not arrange | position an apron, (b) arrange | positions the apron 4 in which only the nozzle hole 3 which concerns on a prior art was formed, (c) shows the nozzle hole 3 and nozzle hole 3 which concern on this invention. It is a figure when the apron 4 which formed the drain hole 4 in the intermediate part of this is arrange | positioned.

  When the apron 4 is not disposed between the table rolls 6, as shown in FIG. 2A, the cooling water ejected from the cooling nozzle 5 collides with the lower surface of the steel strip 1 and travels along the steel strip to radiate. spread. Then, the cooling water that has spread radially collides at an intermediate point between the cooling nozzle 5 and the cooling nozzle 5, changes its direction, and falls downward with a speed. Therefore, when no apron is arranged between the table rolls, the steel strip can be made uniform without causing a cooling deviation in the plate width direction if the cooling ability of the plurality of cooling nozzles 5 arranged in the plate width direction is the same. Can be cooled to.

  On the other hand, when the apron 2 in which only the nozzle hole 3 according to the prior art is formed is arranged, the cooling water ejected from the cooling nozzle 5 collides with the lower surface of the steel strip 1 as shown in FIG. Then, it spreads radially through the steel strip. Then, the cooling water spreading radially collides at an intermediate point between the cooling nozzle 5 and the cooling nozzle 5 and descends toward the apron 2 below with a speed. And since the cooling water which fell to the said apron 2 propagates along the surface of the apron, it is stirred while cooling water stays in the space surrounded by the apron 2 and the steel strip 1.

Further, even when the cooling water descending toward the apron 2 is insufficiently drained, the cooling water is stirred while staying in the space surrounded by the apron 2 and the steel strip 1. As a result, since the cooling water cools the steel strip 1, the plate center portion with the apron is overcooled when the apron is not installed at the full width. On the other hand, only the original cooling ability is exhibited at the plate edge portion without the apron, so that a cooling deviation occurs in the plate width direction. In addition, as a result of simulating under the condition that all the cooling capacities of the plurality of cooling nozzles 5 arranged in the plate width direction are the same, and the apron is installed in the plate center portion of the steel strip without installing the full width, It was confirmed that the plate edge portion without 464 W / m ² K and apron was 301 W / m ² K, and the capability difference was about 1.5 times.

As a result of repeated experiments and theoretical studies, the inventor of the present invention is the cooling water that descends toward the apron when the apron 2 is arranged between the table rolls. Yes, a drain hole 4 is formed in the middle of the nozzle hole 3 and the nozzle hole 3 of the apron 2, and the cooling water that collides with the lower surface of the steel strip 1 and descends toward the apron 2 is discharged from the drain hole 4 As a result, the technical knowledge that the steel strip 1 can be uniformly cooled in the plate width direction while ensuring stable running is obtained. In addition, as a result of implementing the simulation about the case where the drain hole is formed in the intermediate portion between the nozzle hole and the nozzle hole, the plate center portion with the apron is 334 W / m ² K, and the plate edge portion without the apron is 301 W / m. The result is ² K, and the significance of the technical knowledge obtained by the present inventor can also be confirmed from the result.

  3A and 3B are schematic views of the apron 2 used in the cooling device according to the present invention, where FIG. 3A is a plan view and FIG. 3B is a perspective view. As shown in the figure, the apron 2 according to the present invention has a nozzle hole 3 and a drain hole 4 at an intermediate portion between the nozzle hole 3 and the nozzle hole 3. Needless to say, in the apron 2 according to the present invention, the pitch of the nozzle holes 3 and the pitch of the cooling nozzles 5 are the same.

  When the apron 2 according to the present invention is disposed between the table rolls, the cooling water ejected from the cooling nozzle 5 collides with the lower surface of the steel strip 1 and travels through the steel strip as shown in FIG. Expands radially. Then, the cooling water spreading radially collides at an intermediate point between the cooling nozzle 5 and the cooling nozzle 5 and descends toward the apron 2 below with a speed. However, unlike the apron according to the prior art, in the apron 2 according to the present invention, the drain hole 4 is formed in the intermediate portion between the nozzle hole 3 and the nozzle hole 3, that is, the portion where the cooling water falls. Therefore, the cooling water descending toward the apron 2 is quickly discharged from the apron. Therefore, even when the apron is not installed at the full width, the cooling capacity is not lowered or overcooled at the plate center portion where the apron is located, and no cooling deviation occurs in the plate width direction. Further, since the cooling water descending to the apron is quickly discharged from the apron, the cooling water does not stay in the space surrounded by the apron 2 and the steel strip 1, so that the problem of overcooling cannot occur.

  About the arrangement | positioning of the apron 2, it is desirable to arrange | position so that the distance from the upper surface of the apron 2 to the lower surface of the steel strip 1 may be 10 mm or less from a viewpoint of ensuring the more stable driving | running | working of a steel strip. The reason is that it does not occur if the run-out table's conventional apron installation height and the number of semi-finished cases by flying or waving are 10 mm or less. On the other hand, the lower limit is preferably set to a distance of 5 mm or more from the upper surface of the apron 2 to the lower surface of the steel strip 1 in consideration of the impact force when colliding with the steel strip 1.

  The surface layer portion of the apron 2 on the steel strip side is preferably formed of a carbon-based material. Steel, cast iron, etc. can also be used, but from the viewpoint of suppressing the occurrence of scraping of steel strip due to contact, polyparaphenylene benzobisoxazole fiber, aramid fiber, polyparaphenylene benzobisoxazole fiber and aramid fiber A resin-impregnated sheet impregnated with a thermosetting resin is laminated on a base material woven using a double yarn obtained by twisting a blended yarn made by blending a composite fiber with glass fiber, aramid fiber and polynosic fiber. It is desirable to use a carbon-based material such as a molded resin material. Further, not only the surface layer portion on the steel strip side but also the main body portion may be formed of a carbon-based material.

  The width of the apron 2 is desirably 150 to 550 mm. First, it is desirable that it is 150 mm or more from the strength calculation at the time of collision with a steel strip. In addition, if the apron is provided to the full width, it is not possible to expect rebounding where there is no steel strip, so there is a tendency for water to be swept away. It can also cause Therefore, since the minimum plate width of the steel strip is about 550 mm, this is the preferable range as the upper limit.

Next, regarding a plurality of cooling nozzles 5 arranged in the plate width direction, it is desirable that the inner diameter and the water head pressure of the cooling nozzle 5 are the same. If the apron is narrower than the hot-rolled steel strip, there will be an apron at the plate center and no apron at the plate edge. If the pressures are not uniform, there is a possibility that a cooling deviation will occur in the plate width direction.
Further, regarding the behavior of the cooling water ejected from the cooling nozzle 5 so far, the cooling water ejected from the cooling nozzle 5 collides with the lower surface of the steel strip 1 and propagates radially through the steel strip, and spreads radially. It has been explained that the cooling water collides at the midpoint between the cooling nozzle 5 and the cooling nozzle 5 and descends toward the apron. This is based on the assumption that the nozzle inner diameter and the head pressure are the same. It is. If the nozzle inner diameter and the water head pressure of the adjacent cooling nozzles 5 are different, the cooling water collides at a position slightly deviated from the intermediate point between the cooling nozzle and the cooling nozzle, and is formed at an intermediate portion between the nozzle hole 3 and the nozzle hole 3. It may be difficult to quickly discharge the cooling water from the drained holes 4.
Alternatively, from another point of view, it is not necessary to adjust each of the inner diameter and the water head pressure of the cooling nozzles 5 arranged in the plate width direction according to the plate width of the steel strip 1 being conveyed, and uniform cooling is extremely easy. Sex can be secured.

It is a top view of the apparatus which cools the hot-rolled steel strip conveyed on the run-out table which concerns on a prior art from a lower surface, and is the figure which saw through between table rolls. It is sectional drawing which shows the behavior of the cooling water ejected from the cooling nozzle, (a) when an apron is not arranged, (b) when an apron according to the prior art is arranged, and (c) an apron according to the present invention. It is a figure when arrange | positioning. It is a schematic diagram of the apron used for the cooling device which concerns on this invention, (a) is a top view, (b) is a perspective view.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steel strip 2 Apron 3 Nozzle hole 4 Drain hole 5 Cooling nozzle 6 Table roll 7 Runout table

Claims (8)

An apparatus for cooling a hot-rolled steel strip conveyed on a run-out table from the lower surface,
A plurality of cooling nozzles arranged in the plate width direction between the table rolls;
Provided with an apron formed between the table rolls and a nozzle hole and a water drainage hole that is linear in the plate direction in the middle of the nozzle hole ,
An apparatus for cooling a hot-rolled steel strip excellent in uniform cooling and plate feeding stability, wherein the apron is disposed so that the distance from the upper surface of the apron to the lower surface of the hot-rolled steel strip is less than 10 mm . The apparatus for cooling a hot-rolled steel strip according to claim 1 , wherein a surface layer portion of the apron on the hot-rolled steel strip side is formed of a carbon-based material. The apparatus for cooling a hot-rolled steel strip having excellent uniform cooling and plate feeding stability according to claim 1 or 2 , wherein the apron has a width of 150 to 550 mm. The hot rolling excellent in uniform cooling and plate feeding stability according to any one of claims 1 to 3 , wherein the plurality of cooling nozzles arranged in the plate width direction have the same inner diameter and water head pressure. Steel strip cooling device. A method of cooling a hot-rolled steel strip conveyed on a run-out table from the bottom surface,
The apron is arranged so that the distance from the upper surface of the apron to the lower surface of the hot-rolled steel strip is less than 10 mm, and the cooling water is sprayed from a plurality of cooling nozzles arranged in the plate width direction between the table rolls. Uniform cooling and passing plate characterized in that cooling water that collides with the lower surface of the belt and descends toward the apron is discharged from a linear drainage hole formed in the intermediate portion between the nozzle hole and the nozzle hole. Cooling method for hot-rolled steel strip with excellent stability. 6. The method for cooling a hot-rolled steel strip according to claim 5 , wherein a surface layer portion of the apron on the hot-rolled steel strip side is formed of a carbon-based material. The method for cooling a hot-rolled steel strip excellent in uniform cooling and plate feeding stability according to claim 5 or 6 , wherein the apron has a width of 150 to 550 mm. Even apron narrower than the hot rolled strip, to any one of claims 5-7, characterized in that the same multiple inner and hydraulic head pressure of the cooling nozzles disposed in the plate width direction The method for cooling a hot-rolled steel strip, which is excellent in the uniform cooling property and the sheet passing stability described in the above.

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