KR20120024641A - Cooling device, cooling method, manufacturing device, and manufacturing method for hot-rolled steel sheet - Google Patents

Abstract

The present invention provides a hot rolled steel sheet cooling apparatus, a hot rolled steel sheet cooling method, a hot rolled steel sheet manufacturing apparatus, and a hot rolled steel sheet, which are capable of producing a hot rolled steel sheet having ultrafine crystal grains and improving the use efficiency of cooling water. The primary objective is to provide a method. According to the present invention, the average cooling rate of the steel plate surface existing within the radius equivalent position of the work roll of the final stand is V1, the average cooling rate of the steel plate surface existing between the radius equivalent position of the work roll and the housing post exit side of the final stand. When the average cooling rate of the steel plate surface existing between V2, a cooling start point, and a housing post exit side is set to Vm, the cooling device of V1≥V2 and Vm≥400 degreeC / s, the hot rolled steel plate using the said cooling device. Hot rolled steel sheet comprising a cooling method, a final stand of hot finish rolling mill rows and a production apparatus of hot rolled steel sheet provided with the cooling device, and a step of treating the steel sheet rolled at the final stand of hot finish rolling columns using the manufacturing apparatus. It is set as the manufacturing method of.

Description

COOLING DEVICE, COOLING METHOD, MANUFACTURING DEVICE, AND MANUFACTURING METHOD FOR HOT-ROLLED STEEL SHEET}

The present invention relates to a cooling apparatus, a cooling method, a manufacturing apparatus, and a manufacturing method of a hot rolled steel sheet. In particular, the present invention relates to a cooling device, a cooling method and a manufacturing apparatus for a hot rolled steel sheet suitably used when producing a hot rolled steel sheet having ultrafine crystal grains, and a method for producing a hot rolled steel sheet having ultrafine crystal grains. .

Steel materials used for automobiles, structural materials, and the like are required to have excellent mechanical properties such as strength, workability, and toughness. In order to increase these mechanical properties collectively, it is effective to refine the crystal grains of a hot rolled steel sheet. For this reason, many manufacturing methods for obtaining the hot rolled sheet steel which have a microcrystal grain are searched. In addition, when the crystal grains are refined, it is possible to manufacture a high strength hot rolled steel sheet having excellent mechanical properties even if the amount of addition of the alloying elements is reduced.

As a method for refining the crystal grains of a hot rolled steel sheet, at a particularly after stage of hot finishing rolling, high-pressure rolling is performed to refine the austenite particles, and to accumulate rolling distortions in the particles, which are obtained after cooling (or after transformation). Known methods for miniaturizing ferrite particles are known. From the viewpoint of suppressing recrystallization and recovery of austenite particles to promote ferrite transformation, it is effective to cool the steel sheet to a predetermined temperature or lower (for example, 720 ° C or lower) in a short time after rolling. That is, in order to manufacture the hot rolled sheet steel which has microcrystal grains, it is effective to provide the cooling apparatus which can be cooled faster than before conventionally following hot finishing rolling, and to quench the steel plate after rolling.

The technique which enables manufacture of the hot rolled sheet steel which has a fine crystal grain, or the technique applicable to manufacture of a hot rolled sheet steel which has a microcrystalline particle has been disclosed so far. For example, Patent Document 1 discloses a method for producing a hot rolled steel sheet by multi-roll hot rolling of a steel sheet or slab made of carbon steel or low alloy steel containing C: 0.01 to 0.3% by mass, wherein the final rolling pass is Ar _3. A method for producing an ultrafine crystal grain hot rolled steel sheet is disclosed, which is terminated at a temperature of at least a point and cooled to 720 ° C or less within 0.4 seconds thereafter. In addition, Patent Literature 2 arranges the final stand in the hot-rolled rolling mill train, the first cooling device, the second cooling device, and the winding device in order in the steel plate conveying direction. In the production equipment for hot-rolled steel sheets in which an uncooled region is provided between the first cooling device and the second cooling device, the first cooling device has a band-shaped or elliptic classification collision zone on the surface to be cooled. And a jersey roll for blocking the coolant injected from the nozzle, wherein a pool of coolant is formed in a region between the roll of the final stand and the jersey roll, and a first cooling device. The technique which installs a jersey roll is disclosed so that the steel plate conveyed inside may be immersed in the cooling water of a pool. In addition, Patent Literature 3 discloses a cooling facility for supplying cooling water to the upper surface of the steel sheet while passing the steel sheet to a position close to the rolling mill on the entry side and / or the exit side of the rolling mill for hot rolling the steel sheet. The cooling apparatus arrange | positions the position where the cooling water after supplying the header which has a nozzle which injects a rod-shaped cooling water with respect to the upper surface of a steel plate by the dip 30 degrees-60 degrees toward a rolling mill to a steel plate is blocked by the work roll of a rolling mill. The hot rolling facility of the steel plate characterized by being provided to is disclosed. In addition, in Patent Document 3, in order to avoid the situation where the cooling water is dispersed and not in the shape of a rod and the cooling water is not prevented, the distance between the tip of the upper nozzle and the pass line is preferably 500 mm to 1800 mm. Is described.

Patent Document 1: Japanese Patent Publication No. 2005-213595 Patent Document 2: Japanese Patent No. 4029865 Patent Document 3: Japanese Patent Publication No. 2007-61838

According to the technique disclosed by patent document 1, since the steel plate whose temperature is Ar ₃ or more is cooled to 720 degreeC within 0.4 second after completion | finish of a final rolling pass, ultra-fine crystal grain (For example, crystal whose average particle diameter is 2 micrometers or less) It is thought that it becomes possible to manufacture the hot rolled sheet steel which has particle | grains. By the way, patent document 1 does not disclose the detailed structure of the cooling apparatus which can cool a steel plate to 720 degreeC within 0.4 second after completion | finish of a final rolling pass. Moreover, according to the technique disclosed by patent document 2, since the steel plate is immersed in the pool of cooling water formed in the area | region between the roll of the last stand of a hot rolling mill, and a jersey roll, the cooling efficiency of a hot rolled sheet steel can be improved. I think it is done. Here, the quench required when producing a hot rolled steel sheet having ultra-fine crystal grains has a cooling rate of at least 400 ° C / s or more, for example, as shown in Patent Literature 1, and for this purpose, the steel sheet is quenched by nuclear boiling cooling. To be required. By the way, as disclosed in Patent Literature 2, when a pool of cooling water is actively formed and the steel sheet is cooled, it is difficult to increase the collision pressure of the cooling water that collides with the surface of the steel sheet to the extent that nuclear boiling cooling is possible, thereby making it an ultrafine crystal. In order to manufacture the hot rolled sheet steel which has particle | grains, there existed a subject that further technical improvement is needed. In addition, in the quench required when producing a hot rolled steel sheet having ultra-fine crystal grains, it is necessary to set the collision pressure of the cooling water to impinge on the surface of the steel sheet to a predetermined value or more, but in the technique disclosed in Patent Document 3, It only prescribes the injection angle of the rod-shaped cooling water supplied to the main body. In addition, in Patent Document 3, since the cooling water injected into the steel sheet flows to a portion where the steel sheet and the work roll come into contact with each other, cooling from immediately after the portion is possible, but sufficient quenching is not possible with the cooling water flowing over the steel sheet after the collision. In addition, cooling of this part contributes little to formation of ultrafine crystal grains. Therefore, even if this technique is simply used, there is a problem that it is difficult to produce a hot rolled steel sheet having ultrafine crystal grains.

Here, the present invention provides a hot rolled steel sheet cooling apparatus, a hot rolled steel sheet cooling method, a hot rolled steel sheet manufacturing apparatus, and a hot rolled sheet, which are capable of producing a hot rolled steel sheet having ultrafine crystal grains and increasing the use efficiency of cooling water. It is an object to provide a method for producing a steel sheet.

MEANS TO SOLVE THE PROBLEM The present inventors performed the research investigation about manufacture of the hot rolled sheet steel (it is also called "ultrafine grain steel" hereafter) which has an ultrafine crystal grain, and acquired the following knowledge.

(1) As shown in FIG. 11, after rolling to the temperature range of Ar ₃ or more, when cooling to 720 degreeC is completed within 0.2 second, crystal grains can be further refined.

(2) In order to finish cooling of 100 degreeC drop | fall from 820 degreeC to 720 degreeC or more, for example more than ₃ points of Ar within 0.2 second after rolling, it is necessary to quench at the average cooling rate of 500 degreeC / s or more, for example. It is preferable to perform quenching at a cooling rate of 600 ° C / s or more. Here, the rolling point (the bottom dead center of the work roll in contact with the upper surface of the rolled steel sheet and the top dead center of the work roll in contact with the lower surface of the rolled steel sheet is referred to in the final stand of the hot finishing rolling train. The length of the steel plate conveyance direction of the area | region (henceforth a "stand area") from the same to the housing post exit side of the said final stand of L1 and the area | region of the steel plate conveyance direction of the area | region where rapid cooling is possible in the stand area | region is When the length is L2, the cooling rate in the section is Z1, and the length of the steel plate conveying direction in the section where rapid cooling is difficult in the stand-in area is L3, and the cooling rate in the section is Z2, {L2 × Z1 + L3 The cooling rate represented by * Z2} / L1 is an average cooling rate. When the steel sheet is cooled at a cooling rate of 600 ° C./s, the time required to lower the temperature of the steel sheet to 100 ° C. is 0.167 seconds. Therefore, in order to complete cooling within 0.2 second, it is necessary to start cooling within 0.033 second after rolling. For example, when the steel plate is moved at a speed of 10 m / s, the distance moving to 0.033 seconds is 0.33 m. Therefore, it is preferable to start the quench after rolling within the radius equivalent position of the work roll of the last stand in a hot rolling train row, and to quench continuously continuously at least in the last stand in a hot rolling train row.

(3) For example, when the rolling speed of a steel plate is 10 m / s, the distance which a steel plate moves in 0.2 second is 2 m. Moreover, the distance from the reduction point in the last stand of a general hot finishing rolling train to the housing post exit side of the said last stand is also about 2 m. For this reason, the required rapid cooling must be performed in almost the last stand. However, as represented by the rolling point pole vicinity, there exists a part which is difficult to perform rapid cooling between the rolling point and the housing post exit side of a final stand. Therefore, taking into account the presence of a portion where it is difficult to perform rapid cooling, it refers to an area excluding a portion where rapid cooling is difficult in the range of rapid cooling possible (the area from the pressure drop point to the stand exit side. The same will be described below). It is necessary to ensure the required average cooling rate in the area | region from the pressing point of a final stand to the housing post exit side of a final stand by increasing the cooling rate in this.

(4) There is a correlation between the pressure (surface pressure) at which the coolant sprayed on the steel sheet impinges on the steel sheet and the cooling rate of the steel sheet (see Fig. 6), and the cooling rate of the steel sheet is increased by increasing the pressure at which the cooling water impinges on the steel sheet. It becomes possible. In order to manufacture ultrafine grain steel, it is necessary to inject high pressure jet water toward a steel plate, and it is necessary to cool a steel plate by nuclear boiling.

Moreover, from a metallurgical standpoint, it is preferable to cool from an earlier time even within 0.2 second after rolling, and it is preferable to start cooling from the position closer to the rolling down point of a final stand. Similarly, it is desirable to cool more strongly at the position near the pressing point of the final stand. The inventors investigated the effect of particularly strong cooling on the portion close to the reduction point of the final stand, that is, within the radius equivalent position of the work roll, on the refinement of the crystal grains. Specifically, the rolling and cooling tests which changed cooling conditions within the radius equivalent position of a work roll to the housing post exit side after that were performed, and the crystal grain diameter of the ferrite structure of the obtained steel plate was investigated. In this investigation, the distance from the reduction point to the housing post exit side is 1.8 m, the work roll radius is 0.35 m, and the point on the most upstream side of the site where the injected coolant directly collides with the steel sheet (hereinafter referred to as the "cooling start point"). Sheet thickness of 0.15 m, the board | substrate speed | rate, 10 m / s, and the steel plate was 3 mm from the reduction point. In addition, the water supply pressure of cooling water was 1.5 Mpa in the cooling header part. Only the conditions which were able to achieve 2 micrometers or less which are the objectives of a crystal grain size were extracted, and a result is shown in Table 1. FIG.

[Table 1]

In Table 1, the subscript which shows the area | region within the radius equivalent position of a work roll (henceforth "region 1") is "1", and the area | region to the housing post exit side after that (in the following, Subscripts (also referred to as "region 2") are set to "2", and the cooling rates in the respective zones are V1, V2, the impingement pressure on the steel plate of the cooling water is P1, P2, and the flow rate density of the cooling water is W1. , W2. Moreover, the subscript which shows the area | region (henceforth a "full cooling zone" below) from the cooling start point (0.15m) to the housing post exit side (1.8m) is made into "m", and the average value of all cooling zones (Vm, Pm, Wm) also added. As shown in FIG. 6, the cooling rate V and the collision pressure P were correlated, and high collision pressure was required in order to obtain a high cooling rate. In addition, under the condition that the pressure (1.5 MPa) of the cooling water in the header was constant, a high cooling water injection rate was required to obtain a high collision pressure. The numerical value which substitutes this injection speed is the flow volume per unit area, ie, flow volume density (W). When the length of the sprayed cooling water in the steel plate width direction is constant, the cooling area is also constant, so the flow rate density W is an index of the amount of cooling water to be used, and may be an index for comparing the required energy of the pump to supply the cooling water. .

As shown in Table 1, the test No. which cooled to make V1 = V2. Regarding 1, the average cooling rate (Vm) in all the cooling stations was determined by the test No. Test No. 1 in which V1 was made larger than V2 while maintaining it near 615 ° C / s equal to 1. 2 and No. In 3, the refinement | miniaturization effect of a crystal grain increases, and test No. A ferrite particle diameter finer than 1 was obtained. In addition, test No. 3, the test No. 4 and test No. In 5, when V1 was lowered while maintaining V1 constant at 1600 ° C / s, the crystal grain refining effect was somewhat reduced, but the test No. 5 with an average cooling rate of 404 ° C / s. Even under the condition of 5, it was found that a target particle size of 2 m or less was still obtained. Test No. 1 and test No. 4 and test No. Comparing 5, test No. was obtained while obtaining the crystal grain refinement effect of about the same grade. 4 and test No. 5 Wm, the test No. It became smaller than 1 Wm and was able to achieve atomization efficiently with a small amount of cooling water as a whole (the use efficiency of cooling water was able to be improved). It is also possible to increase V1 further to increase the crystal grain refining effect or to increase the efficiency of use of the cooling water. However, excessive local flow density in the region 1 may interfere with the discharge of the cooling water in the rolling mill. As a result, the impact force on the steel sheet of the cooling water injection is reduced by the remaining water, and as a result, V1 may not be increased. For this reason, in consideration of drainage and the like in the rolling mill, the upper limit of the flow rate density W1 is preferably about 20 m 3 / m 2 · min, and the upper limit of the cooling rate V 1 at a plate thickness of 3 mm is correspondingly. It is about 1600 ° C / s.

This invention is completed based on the said knowledge, The summary is as follows.

Hereinafter, the present invention will be described. Incidentally, in order to facilitate understanding of the present invention, reference numerals in the accompanying drawings are appended with parentheses, but the present invention is not limited to the form shown.

The 1st aspect of this invention is arrange | positioned downstream in the final stand 11g in the hot finishing rolling train 11, and can spray high pressure jet water toward the surface of the steel plate 1 with which a pass line is conveyed. It is a cooling device 20 of a hot rolled sheet steel provided with the headers 21 and 22 provided with the some nozzle 21a, 21a, ..., 22a, 22a, ... which were installed so that it may be within the radius equivalent position of the work roll of a final stand. The average cooling rate of the steel plate surface cooled by the high pressure jet water which collided with the surface of the existing steel plate collides with the surface of the steel plate existing between the position corresponding to the radius of the work roll of the final stand and the housing post exit of the final stand. When the average cooling rate of the surface of the steel sheet cooled by one high-pressure jet water is set to V2, V1? V2, and between the cooling start point in the final stand and the housing post exit side of the final stand. The average cooling rate (Vm) of the steel plate surface cooled by the high pressure jet water which hit the surface is 400 degreeC / s or more, The cooling apparatus of the hot rolled sheet steel.

Here, a "downstream side" means the downstream side of the conveyance direction of the steel plate 1. In addition, "high pressure jet water" means the fractionation water which has the pressure which can cool the steel plate 1 for nuclear boiling. In addition, as shown in FIG. 4, the site | part which the steel plate 1 to be rolled and the work rolls 11gw and 11gw of the last stand contact | connects in more detail, as shown in FIG. The bottom dead center of the work roll 11gwu in contact with the upper surface of the steel plate 1, and the top dead center of the work roll 11gwd in contact with the lower surface of the steel plate 1. In the following, the part is also referred to as a "pressing point". The position separated by the radius of the work rolls 11gw and 11gw of the last stand to the conveyance direction downstream side of the steel plate 1. In addition, "the surface of the steel plate which exists in the radius equivalence position of the work stand of a final stand" means between the radius equivalence position of the work roll of a final stand, and the reduction point (rather than the radius equivalent position of the work roll of a final stand). The surface (upper surface and lower surface) of the steel plate 1 which exists exists. In addition, the "average cooling rate of the steel plate surface" is computed about each of several parallelogram area | regions considered when calculating the vertical component of the steel plate conveyance direction average value of the steel plate surface collision pressure of the high pressure jet water mentioned later, for example. Refers to the average value of the cooling rate. In addition, "V1" divides the upper surface (or lower surface) of the steel plate which exists in the radius correspondence position of the work roll of a final stand in plurality by the said parallelogram area, and calculates the cooling rate computed about each parallelogram area | region. Say the mean. At this time, the boundary on the upstream side of the region closest to the work roll is the point (cooling start point) closest to the most upstream side of the portion where the high-pressure jet water collides directly with the steel sheet. In the case where the high-pressure jet spray is provided closest to the roll, it corresponds to the point where the tangent drawn from the center of the nozzle injection hole reaches the steel sheet. In addition, "the housing post exit side of a final stand" means the outer surface (outer surface of a steel plate conveyance direction downstream side) of the housing post 11gh of a final stand. In addition, "V2" divides the upper surface (or lower surface) of the steel plate which exists between the radius correspondence position of the work roll of a final stand and the housing post exit side of a final stand by the said parallelogram area in multiple numbers, and is parallel to each other. It is the average value of the cooling rate computed about the quadrilateral area. In addition, "Vm" divides the upper surface (or lower surface) of the steel plate which exists between the cooling start point in a final stand and the housing post exit side of a final stand by the said parallelogram area, and divides into multiple parallelogram areas. The average value of the cooling rate computed is said.

According to a second aspect of the present invention, the vertical component of the steel plate conveying direction average value of the steel plate surface collision pressure of the high pressure jet number of the high pressure jet which collides with the surface of the steel plate existing within the radius equivalent position of the work roll of the final stand is P1, of the final stand. P1≥P2 when the vertical component of the steel plate conveyance direction average value of the steel plate surface collision pressure of the high pressure jet number which collided with the surface of the steel plate which existed between the radius correspondence position of the work roll and the housing post exit side of the final stand is P2, Moreover, the vertical component (Pm) of the steel plate conveyance direction average value of the steel plate surface collision pressure of the high pressure jet number which collided with the surface of the steel plate which exists between the cooling start point in the final stand and the housing post exit side of the final stand. It is preferable that it is 2.7 kPa or more.

Here, "the vertical component of the steel plate conveyance direction average value of the steel plate surface collision pressure of high pressure jet water" means a steel plate along the line segment of the steel plate conveyance direction in arbitrary positions in the steel plate width direction, for example, the width direction center part. The impact pressure of the high pressure jet water which a surface receives is measured or calculated, and the vertical component of what was averaged in the predetermined | prescribed area | region is called ("average collision pressure" or "average collision pressure" hereafter). In order to cool a steel plate uniformly to a board width direction, it is preferable to make the vertical component of this steel plate conveyance direction average value the same in all the regions of the steel plate width direction. Even when considered as a plane having a width corresponding to at least the nozzle pitch, it must be equal to the vertical component of the steel plate collision pressure obtained on the line segment. Therefore, in obtaining the vertical component of the said steel plate conveyance direction average value, the average collision pressure in the steel plate surface which one nozzle bears may be calculated | required for every nozzle row which runs along the conveyance direction of a steel plate, and may average it in the conveyance direction of a steel plate ( 4 and 9). In the present invention, when the nozzle is a flat spray nozzle, for example, as shown in FIG. 7, the nozzle pitch in the steel plate width direction is A, and the nozzle pitch in the conveying direction of the steel plate, that is, the header spacing is B. In this case, the average impact pressure on the steel plate surface of one nozzle is divided by the force (collision force) of the coolant that has collided with the parallelogram area represented by A × B by the area A × B of the parallelogram. It can be calculated as In the case where the nozzle is a columnar nozzle, on the other hand, when the nozzle pitch in the sheet width direction of the steel sheet is set to A and the nozzle pitch in the conveying direction of the steel sheet, B, the average collision pressure at the steel sheet surface which one nozzle is responsible for is the area. The force (collision force) of the high pressure jet water which collided with the parallelogram area represented by this AxB can be calculated by dividing by the area AxB of the parallelogram area. In addition, "Pm" divides the upper surface (or lower surface) of the steel plate which exists between the cooling start point in a final stand and the final stand housing post exit side in multiple numbers by the said parallelogram area, about each parallelogram area. The average value of the calculated average collision pressure is said.

In addition, in the first aspect of the present invention and the second aspect of the present invention, the quantity of water per unit area of the high pressure jet water injected into the surface of the steel sheet existing within a radius equivalent position of the work roll of the final stand is W1. When the quantity per unit area of the high pressure jet water sprayed on the surface of the steel plate existing between the radius equivalent position of the work roll of a final stand and the housing post exit side of a final stand is set to W2, it is preferable that it is W1≥W2.

Here, the "unit area" is not particularly limited as long as the area when the quantity W1 is derived and the area when the quantity W2 is derived are the same. The said "unit area" can use the area | region of the parallelogram used when deriving the vertical component of the steel plate conveyance direction average value of the steel plate surface collision pressure of high pressure jet water, for example.

Moreover, in the 1st aspect of the said invention, the distance of the high pressure jet water injection port of a nozzle arrange | positioned at the position closest to the work roll of a final stand and a steel plate is arrange | positioned at the position closest to the housing post exit side of D1 and a final stand. When the distance between the high pressure jet water injection port of the nozzle and the steel sheet is D2, it is preferable that D1?

In addition, in the first aspect of the present invention, the high pressure jet water is discharged from the nozzle toward the upper and lower surfaces of the steel sheet in a section from the position corresponding to the radius of the work roll of the final stand to the housing post exit side of the final stand. It is preferable that it is comprised so that injection is possible continuously in the conveyance direction of the.

Here, "from within the radius equivalent position of the work roll of a final stand" means the steel plate which exists between the radius equivalence position of the work roll of a final stand and a reduction point (rather than the radius equivalent position of the work roll of a final stand). The high pressure jet water injected from the nozzles 21a, 21a, ..., 22a, 22a, ... is supplied to the upper surface and the lower surface of (1). The exact starting point of the section which sprays high pressure jet water continuously is the point which is closest to the upstream of the site | part which a high pressure jet water impinges directly on a steel plate within the radius correspondence position of a work roll, ie, the point close to a reduction point. In the case of installing the nozzle which sprays the high pressure jet water closest to the work roll of the final stand, the point where the tangent drawn from the center of the spray hole of the nozzle to the surface of the work roll reaches the surface of the steel sheet is used. It corresponds to the exact starting point of the section which continuously injects. In addition, "the housing post exit side of a final stand" means the outer surface (outer surface of a steel plate conveyance direction downstream side) of the housing post 11gh of a final stand. In addition, "it is comprised so that jet of high pressure jet water from a nozzle can be continuously sprayed in the conveyance direction of a steel plate" means the some nozzle 21a, 21a, ..., 22a arrange | positioned at predetermined intervals in the conveyance direction of the steel plate 1, , 22a, ...) means that high-pressure jet water can be continuously sprayed toward the upper and lower surfaces of the steel sheet 1.

Moreover, in the 1st aspect of the said invention, it is preferable that the vertical component of the steel plate conveyance direction average value of the steel plate surface collision pressure of the high pressure jet water in the said section is 3.5 kPa or more in an upper surface and a lower surface.

In addition, in the first aspect of the present invention, the nozzles 21a, 21a, ..., 22a, 22a, ... are preferably flat spray nozzles.

In addition, in the first aspect of the present invention, a space capable of discharging the cooling water is secured between both the steel plate width direction cross sections of the cooling apparatus 20 and the steel plate width direction cross sections of the final stand 11g. desirable.

Here, "the steel plate width direction both end surfaces of the cooling device 20" means the outer surface of the cooling device 20 in the width direction both ends of the steel plate 1. In addition, the "steel plate width direction both end surface of 11 g of final stands" means the inner surface of the housing post 11gh of the final stand in the width direction both ends of the steel plate 1.

Moreover, in the 1st aspect of the said invention, the upper surface guide provided between the header 21 and nozzles 21a, 21a, ... provided in the upper surface side of the steel plate 1, and the said nozzle and a pass line. It is preferable that 23 is comprised integrally.

Here, the "top guide 23" means that the steel sheet 1 rolled by the final stand 11g is attached to the work rolls 11gwu of the final stand and the nozzles 21a, 21a, ... of the cooling device 20. The member of the cooling apparatus 20 installed in the upper surface side of the steel plate 1 for the purpose of preventing collision, etc. is said.

Moreover, in the 1st aspect of the said invention, the lower surface guide provided between the header 22 and nozzles 22a, 22a, ... provided in the lower surface side of the steel plate 1, and between the said nozzle and a pass line. It is preferable that 24 is comprised integrally.

Here, the "lower surface guide 24" means that the steel sheet 1 rolled by the final stand 11g is attached to the work rolls 11gwd of the final stand and the nozzles 22a, 22a, ... of the cooling device 20. The member of the cooling apparatus 20 provided in the lower surface side of the steel plate 1 for the purpose of preventing collision, etc. is said.

In addition, in the first aspect of the present invention, a plurality of headers 21, 31, 22, and 32 are provided, and at least a part of the header has a conveyance direction of the steel sheet 1 and a width direction of the steel sheet 1. It is preferable that the cooling water can be collectively supplied to the nozzles 31a, 31a, ..., 32a, 32a, ... arranged in a plurality of rows of the plurality of nozzles.

In addition, in the first aspect of the present invention, at least a portion of the header is configured to be capable of collectively supplying the cooling water to the nozzles arranged in a plurality of rows in each of the conveyance direction of the steel sheet and the width direction of the steel sheet. A plurality of headers 21 and 31 are arranged on the side, and among the headers provided on the upper surface side of the steel sheet, the header 31 arranged at least on the uppermost side in the conveying direction of the steel sheet is the conveying direction of the steel sheet and the width direction of the steel sheet. It is preferable that it is a header comprised so that cooling water can be collectively supplied to the nozzles 31a, 31a, ... arrange | positioned in multiple rows in each.

In addition, in the first aspect of the present invention, at least a part of the header is configured to be capable of collectively supplying cooling water to a nozzle arranged in a plurality of rows in each of the conveyance direction of the steel sheet and the width direction of the steel sheet. A plurality of headers 22 and 32 are arranged on the side, and among the headers provided on the lower surface side of the steel sheet, the header 32 arranged at least on the uppermost side in the conveying direction of the steel sheet is the conveying direction of the steel sheet and the width direction of the steel sheet. It is preferable that it is a header comprised so that cooling water can be collectively supplied to the nozzles 32a, 32a, ... arrange | positioned in multiple rows in each.

The 3rd aspect of this invention cools a steel plate using the cooling apparatus of the hot rolled sheet steel which concerns on the said 1st aspect of this invention or the said 2nd aspect of this invention, The cooling method of the hot rolled sheet steel characterized by the above-mentioned. to be.

The 4th aspect of this invention is the last stand 11g in the hot finishing rolling train 11, and the cooling apparatus of the hot rolled sheet steel which concerns on the 1st aspect of the said invention or the 2nd aspect of this invention. (20, 20 ') is provided in the conveyance direction of the steel plate 1 in order, The manufacturing apparatus 10 of the hot rolled sheet steel characterized by the above-mentioned.

The 5th aspect of this invention uses the manufacturing apparatus 10 of the hot rolled sheet steel which concerns on the 4th aspect of this invention, The steel plate rolled by the last stand 11g in the hot finishing rolling train 11. It is a manufacturing method of a hot rolled sheet steel, including the process of processing (1).

In this invention, the average cooling rate V1 cooled by the high pressure jet water sprayed on the surface of the steel plate which exists in the pressure reduction point side rather than the work roll radius correspondence position of a final stand has the work roll radius correspondence position of a final stand, and a final stand. It becomes more than average cooling rate V2 cooled by the high pressure jet water sprayed on the surface of the steel plate which exists between the housing post exit sides of this, and Vm≥400 degreeC / s. Moreover, in this invention, the vertical component P1 of the steel plate conveyance direction average value of the steel plate surface collision pressure of the steel plate surface collision pressure of the high pressure jet number which collided with the surface of the steel plate which exists in the pressure reduction point side rather than the radius correspondence position of the work roll of a final stand is final. It becomes more than the vertical component (P2) of the steel plate conveyance direction average value of the steel plate surface collision pressure of the high pressure jet number which hit the surface of the steel plate existing between the radius equivalent position of the work roll of a stand, and the housing post exit side of the last stand, In addition, Pm ≧ 2.7 kPa. For this reason, according to this invention, a steel plate can be quenched immediately after completion | finish of rolling of a final stand, and the use efficiency of the cooling water used when manufacturing ultra-fine grain steel can be improved. By quenching the steel sheet immediately after the end of rolling, it becomes possible to suppress recovery of austenite structure and the like. Therefore, according to the present invention, a hot rolled steel sheet cooling apparatus, a hot rolled steel sheet cooling method, a hot rolled steel sheet manufacturing apparatus, and a hot rolled sheet, which are capable of producing a hot rolled steel sheet having ultrafine crystal grains and improving the use efficiency of cooling water. It becomes possible to provide the manufacturing method of a steel plate.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows typically a part of manufacturing apparatus of the hot rolled sheet steel which concerns on this invention.
FIG. 2 is an enlarged view of a portion in which the cooling apparatus of the hot rolled steel sheet of the present invention is disposed in FIG. 1. FIG.
It is a figure which shows the example of the form of the cooling apparatus of the hot rolled sheet steel of this invention.
It is a figure explaining the concept of the vertical component of the steel plate conveyance direction average value of the steel plate surface collision pressure of the radially equivalent position of the work roll of a final stand, the exit of the housing post of a final stand, and the high pressure jet water.
5 is a conceptual diagram showing the pressure distribution of the high pressure jet water injected on the upper surface of the steel sheet.
It is a figure which shows the relationship of the steel plate conveyance direction average value of the steel plate surface collision pressure of high pressure jet water, and the average cooling rate of steel plate.
It is a figure explaining the average value per nozzle of the steel plate surface collision pressure of high pressure jet water.
It is a figure which shows the parallelogram area | region considered at the time of deriving the vertical component of the shape of the site | part which the high pressure jet water injected from the nozzle collides with the steel plate surface, and the steel plate conveyance direction average value of the steel plate surface collision pressure of high pressure jet water. Fig. 8A shows a case where the nozzle is a flat spray nozzle, and Fig. 8B shows a case where the nozzle is a columnar nozzle.
Fig. 9 shows the steel sheet conveying direction average values of the radially equivalent positions of the work rolls of the final stand and the housing post exit side of the final stand and the steel plate surface collision pressure of the high pressure jet water in the cooling apparatus of the hot rolled steel sheet according to another embodiment. It is a figure explaining the concept of a vertical component.
It is a figure which extracts and expands and shows the part in which the cooling apparatus of the hot rolled sheet steel of this invention which concerns on another form is arrange | positioned.
It is a figure which shows the relationship between the cooling time required to 720 degreeC, and a ferrite particle diameter obtained.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described, referring drawings.

FIG. 1: is a figure which shows schematically the cooling apparatus 20 of the hot rolled sheet steel of this invention, and a part of the manufacturing apparatus 10 of the hot rolled sheet steel of this invention provided with the said cooling apparatus 20. As shown in FIG. In FIG. 1, the steel plate 1 is conveyed in the direction from the left side (upstream side) to the right side (downstream side), and the up-down direction of the paper surface is a vertical direction. Below, the said upstream-downstream direction may be described in a conveyance direction, and the direction of the plate width of the plate | plate steel plate which is orthogonal to this may be described in the steel plate width direction. In addition, description of the code | symbol which is repeated may be abbreviate | omitted in drawing in order to make it easy to see.

As shown in FIG. 1, the manufacturing apparatus 10 (henceforth simply "manufacturing apparatus 10") of the hot rolled sheet steel of this invention is the hot finishing rolling train 11, and the hot rolling of this invention. The cooling apparatus 20 (henceforth the "cooling apparatus 20") of a steel plate is provided, the conveyance roll 12, and the pinch roll 13 are provided. In addition, although illustration and description are abbreviate | omitted, the heating furnace, the rough rolling column, etc. are arrange | positioned upstream rather than the hot finishing rolling column 11, and the conditions of the steel plate rolled by the hot finishing rolling column 11 are provided. On the other hand, the other side of the pinch roll 13 is arrange | positioned another cooling apparatus, a odor machine, etc., and arrange | positioned the various facilities for shipping a steel plate as a coil.

Hot rolled steel sheet is manufactured as follows approximately. That is, the crude bar extracted from the heating furnace and rolled to a predetermined thickness in the crude rolling mill is continuously rolled to a predetermined thickness in the hot finish rolling column 11 while the temperature is controlled. Then, it cools rapidly by the cooling device 20. Here, the cooling apparatus 20 is the work roll 11gw, 11gw of the last stand (henceforth the upper surface of the steel plate 1) from the inside of the housing post 11gh of the last stand of the hot finishing rolling train 11. The work roll 11gw which contacts with the "work roll 11gwu" and the work roll 11gw which contact | connects the lower surface of the steel plate 1 are provided as close as possible to the "work roll 11gwd." . And the steel plate which passed the pinch roll 13 is cooled to a predetermined winding temperature with another cooling apparatus after that, and is wound up to a coil shape by a winding machine.

As mentioned above, the manufacturing apparatus 10 is equipped with the hot finishing rolling train 11. In this embodiment, seven rolling mills 11a, 1lb, 11c, ..., 11g are parallel along a conveyance direction. Each rolling mill 11a, 1lb, ..., 11g is what is called the rolling mill which comprises each stand, and the rolling reduction rate etc. are set so that the conditions, such as thickness, mechanical property, and surface quality which are necessary for a final product, may be satisfied.

2 and 3 are enlarged views of a portion where the cooling device 20 is disposed. FIG. 2: shows the state of the cooling apparatus 20 which quenched the upper surface and the lower surface of the steel plate immediately after passing through the pressure reduction point of 11 g of final stands, The dotted line of FIG. 2 has shown the high pressure jet water. On the other hand, FIG. 3 has shown the state of the cooling apparatus 20 at the time of replacing the work roll 11gw, 11gw of 11g of final stands. 4 is the vertical component of the steel plate conveyance direction average value of the steel plate surface impact pressure of the high pressure jet water of the exit position of the housing post 11gh of the final stand, and the housing post 11gh of the last stand, and FIG. It is a figure explaining "it may also be called the average value of the collision pressure of cooling water." The paper sheet left side of FIG. 4 is a steel plate conveyance direction upstream, and the paper sheet right side of FIG. 4 is a steel plate conveyance direction downstream. 5 is a conceptual diagram illustrating the pressure distribution of the high pressure jet water injected onto the upper surface of the steel sheet 1. The vertical axis | shaft of FIG. 5 is a vertical component [kPa] of the steel plate conveyance direction average value of the steel plate surface collision pressure of the high pressure jet water sprayed on the upper surface of the steel plate 1, and the horizontal axis | shaft of FIG. 5 is the distance from the reduction point of the final stand. In addition, in FIG. 5, X1 is a position corresponded to the radius of the work roll of a final stand, and X2 is a position of the housing post exit side of a final stand. Hereinafter, the cooling device 20 will be described in detail with reference to FIGS. 2 to 5.

As shown to FIG. 2 and FIG. 3, the cooling apparatus 20 is arrange | positioned downstream of the last stand 11g in the hot finishing rolling train 11. The cooling device 20 has a plurality of flat spray nozzles 21a, 21a, ... (hereinafter, simply referred to as "nozzle 21a", etc.) that inject high-pressure jet water toward the upper surface of the steel plate 1. The connected headers 21 and 21 and flat spray nozzles 22a, 22a, ... which spray high-pressure jet water toward the lower surface of the steel plate 1 (hereinafter, may be simply referred to as "nozzle 22a"). Has multiple headers 22 and 22 connected thereto. A plurality of nozzles 21a, 21a, ... arranged at a predetermined pitch in the steel plate width direction are connected to the header 21, and the plurality of headers 21, 21, ... have a predetermined pitch in the conveying direction of the steel sheet. It is arranged. Similarly, a plurality of nozzles 22a, 22a, ... arranged at a predetermined pitch in the steel plate width direction are connected to the header 22, and the plurality of headers 22, 22, ... are predetermined in the conveying direction of the steel sheet. It is arranged in the pitch of. The headers 21, 21,... Are configured such that the cooling water can be collectively supplied to the plurality of nozzles 21a, 21a,..., Arranged at a predetermined pitch in the width direction of the steel plate 1, and the headers 22, 22,. ...) is comprised so that cooling water can be collectively supplied to the some nozzle 22a, 22a, ... arrange | positioned by the predetermined pitch in the width direction of the steel plate 1. The two rows of nozzles 21a, 21a on the upper surface side of the steel sheet 1 and the two rows of nozzles 22a, 22a on the lower surface side of the steel sheet 1, which are provided on the uppermost side of the conveying direction of the steel sheet 1, are steel sheets. Each axial direction is arrange | positioned so that it may cross | intersect with respect to a perpendicular | vertical plane so that high pressure jet water may be inclined toward the upstream of the conveyance direction of (1). In the cooling device 20, the angle (hereinafter, referred to as "vertical inclination angle") that the axial direction of the nozzles 21a and 22a arranged on the most upstream side of the steel plate 1 with respect to the vertical plane is hereinafter, It becomes more than the in-plane inclination angle provided to the nozzles 21a and 22a which adjoin the conveyance direction downstream of the said nozzle 21a, 22a and the steel plate 1. The nozzles 21a, 21a,..., And the nozzles 22a, 22a,... Disposed near the work rolls 11gw, 11gw are closer to the work rolls 11gw, 11gw. It is arranged to be close to. In addition, as the nozzles 21a, 21a, ... near the work roll 11gwu are closer to the work roll 11gwu, the angle (injection angle) with respect to the upper surface of the steel plate 1 of the injected high-pressure jet water is increased. It is arrange | positioned so that it may become small. Similarly, as the nozzles 22a, 22a, ... in the vicinity of the work roll 11gwd are closer to the work roll 11gwd, the angle (injection angle) with respect to the lower surface of the steel plate 1 of the injected high pressure jet water is smaller. It is arranged to lose.

In the cooling apparatus 20, between the nozzles 21a, 21a, ..., and the upper surface of the steel plate 1, the upper guide 23 which prevents the collision of the nozzles 21a, 21a, ..., and the steel plate 1, etc. 23 is provided, and between the nozzles 22a, 22a, ... and the lower surface of the steel plate 1, the lower surface guide 24 which prevents collision between the nozzles 22a, 22a, ..., the steel plate 1, etc. is prevented. 24) is provided. The cooling apparatus 20 is comprised integrally with the header 21 and the upper surface guide 23 provided in proximity to the work roll 11gwu of the final stand 11g, and the work roll 11gwd of the last stand 11g. The header 22 and the lower surface guide 24 which are provided in proximity to () are comprised integrally. For this reason, for example, when replacing the work rolls 11gw and 11gw of the last stand, as shown in FIG. 3, with the upper surface guide 23 provided near the work roll 11gwu of the last stand. The header 21 can be moved, and the header 22 can be moved together with the lower surface guide 24 provided in proximity to the work roll 11gwd of the final stand. The space through which the choke (not shown) of the) escapes to the operation side is empty, and the work of roll replacement becomes possible.

As shown in FIG.2 and FIG.4, when quenching the steel plate 1 using the cooling apparatus 20, the collision area of the high pressure jet injected from the nozzle 21a is the work roll of the last stand 11g. It reaches the area | region on the pressure reduction point side rather than a radius correspondence position, and the collision area of the high pressure jet injected from the nozzle 22a reaches the area | region on the pressure reduction point side rather than the work roll radius correspondence position of 11 g of final stands. 2 and 3, headers 21, 21,... To which the plurality of nozzles 21a, 21a,..., Arranged at a predetermined pitch in the steel plate width direction are connected to the cooling apparatus 20. And headers 22, 22, ... connected to a plurality of nozzles 22a, 22a, ... arranged at a predetermined pitch in the steel plate width direction are arranged at a predetermined pitch in the conveying direction of the steel sheet. For this reason, by using the cooling apparatus 20, the high pressure jet water is made into the upper surface of the steel plate 1 in the section from the position corresponding to the work roll radius of the final stand 11g to the exit side of the final stand housing post 11gh. And it can spray continuously to the lower surface. In addition, in the cooling device 20 shown in FIG.2 and FIG.4, the average cooling rate V1a of the upper surface of the steel plate 1 located in the pressing point side rather than the work roll radius correspondence position of 11 g of final stands is final. The final stand is the same as the average cooling rate V2a of the upper surface of the steel plate 1 located between the work roll radius equivalent position of the stand 11g and the exit side of the housing post 11gh of the final stand 11g. The average cooling rate V1b of the lower surface of the steel plate 1 located on the pressing point side rather than the work roll radius equivalent position of 11g is the work roll radius equivalent position of the final stand 11g and the housing post of the final stand 11g. High pressure jet water is sprayed toward the steel plate 1 so that it may become equal to the average cooling rate V2b of the lower surface of the steel plate 1 located between the exit sides of 11 gh.

On the other hand, as shown in FIG. 5, the impingement pressure average value P1 of the cooling water injected from the nozzle 21a to the area | region of the pressure reduction point side rather than the work roll radius correspondence position X1 of the last stand 11g is nozzle 21a. ) Is equal to the impingement pressure average value P2 of the cooling water injected between the work roll radius equivalent position X1 of the final stand 11g and the housing post exit side X2 of the final stand 11g. As will be described later, there is a correlation between the average pressure of the cooling water and the average cooling rate of the steel sheet, and the average cooling rate of the steel sheet can be increased by increasing the average pressure of the cooling water. For this reason, according to the cooling apparatus 20, not only the upper surface and lower surface of the steel plate which exists between the work roll radius correspondence position of the final stand 11g, and the outer surface of the housing post 11gh of the final stand 11g, but also the final The upper and lower surfaces of the steel sheet 1 existing within the work roll radius equivalent position of the stand 11g can also be quenched using high pressure jet water. In addition, as described above, in the cooling apparatus 20, the nozzles 21a, 21a, ... in the vicinity of the work roll 11gwu, as the closer to the work roll 11gwu, the steel plate of the jetted high pressure jet water ( It is arrange | positioned so that the angle (injection angle) with respect to the upper surface of 1) may become small (namely, the inclination angle in a vertical plane becomes large), and the nozzles 22a, 22a, ... in the vicinity of the work roll 11gwd are the work roll 11gwd. As it approaches, it is arranged so that the angle (injection angle) with respect to the lower surface of the steel plate 1 of injected high pressure jet water becomes small (that is, the inclination angle in a vertical plane becomes large). For this reason, the high pressure jet water which collided with the upper surface and the lower surface of the steel plate 1 which exist within the work roll radius equivalence position of the final stand 11g advances to the work roll 11gwu, 11gwd side after that, By colliding with 11 gwu and 11gwd, classification | generation occurs in the vicinity (within the work roll radius correspondence position of the last stand) of the work rolls 11gwu and 11gwd. Here, when the jet is generated on the upper and lower surfaces of the steel sheet 1, it becomes possible to increase the pressure of the fractionated water colliding with the upper and lower surfaces of the steel sheet 1. For this reason, according to the cooling apparatus 20, inject | pouring high pressure jet water into the upper surface and lower surface of the steel plate 1 which exists within the work roll radius equivalent position of 11 g of final stands, and the upper surface of the steel plate 1 And the high pressure jet water after impinging on the lower surface can quench the steel sheet 1 immediately after passing through the pressing point. Of course, P1 can also be enlarged by increasing the water supply pressure of the high pressure spray which collides within the work roll radius equivalent position, or changing the nozzle type. That is, by making the cooling device 20 into this form, it becomes possible to cool the upper surface and the lower surface of the steel plate 1 which passed the rolling point more quickly, stronger, and continuously. Therefore, according to this invention, the cooling apparatus 20 which can manufacture ultra-fine grain steel can be provided. In addition, even if the residual water is present on the surface of the steel sheet 1, the high pressure jet water can penetrate the boiling film on the surface of the steel sheet, so that the high pressure jet water is injected into the steel sheet 1 to cool the steel sheet 1 by nuclear boiling. (Quench) It becomes possible.

It is a figure which shows the relationship of the steel plate conveyance direction average value of the steel plate surface collision pressure of high pressure jet water, and the average cooling rate of steel plate. The vertical axis | shaft of FIG. 6 is an average cooling rate [degreeC / s] at the time of cooling the temperature of the steel plate of 3 mm of plate | board thickness in which cooling water does not stay on the surface from both sides (upper surface and lower surface) from 750 degreeC to 600 degreeC. The horizontal axis of 6 is a steel plate conveyance direction average value [kPa] of the steel plate surface collision pressure of high pressure jet water. As shown in FIG. 6, there is a correlation between the average value of the steel plate conveyance direction of the steel plate surface collision pressure of the high pressure jet water and the average cooling rate of the steel plate, and when the steel plate conveyance direction average value of the steel plate surface collision pressure of the high pressure jet water is increased, It is possible to increase the average cooling rate of the steel sheet. In addition, the steel plate conveyance direction average value of the steel plate surface collision pressure of high pressure jet water is A, the nozzle pitch of the steel plate width direction of cooling water which reached the steel plate surface as A, and the nozzle pitch of the steel plate conveyance direction to B as shown in FIG. In this case, the average collision pressure per nozzle, which is derived by dividing the force (collision force) of the coolant colliding with the quadrilateral region represented by the area A × B, by the area A × B of the quadrangle area, is conveyed. Is averaged in the interval of.

In this invention, the vertical component of the steel plate conveyance direction average value of the steel plate surface collision pressure of the high pressure jet water injected from the cooling apparatus 20 to the steel plate 1 shall be 2.7 kPa or more. It is preferable to set it as 3.5 kPa or more from a viewpoint of making into the form which is easy to quench the steel plate 1, suppressing recovery of austenite particle etc .. Moreover, in this invention, it is preferable to quench the steel plate 1 by the average cooling rate of 1000 degreeC / s or more from a viewpoint of making a crystal grain more refined. From the viewpoint of making the steel sheet 1 quenchable at an average cooling rate of 1000 ° C / s or more, in the present invention, the impact pressure average value of the cooling water is more preferably 8 kPa or more. The cooling rate varies with the plate thickness and is approximately inversely proportional to the plate thickness. If the cooling apparatus of the hot-rolled steel sheet of the present invention has the ability to quench a steel sheet having a sheet thickness of 3 mm at an average cooling rate of 1000 ° C./s, the steel sheet having a sheet thickness of 5 mm at an average cooling rate of 600 ° C./s. It becomes possible to quench.

As described above, the average impact pressure per nozzle is equal to the impact force of the high-pressure jet water jetted from the nozzle divided by the cooling area in charge of the nozzle. Therefore, even if the impact force is measured instead of measuring the pressure, the impact pressure average value of the cooling water can be calculated, and the collision force of the high-pressure jet water can be obtained from the flow rate and the flow rate, and the flow rate and the flow rate to the nozzle. Since it depends on water supply pressure, considering a predetermined pressure loss, the steel plate surface impingement pressure average value can also be computed roughly from the water supply pressure to a nozzle. An example of the calculation method of a steel plate surface collision pressure average value is described below.

Steel plate impact pressure average Ps = F / (A? B) [Pa]

Here, A is steel plate width direction nozzle pitch [m], B is conveyance direction nozzle pitch [m], and F is the impact force [N] to the steel plate surface of high pressure jet water. The collision force F can be calculated | required with the following formula | equation.

Impact force F = 44.7? C? Q? P 0 .5 [N]

Wherein 44.7 is a constant containing the 0.5 power of the density of water ^{[N 0 .5 s / ㎡]} , C is (? About 1.0, 0.8), the loss coefficient, q is the flow rate of the flat spray nozzle [㎥ / s], P is water supply Pressure [Pa]. In addition, the flow volume of a flat spray nozzle is determined by the relationship with water supply pressure according to a nozzle type (characteristic).

In addition, in the present invention, when the remaining water is present on the surface of the steel sheet, the pressure of the high pressure jet water injected from the nozzle 21a is reduced by the remaining water, and the high pressure jet water when reaching the surface of the steel sheet 1 is obtained. The collision pressure of is easy to reduce. For this reason, it is preferable to reduce the number of stays of the surface of the steel plate 1 from a viewpoint of making it the form which is easy to quench the steel plate 1, and the like. In view of this, in the present invention, it is preferable that a space capable of discharging the cooling water is secured between the steel plate width direction both end surfaces of the cooling device 20 and the steel plate width direction both end surfaces of the final stand 11g.

In the above description of the cooling device 20 of the present invention, the nozzles 21a, 21a,... Disposed in the vicinity of the work rolls 11gw, 11gw, and the nozzles 22a, 22a,... The shape which arrange | positioned so that the distance to 11 gw, 11 gw) is closer to (ie, D1 <D2) closer to the steel plate 1 was illustrated. By setting it as such, in the cooling apparatus 20, as it approaches the work roll 11gwu, the angle with respect to the upper surface of the steel plate 1 of the high pressure jet water injected from the nozzles 21a, 21a, ... is made small, and As the closer to the work roll 11gwd, the angle with respect to the lower surface of the steel plate 1 of the high pressure jet water jetted from the nozzles 22a, 22a, ... is reduced, V1 = V2 and P1 = P2. The cooling apparatus of the hot rolled sheet steel of this invention is not limited to the said form. In the cooling apparatus of the hot rolled sheet steel of this invention, it can also be set as D1 = D2, and it can also be set as V1> V2 or P1> P2. In the cooling apparatus of the hot rolled sheet steel of the present invention, when the high pressure jet water is injected from the nozzle in the vicinity of the work roll so that the angle (injection angle) to the surface of the steel sheet becomes smaller as the work roll of the final stand is closer, For example, the quantity W1 per unit area of the high pressure jet water sprayed on the surface of the steel sheet existing within the radius equivalent position of the work roll of the final stand, and the radius equivalent position of the work roll of the final stand and the housing post exit side of the final stand. It is also possible to set V1≥V2 or P1≥P2 by spraying the high pressure jet water so that the quantity W2 per unit area of the high pressure jet water sprayed on the surface of the steel plate existing between them becomes W1≥W2.

In addition, in the above description of the cooling device 20 of the present invention, the closer to the work roll 11gwu, the steel plate 1 of the high-pressure jet water jetted from the nozzles 21a, 21a, ... near the work roll 11gwu. Steel plate 1 of high-pressure jet water injected from nozzles 22a, 22a, ... near the work roll 11gwd, so that the angle (injection angle) with respect to the upper surface of the () becomes smaller and closer to the work roll 11gwd. Although the form which sprayed high pressure jet water was illustrated so that the angle (injection angle) with respect to the lower surface of () is reduced, the cooling apparatus of the hot rolled sheet steel of this invention is not limited to the said form. However, the steel sheet existing within the radius equivalent position of the work roll of a final stand by making the high pressure jet water sprayed within the radius equivalent position of the work roll of a final stand actively collide with the said work roll, and generate | occur | producing a classification near the rolling point. It is preferable to inject | pour high pressure jet water so that the injection angle of high pressure jet water may become small, so that the approaching surface may become a form which makes it easy to quench the surface.

In the above description of the cooling device 20 of the present invention, a form in which the flat spray nozzles 21a, 21a, ..., 22a, 22a, ... is provided is illustrated. It is not limited, It is also possible to set it as the form provided with what is called a columnar nozzle. However, it is possible to reduce the clogging of the nozzle and provide a cooling device that is easy to increase the vertical component of the average value of the steel plate conveyance direction of the steel plate surface collision pressure of the high pressure jet water even when there is a residual water on the surface. It is preferable to set it as the form provided with a flat spray nozzle from a viewpoint. In addition, since the flat spray nozzle can produce directivity in the drainage of the cooling water existing on the steel plate surface by studying the arrangement, it is also possible to improve the drainage.

Fig. 8 shows a shape example of a portion where the high pressure jet water jetted from the nozzle impinges on the surface of the steel sheet and a shape example of the quadrilateral area to be considered when deriving the vertical component of the steel plate conveying direction average value of the steel plate surface collision pressure of the high pressure jet water. It is a figure. Fig. 8A shows a case where the nozzle is a flat spray nozzle, and Fig. 8B shows a case where the nozzle is a columnar nozzle. In FIG. 8, the sheet inward / forward direction is the thickness direction of a steel plate. In addition, the site | part colored in FIG. 8 has shown the site | part which the high pressure jet water collided with the steel plate surface.

As shown in Fig. 8A, when the nozzle is a flat spray nozzle, a portion where the high pressure jet water collides with the surface of the steel sheet becomes an elliptical shape or an elongated circular shape. In this case, the area of the quadrilateral area | region (parallel quadrangle area | region) considered when deriving the perpendicular | vertical component of the steel plate conveyance direction average value of the steel plate surface collision pressure of high pressure jet water is the nozzle pitch A and the steel plate in the plate width direction of a steel plate. It can calculate by multiplying the nozzle pitch B in the conveyance direction of a. As shown in Fig. 8B, when the nozzle is a columnar nozzle, a portion where the high-pressure jet water collides with the surface of the steel sheet is circular. In this case, the area of the quadrilateral area | region (rectangular area) considered when deriving the vertical component of the steel plate conveyance direction average value of the steel plate surface collision pressure of high pressure jet water is the nozzle pitch A in the plate width direction of a steel plate, It can calculate by multiplying the nozzle pitch B in a conveyance direction.

In addition, in the said description about the cooling apparatus 20 of this invention, the form which the flat spray nozzle is arrange | positioned not only in the area | region to the housing post exit side of the last stand of a hot rolling train but also a region downstream from the said area is shown. Although the present invention is not limited to this embodiment. However, the case where it is required to rapidly cool a steel plate to temperature lower than 720 degreeC within a short time after completion | finish of rolling can also be assumed. Here, from the viewpoint of providing a cooling device capable of quenching the steel sheet continuously to a temperature lower than 720 ° C., etc., the section up to the housing post exit side of the final stand of the hot rolling train, and downstream from the section It is preferable that the flat spray nozzle is continuously arrange | positioned at the side area | region.

In addition, in the said description about the cooling apparatus 20 of this invention, the header 21 arrange | positioned at the upper surface side of the steel plate 1, and the upper surface guide 23 are comprised integrally, and also the lower surface of the steel plate 1 Although the form in which the header 22 arrange | positioned at the side and the lower surface guide 24 were comprised integrally was illustrated, the cooling apparatus of the hot rolled sheet steel of this invention is not limited to the said form. The cooling apparatus of the hot-rolled steel sheet of the present invention has a form in which the header and the lower surface guide disposed on the lower surface side of the steel sheet are not integrally formed, or a header and the upper surface guide disposed on the upper surface side of the steel sheet are not integrally formed. It is also possible. In order to be able to exchange the roll provided in the final stand of the hot tack column, the header 21 arranged close to the work roll 11gwu, the top guide 23, the header arranged close to the work roll 11gwd ( 22) and the lower surface guide 24 should just be comprised so that a movement is possible, and these can be moved using well-known means, such as a hydraulic cylinder. However, from the viewpoint of making it easy to improve the work efficiency of roll replacement, it is preferable that the header and the upper surface guide disposed on the upper surface side of the steel sheet simultaneously retract or return operation at the same time. . Similarly, it is preferable to set it as the form which integrally comprises the header arrange | positioned at the lower surface side of a steel plate.

In addition, in the said description about the cooling apparatus 20 of this invention, the some header 21, 21, which connected the some nozzle 21a, 21a, ... arrange | positioned by the predetermined pitch in the width direction of the steel plate 1, ... are arranged in a conveyance direction of the steel plate 1 at a predetermined pitch, and a plurality of headers (a plurality of nozzles 22a, 22a, ...) arranged at a predetermined pitch in the width direction of the steel plate 1 are connected ( 22, 22,... Exemplified only the forms in which the steel sheet 1 is arranged at a predetermined pitch in the conveying direction of the steel sheet 1, but the cooling apparatus of the hot rolled steel sheet of the present invention is not limited to the above-described form. In the cooling apparatus of the present invention, a header (hereinafter referred to as a "collective header") configured to be capable of collectively supplying cooling water to a plurality of nozzles arranged at predetermined pitches in the width direction of the steel sheet and the conveying direction of the steel sheet, respectively, It is also possible to set it as the form provided in the upper surface side and / or lower surface side of a steel plate. An example of the form of the cooling apparatus of the hot rolled sheet steel of this invention provided with an aggregate header is shown in FIG. FIG. 9 is a view for explaining a form example of a cooling apparatus for a hot rolled steel sheet provided with an aggregated header. FIG. 9 is a diagram illustrating a radius equivalent position of a work roll of a final stand and a housing post exit and high pressure jet water of a final stand. The concept of the vertical component of the steel plate conveyance direction average value of a steel plate surface collision pressure is shown together. In FIG. 9, the same code | symbol as the code | symbol used in FIG. 4 is attached | subjected to what is comprised similarly to the manufacturing apparatus 10 and the cooling apparatus 20, and the description is abbreviate | omitted suitably.

As shown in FIG. 9, the cooling apparatus 30 (henceforth simply "cooling apparatus 30") of the hot rolled sheet steel of this invention is a steel plate conveyance direction to the upper surface side of the steel plate 1 Aggregate type configured so that cooling water can be collectively supplied to each of the flat spray nozzles 31a, 31a, ... (hereinafter referred to simply as "nozzle 31a", etc.) constituting three rows of flat spray nozzles on the most upstream side. Each of the flat spray nozzles 32a, 32a, ...) constituting the header 31 and forming three rows of flat spray nozzles on the uppermost side of the steel sheet conveying direction on the lower surface side of the steel sheet 1 (hereinafter, simply referred to as "nozzle (32a) "or the like) is provided in the same manner as the cooling apparatus 20 except that the collective header 32 configured to be capable of supplying cooling water collectively is provided. Two rows of nozzles 31a and 31a connected to the collective header 31 so as to be able to inject high pressure jet water obliquely toward the upstream side of the conveying direction of the steel sheet 1. The two rows of nozzles 32a and 32a connected to the collective header 32 and connected to the aggregated header 32 have high pressure jet water toward the upstream side in the conveying direction of the steel sheet 1. It is connected at an angle and can be sprayed. In the cooling apparatus 30, the in-plane inclination angles of the nozzles 31a and 32a arranged on the uppermost side in the conveying direction of the steel sheet 1 are located on the downstream side in the conveying direction of the nozzles 31a and 32a and the steel sheet 1. It is more than the in-plane inclination angle provided to the adjacent nozzles 31a and 32a. Moreover, the high pressure jet water injected from the nozzles 31a and 32a arrange | positioned at the most upstream side of the conveyance direction of the steel plate 1 has reached | attained the area | region of the reduction point side rather than the radius correspondence position of the work roll of a final stand. For this reason, also in such a cooling device 30, it becomes possible to manufacture ultrafine grain steel similarly to the cooling device 20. FIG.

Thus, by using the cooling apparatus 20, 30 of this invention, it becomes possible to manufacture ultrafine grain steel. Therefore, it becomes possible to manufacture ultrafine grain steel by using the manufacturing apparatus 10 provided with the cooling apparatus 20, and the manufacturing apparatus of the hot rolled sheet steel provided with the cooling apparatus 30. As shown in FIG. In addition, the ultrafine grain steel is formed by having a step of processing the steel sheet rolled at the final stand in the hot finishing rolling column by using the manufacturing apparatus or the manufacturing apparatus of the hot rolled steel sheet provided with the cooling device 30. It becomes possible to provide the manufacturing method of a hot rolled sheet steel which can manufacture the same.

In the present invention, the distance between the nozzle disposed on the upper surface side of the steel sheet and the upper surface of the steel sheet is not particularly limited, but by bringing the nozzle close to the surface of the steel sheet, it is easy to increase the impingement pressure average value of the cooling water to quench the steel sheet. It becomes easy to make it. Here, from the viewpoint of making the steel sheet easy to quench, etc., in the present invention, the distance between the nozzle surface (injection surface of high-pressure jet water) facing the steel sheet and the steel sheet surface is preferably less than 500 mm. More preferably, it is 350 mm or less.

In addition, in the said description, although the form in which the inclination angle in a vertical plane was provided to the nozzle arrange | positioned at the steel plate conveyance direction upstream is illustrated, this invention is not limited to the said form. However, the radius of the work roll of the final stand is provided by providing an inclination angle in the vertical plane to one or two or more rows of nozzles including the nozzle row disposed at a position closest to the work roll of the final stand, particularly in the steel sheet conveying direction upstream. It is easy to make high pressure jet water collide with the upper surface and the lower surface of the steel plate which is located nearest to a roll bite even within a considerable position, and it becomes easy to quench the steel plate after rolling. For this reason, from a viewpoint of making it easy to quench the steel sheet, one or two or more rows of nozzles including nozzle rows disposed at a position closest to the work roll of the final stand (upstream side in the steel sheet conveying direction) ( It is preferable to give a vertical inclination angle to the nozzle row arrange | positioned at each of the upper surface side and the lower surface side of a steel plate, and it is preferable that the inclination angle of a vertical surface is enlarged so that the nozzle arrange | positioned upstream of a steel plate conveyance direction. In addition, from a viewpoint of making it easy to quench the steel sheet, the in-plane vertical inclination angle is given to the nozzle row disposed on the uppermost side of the steel sheet conveying direction, and the surface (high pressure jet water) More preferably, the distance between the spray surface) and the surface of the steel sheet is shortest.

In the above description, at least immediately after passing through the pressing point by impinging the high-pressure jet water continuously on the steel sheet in the region from the position corresponding to the radius of the work roll of the final stand in the hot finishing rolling train to the housing post exit side of the final stand. Since the present invention has been described in the form of quenching the steel sheet, the present invention is not limited to the form. In this invention, if it is possible to cool a steel plate to 720 degrees C or less within 0.2 second from a passing through a reduction point, the section which does not make high pressure jet water impinge continuously on a steel plate may exist in the stand | internal area. When there is a part (section in which high-pressure jet water does not collide with the steel plate continuously) exists in the in-stand area, where the rapid cooling is difficult, the cooling speed in the in-stand area except the part is increased, and the in-stand area What is necessary is just to cool a steel plate to 720 degrees C or less within 0.2 second from passage of a reduction point by ensuring the required average cooling rate in the process. As a part which is hard to implement rapid cooling which exists in the area | region inside a stand, the section between the roll bite position shown in FIG. 4 and the steel plate conveyance direction upstream end of continuous cooling range can be illustrated, for example. In addition, for example, like the cooling device 20 'of the hot rolled sheet steel shown in FIG. 10, the conveyance roll 12 is provided also in the lower surface side of the steel plate between the rolling point and the housing post exit side of a final stand. In this case, the site | part on the lower surface side of the steel plate which the collision of high pressure jet water is hindered by the said conveying roll 12 also becomes a part which is difficult to implement rapid cooling. Even if the cooling device 20 'is used, ultrafine particles can be formed by cooling the steel sheet to 720 ° C or less within 0.2 seconds from passing through the reduction point. Therefore, by using the manufacturing apparatus of the hot rolled sheet steel provided with the cooling device 20 ', and going through the cooling process by the cooling device 20', it becomes possible to manufacture ultra-fine grain steel. In addition, it is possible to manufacture ultrafine grain steel by using a hot rolled steel sheet manufacturing device having a cooling device 20 'in a form having a step of processing the steel sheet rolled at the final stand in the hot finish rolling column. It becomes possible to provide the manufacturing method of a hot rolled sheet steel.

Example

The steel plate containing 0.1 mass% of C and 1 mass% of Mn is rolled out using the rolling mill whose roll diameter 700 mm (radius 350 mm) and the distance from a rolling point to a housing post exit side are 1800 mm. The test was made to roll at the exit speed 600mpm so that thickness might be 3 mm, and to quench after that. The rolling end temperature was made 820 degreeC, and the 100 mm downstream side was made into the quenching start position from the reduction point. The average collision pressure P1 of the cooling spray from the quench start position to the roll radius equivalent position 350 mm is changed, and the average collision pressure P2 from the housing post exit side 1800 mm is changed here, and the ferrite particle size finally obtained is compared and investigated. did. In addition, when it could not fully cool to 720 degreeC in the section to the housing post exit side, it cooled using the cooling apparatus following the housing post exit side. In addition, the water supply pressure of cooling water was 1.5 Mpa in the cooling header part. The results are shown in Table 2. Condition No. 1-6 is an Example (example of this invention), and it set it as cooling rate V1≥V2, average collision pressure P1≥P2, and the flow volume W1≥W2 per unit area. Condition No. 7-8 is a comparative example, and let it be V1 <V2, P1 <P2, W1 <W2. In addition, in Table 2, the collision pressure average value of cooling water is described as "collision pressure", and the ferrite particle diameter is described as "particle diameter." In addition, in Table 2, "height D1" is a distance of the high pressure jet water injection port of the nozzle arrange | positioned at the position closest to a roll bite position, and "height D2" is arrange | positioned at the position closest to a housing post exit side. Is the distance between the high pressure jet water jet of the nozzle and the steel plate. In addition, in Table 1, an "X? Ymm section" means a section where the distance from the rolling point is Xmm? Ymm.

TABLE 2

As shown in Table 2, condition No. In 1-6, cooling rate was 400 degreeC / s or more as an average value in all the cooling zones which are V1≥V2 and the distance from a reduction point is 100 mm-1800 mm. For this reason, condition No. In 1-6, the ultrafine grain structure whose ferrite particle diameter is 2 micrometers or less was obtained. In addition, condition No. 1-6 was P1≥P2 and the average value in all the cooling zones whose distance from a rolling point is 100 mm-1800 mm was collision pressure (average collision pressure) 2.7 kPa or more. In addition, condition No. In 1-6, it was W1≥W2 and the flow volume density was 2.8 m <3> / (m <2> min) or more as an average value in the whole cooling zone whose distance from a reduction point is 100 mm-1800 mm. On the other hand, condition No. In 7, it is V1 <V2, and also P1 <P2 and W1 <W2, and the ferrite particle diameter became larger than 2 micrometers. In addition, condition No. In V8, V1≥V2, and P1≥P2 and W1≥W2, however, the average value (Vm) in all the cooling zones of the cooling rate did not satisfy the lower limit (400 ° C / s), and the total cooling zone of the collision pressure. The average value Pm in E also did not satisfy the lower limit (2.7 kPa), and the ferrite grain size was larger than 2 µm. Moreover, condition No. within the scope of the example of this invention. 1 and condition No. At 4, the same ferrite grain size was obtained, but the difference between V1 and V2 was large, and the difference between P1 and P2 was large. As for 4, the average value of flow volume density was small and there was little cooling water quantity. That is, condition No. 4 is condition No. The use efficiency of cooling water was higher than 1. Similarly, condition No. 3 and condition No. The same ferrite grain size was obtained as 6, but the difference between V1 and V2 was large, and the difference between P1 and P2 was large. As for 6, the average value of flow volume density was small and there was little cooling water quantity. That is, condition No. 6 is condition No. The use efficiency of cooling water was higher than 3. As mentioned above, the improvement effect of the refinement | miniaturization of the crystal grain by V1≥V2 and P1≥P2, and the improvement effect of the use efficiency of cooling water by increasing the difference of V1 and V2 and the difference of P1 and P2 was confirmed.

As mentioned above, although this invention was demonstrated in connection with embodiment which is considered practical and desirable at this time, this invention is not limited to embodiment disclosed in this specification, and it reads from a claim and the whole specification. It can be suitably changed in the range which does not deviate from the summary or idea of possible invention, and the cooling apparatus of a hot rolled sheet steel, the cooling method of a hot rolled sheet steel, the manufacturing apparatus of a hot rolled sheet steel, and such a manufacturing method of a hot rolled sheet steel with such a change are also present It should be understood as being included in the technical scope of the invention.

Industrial availability

The cooling apparatus of the hot rolled sheet steel of this invention, the cooling method of a hot rolled sheet steel, the manufacturing apparatus of a hot rolled sheet steel, and the manufacturing method of a hot rolled sheet steel can be used for manufacture of a hot rolled sheet steel which has an ultrafine crystal grain. Moreover, the hot rolled sheet steel which has an ultrafine crystal grain can be used as a raw material used for uses, such as an automobile, a household appliance, a mechanical structure, and a building.

1: steel sheet 10: apparatus for producing hot rolled steel sheet
11: hot finish rolling column 11g: final stand
11gh: housing post of final stand
11gw: work roll of final stand
11gwu: work roll of the final stand
11gwd: work roll of final stand
12: conveying roll 13: pinch roll
20, 20 ': cooling device of hot rolled steel sheet 21: header
21a: nozzle 22: header
22a: nozzle 23: top guide
24: lower surface guide 30: cooling device of hot rolled steel sheet
31: collective header 31a: nozzle
32: collective header 32a: nozzle

Claims (16)

Hot rolled steel sheet provided with the header which has a some nozzle arrange | positioned downstream of the last stand in a hot finishing rolling train row, and injecting high pressure jet water toward the surface of the steel plate conveyed through a pass line. As a cooling device,
The average cooling rate of the surface of the steel sheet cooled by the high pressure jet water impinging on the surface of the steel sheet existing within the radius equivalent position of the work roll of the final stand is V1, the position corresponding to the radius of the work roll of the final stand and the When the average cooling rate of the surface of the steel sheet cooled by the high pressure jet water collided with the surface of the steel sheet existing between the housing post exit side of the final stand is V2, V1? V2, The average cooling rate (Vm) of the surface of the steel sheet cooled by the high pressure jet water collided with the surface of the steel sheet existing between the cooling start point in the final stand and the housing post exit side of the final stand is 400. It is C / s or more, The cooling apparatus of the hot rolled sheet steel. The vertical component of the steel plate conveyance direction average value of the steel plate surface collision pressure of the said high pressure jet water which hit the surface of the said steel plate which existed within the radius correspondence position of the work roll of the said final stand corresponds to the radius of the work roll of P1 and the said final stand. When the vertical component of the steel plate conveyance direction average value of the steel plate surface collision pressure of the said high pressure jet water which hit the surface of the said steel plate which existed between the position and the housing post exit side of the said final stand is P2, it is P1≥P2, Moreover, the vertical component of the steel plate conveyance direction average value of the steel plate surface collision pressure of the said high pressure jet water which collided with the surface of the said steel plate existing between the cooling start point in the said final stand and the housing post exit side of the said final stand ( Pm) is 2.7 kPa or more, The cooling apparatus of the hot rolled sheet steel. The method according to claim 1 or 2,
The quantity per unit area of the high pressure jet water sprayed on the surface of the steel sheet existing within the radius equivalent position of the work roll of the final stand is W1, the radius equivalent position of the work roll of the final stand and the housing post exit side of the final stand. The cooling apparatus of the hot rolled steel sheet characterized by W1≥W2 when the quantity per unit area of the said high pressure jet water sprayed on the surface of the said steel plate which exists in between is W2. 4. The method according to any one of claims 1 to 3,
The distance between the high pressure jet water injection port of the nozzle and the steel plate disposed at the position closest to the work roll of the final stand is D1, and the high pressure jet water injection port of the nozzle arranged at the position closest to the housing post exit side of the final stand. When the distance of the said steel plate is set to D2, it is D1 <= D2, The cooling apparatus of the hot rolled sheet steel characterized by the above-mentioned. 5. The method according to any one of claims 1 to 4,
High pressure jet water can be continuously sprayed from the nozzle toward the upper and lower surfaces of the steel sheet in the conveying direction of the steel sheet in a section from a position corresponding to a radius of the work roll of the final stand to the housing post exit side of the final stand. Cooling apparatus for a hot rolled steel sheet, characterized in that the configuration. 6. The method according to any one of claims 1 to 5,
The vertical component of the steel plate conveyance direction average value of the steel plate surface collision pressure of the said high pressure jet water in the said section is 3.5 kPa or more in the said upper surface and the said lower surface, The cooling apparatus of the hot rolled sheet steel. 7. The method according to any one of claims 1 to 6,
The nozzle is a flat spray nozzle, characterized in that the hot rolled steel sheet cooling device. The method according to any one of claims 1 to 7,
A space capable of discharging the cooling water is secured between the steel plate width direction both end surfaces of the cooling device and the steel plate width direction both end surfaces of the final stand. The method according to any one of claims 1 to 8,
The header of the said steel plate provided in the upper surface side of the said steel plate, and the upper surface guide provided between the nozzle and the said pass line are comprised integrally, The cooling apparatus of the hot rolled sheet steel characterized by the above-mentioned. The method according to any one of claims 1 to 9,
The header and said nozzle provided in the lower surface side of the said steel plate, and the lower surface guide provided between the nozzle and the said pass line are comprised integrally, The cooling apparatus of the hot rolled sheet steel characterized by the above-mentioned. The method according to any one of claims 1 to 10,
A plurality of headers are provided, and at least a part of the headers are configured to be capable of collectively supplying cooling water to the nozzles arranged in a plurality of rows in each of a conveying direction of the steel sheet and a width direction of the steel sheet. Cooling device of hot rolled steel plate. The method of claim 11, wherein
A plurality of the header is disposed on the upper surface side of the steel sheet,
Of the headers provided on the upper surface side of the steel sheet, at least the header disposed on the most upstream side in the conveying direction of the steel sheet is disposed in the nozzles arranged in a plurality of rows in each of the conveying direction of the steel sheet and the width direction of the steel sheet. It is the said header comprised so that collective supply of cooling water is possible, The cooling apparatus of the hot rolled sheet steel. 13. The method according to claim 11 or 12,
A plurality of the headers are disposed on the lower surface side of the steel sheet,
Of the headers provided on the lower surface side of the steel sheet, at least the header disposed on the most upstream side in the conveying direction of the steel sheet is disposed in the nozzles arranged in a plurality of rows in each of the conveying direction of the steel sheet and the width direction of the steel sheet. It is the said header comprised so that collective supply of cooling water is possible, The cooling apparatus of the hot rolled sheet steel. The steel sheet is cooled using the cooling apparatus of the hot rolled steel sheet in any one of Claims 1-13, The cooling method of the hot rolled steel sheet characterized by the above-mentioned. A final stand in a hot finish rolling mill and a cooling device for the hot rolled steel sheet according to any one of claims 1 to 13 are provided in order in the conveying direction of the steel sheet. The manufacturing method of the hot rolled steel sheet is included, using the manufacturing apparatus of the hot rolled sheet steel of Claim 15, Comprising: The process of processing the steel plate rolled by the last stand in a hot finishing mill heat | fever.

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