JP2007105792A - Method for setting arrangement of spray cooling nozzle, and cooling equipment for heated steel strip - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for setting an arrangement of spray nozzles for spray cooling equipment having a wide range of water volume control using two or more kinds of nozzles different in water volume and spraying area, which method is capable of uniform cooling in a direction orthogonal to the travel of a steel strip, wherein the cooling equipment is applied to obtain a steel material excellent and uniform in shape characteristics by controlled-cooling of the heated steel strip obtained by hot rolling while being restrained and passed by restraining rolls. <P>SOLUTION: The spray nozzles are arranged such that the value obtained by integrating the n-th power of the impingement pressure of sprayed cooling water to a surface to be cooled in the direction of the travel of the steel strip between each pair of restraining rolls is within minus 20% from the maximum value in the direction orthogonal to the travel of the steel strip on condition of 0.05≤n≤0.2. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a method for controlled cooling of a hot steel sheet obtained by hot rolling while restraining it with a restraining roll, and more specifically, a hot steel sheet applied to obtain a uniform steel material having good shape characteristics. The present invention relates to a cooling device.

  In order to improve the mechanical properties, workability, and weldability of steel materials, for example, high-temperature steel materials immediately after being hot-rolled are accelerated and cooled while passing on a rolling line, giving a predetermined cooling history to the steel materials. Things are generally done. However, the uneven cooling that occurs when the steel material is cooled causes a shape defect of the steel material and processing distortion, and an urgent improvement is required for the steel material quality that is required to be further improved.

  In order to solve these problems, there is a method of preventing thermal deformation by restraining a steel material with a plurality of pairs of upper and lower restraint rolls. However, with such a method, a steel material having a good shape can be obtained, but the residual stress inside the steel material may appear as deformation during customer processing, and is not a fundamental solution. Therefore, cooling the steel material uniformly is the best solution.

  As a cooling method for achieving uniform cooling, in a cooling method in which water as a cooling medium is sprayed onto a steel material by a conventional spray nozzle, equipment has been designed so that the amount of water is uniformly sprayed in the width direction of the steel material. Fig. 1 shows the nozzle arrangement of a conventional steel cooling device using an angle water distribution flat spray. The spray nozzles 1 are arranged in series in the direction orthogonal to the passing plate at an appropriate nozzle pitch S0 so that the water amount distribution in the entire direction perpendicular to the passing plate is uniform. Regarding the steel plate passing direction, the spray spray areas adjacent to each other are arranged so as not to interfere with each other.

  However, in the cooling device with such a nozzle arrangement, the cooling capacity is higher in the center of the nozzle injection range (spray injection area 2) than in the periphery, so a uniform cooling capacity distribution in the direction perpendicular to the steel plate cannot be obtained. Uneven cooling may occur.

As a method for uniformly cooling using a spray nozzle, Patent Document 1 discloses a method in which variation in cooling water collision pressure within one spray injection range is within ± 20%. Patent Document 2 proposes a method of arranging the spray interference area of the spray nozzle. Further, in Patent Document 3, it is said that uniform cooling can be achieved when all the points in the width direction of the surface to be cooled pass through the refrigerant jet collision area twice or more.

JP-A-63-338320 JP-A-8-238518 Japanese Patent Laid-Open No. 2004-306064

  In the method of Patent Document 1, a method for making the cooling capacity of the entire spray cooling range provided in a plurality of rows in the plate passing direction and the plate passing orthogonal direction uniform is not proposed. Further, in the method of Patent Document 2, the cooling capacity at the center of the nozzle injection range is high outside the nozzle injection interference area, so even if the cooling method of Patent Document 2 is used, a uniform cooling capacity distribution is not obtained. Furthermore, in the method of Patent Document 3, when spray nozzles having a cooling capacity distribution in the refrigerant collision area are arranged in a straight line in the plate direction, the collision occurs even though the refrigerant jet collision area passes twice or more. A cooling capacity difference occurs between the center of the zone and the end of the collision zone, and a uniform cooling capacity distribution cannot be obtained.

  The present invention is for solving the above-mentioned problems, and an object of the present invention is to provide a spray nozzle arrangement setting method for a spray cooling device capable of uniform cooling in the direction perpendicular to the plate passing through, and the amount of water. The present invention also provides a spray nozzle arrangement setting method for a spray cooling device having a wide water amount adjustment range using two or more types of nozzles having different spray areas.

The spray nozzle arrangement setting method of the present invention is summarized as the following configurations (1) to (4) in order to achieve uniform cooling of the hot steel plate in the direction perpendicular to the plate passing direction.
(1) Provided with a plurality of pairs of restraining rolls for restraining the hot steel plate to pass through, and a plurality of rows of spray nozzles capable of controlling the amount of cooling water injected between each pair of restraining rolls in the plate direction and / or in the direction perpendicular to the plate. In the spray nozzle arrangement setting method of the plate cooling device, the value obtained by integrating the nth power of the impinging pressure on the cooling surface of the cooling water in the plate passing direction between the pair of restraining rolls is -20% higher than the maximum value in the plate passing direction. Spray nozzle arrangement setting method, wherein spray nozzles are arranged so as to be within the range.
However, 0.05 ≦ n ≦ 0.2
(2) The spray nozzle arrangement setting method according to (1), wherein a plurality of types of nozzles having different water amounts or cooling water injection areas are used for each nozzle row between each pair of constraining rolls.
(3) The spray nozzle arrangement setting method according to (1) or (2), wherein the spray nozzle has a structure capable of mixing and jetting water and air.
(4) A hot steel sheet cooling apparatus in which the arrangement of spray nozzles is set using the method according to any one of (1) to (3).

  According to the present invention, in a cooling device using a spray nozzle, by adopting a nozzle type and nozzle arrangement that define a cooling factor called a cooling water collision pressure, which has not been studied in the past, high cooling uniformity in the direction perpendicular to the through-plate. Can be manufactured.

  In other words, since the cooling capacity can be arranged by the cooling factor called the cooling water collision pressure, when the nozzle arrangement is set experimentally, the collision pressure is increased to the nth power without actually performing the cooling experiment using the heat pieces. By experimentally obtaining a width direction distribution of values integrated in the plate passing direction, it is possible to find a nozzle arrangement having high cooling uniformity in the plate passing direction. In addition, if the pressure distribution at the collision surface is known for the nozzle to be used, high cooling uniformity is obtained in the direction perpendicular to the plate by calculating the width direction distribution of the value obtained by integrating the collision pressure to the nth power in the plate direction. A nozzle arrangement can be found.

  In addition, according to the spray nozzle arrangement setting method of the present invention, even when two or more types of nozzles having different water amounts and injection areas are used, the same cooling uniformity is achieved in the direction perpendicular to the passage plate. A spray cooling device having a uniform cooling capacity and a wide water amount adjustment range can be realized.

  Furthermore, the present invention is a spray nozzle arrangement setting method capable of achieving the same cooling uniformity even in a spray nozzle having a structure capable of mixing and jetting water and air.

  The present inventors will explain the results of research and development experiments conducted by investigating and studying factors contributing to cooling in spray cooling according to the drawings.

When cooling the stationary medium to be cooled by a single nozzle, as shown in FIG. 2 (c), the flow rate is 100 liters / min and the header pressure is 0.3MPa arranged at a position where the distance L from the cooling surface is 150mm. The average value of the amount of water and the cooling capacity is measured in the range M1, M2, M3 of 20 mm x 20 mm of the water injected from the oval nozzle (spray nozzle 1) in the range of 300 mm x 40 mm (spray spray area 2) It was made dimensionless (normalized) by dividing by the maximum value of the measured value (cooling capacity of range M1). Range M1
Is a 20mm x 20mm range located directly in front of spray nozzle 1, range M2 is a 20mm x 20mm range adjacent to range M1, and range M3 is a 20mm x 20mm range adjacent to range M2 . These ranges M1, M2, M3 are arranged in series along the longitudinal direction of the spray injection region 2. Regarding the cooling capacity, a cooling test was conducted using a rolled steel for general structure (SS400) with a thickness of 20 mm heated to 900 ° C as the object to be cooled, and the heat transfer coefficient measured when the steel surface temperature was 300 ° C. It used for evaluation as a cooling capacity.

  When the cooling capacity distribution in the spray injection area 2 is examined by comparing the cooling capacity in the ranges M1, M2, and M3, as shown in FIG. 2 (a), the water quantity in the single nozzle injection is almost the same. However, it was found that there was a difference in cooling capacity. In other words, in the case of spray cooling, the factors that contribute to cooling are not only the amount of water, but also various factors such as the droplet velocity, droplet diameter, and droplet collision angle with the object to be cooled are intricately acting. Seem.

  The present inventors have found that a cooling factor that can comprehensively represent various cooling factors including these amounts of water is a collision pressure of cooling water.

  The collision pressure distribution of cooling water averaged over the range M1, M2, and M3 of 20 mm x 20 mm was measured with the same nozzle and the same arrangement as those used in Fig. 2 (a) above, and was written together with the cooling capacity distribution. This is shown in FIG. In this way, the cooling power impinges on the 0.1th power and the cooling capacity agrees very well.

Furthermore, the present inventors investigated the relationship between the cooling water collision pressure immediately below the nozzle and the cooling capacity using eight types of nozzles having different water amounts, header pressures, and injection areas as shown in FIG. The spray nozzle 1 shown in FIG. 4 (a) is an oval nozzle in which the spray injection area 2 is elongated in one direction, and the spray nozzle 1 shown in FIG. It is a full cone nozzle. As a result, as shown in Fig. 5, it can be expressed by the same relational expression regardless of the type, specification and injection area of the nozzle. By substituting the cooling water collision pressure P [MPa] into the following expression (1) The heat transfer coefficient h [W / (m 2 · K)] can be obtained.
h = 33300 × P ^0.1 (1)

  In this test, the heat transfer coefficient was proportional to the 0.1th power of the cooling water collision pressure. However, considering the measurement error, the heat transfer coefficient is considered to be proportional to the nth power of the cooling water collision pressure. Values are considered to be in the range of 0.05 to 0.2.

  This indicates that the present invention does not depend on the nozzle type and specification, and it is also effective for a cooling device using two or more types of nozzles having different nozzle types and specifications.

  Further, the present inventors have investigated the relationship between the cooling uniformity in the direction perpendicular to the plate passing and the cooling water collision pressure when the medium to be cooled is cooled using a plurality of nozzles.

  6 (a) and 6 (b) show an outline of the cooling test. As shown in FIG. 6 (a), the inventors have developed an oval nozzle (spray nozzle 1) in which the spray spraying area 2 is between oval plate rollers 5 and 5 before and after conveying a steel plate as the cooled object 3. ) Three upwards, arranged in the direction perpendicular to the through-plate so that the nozzle interval S0 is 150 mm, and the object to be cooled 3 is installed so that the distance L between the nozzle tip and the object to be cooled 3 is 150 mm, A cooling test was performed by moving the object 3 to be cooled at a speed of 1 m / sec. In addition, as shown in FIG. 6B, five oval nozzles (spray nozzles 1) are arranged upward, the nozzle interval S0 is 150 mm, and the sheet passing direction interval S1 is 200 mm. A test was conducted. As in the case of FIG. 2, a cooling test was conducted using a general structural rolled steel (SS400) with a thickness of 20 mm heated to 900 ° C. as the object 3 to be cooled, and the steel surface temperature was 300 ° C. Occasionally measured heat transfer coefficient was used for evaluation as cooling capacity. Note that cooling water was supplied to each spray nozzle 1 via a header 4.

  6A and 6B, the cooling water collision pressure measurement is performed by arranging pressure sensors on the cooling water collision surface of the object 3 to be cooled that are not heated and arranged in the direction perpendicular to the plate at intervals of 20 mm. The cooling water collision pressure was continuously measured at an interval of 0.01 sec while moving the object 3 to be cooled at a speed of 1 m / sec, and the value obtained by adding the cooling water collision pressure measured between the passing plate rollers 5 and 5 was derived. . Furthermore, using this, it divided by the value which added the largest cooling water collision pressure, made dimensionless (normalization), and calculated | required the cooling water collision pressure distribution of the plate orthogonal direction.

  FIG. 7 (a) shows the cooling capacity distribution and the cooling water collision pressure distribution in the direction perpendicular to the passage plate in the nozzle arrangement of FIG. 6 (a). In addition, FIG. 7B shows the cooling capacity distribution and the cooling water collision pressure distribution in the direction perpendicular to the through plate in the nozzle arrangement of FIG. 6B. The vertical axis of these figures divides the cooling capacity value by the maximum cooling capacity value to make it dimensionless (normalized) and the cooling water collision pressure value by the maximum cooling capacity value. Then, a value obtained by making it dimensionless (normalizing) and further raising it to the power of 0.1 is used. As shown in FIG. 7 (a), the cooling water collision pressure and cooling capacity are maximum near 0 mm immediately above the nozzle, and the cooling water collision pressure and cooling capacity are minimum near ± 50 to 75 mm between the nozzles. Although these are somewhat different, the same tendency is shown in FIG. 7 (b), and it can be seen that the crossing plate orthogonal direction cooling capacity distribution agrees well with the 0.1th power distribution of the cooling water collision pressure.

  The present inventors changed the nozzle interval S0 in the direction orthogonal to the plate using the above-described configuration, and integrated the cooling capacity collision distribution in the plate orthogonal direction and the 0.1th power value of the cooling water collision pressure in the plate direction. The relationship between the orthogonal direction distributions was investigated, and the cooling water collision pressure distribution necessary to achieve uniform cooling in the direction orthogonal to the steel sheet was obtained. As a result, as shown in FIG. 8, the value obtained by integrating the 0.1th power value of the collision pressure on the cooling surface of the cooling water in the plate passing direction is within −20% from the maximum value in the plate passing direction. It was found that the cooling capacity is at least within 10%, and uniform cooling is possible in the direction perpendicular to the through plate.

  In the examination of FIG. 8, the 0.1th power was carried out with the 0.05th power and the 0.2th power. In a similar manner, uniform cooling can be performed in the direction perpendicular to the through plate. From this, it can be said that the width direction distribution of the value obtained by integrating the 0.05 to 0.2 power of the collision pressure on the cooling surface of the cooling water becomes an index for uniform cooling in the steel sheet orthogonal direction.

  Furthermore, for the range that can be integrated in the plate passing direction, the nozzle interval S1 in the plate passing direction was changed and investigated, and when the plate passing speed was 0.25 m / sec or more and 2 m / sec or less, and the restraint roll 5, When the distance between 5 is 2 m or less, it has been found that the integration range is preferably the total length between the constraining rolls.

  Even when the nozzle torsion angle θ is changed without changing the nozzle interval S0 in the direction perpendicular to the plate as shown in FIG. 9, two or more types of nozzles having different water amounts and injection areas as shown in FIG. Similarly, even when used in combination, the value of adding the impact pressure to the cooling surface of the cooling water in the direction of the plate is arranged so that it is within -20% of the maximum value in the direction perpendicular to the plate, It is possible to achieve uniform cooling in the direction perpendicular to the through plate.

  If there is no cooling water interference zone, measure or formulate a single cooling water collision pressure for each nozzle type and specification to be placed, and then cool when multiple nozzles are virtually placed. Even if the arrangement is set so that the water collision pressure distribution is calculated and added or integrated in the plate passing direction is within -20% of the maximum value in the plate passing direction, uniform cooling in the plate passing direction is achieved. It is possible.

  In addition, even when water and air are mixed and injected, by placing the impact pressure on the cooling surface in the direction of the plate, so that the value is within -20% of the maximum value in the direction perpendicular to the plate, The cooling capacity is within about 10%, and it is possible to achieve uniform cooling in the direction perpendicular to the through plate.

  FIG. 11 shows the arrangement of spray nozzles in the cooling test apparatus used in the study of the present invention. FIG. 11 (a) shows a cooling device in which flat nozzles 1 are arranged so as to have the same amount of cooling water in the direction perpendicular to the passage set by the conventional spray nozzle arrangement setting method, and FIG. The oval nozzle (spray nozzle 1) is set so that the nth power of the cooling water collision pressure set in the spray nozzle arrangement setting method of the invention is integrated within the plate direction in the direction perpendicular to the plate and is within -20% of the maximum value. ) Are shown respectively. In this embodiment, n = 0.1. Each of these cooling devices was subjected to a cooling test and compared. These are the same nozzle arrangement (S0 = 75mm, L = 150mm), water volume, 20mm thick x 300mm wide x 200mm long general structural rolled steel (SS400) about 900 ° C to about 400 ° C about 20 Cooled in seconds. FIG. 12 shows a comparison of the water amount ratio, the ratio of the cooling water collision pressure to the power of 0.1, and the surface temperature distribution after cooling. The surface temperature distribution after cooling was measured using a radiation thermometer.

  As apparent from FIG. 12, the conventional spray nozzle arrangement method has a more uniform distribution of cooling water in the direction perpendicular to the plate than the spray nozzle arrangement method of the present invention, but the temperature unevenness is at the same pitch as the spray nozzle interval. It has occurred. However, the spray nozzle arrangement method in which the value obtained by integrating the 0.1th power value of the cooling water collision pressure of the present invention in the plate direction is within -20% of the maximum value in the plate orthogonal direction is the conventional spray nozzle arrangement. The surface temperature distribution is more uniform. Therefore, in the cooling device in which the nozzle arrangement is set by the spray nozzle setting method of the present invention, uniform cooling can be performed in the direction perpendicular to the through plate.

It is a nozzle arrangement diagram in which the conventional amount of water is constant in the direction perpendicular to the plate. Within the same nozzle, (a) is a graph showing the relationship between the amount of water and the cooling capacity, (b) is a graph showing the relationship between the cooling water collision pressure and the cooling capacity, and (c) is a range within the spray nozzle 1 and the spray injection area 2. FIG. 4 is a side view (left view) and a front view (right view) showing a positional relationship with M1, M2, and M3. It is a table | surface which shows the water quantity of 8 types of nozzles, nozzle load pressure, the injection range, and a cooling water collision pressure. (a) is explanatory drawing which shows the injection area | region of an oval nozzle, (b) is explanatory drawing which shows the injection area | region of a full cone nozzle. It is a graph which shows the relationship between a cooling water collision pressure and cooling capacity about 8 types of nozzles from which the water quantity, header pressure, and injection area which are shown in FIG. 3 differ. (a) is a side view (b) and a plan view (b) for explaining a cooling test arrangement in which one row of nozzles is arranged in the direction perpendicular to the through-plate, and (b) is two rows of nozzles in the direction orthogonal to the through-plate. FIG. 6 is a side view (b) and a plan view (b) for explaining a cooling test arrangement arranged in a zigzag pattern. (a) is a graph showing the cross-plate orthogonal direction cooling capacity distribution and cooling water collision pressure distribution in the nozzle arrangement of FIG. 6 (a), and (b) is the cross-plate orthogonal direction cooling capacity distribution in the nozzle arrangement of FIG. 6 (b). It is a graph which shows a cooling water collision pressure distribution. It is a graph which shows the relationship between the minimum value of the crossing board orthogonal direction of the value which added the collision pressure to the cooling surface of a cooling water in the boarding direction, and the cooling capacity minimum value of the crossing board orthogonal direction. FIG. 4 is a side view (A) and a plan view (B) for explaining a cooling test arrangement in which nozzles having a twist angle are arranged in a row. They are a side view (A) and a plan view (B) for explaining a cooling test arrangement in which two rows of spray nozzles of different types and specifications are arranged. It is the cooling test apparatus used for examination of this invention. (a) is a side view (b) and a plan view (b) for explaining a cooling test apparatus using a conventional spray nozzle setting method, and (b) is a cooling test apparatus using the spray nozzle setting method of the present invention. Side view (a) and plan view (b) for explaining It is the graph which compared the water amount distribution of a steel plate orthogonal direction, cooling water collision pressure distribution, and steel material surface temperature distribution with the cooling device of this invention, and the conventional cooling device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Spray nozzle 2 Spray spray area 3 To-be-cooled body 4 Header 5 Through plate roller
L Distance from nozzle tip to cooling surface
S0 Through plate orthogonal nozzle spacing
S1 Feeding plate direction nozzle spacing θ Nozzle twist angle

Claims (4)

A through-plate cooling device comprising a plurality of pairs of restraining rolls for restraining and passing hot-steel plates, and a plurality of rows of spray nozzles that can control the amount of cooling water injected between each pair of restraining rolls. In the spray nozzle arrangement setting method, the value obtained by integrating the nth power of the impinging pressure on the cooling surface of the cooling water in the threading direction between the pair of restraining rolls is within -20% of the maximum value in the direction perpendicular to the threading plate A spray nozzle arrangement setting method, wherein the spray nozzle is arranged as described above.
However, 0.05 ≦ n ≦ 0.2 2. The spray nozzle arrangement setting method according to claim 1, wherein a plurality of types of nozzles having different water amounts or cooling water injection areas are used for each nozzle row between each pair of constraining rolls. 3. The spray nozzle arrangement setting method according to claim 1, wherein the spray nozzle has a structure capable of mixing and jetting water and air. A hot steel sheet cooling apparatus in which the arrangement of spray nozzles is set using the method according to any one of claims 1 to 3.

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