JP7014245B2 - Steel bar cooling method and cooling mist spraying device, and steel bar manufacturing method - Google Patents

Description

In the present invention, a bundle of steel bars (hereinafter referred to as a bundle of steel bars) is obtained by binding a predetermined number of steel bars cut to a predetermined length after hot rolling is completed, the steel bars are fed to the cooling bed, and the steel bars are discharged from the cooling bed to a predetermined length. A cooling method in which atomized cooling water (hereinafter referred to as cooling mist) is sprayed onto an aggregate (hereinafter referred to as a stacked body) in which the steel bar bundles are stacked in a grid shape in a plurality of stages. It relates to a spraying device and a method for manufacturing steel bars.

Generally, steel bars are made by feeding steel pieces (for example, billets) obtained by continuous casting to a heating furnace, heating them to a predetermined temperature, and then hot rolling them to make a long round bar-shaped material, and then cooling the floor. It is manufactured through a process of air-cooling in the air and then cutting to a predetermined length. Since the steel bars thus obtained are used in straightening and inspection processes, it is necessary to cool the steel bars to 50 ° C or lower from the viewpoint of improving the accuracy of those operations and improving the durability of the equipment used.

Therefore, a technique for further cooling a steel bar discharged from a cooling bed and cut to a predetermined length is being studied.

For example, a technique is being studied in which a steel bar bundle in which a fixed number of steel bars are bundled is transported by a crane or the like to form a grid-shaped stack, and the steel bar is air-cooled as it is. Since this cooling technology is a technology for slowly cooling by dissipating heat to the atmosphere, it is possible to prevent deformation such as warping and bending of the steel bar. However, it is inevitable that the time required for cooling will be long, and although it will change depending on the dimensions of the steel bars, the arrangement of the steel bars in the stack, the temperature around the stack, the air volume, etc., it will be cooled to 50 ° C or less. However, it takes about 3 to 5 days. Therefore, there are problems such as insufficient storage space for stacks or a large amount of labor for inventory management.

Patent Document 1 discloses a technique in which a steel bar bundle is air-cooled, cooled to the _MS point, and then immersed in water. With this technique, it is not necessary to stack steel bar bundles as a stack, and cooling can be performed in a short time, so that the work efficiency of the cooling process can be improved. However, since the temperature of the cooling water in the water tank rises due to repeated immersion water cooling, it is necessary to circulate the cooling water between the water tank and the cooling tower in order to stably maintain the cooling capacity.

Therefore, the technique disclosed in Patent Document 1 requires not only a water tank and a cooling tower but also a pipe for circulating cooling water, which complicates the equipment and requires a great deal of labor for its maintenance. In addition, there is a problem that deformation such as warpage and bending of the steel bar is likely to occur due to rapid cooling by immersion water cooling.

Japanese Unexamined Patent Publication No. 2017-221968

An object of the present invention is to solve the problems of the prior art and to provide a cooling method capable of cooling a steel bar efficiently with a simple device without causing warping or bending, and further. It is an object of the present invention to provide a cooling mist spraying device suitable for the cooling method, and a method for manufacturing a steel bar to which the cooling method is applied.

The present inventor has studied a technique for efficiently cooling steel bars with a simple device. Then, attention was paid to the fact that the stacking body in which the steel bar bundles are stacked in the shape of a multi-tiered girder has excellent air permeability to the blast in the horizontal direction. In other words, if a technology for efficiently cooling steel bars by blowing air is developed, it is not necessary to install large-scale equipment (for example, a water tank, a cooling tower, piping, etc.), and simple equipment (for example, a blower, etc.) can be used for cooling.

As a result of conducting research in this way, it was found that if a horizontal airflow is supplied to the stack of steel bars, the airflow easily passes through the inside of the stack, so that the entire stack can be cooled efficiently.

Next, in order to further increase the cooling capacity, the cooling means used in combination with the horizontal air flow was studied. As a result, it is possible to further improve the cooling capacity by turning the cooling water into fine mist-like water droplets and spraying them together with a horizontal air flow, and since the cooling speed is slower than the immersion water cooling, the warp of the steel bar It turned out that it can prevent bending. A water tank or a cooling tower is not required for cooling with such a cooling mist.

If the surface of the steel bar is scaled (for example, deposits, rust, etc.) by spraying the cooling mist, the scale can be removed after the spraying of the cooling mist is stopped, and the steel bar can be straightened or inspected without any problem. be able to.

The present invention has been made based on such findings.
That is, in the present invention, steel bars cut to a predetermined length after hot rolling is completed, are fed to the cooling bed, and are discharged from the cooling bed are bundled to form a steel bar bundle, and two bundles of the steel bars are bundled. As described above, the first stage is formed by stacking them flat with each other at intervals and substantially parallel to each other, and then, as the second stage, two or more bundles of steel bars are spaced apart from each other and flat at a substantially right angle to the steel bundles of the first stage. In a cooling method in which two or more stages of stacks are formed and cooled by stacking them in a grid shape and then stacking steel bars from the third stage onward in a grid shape as needed. This is a cooling method in which a steel bar is cooled by spraying a cooling mist composed of water droplets having an average particle diameter of 300 μm or less on the sides or corners.
Further, in the present invention, a fixed number of steel bars cut to a predetermined length after hot rolling is completed, are fed to the cooling bed, and are discharged from the cooling bed are bundled to form a steel bar bundle. Two or more bundles of steel bars are spaced apart from each other and stacked almost in parallel to form the first stage, and then two or more bundles of steel bars are spaced apart from each other as the second stage and the first stage steel bundles are separated from each other. In a cooling method in which steel bars from the third stage onward are stacked in a grid pattern by stacking them flat at almost right angles, and then a stack of two or more stages is formed and cooled by stacking steel bars from the third stage onward in a grid pattern as needed. This is a cooling method for cooling steel bars by spraying a cooling mist composed of water droplets having an average particle diameter of 300 μm or less on the side surfaces or corners of a stack.
In the present invention, in order to obtain water droplets having a desired average particle size, a mist nozzle designed and manufactured so as to obtain water droplet mist having a predetermined particle size on the precondition of a predetermined amount of water, water pressure, etc. is used. do.
That is, in the present invention, the average particle size (Sauter average particle size) of the water droplets of the cooling mist is 300 μm or less, so that a cooling mist composed of water droplets having an average particle size (Sauter average particle size) of 300 μm or less can be obtained. It means that the cooling mist is injected by the mist nozzle designed and manufactured.

In the method for cooling steel bars of the present invention, it is preferable to spray the cooling mist horizontally on the side surface of the stack, and the average particle size of the water droplets of the cooling mist is preferably in the range of 20 to 150 μm, and 20 to 20 to. It is more preferably within the range of 120 μm.
The horizontal direction referred to in the present invention includes a direction within a range of ± 10 degrees in the vertical direction with respect to the horizontal direction. It is preferably within the range of ± 5 degrees.

Further, in the present invention, steel bars cut to a predetermined length after hot rolling is completed and fed to the cooling bed and discharged from the cooling bed are bound to form a steel bar bundle, and the steel bar bundle is 2 The first stage is formed by stacking the bundles or more at intervals and stacking them almost parallel to each other, and then as the second stage, two or more bundles of steel bars are spaced apart from each other and substantially perpendicular to the first stage steel bundles. It is a spraying device that sprays cooling mist onto a stack of two or more stages formed by stacking steel bundles of the third and subsequent stages in a grid shape by stacking them flat and then stacking them in a grid shape as needed. The mist nozzle that generates mist, the blower that generates an air flow for blowing the cooling mist from the mist nozzle to the side surface or corner of the stack, and the average particle size of the water droplets of the cooling mist sprayed on the stack are controlled to 300 μm or less. It is a cooling mist spraying device having a control unit and a cooling mist.
Further, in the present invention, a fixed number of steel bars cut to a predetermined length after hot rolling is completed, are fed to the cooling bed, and are discharged from the cooling bed are bundled to form a steel bar bundle. Two or more bundles of steel bars are spaced apart from each other and stacked almost in parallel to form the first stage, and then two or more bundles of steel bars are spaced apart from each other as the second stage and the first stage steel bundles are separated from each other. It is a spraying device that sprays cooling mist on two or more stages of stacks formed by stacking steel bars from the third stage onward in a grid shape as needed by stacking them flat at almost right angles. There are mist nozzles that generate cooling mist, blowers that generate airflow to blow the cooling mist from the mist nozzles to the sides or corners of the stack, and the average particle size of the water droplets of the cooling mist that blows onto the stack. It is a cooling mist spraying device having a control unit for controlling to 300 μm or less.

In the cooling mist spraying device of the present invention, it is preferable to spray the cooling mist horizontally on the side surface of the stack, and the average particle size of the water droplets of the cooling mist controlled by the control unit is in the range of 20 to 150 μm. It is preferably in the range of 20 to 120 μm.

Further, the present invention is a method for manufacturing a steel bar, in which a steel bar bundle cooled by any of the above cooling methods is recovered from a stack and the steel bar bundle is further unbundled.

In the method for producing steel bars of the present invention, it is preferable to recover the cooled steel bar bundle from the stack, further unbundle the steel bar bundle to take out the steel bar, and then remove the scale of the steel bar.

According to the present invention, it is possible to cool a steel bar efficiently with a simple device without causing warping or bending, which is extremely effective in industry.

It is a perspective view which shows the example of the stacking body which piled up the steel bar bundle in the shape of a grid. It is a perspective view which shows typically the example of the cooling mist spraying apparatus. It is a top view schematically showing the example of cooling the stack shown in FIG. 1 by the spraying apparatus shown in FIG. It is a top view schematically showing the example of cooling the stack shown in FIG. 1 by the spraying apparatus shown in FIG.

For steel bars, steel pieces (for example, billets) obtained by continuous casting are sent to a heating furnace to heat them to a predetermined temperature, and then hot rolling is performed to make a long round bar-shaped material, which is then placed on a cooling bed. It is manufactured through the steps of air cooling and then cutting to a predetermined length (that is, the length required by the product standard, for example, about 4 to 13 m). In order to further cool the steel bars thus obtained, a predetermined number of steel bars are bundled to form a steel bar bundle, and the steel bars are stacked in a grid shape to form a stack. FIG. 1 is a perspective view schematically showing an example of a stack.

Here, the stack 2 will be described with reference to FIG.
First, a predetermined number of steel bars 3 are bundled to form a steel bar bundle 4, and a large number of steel bars 4 are stacked in a grid shape. The number of steel bars 3 constituting the steel bar bundle 4 may be different for each steel bar bundle 4. However, from the viewpoint of improving the work efficiency of the process of bundling the steel bars 3 to produce the steel bars 4 and / or from the viewpoint of improving the stability of the stack 2 when a large number of steel bars 4 are stacked in a grid shape. , It is preferable that the number of steel bars 3 constituting the steel bar bundle 4 is constant. For example, a fixed number of steel bars (10 in the example of FIG. 1) are bundled to form a steel bar bundle 4, and a large number of steel bars 4 are stacked in a grid shape. At this time, in order to further stabilize the stacking body 2, it is more preferable to unify the arrangement of the steel bars 3 in each steel bar bundle 4 (3-4 pieces-3 pieces in the example of FIG. 1) and bind them together. In FIG. 1, the binding band for binding the steel bars 3 is not shown.

Then, as the first stage of the stacking body 2, two or more bundles of steel bars 4 (6 bundles in the example of FIG. 1) are arranged substantially in parallel, and the steel bars 4 are stacked flat with a space between them. The interval is a passage for the cooling mist, which will be described later, to pass through the inside of the stack 2, and an interval is provided between the steel bar bundles 4 adjacent to each other. However, the spacing does not necessarily have to be the same.

The reason why the steel bar bundles 4 are arranged substantially in parallel is to allow the cooling mist to efficiently pass between the adjacent steel bar bundles 4. It is preferable that the steel bar bundles 4 are arranged exactly in parallel, but even if they are not necessarily parallel, there is no problem as long as the cooling mist can pass through. Therefore, a deviation within ± 10 ° with respect to the average value in the direction of the steel bar bundle 4 is allowed. The deviation in the direction of the steel bar bundle 4 is more preferably within ± 5 °. Almost parallel means that the deviation is within this range with respect to the average value in the direction of the steel bar bundle 4.

Further, in order to prevent the steel bars 3 in the steel bar bundle 4 from coming into contact with the floor surface of the storage place and causing scratches, a gantry 1 is installed on the floor surface, and the steel bar bundle 4 is placed on the gantry 1. Is preferable.

Next, as the second stage of the stacking body 2, two or more bundles of steel bars 4 (6 bundles in the example of FIG. 1) are arranged substantially at right angles to the steel bundles 4 of the first stage, and between the steel steel bundles 4. By stacking them flat at intervals, they are stacked in a grid shape.

When arranging two or more bundles of steel bars 4 as the second stage of the stacking body 2 by a crane or the like, the direction of the steel rod bundles 4 is made substantially perpendicular to the steel bundles 4 of the first stage of the stacking body 2. This is to facilitate the insertion of a hanging tool (for example, a claw or the like) that lifts the steel bar bundle 4 in the second stage. The second-stage steel bar bundles 4 are preferably aligned exactly at right angles to the first-stage steel bar bundles 4, but the hangers may be easily inserted even if they are not necessarily at right angles. There is no problem. Therefore, a deviation within ± 10 ° with respect to the average value in the direction of the steel bar bundle 4 is allowed. The deviation in the direction of the steel bar bundle 4 is more preferably within ± 5 °. The term "nearly right angle" means that the deviation is within this range with respect to the average value in the direction of the steel bar bundle 4.

When stacking the stacking bodies 2 in three or more stages, the steel bar bundles 4 of the third and subsequent stages are continuously stacked in a grid shape in the same manner as the steel strip bundles of the second stage, and the stacking bodies as shown in FIG. 1 are stacked. Form 2.

A cooling mist is sprayed on the side surface or the corner of the stacked body 2 thus obtained to cool the steel bar bundle 4. An example of the cooling mist spraying device of the present invention is shown in FIG. 2 as a perspective view.
The side surface refers to a flat surface portion other than the square portion on the side surface portion when the stacked body 2 is regarded as a substantially square pillar shape (rectangular parallelepiped shape).

In the blowing device 7 shown in FIG. 2, a plurality of mist nozzles 6 are arranged around or in front of the axial flow type blower 5, and the airflow generated by the blower 5 causes cooling mist to be stacked from the mist nozzle 6. Spray on 2. In FIG. 2, the hose that supplies the cooling water to the mist nozzle 6 is not shown.

Further, although not shown, a high-pressure air nozzle may be used as the blower 5 to blow the cooling mist from the mist nozzle 6 onto the stack 2. Alternatively, it is possible to use a bifluid nozzle of air and water.

Further, although not shown, the spraying device 7 has a control unit that controls the average particle size of the water droplets of the cooling mist to be sprayed on the stack 2 within a predetermined range. The control unit can also control the mist nozzle 6 to spray the cooling mist horizontally on the side surface of the stack 2. The control unit can also control other functions of the spraying device 7. The control unit is not particularly limited, but may be an information processing device such as a computer having a CPU (Central Processing Unit).

It is preferable that the spraying device 7 is arranged on the side surface of the stack 2 so as to face the distance between the steel bar bundles 4 (see FIG. 3). That is, by spraying the cooling mist on the side surface of the stacking body 2 together with the horizontal air flow, the cooling mist enters the stacking body 2 from the distance between the steel bar bundles 4 and further smoothly passes through the inside of the stacking body 2. , The entire stack 2 can be efficiently cooled.
Further, it is preferable to perform the spraying at a speed at which the horizontal airflow reaches the central portion of the stack 2. By doing so, the cooling mist enters the stacking body 2 and smoothly passes through the inside of the stacking body 2, so that the entire stacking body 2 can be efficiently cooled. Further, it is more preferable to blow an air flow that passes through the stack 2 at 0.5 m / sec or more and 5 m / sec or less. If it is less than 0.5 m / sec, the entire stack 2 cannot be cooled efficiently, and it may take time to cool. On the other hand, if it is larger than 5 m / sec, the cooling mist passes through the stack 2 before it evaporates, and not only the cooling efficiency is lowered, but also the cooling mist is scattered to other places and the surrounding area is water. There is a fear of getting wet. It is preferable to install the spraying device 7 near the steel bar bundle if it does not interfere with the stacking of the steel bar bundle. This is because the cooling mist is attenuated by the surrounding atmosphere by the time it reaches the stack 2, so that it is necessary to blow at a higher wind speed in order to obtain a desired wind speed. The wind speed of the above airflow can be measured by a known anemometer.

The water droplets of the cooling mist sprayed on the stack 2 evaporate by heat exchange with the steel bar bundle 4 (that is, the steel bar 3). Therefore, it is not necessary to install equipment for collecting water droplets (for example, a water tank tower) and equipment for circulating use as cooling water (for example, cooling tower, piping, etc.). When scale (for example, rust) is generated on the surface of the steel bar 3 by spraying the cooling mist, the steel bar bundle 4 is collected from the stack 2 and further released from the bundle (hereinafter referred to as unbundle) to release the steel bar 3 After taking out the scale, the scale is removed and sent to a subsequent process (for example, processing, inspection, etc.). The means for unbunching the steel bar bundle 4 and the means for removing the scale are not particularly limited, and conventionally known techniques are used.

The smaller the average particle size of the water droplets of the cooling mist, the smaller the amount of heat required for evaporation, and the easier it is to evaporate. However, if the average particle size is less than 20 μm, the water droplets of the cooling mist enter the inside of the stack 2 together with the air flow and then evaporate before reaching the central portion. Therefore, it is necessary to cool the entire stack 2. It can be difficult.
On the other hand, as the average particle size is larger, the amount of heat required for evaporation increases, and the time required for cooling can be shortened. However, if the average particle size exceeds 300 μm, water droplets will remain even after the entire stack 2 has been cooled, so equipment for collecting water droplets and equipment for circulating use as cooling water must be installed. However, it takes a lot of labor to maintain complicated equipment. Further, since the water droplets are large, it is difficult to get on the air flow, and it is difficult to cool the entire stacking body 2. Therefore, the average particle size of the water droplets of the cooling mist is set to 300 μm or less. If it is 300 μm or less, there is almost no residue of water droplets after cooling, and equipment for collecting water droplets becomes unnecessary. More preferably, it is in the range of 20 to 150 μm, and if it is within this range, the cooling mist easily reaches the inside of the steel bar by the above-mentioned air flow, the cooling efficiency is improved, and the cooling steel bar 3 is stored in the place. The floor surface does not get extremely wet, which improves workability. The larger the average particle size of the water droplets, the larger the cooling capacity, so that the time required to cool the steel bar to a desired temperature can be shortened, but the floor surface of the storage place for the steel bar 3 after cooling tends to remain wet. On the other hand, the smaller the average particle size of the water droplets, the easier it is for the floor surface of the steel bar 3 to dry after cooling, but the cooling capacity is small, so the time required to cool the steel bars to the desired temperature is longer. become longer. Therefore, when carrying out the present invention, the average particle size of water droplets is in the range of 20 to 150 μm in consideration of the balance between the time required for cooling and the tolerance of the wetness of the floor surface of the storage place after cooling. You can select within. More preferably, the average particle size of the water droplet is 20 to 120 μm.
The method for controlling the particle size of the water droplets of the cooling mist is not particularly limited, and a mist nozzle designed to generate a cooling mist having a desired particle size by using a known method is used. It's fine. Further, as described above, the control unit (not shown) controls the stacking body 2 to spray the cooling mist composed of water droplets having a predetermined average particle diameter onto the mist nozzle 6.
In the present invention, in order to obtain water droplets having a desired average particle size, a mist nozzle designed and manufactured so as to obtain water droplet mist having a predetermined particle size on the precondition of a predetermined amount of water, water pressure, etc. is used.
That is, in the present invention, the average particle size (Sauter average particle size) of the water droplets of the cooling mist is 300 μm or less, so that a cooling mist composed of water droplets having an average particle size (Sauter average particle size) of 300 μm or less can be obtained. It means that it is injected by a mist nozzle that has been designed and manufactured.

When the metallurgical transformation of the steel bar 3 occurs by spraying the cooling mist onto the stack 2 to cool the steel bar 3, the steel bar 3 is deformed (for example, warped, bent, etc.), or the mechanical properties of the steel bar 3 are changed. Problems such as changes may occur, which may hinder the progress of the subsequent process. Therefore, it is preferable to spray the cooling mist after the metallurgical transformation of the steel bar 3 is completed.

In order to carry out a cooling experiment using round bar steel as the bar steel, steel bar bundles were piled up in a grid shape to form a stack. The stacking body consists of 9 bundles of steel bars, which are bundled with 17 round steel bars, arranged in parallel at intervals of 9 bundles to form the first stage. They were arranged at right angles and stacked in a grid pattern to form a total of 10 stages. Therefore, it is a stacking body larger than the example shown in FIG. In this way, nine stacks were formed.

Then, the cooling mist was sprayed onto the stack from the spraying device (see FIG. 2). The conditions for spraying the cooling mist are as shown in Table 1.

The spraying device uses a large factory fan (diameter 450 mm) as a blower, and has four mist nozzles arranged in front of it. The total flow rate of the cooling water sprayed as the cooling mist was 4 L / min, and the water temperature was 30 ° C. The wind speed of the large fan was 7 m / sec, and the wind speed of the airflow passing through the opposite side of the steel bar bundle was 1.5 m / sec when it was installed at a position 300 mm away from the stack.

Round steel bar is a carbon steel for machine structure containing 0.42 to 0.48% by mass of C, and has a diameter of 55 mm and a length of 7 m. The temperature of the round bar steel when the stacking was completed was 350 ° C., which was a temperature at which no metallurgical transformation occurred even when cooled from this state.

While cooling this stack, the time required for the maximum temperature of the round bar steel to drop to 50 ° C was measured. The maximum temperature of the round bar steel was measured from above using a two-dimensional radiation thermometer, and was measured by detecting the maximum temperature within the measurement range. The results are shown in Table 1 as the cooling time. The average atmospheric temperature of the stacking area was 34 ° C.

Reference example 1 in Table 1 is an example in which a cooling mist (average particle diameter 150 μm) is sprayed horizontally and diagonally on the corners of the stack (that is, the intersections of steel bar bundles) using a spraying device (see FIG. 4). ). In Reference Example 1 , when the maximum temperature of the round bar steel dropped to 50 ° C, the surface of the round bar steel and the floor surface of the storage place were partially wet, but it was not necessary to collect water droplets, and the round bar steel was deformed. No (for example, warpage, bending, etc.) was observed. The time required to cool down to 50 ° C was 45 hours.

The second aspect of the invention is an example in which a cooling mist (average particle diameter 150 μm) is sprayed horizontally on the side surface of the stack using a spraying device (see FIG. 3). In Example 2 of the present invention, when the maximum temperature of the round bar steel was lowered to 50 ° C., the surface of the round bar steel and the floor surface of the storage place were partially wet, but it was not necessary to collect water droplets and the round bar steel was deformed. No (for example, warpage, bending, etc.) was observed. In addition, the time required for the temperature to drop to 50 ° C. was 31 hours, which was shorter than that in Reference Example 1 . This is because by spraying the cooling mist on the side surface of the stack, the cooling mist enters the inside of the stack and passes through the stack more smoothly, so that the cooling capacity is improved.

The third aspect of the invention is an example in which a cooling mist (average particle diameter 80 μm) is sprayed horizontally on the side surface of the stack using a spraying device (see FIG. 3). In Example 3 of the present invention, when the maximum temperature of the round bar steel was lowered to 50 ° C., the surface of the round bar steel was wet, but the floor surface of the storage place was not wet, it was not necessary to collect water droplets, and the round bar steel was not necessary. No deformation (for example, warpage, bending, etc.) was observed. In addition, the time required for the temperature to drop to 50 ° C. was 32 hours, which was shorter than that of Reference Example 1 . This is because by spraying the cooling mist on the side surface of the stack, the cooling mist enters the inside of the stack and passes through the stack more smoothly, so that the cooling capacity is improved.

The fourth aspect of the invention is an example in which a cooling mist (average particle diameter 40 μm) is sprayed horizontally on the side surface of the stack using a spraying device (see FIG. 3). In Example 4 of the present invention, when the maximum temperature of the round bar steel was lowered to 50 ° C., the surface of the round bar steel was partially wet, but the floor surface of the storage place was not wet and it was not necessary to collect water droplets. .. Moreover, no deformation (for example, warping, bending, etc.) of the round bar steel was observed. In addition, the time required for the temperature to drop to 50 ° C. was 33 hours, which was shorter than that of Reference Example 1 . This is because by spraying the cooling mist on the side surface of the stack, the cooling mist enters the inside of the stack and passes through the stack more smoothly, so that the cooling capacity is improved.

The fifth aspect of the invention is an example in which a cooling mist (average particle diameter 20 μm) is sprayed horizontally on the side surface of the stack using a spraying device (see FIG. 3). In Example 5 of the present invention, when the maximum temperature of the round bar steel drops to 50 ° C., the surface of the round bar steel and the floor surface of the storage place do not get wet, it is not necessary to collect water droplets, and the round bar steel is deformed (for example, warped). , Bending, etc.) were not observed. In addition, the time required for the temperature to drop to 50 ° C. was 34 hours, which was shorter than that of Reference Example 1 . This is because by spraying the cooling mist on the side surface of the stack, the cooling mist enters the inside of the stack and passes through the stack more smoothly, so that the cooling capacity is improved.

The sixth aspect of the invention is an example in which a cooling mist (average particle diameter of 15 μm) is sprayed horizontally on the side surface of the stack using a spraying device (see FIG. 3). In Example 6 of the present invention, when the maximum temperature of the round bar steel drops to 50 ° C., the surface of the round bar steel and the floor surface of the storage place do not get wet, it is not necessary to collect water droplets, and the round bar steel is deformed (for example, warped). , Bending, etc.) were not observed. In addition, the time required for the temperature to drop to 50 ° C. was 42 hours, which was longer than that of Example 5. This is because the amount of cooling mist that evaporates before reaching the central part of the stack has increased, and the cooling capacity has decreased.

In Reference Example 1 and Invention Examples 2 to 6, scale was generated on some round bar steels after the spraying of the cooling mist was stopped, but the scale could be easily removed by shot blasting.

On the other hand, Comparative Example 1 is an example in which the stack is gently cooled by dissipating heat to the atmosphere without spraying the cooling mist. Therefore, it took 91 hours for the maximum temperature of the round bar steel to drop to 50 ° C., which was significantly increased as compared with Reference Example 1 and Invention Examples 2 and 3.

Comparative Example 2 is an example in which a blowing device is used, but the blower is stopped, cooling mist (average particle diameter 40 μm) is generated from the mist nozzle, and the cooling mist is drifted by the natural wind of the storage place. Therefore, since the mist was not sprayed on the stack, the cooling mist scattered over a wide area and adhered not only to the stack but also to the floor of the storage area, the spraying device, and the thermal image camera. The cooling experiment of the stack was stopped.

Comparative Example 3 is an example in which cooling water (average particle diameter 400 μm) is sprayed horizontally on the side surface of the stack using a spraying device (see FIG. 3). Since the particle size was large, it was difficult to get into the air flow, only the blower side of the stack 2 was cooled, and the floor surface of the storage place got wet a lot, the cooling experiment of the stack was stopped.

After the cooling experiment described above is completed, any steel bar bundle is recovered from the stacks of Reference Example 1 , Invention Examples 2 to 6 and Comparative Examples 1 to 3, and further bundled to form one round bar steel. When it was taken out and the structure was observed under a microscope, all of them had a ferrite-pearlite structure, and no abnormal structure was observed.

Although an example of cooling a round bar steel (that is, a steel bar having a circular cross section) is shown here, the object of the present invention is not limited to the round bar steel, and the square bar steel (that is, a polygon having a rectangular cross section or the like) is used. Needless to say, it can also be applied to cooling steel bars.

1 Stand 2 Stacked body 3 Bar steel 4 Bar steel bundle 5 Blower 6 Mist nozzle 7 Spraying device

Claims (10)

After hot rolling is completed, the steel bars are fed to the cooling bed, and after being discharged from the cooling bed, steel bars cut to a predetermined length are bound to form a steel bar bundle, and two or more bundles of the steel bars are spaced apart from each other. The first stage is formed by stacking them in parallel in parallel with a deviation of within ± 10 ° from the average value in the longitudinal direction of the steel bars , and then two or more bundles of steel bars are spaced apart from each other as the second stage. By stacking flatly at right angles to the steel bars of the first stage with a deviation of within ± 10 ° from the average value in the longitudinal direction of the steel bars of the second stage, they are piled up in a grid pattern, and then three or more stages are continued. In the cooling method in which the steel bars of the third and subsequent stages are stacked in a grid shape to form a stack of two or more stages and cooled.
A method for cooling a steel bar, which cools the steel bar by horizontally blowing a cooling mist composed of water droplets having an average particle diameter of 300 μm or less on the side surface of the stack. After hot rolling is completed, the steel bars are fed to the cooling bed, and after being discharged from the cooling bed, steel bars cut to a predetermined length are bundled in a fixed number to form a steel bar bundle, and two bundles of steel bars are bundled. The first stage is formed by stacking them in parallel with each other at intervals and within ± 10 ° from the average value in the longitudinal direction of the steel bars , and then as the second stage, two or more bundles of steel bars are stacked with each other. Stacked in a grid shape by stacking flatly at right angles to the steel strips of the first stage at intervals and within ± 10 ° from the average value in the longitudinal direction of the steel bars of the second stage . In the case of continuing to stack in three or more stages, in a cooling method in which the steel bar bundles in the third and subsequent stages are stacked in a grid shape to form a stack of two or more stages and cooled.
A method for cooling a steel bar, which cools the steel bar by horizontally blowing a cooling mist composed of water droplets having an average particle diameter of 300 μm or less on the side surface of the stack. The method for cooling a steel bar according to claim 1 or 2 , wherein the average particle size of the water droplets of the cooling mist is in the range of 20 to 150 μm. The method for cooling a steel bar according to claim 3 , wherein the average particle size of the water droplets of the cooling mist is in the range of 20 to 120 μm. After hot rolling is completed, the steel bars are fed to the cooling bed, and after being discharged from the cooling bed, steel bars cut to a predetermined length are bundled to form a steel bar bundle, and two or more bundles of steel bars are spaced apart from each other. The first stage is formed by stacking them in parallel in parallel with a deviation of within ± 10 ° from the average value in the longitudinal direction of the steel bars , and then two or more bundles of steel bars are spaced apart from each other as the second stage. By stacking flatly at right angles to the steel bars of the first stage with a deviation of within ± 10 ° from the average value in the longitudinal direction of the steel bars of the second stage, they are piled up in a grid pattern, and then three or more stages are continued. A spraying device that sprays cooling mist onto a stack of two or more stages formed by stacking the steel bar bundles of the third and subsequent stages in a right-angled shape.
The mist nozzle that generates the cooling mist and
A blower that generates an air flow for horizontally blowing the cooling mist from the mist nozzle to the side surface of the stack.
A control unit that controls the average particle size of water droplets of the cooling mist to be sprayed horizontally on the side surface of the stack to 300 μm or less.
Cooling mist spraying device with. After hot rolling is completed, the steel bars are fed to the cooling bed, and after being discharged from the cooling bed, steel bars cut to a predetermined length are bundled in a fixed number to form a steel bar bundle, and two bundles of steel bars are bundled. The first stage is formed by stacking them in parallel with each other at intervals and within ± 10 ° from the average value in the longitudinal direction of the steel bars , and then as the second stage, two or more bundles of steel bars are stacked with each other. Stacked in a grid shape by stacking flatly at right angles to the steel strips of the first stage at intervals and within ± 10 ° from the average value in the longitudinal direction of the steel bars of the second stage . When continuously stacking in three or more stages, it is a spraying device that sprays cooling mist on a stack of two or more stages formed by stacking the steel bar bundles in the third and subsequent stages in a right-angled shape.
The mist nozzle that generates the cooling mist and
A blower that generates an air flow for horizontally blowing the cooling mist from the mist nozzle to the side surface of the stack.
A control unit that controls the average particle size of water droplets of the cooling mist to be sprayed horizontally on the side surface of the stack to 300 μm or less.
Cooling mist spraying device with. The cooling mist spraying device according to claim 5 or 6 , wherein the control unit controls the average particle size within the range of 20 to 150 μm. The cooling mist spraying device according to claim 7 , wherein the control unit controls the average particle size within the range of 20 to 120 μm. A method for manufacturing a steel bar, in which a steel bar bundle cooled by the method according to any one of claims 1 to 4 is recovered from a stack and the steel bar bundle is further unbundled. The method for manufacturing a steel bar according to claim 9 , wherein the cooled steel bar bundle is recovered from the stack, the steel bar bundle is unwound, the steel bar is taken out, and then the scale is removed.

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