CN111744973A - Method for cooling steel bar, device for blowing cooling mist, and method for manufacturing steel bar - Google Patents
Method for cooling steel bar, device for blowing cooling mist, and method for manufacturing steel bar Download PDFInfo
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- CN111744973A CN111744973A CN202010223966.7A CN202010223966A CN111744973A CN 111744973 A CN111744973 A CN 111744973A CN 202010223966 A CN202010223966 A CN 202010223966A CN 111744973 A CN111744973 A CN 111744973A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B45/00—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills
- B21B45/02—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills for lubricating, cooling, or cleaning
- B21B45/0203—Cooling
- B21B45/0209—Cooling devices, e.g. using gaseous coolants
- B21B45/0215—Cooling devices, e.g. using gaseous coolants using liquid coolants, e.g. for sections, for tubes
- B21B45/0224—Cooling devices, e.g. using gaseous coolants using liquid coolants, e.g. for sections, for tubes for wire, rods, rounds, bars
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
- B21B1/16—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling wire rods, bars, merchant bars, rounds wire or material of like small cross-section
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Abstract
The invention provides a method for cooling a steel bar efficiently by a simple device without warping or bending, a cooling mist blowing device suitable for the method for cooling the steel bar, and a method for manufacturing the steel bar using the method for cooling the steel bar. In the cooling method, the rod steels (3) are bundled to form the rod steel bundles (4), the two or more rod steel bundles (4) are laid in parallel with an interval therebetween to form a first layer, then the two or more rod steel bundles (4) are laid in parallel with an interval therebetween to form a second layer, the two or more rod steel bundles (4) are stacked in a cross shape with an interval therebetween and substantially perpendicular to the rod steel bundles (4) of the first layer, and then the rod steel bundles (4) of the third and subsequent layers are stacked in a cross shape as necessary, thereby forming the two or more laminates (2) to be cooled, wherein the rod steels (3) are cooled by blowing cooling mist consisting of water droplets having an average particle size of 300 [ mu ] m or less to the side surfaces or corners of the laminates (2).
Description
Technical Field
The present invention relates to a cooling method for cooling an integrated body (hereinafter, referred to as a laminated body) in which a plurality of steel rods cut into a predetermined length after hot rolling is completed and transported to a cooling bed and discharged from the cooling bed are bundled by a predetermined number of the steel rods to form bundles of the steel rods (hereinafter, referred to as steel rod bundles), and the bundles of the steel rods are stacked in a cross shape of a plurality of layers by spraying cooling water (hereinafter, referred to as cooling mist).
Background
Generally, a bar steel is manufactured through the following processes: a billet (for example, a square billet or the like) obtained by continuous casting is conveyed to a heating furnace and heated to a predetermined temperature, and then hot-rolled to form a long round bar-shaped billet, which is then cooled in air by a cooling bed and cut into a predetermined length. Since the thus obtained steel bar is subjected to straightening and inspection processes, it is necessary to cool the steel bar to 50 ℃ or less from the viewpoint of improving the accuracy of these operations and improving the durability of the equipment used.
Therefore, a technique of further cooling the steel bar discharged from the cooling bed and cut into a predetermined length has been studied.
For example, a technique has been studied in which bundles of a fixed number of steel bars are transported by a crane or the like to form a stacked body in a cross shape, and the stacked body is directly air-cooled. This cooling technique is a technique of slowly cooling by radiating heat to the atmosphere, and therefore can prevent deformation such as warping or bending of the steel bar. However, the time required for cooling is inevitably long, and varies depending on the size of the steel rods, the arrangement of the steel rods in the stacked body, the temperature around the stacked body, the air volume, and the like, but it takes about 3 to 5 days to cool the steel rods to 50 ℃. Therefore, there are problems that the place for placing the laminate is insufficient, and that much labor is required for stock management.
Therefore, the technique disclosed in patent document 1 requires not only a water tank and a cooling tower but also piping for circulating cooling water, and thus has a problem that maintenance thereof requires a lot of labor because the equipment becomes complicated. Further, rapid cooling by immersion water cooling also causes a problem that deformation such as warping and bending of the steel bar is likely to occur.
Documents of the prior art
Patent document
Patent document 1: japanese patent laid-open publication No. 2017-221968
Disclosure of Invention
Problems to be solved by the invention
The present invention has been made to solve the problems of the prior art and an object of the present invention is to provide a cooling method capable of cooling a steel bar efficiently by a simple apparatus without causing warpage or bending, and also to provide a cooling mist blowing apparatus suitable for the cooling method and a method for manufacturing a steel bar to which the cooling method is applied.
Means for solving the problems
The inventors of the present invention have studied a technique for efficiently cooling a steel bar with a simple apparatus. Further, attention is paid to the fact that a laminated body in which steel rods are stacked in a multi-layer cross shape has excellent air permeability with respect to air blowing in the horizontal direction. That is, if a technique for efficiently cooling the bar steel by blowing air is developed, it is not necessary to provide large-scale equipment (for example, a water tank, a cooling tower, piping, etc.), and cooling can be performed by simple equipment (for example, a blower, etc.).
As a result of the research, it was found that if a horizontal air flow is supplied to the stacked body of the bundle of rod steels, the air flow easily passes through the inside of the stacked body, and therefore the entire stacked body can be efficiently cooled.
Next, in order to further improve the cooling capacity, a cooling unit used in combination with a horizontal airflow is studied. As a result, it was found that cooling capacity can be further improved by making cooling water into mist-like fine water droplets and blowing the droplets together with a horizontal air flow, and that warping and bending of the bar can be prevented because the cooling rate is slower than that of immersion water cooling. In such cooling by the cooling mist, a water tank or a cooling tower is not required.
When scale (e.g., deposit, rust, etc.) is generated on the surface of the steel bar by blowing the cooling mist, if the scale is removed after the blowing of the cooling mist is stopped, the steel bar can be subjected to straightening and inspection without trouble.
The present invention has been completed based on such findings.
That is, the present invention is a cooling method in which a steel bar is formed by bundling steel bars which are conveyed to a cooling bed after hot rolling is completed and are cut into a predetermined length after being discharged from the cooling bed, a first layer is formed by laying two or more of the steel bar bundles substantially in parallel at an interval, then, as a second layer, two or more of the steel bar bundles are laid substantially at right angles to the steel bar bundles of the first layer at an interval, thereby being stacked in a cross shape, and then, as necessary, the steel bar bundles of a third layer and subsequent layers are stacked in a cross shape, thereby forming a stacked body of two or more layers and cooling, wherein the steel bar is cooled by blowing cooling mist made of water droplets having an average particle size of 300 μm or less to the side surfaces or corners of the stacked body.
The present invention is a cooling method for cooling a steel bar by bundling a fixed number of steel bars cut into a predetermined length after hot rolling is completed, which are transported to a cooling bed and discharged from the cooling bed, to form a bundle of steel bars, laying two or more bundles of steel bars in parallel at a distance from each other to form a first layer, laying two or more bundles of steel bars in parallel at a distance from each other to form a second layer, laying two or more bundles of steel bars in parallel at a substantially right angle to the bundle of steel bars of the first layer at a distance from each other to form a cross, and then stacking the bundles of steel bars of a third layer or later in a cross as necessary to form a stacked body of two or more layers, wherein a cooling mist consisting of water droplets having an average particle size of 300 μm or less is blown to a side surface or a corner of the stacked body to cool the steel bar.
In the present invention, in order to obtain water droplets having a desired average particle size, a mist nozzle designed and produced to obtain a mist of water droplets having a predetermined particle size on the premise of a predetermined amount of water, a water pressure, and the like is used.
That is, in the present invention, the average particle diameter (sauter average particle diameter) of the water droplets of the cooling mist is 300 μm or less means a case where the cooling mist is sprayed through a mist nozzle designed and produced so as to obtain the cooling mist composed of water droplets having an average particle diameter (sauter average particle diameter) of 300 μm or less.
In the method for cooling a steel bar according to the present invention, preferably, cooling mist is blown horizontally to the side surface of the stacked body, and the average particle diameter of water droplets of the cooling mist is preferably in the range of 20 to 150 μm, more preferably in the range of 20 to 120 μm.
The horizontal direction in the present invention also includes a direction within a range of ± 10 degrees in the vertical direction with respect to the horizontal direction. Preferably within a range of ± 5 degrees.
Further, the present invention is a blowing device for blowing cooling mist to a laminate of two or more layers, the laminate being formed by: the present invention provides a blowing device for a bar-shaped steel bar bundle, which is a device for stacking bar-shaped steel bars in a well-like shape by bundling bar-shaped steel bars cut into a predetermined length after hot rolling is completed and conveyed to a cooling bed and discharged from the cooling bed, forming a bar-shaped steel bundle, laying the two or more bar-shaped steel bundles substantially in parallel at an interval from each other to form a first layer, laying the two or more bar-shaped steel bundles substantially at right angles to the bar-shaped steel bundle of the first layer at an interval from each other as a second layer, and then stacking the bar-shaped steel bundles of a third layer and thereafter in a well-like shape as necessary, the blowing device including: a mist nozzle generating a cooling mist; a blower that generates an air flow for blowing cooling mist from the mist nozzle to a side surface or a corner of the laminate; and a control unit for controlling the average particle diameter of water droplets of the cooling mist blown to the laminate to 300 [ mu ] m or less.
Further, the present invention is a blowing device for blowing cooling mist to a laminate of two or more layers, the laminate being formed by: a blowing device for forming a bundle of rod steels by bundling a fixed number of rod steels cut into a predetermined length after hot rolling is completed and conveyed to a cooling bed and discharged from the cooling bed, forming a first layer by laying two or more bundles of rod steels substantially parallel to each other at intervals, stacking the bundles in a cross shape by laying two or more bundles of rod steels substantially perpendicular to the bundle of rod steels of the first layer at intervals as a second layer, and stacking the bundles of rod steels of a third layer and subsequent layers in a cross shape as necessary, the blowing device comprising: a mist nozzle generating a cooling mist; a blower that generates an air flow for blowing cooling mist from the mist nozzle to a side surface or a corner of the laminate; and a control unit for controlling the average particle diameter of water droplets of the cooling mist blown to the laminate to 300 [ mu ] m or less.
In the cooling mist blowing device according to the present invention, the cooling mist is preferably blown to the side surface of the laminate in the horizontal direction, and the average particle diameter of the water droplets of the cooling mist controlled by the control unit is preferably in the range of 20 to 150 μm, and may be in the range of 20 to 120 μm.
The present invention is also a method for manufacturing a steel bar, which includes collecting a bundle of steel bars cooled by any one of the above-described cooling methods from a stacked body, and further unbundling the bundle of steel bars.
In the method for producing a steel bar according to the present invention, it is preferable that the cooled steel bar bundle is recovered from the stacked body, and after the steel bar bundle is further unbundled and taken out, the scale of the steel bar is removed.
Effects of the invention
According to the present invention, the bar steel can be efficiently cooled by a simple apparatus without warping or bending, and an industrially significant effect is obtained.
Drawings
Fig. 1 is a perspective view schematically showing an example of a laminated body in which rod steel bundles are stacked in a cross shape.
Fig. 2 is a perspective view schematically showing an example of the blowing device for the cooling mist.
Fig. 3 is a plan view schematically showing an example of cooling the laminate shown in fig. 1 by the blowing device shown in fig. 2.
Fig. 4 is a plan view schematically showing an example of cooling the laminate shown in fig. 1 by the blowing device shown in fig. 2.
Description of the reference symbols
1 stand
2 laminated body
3 bar steel
4-bar steel bundle
5 blower
6-mist nozzle
7 blowing device
Detailed Description
The steel bar is manufactured through the following steps: a billet (for example, a square billet or the like) obtained by continuous casting is conveyed to a heating furnace, heated to a predetermined temperature, and then hot-rolled to form a long billet in the shape of a round bar, and then air-cooled by a cooling bed, and then cut into a predetermined length (that is, a length required by product standards, for example, about 4 to 13 m). In order to further cool the thus obtained steel rods, a predetermined number of steel rods are bundled to form a bundle of steel rods, and the bundle of steel rods are stacked in a matrix to form a stacked body. Fig. 1 is a perspective view schematically showing an example of a laminate.
Here, the laminated body 2 will be described with reference to fig. 1.
First, a predetermined number of the bar steels 3 are bundled to form the bar bundles 4, and a plurality of the bar bundles 4 are stacked in a matrix shape. The number of the steel rods 3 constituting the steel rod bundle 4 may be different for each steel rod bundle 4. However, the number of the steel rods 3 constituting the steel rod bundle 4 is preferably fixed from the viewpoint of improving the work efficiency of the step of bundling the steel rods 3 to produce the steel rod bundle 4 and/or from the viewpoint of improving the stability of the stacked body 2 when a large number of the steel rod bundles 4 are stacked in a matrix. For example, the steel rods 3 are bundled by a fixed number (10 in the example of fig. 1) to form the steel rod bundles 4, and a large number of the steel rod bundles 4 are stacked in a matrix. In this case, in order to further stabilize the stacked body 2, it is more preferable to bundle the steel rods 3 in the steel rod bundles 4 in a uniform arrangement (3 to 4 to 3 in the example of fig. 1). In fig. 1, a binding band for binding the bar 3 is not shown.
Then, as the first layer of the laminated body 2, two or more bundles 4 (6 bundles in the example of fig. 1) of rod steels are arranged in parallel and laid flat with a space provided between the bundles 4. This gap is a passage through which a cooling mist described later passes through the interior of the stacked body 2, and a gap is provided between the bundle bars 4 adjacent to each other. However, the widths of the spaces are not necessarily the same.
The bundle bars 4 are arranged substantially in parallel in order to allow the cooling mist to efficiently pass between the adjacent bundle bars 4. The steel bar bundles 4 are preferably arranged strictly parallel, but even if not necessarily parallel, there is no problem as long as the cooling mist can pass through. Thus, for the average value of the directions of the bundle of rod steel 4, a deviation within ± 10 ° is tolerated. The deviation of the direction of the bundle of steel rods 4 is more preferably within ± 5 °. The term substantially parallel means that the average value of the directions of the steel bar bundles 4 is deviated within the above range.
In order to prevent the bar 3 in the bundle of bar steels 4 from contacting the ground surface of the place where the bar is placed and causing a flaw, it is preferable to provide a mount 1 on the bottom surface and place the bundle of bar steels 4 on the mount 1.
Next, as a second layer of the laminated body 2, two or more bundles of rod steels 4 (6 bundles in the example of fig. 1) are arranged substantially at right angles to the bundles of rod steels 4 of the first layer, and are laid so as to provide spaces between the bundles of rod steels 4, thereby being stacked in a crisscross pattern.
When two or more steel bar bundles 4 are arranged in the second layer of the stacked body 2 by a crane or the like, the purpose of making the direction of the steel bar bundles 4 substantially perpendicular to the steel bar bundles 4 of the first layer of the stacked body 2 is to facilitate insertion of a hanger (e.g., a claw or the like) for lifting up the steel bar bundles 4 of the second layer. The steel bar bundles 4 of the second layer are preferably arranged strictly at right angles to the steel bar bundles 4 of the first layer, but there is no problem if the spreader can be easily inserted, even if not necessarily at right angles. Thus, for the average value of the directions of the bundle of rod steel 4, a deviation within ± 10 ° is tolerated. The deviation of the direction of the bundle of steel rods 4 is more preferably within ± 5 °. The substantially right angle means that the average value of the directions of the steel bar bundles 4 is deviated within the range.
In the case where the laminated body 2 is stacked into 3 or more layers, the steel rod bundles 4 of the third and subsequent layers are sequentially stacked in a matrix in the same manner as the steel rod bundles 4 of the second layer, whereby the laminated body 2 shown in fig. 1 is formed.
Cooling mist is blown to the side surfaces or corners of the thus obtained laminated body 2 to cool the rod steel bundle 4. Fig. 2 is a perspective view of an example of the cooling mist blowing device of the present invention.
The side surface is a planar portion other than a corner portion of the side surface portion when the stacked body 2 is regarded as a substantially quadrangular shape (rectangular parallelepiped shape).
The blowing device 7 shown in fig. 2 is a device in which a plurality of mist nozzles 6 are arranged around or on the front surface of the axial flow fan 5, and cooling mist is blown from the mist nozzles 6 to the stacked body 2 by the air flow generated by the fan 5. In fig. 2, a hose for supplying cooling water to the mist nozzle 6 is not shown.
Although not shown, the following configuration may be adopted: a high-pressure air nozzle is used as the blower 5 to blow the cooling mist from the mist nozzle 6 toward the laminate 2. Alternatively, a two fluid nozzle of air and water may be used.
Although not shown, the blowing device 7 includes a control unit that controls the average particle diameter of the water droplets of the cooling mist blown onto the stacked body 2 to be within a predetermined range. The control unit may control the mist nozzle 6 to blow the cooling mist horizontally toward the side surface of the stacked body 2. The control unit may also control other functions of the blowing device 7. The control Unit is not particularly limited, and may be an information Processing device such as a computer having a CPU (Central Processing Unit).
The blowing device 7 is preferably disposed to face the side surface of the stacked body 2, particularly, the gap between the rod bundles 4 (see fig. 3). That is, the cooling mist is blown to the side surfaces of the stacked body 2 together with the horizontal air flow, and thus the cooling mist enters the stacked body 2 from the gap between the bar bundles 4 and smoothly passes through the inside of the stacked body 2, whereby the entire stacked body 2 can be efficiently cooled. It is preferable that the blowing is performed at a speed at which the horizontal air flow reaches the central portion of the stacked body 2. This allows the cooling mist to enter the stacked body 2 and to pass through the stacked body 2 smoothly, thereby efficiently cooling the entire stacked body 2. Further, it is more preferable to blow an air flow passing through the laminate 2 at a speed of 0.5m/sec or more and 5m/sec or less. If the ratio is less than 0.5m/sec, the entire laminate 2 may not be efficiently cooled, and time may be required for cooling. If the amount exceeds 5m/sec, the cooling mist passes through the laminate 2 before being evaporated, and not only does the cooling efficiency decrease, but the cooling mist may scatter to other locations and be wetted with water. The blowing device 7 is preferably provided in the vicinity of the bundle of rod steels as long as it does not interfere with the stacking of the bundle of rod steels. This is because the cooling mist is attenuated by the ambient air before reaching the laminated body 2, and therefore needs to be blown at a higher wind speed to obtain a desired wind speed. The wind speed of the airflow can be measured by a known anemometer.
The water droplets of the cooling mist blown to the laminated body 2 are evaporated by heat exchange with the bundle of rod steels 4 (i.e., the rod steel 3). Therefore, it is not necessary to provide a facility (e.g., a water tank tower) for collecting the water droplets and a facility (e.g., a cooling tower, a pipe, etc.) for circulating the water droplets as cooling water. When scale (for example, rust) is generated on the surface of the steel rod 3 by the blowing of the cooling mist, the steel rod bundle 4 is collected from the stacked body 2, and the bundle is further released (hereinafter, referred to as unbundling) to take out the steel rod 3, and then the scale is removed and conveyed to a subsequent step (for example, processing and inspection). The means for unbundling and descaling the bundle of rod steels 4 is not particularly limited, and conventionally known techniques are used.
The smaller the average particle diameter of the water droplets of the cooling mist, the less heat is required for evaporation, and therefore evaporation is easy. However, if the average particle size is less than 20 μm, the water droplets of the cooling mist may evaporate before reaching the central portion after entering the interior of the laminate 2 together with the air flow, and thus it may be difficult to cool the entire laminate 2.
On the other hand, the larger the average particle size is, the more the heat amount required for evaporation increases, and the time required for cooling can be shortened. However, if the average particle size exceeds 300 μm, water droplets remain after the entire laminate 2 is cooled, and therefore, it is necessary to provide a facility for collecting water droplets and a facility for recycling water droplets as cooling water, and maintenance of complicated facilities requires a lot of labor. In addition, since water droplets are large, it is difficult to catch air flow, and it is difficult to cool the entire laminate 2. Therefore, the average particle diameter of the water droplets of the cooling mist is set to 300 μm or less. If it is 300 μm or less, there is little residue of the water droplets after cooling, and therefore, a facility for recovering the water droplets is not required. More preferably in the range of 20 to 150 μm, and if it is in this range, the cooling mist easily gets into the inside of the bar by the air flow, the cooling efficiency is improved, and the floor of the place where the bar 3 is placed after cooling is not excessively wetted, and the workability is improved. When the average particle diameter of the water droplets is large, the cooling capacity is increased, and therefore, the time required to cool the steel bar to a desired temperature can be shortened, but the wet of the floor surface of the place where the steel bar 3 is placed after cooling is likely to remain. On the other hand, when the average particle diameter of the water droplets is small, the floor surface of the place where the cooled bar 3 is placed is easily dried, but the cooling capacity is small, so that the time required to cool the bar to a desired temperature becomes long. Therefore, in the case of carrying out the present invention, the average particle diameter of the water droplets may be selected within the range of 20 to 150 μm in consideration of the balance between the time required for cooling and the allowance of the degree of wetting of the floor surface of the place where the water droplets are placed after cooling. More preferably, the average particle diameter of the water droplets 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 any known method may be used as long as a mist nozzle designed to generate a cooling mist having a desired particle size is used. As described above, the control unit (not shown) controls the mist nozzle 6 to blow the cooling mist of water droplets having a predetermined average particle diameter toward the stacked body 2.
In the present invention, in order to obtain water droplets having a desired average particle diameter, a mist nozzle designed and produced to obtain a mist of water droplets having a predetermined particle diameter on the premise of a predetermined amount of water, a water pressure, and the like is used.
That is, in the present invention, the average particle diameter (sauter average particle diameter) of the water droplets of the cooling mist is 300 μm or less means a case where the cooling mist is sprayed by a mist nozzle designed and manufactured to obtain the cooling mist composed of water droplets having an average particle diameter (sauter average particle diameter) of 300 μm or less.
When the metallurgical phase transformation of the steel bar 3 occurs by blowing the cooling mist to the stacked body 2 and cooling, problems such as deformation (for example, warpage, bending, etc.) of the steel bar 3 and changes in mechanical properties of the steel bar 3 occur, and the progress of the subsequent process may be hindered. Therefore, it is preferable to blow cooling mist after the metallurgical phase transformation of the steel bar 3 is completed.
Examples
In order to perform a cooling experiment using round bar steel as the bar steel, the bar steel bundles were stacked in a cross shape to form a laminated body. In the laminate, the first layer was formed by arranging the bundle of 17 round bar steels in parallel with each other at intervals of 9 bundles, and the second and subsequent layers were also formed by stacking the bundle of 9 bundles in a grid pattern so as to form a total of 10 layers. Therefore, the laminate is larger than the example shown in fig. 1.
In this way 9 stacks were formed.
Then, a cooling mist is blown from a blowing device (see fig. 2) to the laminate. The blowing conditions of the cooling mist are shown in table 1.
The blowing device used a large factory fan (450 mm in diameter) as a blower and 4 mist nozzles were arranged in front of the blower. The total flow rate of cooling water blown as cooling mist was 4L/min, and the water temperature was 30 ℃. The large fan had a wind speed of 7m/sec, was disposed at a distance of 300mm from the stacked body, and the wind speed of the air flow passing to the opposite side of the bundle of bar steel was 1.5 m/sec.
The round bar steel is a carbon steel for machine structure containing 0.42-0.48 mass% of carbon (C), and has a diameter of 55mm and a length of 7 m. The temperature of the round bar steel at the time of completion of the stacking was 350 ℃, which is a temperature at which no metallurgical phase transformation occurred even when cooling was performed from this state.
While the laminated body was cooled, the time required for the maximum temperature of the round bar steel to fall to 50 ℃ 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 in the measurement range. The results are shown in table 1 as cooling times. The atmospheric temperature of the place where the laminate was placed was 34 ℃.
[ Table 1]
The invention example 1 in table 1 is an example in which a cooling mist (having an average particle diameter of 150 μm) was blown in the horizontal and diagonal directions to the corners of the laminate (i.e., the intersection of the steel rod bundles) by using a blowing device (see fig. 4). In the invention example 1, when the maximum temperature of the round bar steel was lowered to 50 ℃, the surface of the round bar steel and the floor of the place where the round bar steel was placed were locally wetted, but there was no need to collect water droplets, and deformation (e.g., warping, bending, etc.) of the round bar steel was not observed. In addition, the time required for the reduction to 50 ℃ was 45 hours.
In the invention example 2, cooling mist (having an average particle diameter of 150 μm) was blown horizontally to the side face of the laminate by using a blowing device (see fig. 3). In the invention example 2, when the maximum temperature of the round bar steel was lowered to 50 ℃, the surface of the round bar steel and the floor of the place where the round bar steel was placed were locally wetted, but there was no need to collect water droplets, and deformation (e.g., warping, bending, etc.) of the round bar steel was not observed. In addition, the time required for the temperature to fall to 50 ℃ was shortened to 31 hours as compared with inventive example 1. This is because the cooling mist is blown to the side surface of the laminate, and the cooling mist enters the interior of the laminate and smoothly passes through the interior, thereby improving the cooling capability.
In the invention example 3, cooling mist (having an average particle diameter of 80 μm) was blown horizontally to the side face of the laminate by using a blowing device (see fig. 3). In the invention example 3, when the maximum temperature of the round bar steel was lowered to 50 ℃, the surface of the round bar steel was wet, but the ground surface of the place where the round bar steel was placed was not wet, and it was not necessary to collect water droplets, and deformation (e.g., warping, bending, etc.) of the round bar steel was not observed. In addition, the time required for the temperature to fall to 50 ℃ was 32 hours, which was shortened as compared with inventive example 1. This is because the cooling mist is blown to the side surface of the laminate, and the cooling mist enters the interior of the laminate and smoothly passes through the interior, thereby improving the cooling capability.
In the invention example 4, cooling mist (having an average particle diameter of 40 μm) was blown horizontally to the side face of the laminate by using a blowing device (see fig. 3). In the invention example 4, when the maximum temperature of the round bar steel was lowered to 50 ℃, the surface of the round bar steel was locally wetted, but the ground of the place where the round bar steel was placed was not wetted, and it was not necessary to collect water droplets. Moreover, no deformation (e.g., warpage, bending, etc.) of the round bar steel was observed. In addition, the time required for the temperature to fall to 50 ℃ was 33 hours, which was shortened as compared with inventive example 1. This is because the cooling mist is blown to the side surface of the laminate, and the cooling mist enters the interior of the laminate and smoothly passes through the interior, thereby improving the cooling capability.
In the invention example 5, cooling mist (having an average particle diameter of 20 μm) was blown horizontally to the side face of the laminate by using a blowing device (see fig. 3). In the invention example 5, when the maximum temperature of the round bar steel was lowered to 50 ℃, the surface of the round bar steel and the floor of the place where the round bar steel was placed were not wetted, there was no need to collect water droplets, and deformation (e.g., warping, bending, etc.) of the round bar steel was not observed. In addition, the time required for the temperature to fall to 50 ℃ was 34 hours, which was shortened as compared with inventive example 1. This is because the cooling mist is blown to the side surface of the laminate, and the cooling mist enters the interior of the laminate and smoothly passes through the interior, thereby improving the cooling capability.
In the invention example 6, cooling mist (having an average particle diameter of 15 μm) was blown horizontally to the side face of the laminate by using a blowing device (see fig. 3). In the invention example 6, when the maximum temperature of the round bar steel was lowered to 50 ℃, the surface of the round bar steel and the floor of the place where the round bar steel was placed were not wetted, there was no need to collect water droplets, and deformation (for example, warping, bending, etc.) of the round bar steel was not observed. In addition, the time required for the temperature to fall to 50 ℃ was 42 hours, which was longer than that of inventive example 5. This is because the amount of cooling mist evaporated increases before reaching the central portion of the stacked body, and the cooling capacity decreases.
In addition, in invention examples 1 to 6, although the scale was generated on a part of the round bar steel after the blowing of the cooling mist was stopped, the scale could be easily removed by the shot blasting method.
On the other hand, comparative example 1 is an example in which the laminate was cooled slowly by heat dissipation into the atmosphere without blowing the cooling mist. Therefore, it took 91 hours for the maximum temperature of the round bar steel to fall to 50 ℃, which was significantly increased as compared with the invention examples 1 to 3.
Comparative example 2 is an example in which the blower was stopped, the cooling mist (average particle size 40 μm) was generated from the mist nozzle, and the cooling mist was allowed to drift by natural wind in the place where the mist was placed, although the blower was used. Therefore, since the mist is not blown to the laminate, the cooling mist is scattered in a wide range and is attached to the laminate in a large amount, and also to the floor surface of the place where the laminate is placed, the blowing device, and the thermal imaging camera in a large amount, and therefore, the cooling experiment of the laminate is stopped.
Comparative example 3 is an example in which cooling water (average particle size of 400 μm) was blown horizontally onto the side surfaces of the laminate by using a blowing device (see fig. 3). The grain size was large, and it was difficult to get on the air flow, and only the blower side of the laminate 2 was cooled, and the floor surface of the place where the laminate was placed was heavily wetted, and therefore the laminate cooling experiment was stopped.
After the cooling test described above was completed, arbitrary bundles of rod steels were collected from the laminated bodies of invention examples 1 to 6 and comparative examples 1 to 3, and the bundles were unbundled to take out one round rod steel, and the microstructure was observed with a microscope, and all the steel were ferrite-pearlite structures, and no abnormal structure was observed.
In addition, although an example of cooling round bar steel (i.e., bar steel having a circular cross section) is shown here, the object of the present invention is not limited to round bar steel, and it is needless to say that the present invention can also be applied to cooling square bar steel (i.e., bar steel having a polygonal cross section such as a rectangular cross section).
Claims (12)
1. A method for cooling a steel bar, comprising the steps of bundling steel bars which have been conveyed to a cooling bed after completion of hot rolling and have been cut into a predetermined length after being discharged from the cooling bed to form a bundle of steel bars, laying two or more bundles of steel bars substantially parallel to each other at a distance from each other to form a first layer, stacking the bundles of steel bars in a cross shape as a second layer by laying the bundles of steel bars substantially parallel to the bundle of steel bars of the first layer at a distance from each other at a right angle to the bundle of steel bars of the first layer, and stacking the bundles of steel bars of a third layer or later as necessary in a cross shape to form a stacked body of two or more layers for cooling,
and cooling the steel bar by blowing a cooling mist comprising water droplets having an average particle diameter of 300 [ mu ] m or less onto the side surfaces or corners of the laminate.
2. A method for cooling a steel bar, comprising binding a fixed number of steel bars cut into predetermined lengths after hot rolling, transported to a cooling bed, discharged from the cooling bed, to form bundles, laying two or more bundles of the steel bars in parallel at intervals to form a first layer, laying two or more bundles of the steel bars in parallel at substantially right angles to the bundles of the steel bars in the first layer at intervals to form a second layer, stacking the second layer in a cross shape, and stacking the third and subsequent bundles of the steel bars in a cross shape as needed to form a stacked body of two or more layers, wherein the steel bars are cooled,
and cooling the steel bar by blowing a cooling mist comprising water droplets having an average particle diameter of 300 [ mu ] m or less onto the side surfaces or corners of the laminate.
3. The method for cooling a steel bar according to claim 1 or 2,
the cooling mist is blown horizontally to the side surface of the laminate.
4. The method for cooling a steel bar according to any one of claims 1 to 3, wherein,
the average particle diameter of the water drops of the cooling mist is within the range of 20-150 mu m.
5. The method for cooling a steel bar according to claim 4,
the average particle diameter of the water drops of the cooling mist is within the range of 20-120 mu m.
6. A cooling mist blowing device for blowing cooling mist to a laminate of two or more layers, the laminate being formed by: bundling the steel rods which are conveyed to a cooling bed after the completion of hot rolling and are cut into a predetermined length after being discharged from the cooling bed to form a bundle of steel rods, laying two or more bundles of steel rods substantially parallel to each other at a distance from each other to form a first layer, then laying two or more bundles of steel rods substantially perpendicular to the bundle of steel rods of the first layer at a distance from each other as a second layer to stack them in a cross shape, and then stacking the bundles of steel rods of a third layer and later as necessary in a cross shape,
the blowing device includes:
a mist nozzle that generates the cooling mist;
a blower that generates an air flow for blowing the cooling mist from the mist nozzle to a side surface or a corner of the stacked body; and
and a control unit for controlling the average particle diameter of water droplets of the cooling mist blown onto the laminate to 300 [ mu ] m or less.
7. A cooling mist blowing device for blowing cooling mist to a laminate of two or more layers, the laminate being formed by: a method of manufacturing a steel bar bundle includes binding a fixed number of steel bars cut into a predetermined length after hot rolling is completed, and conveying the steel bars to a cooling bed, discharging the steel bars from the cooling bed, bundling the steel bars into a bundle of steel bars, laying the bundle of steel bars in parallel at an interval to form a first layer, laying the bundle of steel bars in parallel at an interval to form a second layer, stacking the bundle of steel bars in a cross shape, and stacking the bundle of steel bars in a cross shape after a third layer, if necessary,
the blowing device includes:
a mist nozzle that generates the cooling mist;
a blower that generates an air flow for blowing the cooling mist from the mist nozzle to a side surface or a corner of the stacked body; and
and a control unit for controlling the average particle diameter of water droplets of the cooling mist blown onto the laminate to 300 [ mu ] m or less.
8. The cooling mist blowing device according to claim 6 or 7,
the control unit causes the mist nozzle to blow the cooling mist horizontally toward the side surface of the stacked body.
9. The cooling mist blowing device according to any one of claims 6 to 8,
the control unit controls the average particle diameter to be within a range of 20 to 150 [ mu ] m.
10. The cooling mist blowing apparatus according to claim 9,
the control unit controls the average particle diameter to be within a range of 20 to 120 [ mu ] m.
11. A method for manufacturing a steel bar, wherein,
recovering the bundle of steel rods cooled by the method according to any one of claims 1 to 5 from the laminate, and further unbundling the bundle of steel rods.
12. The method of manufacturing a steel bar according to claim 11,
the cooled steel bar bundle is collected from the stacked body, and the steel bar bundle is unbundled to take out the steel bar, and then the scale is removed.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2019060914 | 2019-03-27 | ||
| JP2019-060914 | 2019-03-27 | ||
| JP2020038384A JP7014245B2 (en) | 2019-03-27 | 2020-03-06 | Steel bar cooling method and cooling mist spraying device, and steel bar manufacturing method |
| JP2020-038384 | 2020-03-06 |
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| Publication Number | Publication Date |
|---|---|
| CN111744973A true CN111744973A (en) | 2020-10-09 |
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| Application Number | Title | Priority Date | Filing Date |
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| CN202010223966.7A Pending CN111744973A (en) | 2019-03-27 | 2020-03-26 | Method for cooling steel bar, device for blowing cooling mist, and method for manufacturing steel bar |
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