JP2004162167A - Cooling unit for steel strip - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce a resistance coefficient of a nozzle part and to realize the compactness of a cooling facility in the cooling unit desired to be high cooling speed. <P>SOLUTION: In the cooling unit for steel strip, with which the moving steel strip is cooled by projecting a plurality of nozzles on the surface of a cooling box while holding the distance of 50-100mm from the tip part of the nozzle to the steel strip surface and spouting cooling medium from these nozzles, D/d of the spouted nozzle is made to be 1.5≤D/d ≤3.0. Wherein, d is the inner diameter at the tip part of the nozzle (steel strip side) and D is the inner diameter at the base part of the nozzle (cooling box side). <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a device for cooling a continuously running steel strip, for example, in a continuous annealing facility for steel strip, a continuous hot-dip galvanizing facility, a color coating line, and a stainless pickling annealing line.
[0002]
[Prior art]
As is well known, continuous annealing furnace equipment includes a step of continuously heating, soaking and cooling a steel strip and, if necessary, overaging. Incidentally, in order to obtain the desired properties of the steel strip, it is important to uniformly and rapidly cool the steel strip in addition to the heating temperature and the soaking time. Various cooling media are currently used as a method for cooling the steel strip, and the cooling rate of the steel strip varies depending on the selection of the refrigerant.
[0003]
Of these, when water is used as the refrigerant, a considerably high cooling rate is obtained and cooling to the super-quenched region is the function, but the biggest change is that the shape change of the steel strip called cooling buckle due to quenching distortion occurs. It is a difficult point. Further, an oxide film is formed on the surface of the steel strip due to contact with water, and a separate device for removing the oxide film is required, which is not economically advantageous.
[0004]
In order to solve this problem, there is a roll cooling method in which water or other cooling medium is passed through the inside of the roll and a steel strip is brought into contact with the cooled roll surface to cool the roll.
This method has the following problems. That is, not all steel strips passing through the continuous annealing furnace maintain flatness. Therefore, when the steel strip comes into contact with the cooling roll, it may be locally non-contacted, and the non-contact may cause uneven cooling in the width direction of the steel strip, which may cause deformation of the shape of the steel strip. Therefore, means for flattening the steel strip before contact with the cooling roll is required, which has increased equipment costs.
[0005]
As another cooling means, a cooling method using gas as a refrigerant has been put to practical use and has achieved many achievements. This method has a lower cooling rate than the water cooling or the roll cooling described above, but can relatively uniformly cool the steel strip in the width direction. In order to increase the cooling rate, which is the biggest difficulty in gas cooling, the tip of the nozzle that injects the gas is brought as close as possible to the steel strip to increase the heat transfer coefficient and increase the cooling rate, or the concentration of hydrogen gas as a cooling medium Which employs a material having a higher heat transfer coefficient.
[0006]
Patent Document 1 discloses a technique for increasing the heat transfer coefficient by bringing the tip of a nozzle for jetting close to a steel strip. This technique enables efficient cooling by reducing the distance between the tip of the nozzle and the steel strip. Specifically, the length of the protruding nozzle projecting from the surface of the cooling gas chamber provided in the cooling gas chamber is set to 100 mm-Z or more, and a portion where the gas injected from the protruding nozzle hits the steel strip and escapes to the back is provided. I have. This discloses that the injected gas is prevented from staying on the steel strip surface, and the cooling uniformity in the width direction of the steel strip is improved. Z indicates the distance between the tip of the protruding nozzle and the steel strip.
[0007]
[Patent Document 1]
Japanese Patent Publication No. 2-16375
In addition, an experiment is conducted in which the protrusion height of the nozzle is variously changed from 50 mm-Z to 200 mm-Z to derive the optimum point of the heat transfer coefficient. As a cooling device used in a cooling zone of a continuous annealing furnace, a cooling device having an efficient cooling capacity has been proposed from this experiment. The cooling device, the heat transfer coefficient was usually 100kcal / m ² h ℃ has become possible to raise up 400kca1 / m ² h ℃.
[0009]
However, it has been desired to further improve the cooling rate, and there has been a limit to the existing cooling device that circulates an atmosphere gas of about 95% N ₂ + 5% H ₂ as a normal cooling medium.
In order to solve this problem, it has been considered to use hydrogen gas as a cooling medium. It has been known for a long time that the cooling capacity is improved by employing hydrogen gas, but it has not been applied to actual machines due to the danger of hydrogen gas.
[0010]
Patent Document 2 discloses a technique for rapidly cooling by increasing the hydrogen gas concentration. According to this technique, in a rapid cooling zone, the cooling gas is blown onto a steel strip at a hydrogen concentration of 30% to 60% and a blowing speed of 100 m / sec to 150 m / sec. As described above, a specific technology for adopting hydrogen gas has been developed and is being commercialized.
[0011]
[Patent Document 2]
JP-A-9-235626
[Problems to be solved by the invention]
Usually, since the H ₂ concentration is increased from the cooling by the atmosphere gas mainly composed of N ₂ gas and the discharge flow rate from the nozzle is required to be 100 m / sec to 150 m / sec, a large amount of gas is blown to the steel strip. Is required. Further, a pressure for ejecting 100 m / sec to 150 m / sec from the nozzle is also required. In general, these cooling devices employ a circulation type cooling device in which a cooling medium blown by a steel strip is circulated through a duct and then blown again. In this circulation type cooling device, the cooling medium blown to the steel strip is discharged into the furnace, and is sucked by a circulation blower from a suction duct provided in the furnace body. In front of the circulating blower, a heat exchanger that cools the cooling medium whose temperature has been raised by blowing the steel strip to the blowing temperature is installed, and the steel strip is cooled while circulating by these devices.
[0013]
The required pressure in these circulating devices is the highest required when ejecting from the nozzle, and it has been desired to reduce the pressure loss of this nozzle as much as possible.
[0014]
[Means for Solving the Problems]
In order to solve the above problems, the present invention provides:
(1) On the surface of the cooling box, a plurality of nozzles projecting from the tip of the nozzle to the steel strip surface at a distance of 50 to 100 mm are projected, and a coolant is jetted from the nozzle to cool the running steel strip. 3. The cooling device for a steel strip according to claim 1, wherein D / d of the nozzle to be discharged is 1.5 ≦ D / d ≦ 3.0.
Where d is the inner diameter of the nozzle tip (steel strip side)
D is the inner diameter of the nozzle base (cooling box side)
[0015]
(2) The cooling device for a steel strip according to (1), wherein the nozzle has a nozzle base fixed to a mounting hole provided in a cooling box by pipe joining.
[0016]
(3) The nozzle according to (1), wherein the diameter of the nozzle mounting hole provided in the cooling box is within a range of [nozzle length L-10 mm (10 mm from the nozzle base to the tip side) ± 3 mm]. The steel strip cooling device according to (2).
[0017]
(4) The cooling device for a steel strip according to any one of (1) to (3), wherein the nozzle is mounted such that the nozzle base does not protrude from the inner surface of the cooling box.
[0018]
(5) The above-mentioned (1), wherein the refrigerant is a mixed gas composed of N ₂ and H _{2 and} other inert gases, and the remaining H ₂ concentration is 0 to 100%, and N or another inert gas is used. A cooling device for the steel strip according to the above.
[0019]
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Hereinafter, the present invention will be described in detail based on an embodiment shown in the drawings.
FIG. 1 is a side sectional view of a cooling device of a continuous annealing equipment to which the present invention is applied, FIG. 2 is a view taken along a line AA in FIG. 1, FIG. 3 is a detailed view of a nozzle of the present invention, and FIG. FIG. 5 is a graph showing the resistance coefficient of the nozzle, FIG. 6 is a schematic diagram showing the application of the cooling device of the present invention to a continuous coating line, and FIGS. It is the schematic which applied the example of this invention to the cooling device which cools a steel strip after plating.
[0020]
In FIG. 1, a pair of cooling devices 2 that are installed between upper and lower rolls 9 and 11 that convey a steel strip 12 and that eject gas are provided between the rolls so as to face the surface of the steel strip 12. Are arranged in a plurality of stages along the flow of the steel strip 12. A press roll 10 for preventing the steel strip from flapping is arranged between the upper and lower sides of the cooling device 2 so as to sandwich the steel strip 12.
[0021]
FIG. 2 is a view taken in the direction of arrows AA in FIG. 1. The gas blown to the steel strip 12 by the cooling device 2 is reused as a cooling gas through a circulation system. That is, the blown gas is sucked from a gas suction port provided in the furnace body 1, passes through the suction side duct 5, the heat exchanger 6, the circulation blower 7, and the discharge side duct 8, and further passes through the cooling box 3 in the furnace body. Is sprayed again from the nozzle provided on the steel strip 12 side of the cooling box 3 toward the steel strip 12 by the circulation system connected to the cooling box 3. Thus, the gas in the furnace sprayed on the steel strip 12 is circulated and used.
[0022]
The cooling device 2 includes a cooling box 3 and a protruding nozzle 4 provided on the steel strip 12 side of the cooling box 3. The protruding nozzle 4 is selected and arranged so that the ratio (D / d) of the base B side nozzle inner diameter D to the tip A side nozzle inner diameter d is 1.5 to 3.0. Further, the tip nozzle is arranged so that the opening area thereof is 2 to 4% of the surface area of the cooling box.
[0023]
FIG. 3 shows the nozzle shape of the present invention, where D is the inside diameter of the nozzle base B side (here, the nozzle base B side is the side attached to the cooling box 3), and D0 is the outside diameter of the nozzle base B side. Where d is the inner diameter of the nozzle tip A side, L is the total length of the nozzle, DN is the range of (nozzle full length L) − (10 mm ± 3 mm) with the nozzle base B as tact, in other words, the tip B from the nozzle base B side. The outside diameter of the nozzle in the range of 10 mm ± 3 mm on the side is indicated. Since the nozzle 4 has a conical shape, the nozzle 4 was manufactured by winding a plate of SUS (stainless steel). The nozzle can be manufactured by drawing a steel pipe, shaving, or casting in addition to plate winding. An experiment was conducted by manufacturing various nozzles having a total length L of 200 mm and various D / d.
[0024]
FIG. 4 shows a state in which the nozzle of the present invention is attached to the cooling box 3, and a hole having a DN diameter is provided on the surface of the cooling box 3 in the direction of the steel strip 12. The number of holes is set such that the opening area is 2 to 4% of the surface area of the cooling box.
The DN diameter was a nozzle diameter in a range of 10 mm ± 3 mm from the nozzle base B to the tip B shown in FIG.
[0025]
More specifically, first, a hole having a DN diameter is formed in the surface of the cooling box 3. The outer diameter D0 nozzle of the base B is inserted into this hole, and is driven into the cooling box 3 with a punch (not shown) as shown in FIG. When the nozzle 4 is driven, it is driven so that the base B of the nozzle does not protrude from the inner surface of the cooling box as shown in FIG. In FIG. 4, the nozzle base B is driven so as to be inserted into the cooling box 3 while leaving 10 mm from the plane thereof. Then, the base side nozzle inner diameter D is expanded from the base B side of the driven nozzle 4 by a pipe expander, and is crimped to the hole DN provided in the cooling box 3. By crimping with a pipe expander, the mounting accuracy of the nozzle 4 is improved, even if it has been conventionally mounted by welding.
The reason for limiting the position of the DN diameter as described above is that if it is not less than the upper limit (exceeding 10 mm + 3 mm), it becomes difficult to insert it into the cooling box, and if it is less than the lower limit, the adhesion is inferior.
In FIG. 4, the tip on the base side of the nozzle is buried from the inner surface of the cooling box 3 in order to reduce the resistance coefficient of the nozzle. However, if the resistance coefficient is reduced, it can be adjusted to the inner surface of the cooling box 3. is there.
[0026]
The pressure loss of the manufactured nozzle was determined by an experimental device, and the respective resistance coefficients were calculated. The result is shown in FIG. It was found that when D / d = 1.0, that is, when D / d = 1.5 to 3.0 as compared with the conventional straight nozzle, the resistance coefficient was small, and the resistance coefficient near 2.0 was the smallest. As described above, the resistance coefficient of the conventional nozzle is about 30% smaller than that of the conventional straight nozzle.
[0027]
FIG. 6 shows the arrangement of the coating and drying / baking furnaces in the continuous coating line. The surface of the steel strip S1 is coated with a coating by a coater facility 14, and is dried and baked in a drying and baking furnace 15 along a predetermined temperature pattern. Then, it is cooled by the cooling device 16 to near normal temperature. Conventionally, this cooling device 16 has achieved the surface quality of the paint before cooling and the rapid cooling at the subsequent stage by cooling the former stage with air and the latter stage with water. By using a cooling facility using the nozzle according to the present invention as the cooling facility 16, a facility with high cooling efficiency can be obtained without using water cooling.
[0028]
FIG. 7 shows an example in which a cooling facility using a nozzle according to the present invention is applied to a cooling facility after a plating alloying process in a continuous galvanizing facility. The steel strip S2 is introduced into a plating pot 19 through a turndown roll 18 provided in a turndown section 17. After being vertically pulled up via the sink roll 20 and adjusted to a predetermined plating thickness by the plating machine 21, it is heated to the alloying treatment temperature by the alloying heating device 22, and subsequently kept in the holding furnace 23. The alloyed steel strip S2 is cooled by the cooling device 24 and the cooling device 27 provided in the down path, and is sent to the immersion cooling device 28 which is the final cooling. By applying the cooling equipment using the nozzle according to the present invention to the cooling devices 24 and 27, the cooling efficiency can be increased and the entire alloying furnace can be lowered, and the steel strip S2 after the alloying process can be used. It is possible to measure the soundness of the alloy layer by rapidly cooling the alloy layer.
[0029]
FIG. 8 shows an example in which a cooling facility using a tapered circular nozzle according to the present invention is applied to a cooling facility after plating of a continuous galvanizing facility. After the steel strip S2 is adjusted to a predetermined plating thickness by the plating machine 21, the steel strip S2 is cooled by the cooling device 24 and the cooling device 27 provided in the down path, and sent to the immersion cooling device 28 which is the final cooling. By applying the cooling equipment using the nozzle according to the present invention to the cooling devices 24 and 27, the cooling efficiency can be increased and the entire alloying furnace can be lowered.
[0030]
FIG. 9 shows an example of a continuous annealing pickling facility for a stainless steel strip. The stainless steel strip S3 is heated and soaked at a predetermined annealing temperature in the heating zone 29, and then cooled in the cooling zone 30 at a predetermined cooling rate to the end point temperature. Subsequently, the scale formed on the surface of the stainless steel strip is removed by the rolls disposed on the upper and lower surfaces of the stainless steel strip S3 in the descaling device 31. Then, it is introduced into the pickling tank 32. By applying the cooling facility using the nozzle according to the present invention to the cooling facility 30, the cooling efficiency can be increased and a compact device configuration can be achieved.
[0031]
【The invention's effect】
As described above, in order to obtain a high cooling rate, it is more important to increase the ejection speed from the nozzle, to reduce the resistance coefficient of the nozzle, and to make the circulating equipment compact. The effect is very large. In addition, since the conventional welding structure is replaced with a crimping structure using a pipe expander, distortion of the nozzle due to welding is eliminated, and manufacturing accuracy is improved.
[Brief description of the drawings]
FIG. 1 is a side sectional view of a cooling device of a continuous annealing facility to which the present invention is applied.
FIG. 2 is a view taken in the direction of arrows AA in FIG. 1;
FIG. 3 is a detailed view of the nozzle of the present invention.
FIG. 4 is a view showing a procedure for mounting the nozzle of the present invention.
FIG. 5 is a graph showing a resistance coefficient of a nozzle.
FIG. 6 is a schematic view of a continuous coating line to which the present invention is applied.
FIG. 7 is a schematic diagram of a continuous galvanizing equipment to which the present invention is applied.
FIG. 8 is a schematic view of another continuous hot-dip galvanizing equipment to which the present invention is applied.
FIG. 9 is a schematic view of a stainless steel continuous annealing and pickling facility to which the present invention is applied.
[Explanation of symbols]
1: Cooling zone 2: Cooling device 3: Cooling box 4: Nozzle 5: Suction side duct 6: Heat exchanger 7: Circulating blower 8: Discharge side duct 9: Top roll 10: Holding roll 11: Bottom roll 12: Steel strip 13 : Partition wall 14: Coater equipment 15: Drying / baking furnace 16: Cooling device 17: Turndown section 18: Turndown roll 19: Plating pot 20: Sink roll 21: Plating tank 22: Heating device 23: Heat retention furnace 24: Cooling device 25: top roll 26: top roll 27: cooling device 28: immersion cooling device 29: heating zone 30: cooling zone 31: descaling device 32: pickling tank A: nozzle tip B: nozzle base

Claims (5)

A plurality of nozzles that maintain a distance from the tip of the nozzle to the steel strip surface of 50 to 100 mm protruding from the surface of the cooling box, and a cooling device for the steel strip that cools the running steel strip by ejecting a coolant from the nozzle. , Wherein the D / d of the nozzle for discharging is set to 1.5 ≦ D / d ≦ 3.0.
Here, d: nozzle tip inner diameter (steel strip side)
D: Nozzle base inner diameter (cooling box side) The steel strip cooling device according to claim 1, wherein the nozzle has a nozzle base fixed to a mounting hole provided in a cooling box by pipe joining. The nozzle mounting hole diameter provided in the cooling box has a hole diameter in a range of [nozzle total length L-10 mm (position of 10 mm from the nozzle base to the tip side) ± 3 mm]. A cooling device for the steel strip according to the above. The steel strip cooling device according to any one of claims 1 to 3, wherein the nozzle is mounted such that the nozzle base does not protrude from the inner surface of the cooling box. 2. The refrigerant according to claim 1, wherein the refrigerant is a mixed gas composed of N _2, H _{2 and} other inert gases, and the H ₂ concentration is 0 to 100%, and the remainder is N ₂ or other inert gases. 3. Steel strip cooling system.

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